Class 7 – Page 4 – Maharashtra Board Solutions

Materials We Use Class 7 Science Chapter 15 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 15 Materials We Use Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 15 Materials We Use Question Answer Maharashtra Board

Class 7 Science Chapter 15 Materials We Use Question Answer Maharashtra Board

1. Fill appropriate terms in the blanks:
(white cement, soap, detergent, wearing of bones, tooth decay, hard, soft, portiand, fatty acid)

Question a.
The substance that helps water to remove dirt from the surface of material is called …………… .
Answer:
soap

Question b.
Fluoride is used in toothpaste to prevent …………… .
Answer:
tooth decay

Question c.
Soap is a salt of …………… and sodium hydroxide.
Answer:
fatty acid

Question d.
Synthetic detergents can be used in …………… water as well.
Answer:
hard

Question e.
For construction purposes …………… Cement is the most commonly used cement.
Answer:
white cement

2. Write answers to the following questions.

Question a.
How does the use of a detergent help to clean soiled clothes?
Answer:

A molecule of a detergent holds on to a water molecule at one end and an oil molecule at the other.
As a result the molecules of oil mix with the water.
This is how detergent acts on our soiled clothes. So detergent removes any oil or dirt sticking on to our clothes.
Due to the property of holding on to both oil and water, soap water spreads easily on many types of surfaces.
This property of spreading on a surface is called surface activity.
Detergents are surface active.
One effect of surface activity is lather formation.

Question b.
How will you check with the help of soap powder whether water is hard?
Answer:

In the hard water, (of a well or a tube-well), soap does not give lather but forms a scum.
As a result, soap loses its cleansing property. So with help of soap we will come to know that it is a hard water.

Question c.
What are the important ingredients of a tooth paste and what is the function of each?
Answer:

The important ingredients of a toothpaste are calcium carbonate and calcium hydrogen phosphate.
They remove the dirt on teeth. These ingredients also polish the teeth.
A certain proportion of fluoride in the tooth paste helps prevent tooth decay.
It is essential for the enamel covering of teeth.

Question d.
What are the ingredients of cement?
Answer:

Cement is a dry, greenish grey powder with fine particles.
It is made from silica (sand), alumina (aluminium oxide), lime, iron oxide and magnesia (magnesium oxide).

Question e.
What will happen if cement is not used in making concrete?
Answer:

In making concrete strong, the ingredients cement, water, sand and gravel should usually be mixed in the ratio of 1 : 2 : 3 : 0.5 to achieve maximum strength.
If enough cement is not used then the concrete will eventually fall apart, as cement is used as a binding agent.

Question f.
Make a list of detergents, that you use. Answer: There are two types of detergents that we use, (a) Natural (b) Man-made detergents.

Natural detergents are soap nut (ritha) soap pod (shikekai).
Man-made detergents are soap, hard soaps, soft soaps.
Synthetic detergents have taken the place of soap.
- Detergents are commonly available as powders or concentrated solution.
- Detergents are for laundry, washing clothes and cleaning dishes.
Alkaline detergents used for hard surface cleaning.

Question g.
What should be expected from a detergent for delicate garments?
Answer:

Detergents should not be strong, they may spoil the texture, colour of delicate garments.
Now a days many detergents are available especially for woollen, delicate clothes.
They should not contain bleach, phosphorous which will harm delicate clothes.

Question h.
What is meant by surface activity? Name three chemicals responsible for the surface activity of various detergents.
Answer:

Due to the property of holding on to both oil and water, soap water spreads easily on many types of surfaces.
The property of a substance of spreading on a surface is called surface activity and the substance is called surfactant.
Detergents are surface active.
They increase the spreading and wetting ability of water by reducing its surface tension.
Chemicals responsible for the surface activity of various detergents is phenol, Aprotinin.

3. What are the similarities and differences between:

Question a.
Natural detergents and Man-made detergents
Answer:

Natural detergents	Man-made detergents
1. Soap nut (ritha) and soap pod (shikekai) are the natural detergents.	1. Soap is man-made detergent soft soap and hard soap.
2. Natural detergents do not have harmful effect on human skin or on silk or woollen clothes.	2. Soap has effect on skin and cloth because it has chemicals in it.
3. Soap nut, soap pod contain a chemical saponin.	3. Soap has acid in it, soap is sodium and potassium salt of fatty acids.
4. It is naturally available.	4. It is man made using chemicals and oil.

Question b.
Soap and Synthetic detergents
Answer:

Soap	Synthetic detergents
1. Soap is man-made detergent, it is in use since ancient times.	1. Synthetic detergent have taken the place of soap.
2. Soap loses its cleansing property in hard water it does not give lather.	2. Synthetic detergent can be used in hard water also.
3. Soap was prepared by using animal fat and wood ash.	3. Synthetic detergent are obtained by subjecting fats, kerosene to various chemical processes.
4. Variety of soaps are available, soft soap for bathing, hard soap for washing, cleaning.	4. Variety of synthetic detergents are available – Ariel, Surf Excel, etc.

Question c.
Bath soap and Soap for washing clothes
Answer:

Bath soap	Soap for washing clothes
1. Soft soap is used for bathing.	1. Hard soap is used for washing clothes.
2. Soft soap is potassium salt is fatty acids.	2. Hard soap is sodium salt of fatty acid.
3. Soft soap dissolves more easily readily in water.	3. Hard soap do not dissolve easily in water.
4. Now a days many perfumes, moisturizes are mixed to make it more attractive and useful.	4. In this type of soap now a days germicides, anti foaming agents are mixed to make it more useful.

Question d.
Modern cement and Ancient cement
Answer:

Modem cement	Ancient cement
1. Cement manufactured from 60% lime, silica 25% and alumina 5%. the rest is iron oxide and gypsum.	1. Romans used to make aqueous cement by mixing volcanic ash in moistened lime. It was very durable.
2. It is the most commonly used cement for Construction work.	2. It is Roman cement volcanic ash prevent cracks from spreading.
3. It is called Portland Cement.	3. It is called Aqueous Cement.

4. Explain why –

Question a.
Soap cannot be used in hard water.
Answer:

In the hard water of a well or a tube well, soap does not give lather but forms a scum.
As a result soap loses its cleansing property. So soap cannot be used in hard water.

Question b.
Oil does not mix in water. However, oil and water become homogenous if a sufficient quantity of detergent is added.
Answer:

A molecule of a detergent holds on to a water molecule at one end and an oil molecule at the other.
As a result the molecules of oil mix with the water, and we will see that the water and oil have become homogenous and the colour of the mixture appears milky.

Question c.
Synthetic detergents are superior to soap.
Answer:

Soap is a man-made detergent which has been in use since ancient times.
It was prepared by using animal fat and wood ash. In hard water, soap does not give lather, it loses its cleansing property.
So we can not use soap in hard water. Now synthetic detergents have taken the place of soap.
They can be used in hard water as well
Synthetic detergents have many more advanced properties like they are added with perfumes, conditioner for fabric, etc.

Question d.
Often coloured spots are formed on clothes during washing.
Answer:

Curry stains stick fast to the criss-crossing threads of the material of our clothes.
Curry contains turmeric a natural indicator which turns red in a basic solution.
Soaps are sodium salts of fatty acids and are basic in nature.
While washing the clothes, turmeric reacts with soap solution and turns red forming red spots on the clothes.
But the spots disappear after washing the clothes with plenty of water.

Question e.
Tobacco masheri should not be used for cleaning teeth.
Answer:

Masheri is the smokeless form of tobacco. It is tobacco, containing teeth cleaning powder
It contains tobacco leaves.
Tobacco contains toxic and Carcinogenic chemicals which can cause cancer, oral cancer, mouth and throat cancer, gum disease, tooth decay.
Its use can cause abnormal delivery in pregnant women.

Project:

Question 1.
Visit a cement factory. See how cement is prepared and discuss the process.

Question 2.
Write a conversation based on cement houses, mud-houses and wattle-and-daub houses.

Class 7 Science Chapter 15 Materials We Use Important Questions and Answers

Fill in the blanks:

Question 1.
The principal ingredients of a toothpaste are ………………. and ………………. which remove the dirt on the teeth.
Answer:
Calcium carbonate, calcium hydrogen phosphate

Question 2.
………………. in the toothpaste helps prevent tooth decay.
Answer:
Fluoride

Question 3.
The property of a substance of spreading on a surface is called ………………. .
Answer:
surface activity

Question 4.
………………. and ………………. are the natural detergent in common use.
Answer:
Soap nut, Soap pod

Question 5.
Soap nut and soap pod contain a chemical named ………………. .
Answer:
Saponin

Question 6.
………………. is a man-made detergent.
Answer:
Soap

Question 7.
………………. is used for washing clothes.
Answer:
Hard soap

Question 8.
………………. is used for bathing.
Answer:
Soft soap

Question 9.
Hard soap is ………………. salt of fatty acids.
Answer:
Sodium

Question 10.
Soft soap is ………………. salt of fatty acids.
Answer:
Potassium

Name the following:

Question 1.
A substance which is spread on a given surface and used for cleaning.
Answer:
Surfactant

Question 2.
A chemical contained in soap nut and pod.
Answer:
Saponin

Question 3.
An element which helps prevent tooth decay which is used in toothpastes.
Answer:
Fluoride

Question 4.
The latin word which means detergent.
Answer:
Detergere

Question 5.
A cement used for construction purpose.
Answer:
Portland cement

Question 6.
A mixture of cement, water, sand and gravel.
Answer:
Concrete

Question 7.
A natural detergent.
Answer:
Soap nut

Choose the correct option:

Question 1.
Which one of these material grows on an animal
(cotton, rubber, wood, wool)
Answer:
Wool

Question 2.
Which of these is man-made?
(oranges, apples, plastic bags, tomatoes)
Answer:
Plastic bags

Question 3.
The statue is made from marble, marble is a ………….. material.
(weak, elastic, man-made, natural)
Answer:
Natural

Question 4.
Toy Duck is made from plastic. Plastic is a ………….. material.
(natural, man-made, raw, precious)
Answer:
Man-made

Question 5.
Which of these materials is natural?
(Nylon, Rock, Plastic, Polythene)
Answer:
Rock

Question 6.
Which one of these is a natural material?
(Lemonade, Cola, Water, Ice cream)
Answer:
Water

Question 7.
The toy plane made from wood. Wood is a ………….. material.
(man-made, natural, weak)
Answer:
Natural

Question 8.
Which one of these materials is natural?
(Nylon, cotton, polythene, polyesters)
Answer:
Cotton

Match the following:

Question 1.

Column ’A’	Column ’B’
1. Fluoride	a. Man-made detergent
2. Soap nut	b. Sodium salt of fatty acid
3. Soap	c. Man-made material
4. Cotton	d. Prevents tooth decay
5. Nylon	e. Potassium salt of fatty acid.
6. Hard soap	f. Natural detergent
7. Calcium carbonate	g. Natural material
8. Soft soap	h. Main ingredients of toothpaste

Answer:

Column ’A’	Column ’B’
1. Fluoride	d. Prevents tooth decay
2. Soap nut	f. Natural detergent
3. Soap	a. Man-made detergent
4. Cotton	g. Natural material
5. Nylon	c. Man-made material
6. Hard soap	b. Sodium salt of fatty acid
7. Calcium carbonate	h. Main ingredients of toothpaste
8. Soft soap	e. Potassium salt of fatty acid.

Find out:

Answer the following questions:

Question 1.
What is the source of the fluoride in a tooth paste or tooth powder?
Answer:
A naturally occurring mineral found in tooth paste and drinking water. Sodium Fluoride (NaF) is the source of fluoride in toothpaste.

Question 2.
Note down all the information given on a tooth powder/toothpaste container or carton and discuss.
Answer:
1. The carton shows the name of the company and name of toothpaste and its contains all the ingredients present in toothpaste.

2. Licence No. of company, Regd. Trade Mark of Colgate Palmolive Co-manufactured by Colgate-Palmolive (India) Ltd. Licenced user of Trade Mark made in India. Tooth paste contains 1000 ppm max of available fluoride when packed.

3. Ingredients: Calcium carbonate, sorbitol, sodium lauryl sulphate, silica, sodium silicate flavour, sodium monoflouro phosphate, sodium bicarbonate, benzyl alcohol.

4. Direction for use: Brush thoroughly atleast twice a day.
5. Children under 6 years of age should have adult supervision and use only appropriate amount.

Question 3.
Now a days why are the roads made of concrete?
Answer:

Concrete is prepared by mixing cement, limestone, sand, gravel, and water. It is solid, more durable and strong.
There is no erosion for many years and roads are smoother. So the roads are made of concrete.

Question 4.
What causes the hardness of water?
Answer:

Hardness is a measure of amount of dissolved salts in water.
It is caused by dissolved salts like carbonates, chlorides mostly of calcium and magnesium
Presence of these makes washing of clothes by soap difficult.
Hard water is water that has high mineral content.
Hard water is formed when water percolates through deposits of limestone and chalk.

Can you tell?

Answer the following questions:

Question 1.
Which substances were used earlier for cleaning teeth?
Answer:
In olden times neem twigs, coal powder ash, tooth powder, salt, pomegranate rind, were used for cleaning teeth.

Question 2.
What do we use today to clean our teeth?
Answer:
Now a days we use variety of toothpastes and tooth powders to clean our teeth.

Question 3.
What do we use for cleansing our body?
Answer:
Soap, many liquid body wash are also used to clean our body.

Question 4.
What are the materials used for construction?
Answer:
Metals, wood, stone, cement, concrete, timber, bricks, metal sheet, soil, Earth, marble, aluminium, iron, steel, bamboo, glass, plastic.
Concrete: is a wet mixture of sand, gravel, cement, and water used to create building foundations, footpaths or roads.

Question 5.
Which of the houses seen in the pictures here have a strong structure? Why?

Answer:
The houses made from stone, bricks, and cement and concrete have a strong structure.

Write short notes on or Explain:

Question 1.
Natural detergent
Answer:

It is naturally available soap nut (ritha) and soap pod (shikekai) are the natural detergents in common use.
They contain a chemical named saponin.
Soap nut and soap pod do not have any harmful effect on human skin or on silk, woollen threads, and cloth.

Question 2.
Man-made detergents
Answer:

Detergent which is made by processing naturally available material, soap is a man-made detergent which has been in use since ancient times.
In those days soap was prepared by using animal fat and wood ash.
Therefore two types of soap (a) Hard Soap is used for washing clothes. It is a sodium salt of fatty acids, (b) Softsoap is used for bathing. It is a potassium salt of fatty acids.
It does not cause irritation of the skin.
But we can’t use soap in hard water because soap does not give lather but forms a scum. So, soap loses its cleansing property so now synthetic detergent have taken the place of soap.
Synthetic detergents are obtained by subjecting these raw materials (fats and kerosene) to a variety of chemical processes. These can be used in hard water as well.

Question 3.
Soap
Answer:
Two types of soap are:
1. Hard soap is used for washing clothes. It is a sodium salt of fatty acids.
2. (a) Softsoap is used for bathing. It is a potassium salt of fatty acids, (b) It does not cause irritation of the skin, (c) But we can’t use soap in hard water because soap does not give lather but forms a scum, (d) So, soap loses its cleansing property so now synthetic detergents have taken place of soap, (e) Synthetic detergents are obtained by subjecting these raw materials (fats and kerosene) to a variety of chemical processes, (f) These can be used in hard water as well.

Question 4.
Concrete
Answer:

Concrete is prepared by mixing cement, water, sand and gravel.
For making a strong and leak proof slab certain substances are mixed in concrete.
Now a days, roads are made of concrete because they are very durable, strong and smooth.

Question 5.
Surface activity
Answer:

Soap molecule has the property of holding on to both oil and water soap water spreads easily on many types of surfaces.
The property of a substance of spreading on a surface is called surface activity and the substance is said to be a surfactant.
Detergents are surface-active. One effect of surface activity is lather formation.

Question 6.
Explain the method of preparation of soap.
Answer:
Material required for preparation soap are 15 g sodium hydroxide, 60 ml coconut oil, 15 g salt, perfume, a glass rod, beaker, tripod, wire gauze, burner, water mould etc.
Procedure:

Take 60 ml of coconut oil in a beaker.
Dissolve 15 g sodium hydroxide in 50 ml water. Mix the sodium hydroxide solution in the oil slowly, while stirring with a glass rod.
Heat the mixture, and boil it for 10 – 12 minutes, stirring it all the while.
Take care that the mixture does not boil over while heating.
Dissolve 15 g salt in 200 ml water, pour this solution into the above mixture and stir.
The soap formed by the chemical reaction now floats on the water. After some time, it becomes thick.
Now separate the thick soap and add the perfume to it, shape the bar of soap using the mould.
In this process, fat and alkali combine to form salts of fatty acids.
Chemically, soap is a sodium or potassium salt 4 of fatty acids.

7th Std Science Questions And Answers:

Cell Structure and Micro-organisms Class 7 Science Chapter 11 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 11 Cell Structure and Micro-organisms Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 11 Cell Structure and Micro-organisms Question Answer Maharashtra Board

Class 7 Science Chapter 11 Cell Structure and Micro-organisms Question Answer Maharashtra Board

1. Answer the following questions.

Question a.
What is a cell?
Answer:
The cell is the fundamental, structural and functional unit of living organism.

Question b.
Name the different organelles in a cell.
Answer:
The nucleus, endoplasmic reticulum, Golgi bodies, lysosomes, mitochondria, vacuoles, plastids, chloroplasts are the different organelles in a cell.

Question c.
What are micro-organisms?
Answer:
The organisms which cannot be seen with our eyes but can only be observed under a microscope are called micro-organisms.

Question d.
Which are the different types of micro-organisms?
Answer:
Algae, fungi, bacteria, protozoa and viruses are various types of micro-organism. Some are unicellular and others are multicellular. Some of them are useful and some are harmful.

2. Fill in the blanks with the proper word.

Question a.
The organelle called the ……………. is present in the plant cells only.
Answer:
chloroplasts

Question b.
Garbage is converted into ……….. by microorganisms.
Answer:
fertilizer

Question c.
In the cell, photosynthesis is carried out with the help of …………… .
Answer:
chloroplast

Question d.
An electron microscope is necessary for the study of ……………… .
Answer:
micro-organism

Question e.
The process of preparing their own food in presence of sunlight and chloroplast by plants cells is known as ……….. .
Answer:
photosynthesis.

3. What is the difference between us?

Question a.
Plant cell and animal cell.
Answer:

Plant cell	Animal cell
1. Plant cell has cell wall.	1. Cell wall is absent in animal cell.
2. Plant cell has definite shape due to presence of cell wall.	2. Animal cell do not have definite shape.
3. Plant cell has one big vacuole.	3. Animal cells have many small vacuoles.
4. Plant cell has chloroplast so they produce their own food.	4. Animal cells do not have chloroplast, so they cannot produce their own food.
5. Plant cell has plastids.	5. Plastids are absent in animal cell.
6. Centrosomes are absent in plant cell.	6. Centrosomes are present near the nucleus.
7. Lysosomes are absent in plant cell.	7. Lysosomes are present in animal cell.

Question b.
Prokaryotic cell and Eukaryotic cell
Answer:

Prokaryotic cell	Eukaryotic cell
1. No well defined nucleus.	1. Well defined nucleus with a nuclear membrane
2. Ribosomes are small.	2. Ribosomes are large.
3. A single length of DNA is present.	3. Several lengths of genetic materials (DNA) is present.
4. No other cell organelles are present.	4. Several organelles like mitochondria, chloroplasts, etc. are present.
5. Examples: Bacteria, blue green algae	5. Examples: Euglena, Amoeba, all plant and animal cells

4. Sketch and describe in your on words, the plant cell and animal cell.

Question a.
Sketch and describe ¡n your on words, the plant cell and animal cell.
Answer:
There are two types of cell-animal cells and plant cells. These cells contain various types of membrane beyond cell-organelles. Plant cells have a definite shape due to the presence of cell wall. Besides, unlike animal cells, plant cells contain single large vacuole. All these cells are known as eukaryotic cells. It cell has four main parts: the cell wall, cell membrane, cytoplasm and cell organelles.
1. Cell wall: The cell wall is the outermost covering of a cell. It is present only in plant cells.

2. Plasma membrane: The plasma membrane, also called the cell membrane, is a kind of thin covering, (a) It is extremely delicate and flexible, (b) It is the outermost covering of animal cells.

3. Cytoplasm: The liquid part in the cell, present around the nucleus is called cytoplasm, (a) It occupies the space between the plasma membrane and nucleus, (b) Cell organelles are scattered in the cytoplasm.

4. Cell organelles: These mainly include the nucleus, endoplasmic reticulum, Golgi bodies, lysosomes, mitochondria, vacuoles, plastids etc.

Plant cells contain chloroplasts.
(a) The nucleus is the most important organelle of the cell, (b) There is a porous double membrane around it. (c) The nucleus controls all functions of the cell, (d) The endoplasmic reticulum is a sprawling net-like organelle. Its function is to make necessary changes in the proteins produced by ribosomes and send them to the Golgi bodies, (e) Golgi bodies are made up of several flat sacs. Their function is the proper distribution of proteins.

(f) Mitochondria and plastids are organelles with double outer coverings, (g) As mitochondria produce energy, they are called the powerhouses of the cell, (h) The chloroplasts in plant cells carry out the function of photosynthesis, (i) Vacuoles help to throw out waste products of the cell, (j) Vacuoles in animal cells are small whereas there is only one large vacuole in a plant cell.

5. Explain the uses and the harmful effects of micro-organisms.

Question a.
Explain the uses and the harmful effects of, micro-organisms.
Answer:
Micro-organisms which are helpful are called useful micro-organisms.
Uses:
1. Micro-organisms present in nodules of leguminous plants, convert atmospheric nitrogen into its compounds and these compounds help to increase the soil fertility and protein content in the soil.

2. Some micro-organisms are useful in process of fermentation, making the food easily digestible and more nutritious. For producing milk products like butter, buttermilk, cheese, paneer, etc.

3. Microbes present in soil, dung etc. decompose garbage and convert into manure of best quality and surrounding is kept clean.

4. Microbes are also useful for sewage disposal. They help in decomposition of organic compounds in it.
5. Microbes are used in production of vaccines.

6. Microbes are also used in processes like tanning of skin, production of ropes and strings, from agave.
7. Some microbes use oil for their growth. Such microbes are used to clear a layer of oil floating on the surface of an ocean or lake formed due to leak or spill.

8. Farm waste, human urine and faeces, wet garbage etc. is collected and used in a biogas plant to produce biogas and fertilizer.

Harmful effects:
1. Disease producing micro-organisms are called pathogens, they are harmful micro-organisms.

2. Fungus grows on moist food, and microbes release enterotoxins into the food. Such toxins spoil the foods. Eating such spoiled food causes food poisoning i.e. loose motions and vomiting.

3. Pathogens may be present in water bodies contaminated with sewage, and dirt from surroundings, in food with flies sitting on it. If such contaminated food or water is consumed, we may fall ill with diseases like amoebiasis, typhoid, cholera, hepatitis, gastro, etc.

4. Pathogens are released in the air by a person having infection of the respiratory, sneezes or coughs. A healthy person may get infected by pathogens on breathing in the same air and contract diseases like common cold, cough, diphtheria, pneumonia, tuberculosis, etc.

5. Microbes that cause diseases like malaria, dengue, elephantiasis, yellow fever, chikunguniya, zike
fever etc. gain entry into the human body through the bite of a female mosquito.

6. Give reasons.

Question a.
Diseases spread on a large scale during periods of heavy rainfall and floods.
Answer:

Due to floods there is shortage of clean, safe drinking water.
It gets contaminated with sewage and dirt having disease causing pathogens, causing disease of alimentary canal, typhoid, cholera, dysentery.
Due to stagnant water, many mosquitoes breed on it and cause diseases like malaria, dengue, etc.

Question b.
There is a possibility of food poisoning if we eat stale food.
Answer:

Fungus grows quickly on moist and stale food. Micro-organisms grown on the food release toxic materials like enterotoxin into the food.
Such toxins spoil the food.
Eating such spoiled food may cause loose motions and vomiting. So, we should eat food which is freshly prepared.

Question c.
Soil is turned over during tilling.
Answer:

Tilling is done to loosen the soil in initial agricultural practice.
Loose soil allows the penetration of roots of the plant.
By turning of soil, it allows uniform mixing of manure and fertilizer.
It increases the fertility of soil. Seeds also germinate easily in aerated soil. Hence, soil is turned during tilling.

Question d.
Fungus grows quickly in moist or humid condition.
Answer:

Fungus needs water and moisture for its growth.
Humidity brings about spore germination and the fungus is able to grow and reproduce quickly in moist or humid condition.

Question e.
A refrigerator is used in almost every home.
Answer:

Refrigerator is used to keep food item in healthy condition and to keep them fresh.
If the food items are kept outside, they spoil very fast due to growth of micro-organisms and they make food spoiled and harmful.
The optimum temperature for the growth of micro-organism is 15°C to 35°C.
In refrigerator the temperature is kept very low. So, the food is preserved in refrigerator.

Question f.
Bread rises during baking.
Answer:

The process of fermentation is used in baking, for example, in making bread. Yeast is added to make the dough rise.
The fermentation is a chemical process of conversion of one type of carbon compound into another type of carbon compound by the action of micro-organisms.
Heat is generated in this process. Carbon dioxide (CO₂) and some other gases are released.
These gases cause an increase in volume so the bread dough rises.

Question g.
Fodder is soaked in water before offering to cattle.
Answer:

In dry fodder only some part of it is useful for cattle and rest is wasted.
When fodder is soaked in water, it sprouts.
So, to make the fodder more nutritious and more easy to digest it is soaked in water before offering to cattle.

7. When will you use a simple microscope and when a compound microscope?

Question a.
When will you use a simple microscope and when a compound microscope?
Answer:

I will use a simple microscope to magnify the objects and to see the growth of a fungi or mucor on a piece of moist bread.
I will use a compound microscope in Research Laboratory and high school science lab to observe micro-organisms which we are not able to see with our naked eye.

Project:

Question 1.
Visit a bakery in your area, collect information about the process of manufacture of their products and make one of them at home.

Class 7 Science Chapter 11 Cell Structure and Micro-organisms Important Questions and Answers

Fill in the blanks and rewrite the sentences:

Question 1.
………… is the fundamental, structural and functional unit of living organism.
Answer:
Cell

Question 2.
The four main parts of the plant cell are …………, …………, ………… and ………… .
Answer:
cell wall, cell membrane, cytoplasm, cell organelle

Question 3.
Plant cell contains ………… which carry out the process of photosynthesis.
Answer:
chloroplast

Question 4.
…………… are called the power houses of the cell.
Answer:
Mitochondria

Question 5.
The outermost covering of plant cell is …………. .
Answer:
cell wall

Question 6.
The outermost covering of animal cell is ………….
Answer:
plasma membrane

Question 7.
The ………… is the most important organelle of the cell.
Answer:
nucleus

Question 8.
………… is a national movement started several years ago to increase awareness about public hygiene and personal hygiene.
Answer:
Swach Bharat Abhiyan

Question 9.
The body temperature of a healthy human being is about ………… .
Answer:
37°C

Question 10.
Micro-organisms use food stuffs for their own nutrition and release toxic materials called ………. .
Answer:
enterotoxins

Name the following:

Question 1.
An instrument used to observe cells.
Answer:
Microscope

Question 2.
I control the function of a cell.
Answer:
Nucleus

Question 3.
I am like a policeman. I do not allow anything and everything to get in and out of the cell.
Answer:
Cell membrane

Question 4.
Outermost layer of the plant cell.
Answer:
Cell wall

Question 5.
Outermost layer of the animal cell.
Answer:
Cell membrane

Question 6.
I am the jelly like substance containing all the organelles.
Answer:
Cytoplasm

Question 7.
I contain thread like structures called chromosome.
Answer:
Nucleus

Question 8.
Which part of the cell contain organelles.
Answer:
Cytoplasm

Question 9.
The unit of measurement used for expressing dimension, size of the cell.
Answer:
Nanometer, micrometer

Question 10.
The power house of the cell.
Answer:
Mitochondria

Question 11.
Largest organelle in the plant cell.
Answer:
Vacuole

Question 12.
It is necessary for photosynthesis.
Answer:
Chlorophyll

Question 13.
The living substance in the cell.
Answer:
Cytoplasm

Question 14.
A group of cells.
Answer:
Tissue

Question 15.
Empty structures in cytoplasm.
Answer:
Vacuole

State whether the following statements are True or False. Correct and rewrite the false statement:

Question 1.
Cells can be easily seen with naked eyes.
Answer:
False. We can’t see cells with naked eyes, can be seen under microscope

Question 2.
A single cell can perform all the functions in a unicellular organism.
Answer:
True

Question 3.
Cell wall is present in both plant cells and animal cells.
Answer:
False. Cell wall is present only in plant cell

Question 4.
Vacuoles are not found in plant cell.
Answer:
False. Large vacuole is found in plant cell

Question 5.
Tissue is a group of dissimilar cells.
Answer:
False. Tissue is a group of similar cells.

Question 6.
Unicellular organisms have one celled body.
Answer:
True.

Question 7.
The basic living unit of an organism is an organ.
Answer:
False. The basic living unit of an organism is the cell.

Question 8.
The unit of measurement used for expressing dimension size of the cell is centimetre.
Answer:
False. It is nanometer.

Question 9.
Micro-organism cannot grow in extreme adverse conditions.
Answer:
False. Some micro-organisms can survive in extreme adverse conditions e.g. ocean floor, ice polar region, hot water spring.

Question 10.
Some micro-organisms can grow without oxygen.
Answer:
True

Question 11.
Amoeba has irregular shape.
Answer:
True

Question 12.
The process of fermentation is used for making yogurt from milk.
Answer:
True

Question 13.
Micro-organisms need an optimum temperature of 55°C to 70°C to grow.
Answer:
False. They need temperatures between 15°C to 35°C to grow well.

Question 14.
Cells with membrane bound organelles inside them are called prokaryotic cells.
Answer:
False. Cells with membrane bound organelles inside them are called eukaryotic cells.

Question 15.
Golgi bodies are the power houses of the cells.
Answer:
False. Mitochondria are the power houses of the cell.

Choose the correct word.

Question 1.
Which one of the following terms is not a part of the nucleus?
(a) ribosome
(b) DNA
(c) chromosome
(d) gene
Answer:
(a) ribosome

Question 2.
A suitable term for the various components of cell is.
(a) tissue
(b) cell organelle
(c) chromosome
(d) gene
Answer:
(b) cell organelle

Question 3.
The jelly like fluid substance present in the cells is called.
(a) protoplasm
(b) chromosome
(c) chloroplast
(d) cytoplasm
Answer:
(d) cytoplasm

Question 4.
The units of measurement used for expressing dimension size of the cell are,
(a) centimetre
(b) micrometre
(c) nanometre
(d) metre
Answer:
(c) nanometre, (b) micrometre.

Question 5.
The largest cell in the human body
(a) nerve
(b) muscle
(c) liver
(d) kidney
Answer:
(a) nerve

Question 6.
The barrier between protoplasm and other environment in animal cell
(a) plasma membrane
(b) cell wall
(c) nucleus membrane
Answer:
(a) plasma membrane

Question 7.
The term cell wall is given by
(a) Leeuwenhoek
(b) Robert Hooke
(c) Fleming
Answer:
(b) Robert Hooke

Question 8.
The cell theory was proposed by.
(a) Watsonar Cricks
(b) Schleiden
(c) Schwann
(d) Mengal Morgan
Answer:
(b) Schleiden, (c) Schwann.

Question 9.
Which of the following features will help you in distinguishing a plant cell from an animal cell.
(a) cell wall
(b) cell membrane
(c) mitochondria
(d) nucleus
Answer:
(a) cell wall

Question 10.
The gas released during the preparation of bread,
(a) O₂
(b) CO₂
(c) nitrogen
(d) sulphur oxide
Answer:
(b) CO₂

Question 11.
The structural-functional unit of life is called.
(a) cell
(b) tissue
(c) organ
(d) organism
Answer:
(a) cell

Question 12.
Which organelle is called power house of the cell?
(a) centrosome
(b) lysosome
(c) plastid
(d) mitochondria
Answer:
(d) mitochondria

Question 13.
Living substance of cell is called.
(а) cytoplasm
(b) protoplasm
(c) nucleus
(d) chromosome
Answer:
(а) cytoplasm

Give scientific reasons:

Question 1.
Mitochondria are called the power houses of the cell.
Answer:

Mitochondria are tiny organelles inside the cells that are involved in releasing energy from food.
This process is known as cellular respiration.
It is for this reason that mitochondria are often referred to as the power houses of the cell.

Question 2.
A compound microscope is used for observing cells.
Answer:

Cell are extremely minute in size.
We cannot see cells with naked eye.
An object when kept on a glass slide is magnified many times by the lenses of this microscope.
Hence, compound microscope is used for observing cells.

Question 3.
Cells are the basic structural units of living organism.
Answer:

Cells are the smallest unit from which a living organism is made.
A cell contains all the necessary structures which are required to carry out various biological processes.
A group of cells makes a tissue, which further makes an organ and many organs together make an organ system and finally organism. Thus, the cells are the basic structural units of living organism.

Answer the following in short:

Question 1.
What is a vaccine?
Answer:
Vaccine is a live micro-organism which is weak but in a very small amount, and is injected into a person so that antibodies are produced against that micro-organism.

Question 2.
What are the similarities between the Plant cell and Animal cell?
Answer:
They both have cell membrane, cytoplasm, nucleus, ribosomes, golgi bodies, mito-chondria, vacuoles and chromosomes.

Question 3.
What do micro-organisms need for growth?
Answer:
Micro-organisms need soil, water and decaying material. Temperature suitable for microbial growth is 15 to 35°C moist, humid and warm climate.

What is the difference between us:

Question 1.
Simple microscope and Compound microscope.
Answer:

Simple microscope	Compound microscope
1. It consists of single lens.	1. It consists of 2 lenses.
2. Magnification power is upto 300X	2. Magnification power is upto 2000X.
3. It uses natural light source.	3. It uses illumination as light source.
4. It is used to observe small objects.	4. It is used to observe very tiny objects or cells which we cannot see with naked eye.

Answer in details:

Question 1.
Explain the functions of organelles in a cell.
Answer:
1. Functions of cell wall: It consist of cellulose. It is present in plant cell only. It is a protective layer outside the cell membrane. It provides structural support and protection.

2. Function of cell membrane: It controls the movement of substances in and out of the cell. It protect the cell from its surrounding.

3. Function of cytoplasm: It is the jelly like liquid, it occupies space between cell membrane and nucleus. All the organelles are scattered in it.

4. Function of Nucleus: It is the brain of the cell. It directs all cell activities, and contains genetic material called chromosomes made of DNA.

5. Function of mitochondria: It is the power house of cell. It produces energy in the form of ATP from the food.

6. Vacuoles: It is the largest organelle in the plant cell surrounded by membrane. It holds material and waste. It maintains proper pressure. It helps to throw out waste products of cell.

Explain:

Question 1.
Ram ate chaat from a street hawker, when he reached home he fell ill and complained of stomach ache. What could be the reason?
Answer:

he chaat Ram ate from a street hawker must be contaminated with harmful micro-organism due to dirty water used in it or stale potato used in it.
Toxins are produced by micro-organisms in food.
Ram ate that and suffered from food poisoning.

Question 2.
With the help of diagram describe Prokaryotic cell.

Answer:

Prokaryotic cell do not have well-defined nucleus.
The plasma membrane, cytoplasm and nucleoid are the only components.
The prokaryotic cells have smaller ribosomes compared to eukaryotic cells.
Bacteria and blue green algae are examples of prokaryotic cell.

Question a.
Draw neat and labelled diagram of plant cell.
Answer:

Question b.
Draw neat and labelled diagram of animal cell.
Answer:

Name the types of cells shown in the diagrams.

Question 1.

Answer:

(a) A fat cell
(b) A nerve cell
(c) A sperm cell
(d) Spirogyra
(e) Red Blood cells

Try this:

Answer the following questions:

Question 1.
Keep a moistened piece of bread or bhakari in a closed box. What will you observe after 3-4 days?
Answer:

I will observe growth of fungus or mucor. White cotton like layer or black spots.
As we know fungus grows in presence of moisture.

Question 2.
Observe a drop of muddy water or water from a stagnant puddle, under the compound microscope.
Answer:

We will observe, living things, micro-organism, bacteria, fungi.
It will be swarming withbacteria,paramoecium, amoeba, ciliated bacteria and protozoa, etc.

Question 3.
Take a drop of yoghurt or buttermilk on a glass slide and observe it under a compound microscope.
Answer:

I will see Lactobacillus rod shapted bacteria and streptococcus spherical shape bacteria which may be in clusters.
Lactobacillus use lactose present in the milk and produce lactic acid which gives tangy taste to yoghurt.

Find out:

Answer the following questions:

Question 1.
Which diseases do micro-organism cause in plants and animals?
Answer:
Diseases caused by micro-organism in plants and animals are:

Plants	Animals
Cankers, Downy Mildew, Ergot, Root rot, Rust, Seed Decay, Smut, Soft rot, Wilts, Leaf spot, Crown gel, Curly top, Mosaic leaf, Yellowing of leaf etc.	Anthrax in cattle, Dysentery in monkey, Diphtheria in rabbit, Tuberculosis in cattle, Plaque in rats.

Question 2.
Why are infants vaccinated according to fixed time schedule?
Answer:
Vaccination is done to protect the child against diseases.
1. If a baby is vaccinated by true vaccine schedule, that baby will have immunity to over 14 diseases by the age of two. With the recommended schedule, babies visit their doctor 5 times in the first 15 months and receive protection against upto 14 diseases in as little as 18 shots.
2. We immunize children so young against these diseases because infancy is the time period that kids are most vulnerable to life threatening diseases.
3. It is not advisable to skip or delay vaccines as this will leave the child vulnerable to disease for a longer period of time.

Can you tell?

Answer the following questions:

Question 1.
Observe cells from various parts of plants like leaves, bark, root tips, etc.
Answer:
Question a.
Are the cells that you observed, all alike?
Answer:
No, all cells do not look alike, each one has different shape and size.

Question b.
What are their shapes?
Answer:

The cells of leaves, show a green pigment because of chloroplast.
The shape of the cell may be spherical or polygonal.
The shape of root tips are oval or polygonal and the cells of back are hexagonal in shape.

Question 2.
Observe the roots of the pea, bean and fenugreek plants. What could be the functions of the nodules on their roots.
Answer:

Micro-organisms are present in the root nodules.
They fix the atmospheric nitrogen and make it available for plants.

Question 3.
What happens if clothes remain damp in the rainy season?
Answer:

During rainy season the humidity in the air is quite high and also.
Due to presence of moisture in clothes it becomes breeding ground for fungus.
It is the favourable condition for growth of fungus.
We can see white cotton like growth of fungus on clothes.

Question 4.
What are the black or white spots sometimes seen on gunny bags?
Answer:
These spots are the growth of many microbes such as fungi, mucus, mold, etc.

Question 5.
Why are leather articles like purses, wallets, belts, footwear always polished before storing away?
Answer:
They are polished so as to protect them from the growth of fungus.

Polish creates a layer of wax on them so that moisture cannot enter from atmosphere.
It prevents the growth of fungus, which damages the leather.

Question 6.
What is the powdery material found on old currency notes or old rubber or paper?
Answer:

The powdery material is the spores of fungi.
All the materials like gunny bags, cotton clothes, paper, rubber, etc. are plant products and leather is an animal product.
In a humid atmosphere, fungi and some other micro-organisms grow on these articles and spoil or damage them.

Question 7.
Why children are vaccinated?
Answer:

A vaccine is produced in a laboratory with the help of microbes, that gives immunity against particular diseases.
Vaccine is actually a live micro-organism which is weak.
When injected into a person in small amount, antibodies are produced.
It increases the resistance power against the disease produced by that micro-organism. So, the possibility of contracting that disease is greatly reduced.

Question 8.
Try this and answer the following questions:

In pot A	In pot B
Soil + garden waste + dung + fruit peel vegetable stalks	Pieces of glass + scrap metal + plastic bags + Soil.

Question a.
Did the garbage in pot B remain unchanged.
Answer:

Yes, the garbage in pot B remained unchanged because micro-organisms need nutrients for their growth.
In pot B there was no medium for growth of micro-organisms.

Question b.
Where did the garbage in pot ‘A’ disappear? Why?
Answer:

Microbes present in soil, dung, etc. decompose the garbage to obtain food material.
As a result garbage is soon converted into manure of the best quality and our surroundings are kept clean.

Question 9.
What does your mother do to make yoghurt from milk?
Answer:

Few drops of yoghurt or buttermilk are mixed with lukewarm milk and it is kept at room temperature for 8-10 hours.
Microbes present in the drops of yoghurt quickly multiply and the milk gets converted into yoghurt. This is a process of fermentation.

Question 10.
Who discovered the process of fermentation?
Answer:

Louis Pasteur established that fermentation is initiated by living organisms.
It involves yeast microbes, breaking down molecules of complex carbohydrates into simple sugar, alcohol and CO₂.

Use your brain power!

Answer the following questions:

Question 1.
How will you know that a foodstuff is spoilt?
Answer:

When the food is kept for a long time it allows the growth of bacteria and fungi.
We can see the white layer of bacterial or fungal growth on it, it causes a typical odour, or smell, and also the food tastes sour due to presence of enterotoxins produced by fungi in the food.

Question 2.
What precautions will you take while purchasing food? Why?
Answer:

We will see the expiry date. If the food is kept for a long period of time, it may allow the growth of many microbes which can cause disease or food poisoning.
We will check for any fungal growth, any white or black spots on it.

Question 3.
Why do food poisoning incidents occur during marriage or other community feasts?
Answer:
1. During marriage feast, food is prepared in very large quantity and food may not be properly washed or if it is cooked with water contaminated, with sewage or dirt which has many disease causing microbes, or the people handling the food may be having dirty hands

2. Also the utensils used for cooking and storing food may be dirty, contaminated with dirt and may produce microbes. The consumption of such food is responsible for food poisoning.

Question 4.
How do the cells acquire definite shapes?
Answer:
The cells acquire definite shapes due to the presence of cell wall.

Question 5.
How are cells protected?
Answer:

Plant cells are protected due to presence of cell wall.
Animal cells are protected by the double plasma membrane.

Question 6.
What are the needs of cells?
Answer:

The most important things for a cell are oxygen and glucose.
Cell uses these during process of glycolysis and makes ATP which is energy source.

Question 7.
Can the point of a needle accommodate micro-organism?
Answer:
Yes, they are smaller than the point of a needle.

Question 8.
Why should dry and wet waste be collected separately?
Answer:

Dry waste consist of plastic, glass, metals, paper, etc. It is easier to segregate dry waste so that it is easier for treatment and recycling of waste.
Wet waste consists of organic matter. Wet garbage is converted into manure of the best quality and surroundings are kept clean.

Question 9.
Why is yoghurt mixed in the batter or dough for making rava-idli, butter naan?
Answer:

The microbes present in yoghurt are allowed to grow in batter or dough.
They break down these substances producing new compound and gases are released as they grow and multiply in them which allows the batter, dough to rise.
This process is called fermentation.
This makes the food soft and nutritious.

Question 10.
How do preparation like yoghurt, idli, dosa become easy to digest?
Answer:
Fermentation does detoxification and splits complex carbohydrates and proteins into simple ones. Thus, making it easy to digest.

Question 11.
What is the co-relation between the normal body temperature of humans which is 37°C and the optimum temperature for the growth of micro-organism, 15 °C to 35 °C?
Answer:

Each micro-organism needs a specific environment for growth and reproduction.
Optimum temperature for the growth of micro-organism is 15°C to 35°C.
Normal body temperature of human body is 37°C. At that temperature micro-organism can not grow and cause disease.

Question 12.
How do micro-organism survive the adverse conditions?
Answer:

During adverse conditions micro-organisms form a thick covering around themselves and stop their life processes.
On return of favourable conditions they come out of the protective covering and continue their life processes.

7th Std Science Questions And Answers:

Motion, Force and Work Class 7 Science Chapter 7 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 7 Motion, Force and Work Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 7 Motion, Force and Work Question Answer Maharashtra Board

Class 7 Science Chapter 7 Motion, Force and Work Question Answer Maharashtra Board

1. Fill ¡n the blanks with the proper words from the brackets.
(stationary, zero, changing, constant, displacement, velocity, speed. acceleration, stationary but not zero. inc reuses)

Question a.
If a body traverses a distance in direct proportion to the time, the speed of the body is ……………… .
Answer:
constant

Question b.
If a body is moving with a constant velocity, its acceleration is ……………… .
Answer:
zero

Question c.
……………. is a scalar quantity.
Answer:
Speed

Question d.
…………….. is the distance traversed by a body in a particular direction in unit time.
Answer:
Velocity

2. Observe the figure and answer the questions.

Question a.
Observe the figure and answer the questions

Sachin and Sarneer started on a motorbike from place A, took the turn at 13, did a task at C, travelled by the route CD to D and then went on to E. Altogether, they took one hour for this journey. Find out the actual distance traversed by them and the displacement from A to E. From this, deduce their speed. What was their velocity from A to E in the direction AE’? Can this velocity be called average velocity?
Answer:
1. Actual distance = \(\overline{\mathrm{AB}}\) + \(\overline{\mathrm{BC}}\) + \(\overline{\mathrm{CD}}\) + \(\overline{\mathrm{DE}}\) = 3 + 4 + 5 + 3
Actual distance = 15 km

2. Displacement = \(\overline{\mathrm{AB}}\) + \(\overline{\mathrm{BD}}\) + \(\overline{\mathrm{DE}}\)
= 3 + 3 + 3
Displacement = 9 km

3. Speed = \(\frac{\text { Distance travelled }}{\text { Total time }}\)
Distance = 15 km = 15 × 1000 = 15000 m
Time = 1 hr = 1 × 60 × 60 = 3600 sec.
s = \(\frac{15000}{3600}\) or s = \(\frac{15 \mathrm{~km}}{1 \text { hour }}\) = 15km/hour
= 4.16 m/sec. or 15 km/hour

4. Velocity = \(\frac{\text { Distance travelled }}{\text { Total time }}\)
Displacement = 9 km = 9 × 1000 = 9000 m
Time = 1 hr = 1 × 60 × 60 = 3600 sec
V = \(\frac{9000}{3600}\) or V = \(\frac{9 \mathrm{~km}}{1 \text { hour }}\) = 9 km/hour
= 2.5 m/sec. or 9 km/hour

5. Yes, this velocity can be called as average velocity.

3. From the groups B and C, choose the proper words, for each of the words in group A.

Question a.
From the groups B and C, choose the proper words, for each of the words in group A.

Answer:

Group ‘A’	Group B’	Group ‘C’
Work	Joule	erg
Force	Newton	dyne
Displacement	Metre	cm

4. A bird sitting on a wire, flies, circles around and comes back to its perch. Explain the total distance it traversed during its flight and its eventual displacement.

Question a.
Answer:
The total distance the bird has traversed is the length of the distance covered by circling, but the eventual displacement are the bird is zero as its initial and final position are one and the same.

5. Explain the following concepts in your own words with everyday examples: force, work, displacement, velocity, acceleration, distance.

Question a.
Explain the following concepts in your own words with everyday examples: force, work, displacement, velocity, acceleration, distance.
Answer:
1. Force: The interaction that brings about the acceleration is called force.
e.g: An ox is pulling a cart, applying brakes to a bicycle, lifting heavy iron object with a crane.

2. Work: When an object is displaced by applying a force on it, work is said to be done.
e.g: A bucketful of water is to be drawn from a well and taken to the home by walking from well to home.

3. Displacement: The minimum distance
traversed by a moving body in one direction from the original point to reach the final point is called displacement.
e.g: A rolling of a ball from point A to point B in the same direction.

4. Velocity: Velocity is the distance traversed by a body in a specific direction in unit time.
e.g: A truck is covering a distance of 40km from A to D in a straight line in 1 hour.

5. Acceleration: It is change in velocity per second. It can be deduced.
Acceleration = \(\frac{\text { Change in velocity }}{\text { Time taken for change }}\)
e.g:

(i) In the above example a truck covered the distance AB at velocity of 60 km/hr, BC at 30 km/hr and CD at 40 km/hr. (ii) It means that the velocity for the distance CD is greater than the velocity for the distance BC. (iii) From the number of seconds required for this change in velocity to take place, the change in velocity per second can be deduced. This is called acceleration (iv) Distance: The length of the route actually traversed by a moving body irrespective of the direction is called distance.
e.g: Ranjit travelled 1km. from his home to school.

6. A ball is rolling from A to D on a flat and smooth surface. Its speed is 2 cm/s. On reaching B, it was pushed continuously up to C. On reaching D from C, its speed had become 4 cm/s. It took 2 seconds for it to go from B to C. What is the acceleration of the ball as it goes from B to C.

Question a.
A ball is rolling from A to D on a flat and smooth surface. Its speed is 2 cm/s. On reaching B, it was pushed continuously up to C. On reaching D from C, its speed had become 4 cm/s. It took 2 seconds for it to go from B to C. What is the acceleration of the ball as it goes from B to C.

Answer:
As its initial and final positions are one and the same.
Initial Velocity = 2 cm/s.
Final Velocity = 4 cm/s
Time taken for the change in velocity from B to
D = 4 cm/s – 2 cm/s = 2 cm/s

7. Solve the following problems.

Question a.
A force of 1000 N was applied to stop a car that was moving with a constant velocity. The car stopped after moving through 10m. How much is the work done?
Answer:
Force (F) = 1000 N
displacement (s) = 10m
work done (W) = ?
W = Fs
= 1000 × 10
W = 10,000 Joule

Question b.
A cart with mass 20 kg went 50 m in a straight line on a plain and smooth road when a force of 2 N was applied to it. How much work was done by the force?
Answer:
Force (F) = 2 N
Displacement (s) = 50 m
Work done (W) = ?
W = Fs
= 2 × 50
W = 100 Joule

Project:

Question a.
Collect information about the study made by Sir Isaac Newton regarding force and acceleration and discuss it with your teacher.

Class 7 Science Chapter 7 Motion, Force and Work Important Questions and Answers

Fill in blanks:

Question 1.
Displacement is a …………. quantity.
Answer:
vector

Question 2.
The …………. of an object can change even while it is moving along a straight line.
Answer:
velocity

Question 3.
The …………. velocity can be different at different times.
Answer:
instantaneous

Question 4.
Change in velocity per second is called …………. .
Answer:
acceleration

Question 5.
The interaction that brings about the acceleration is called …………. .
Answer:
force

Question 6.
The scientist …………. was the first to study force and the resulting acceleration.
Answer:
Sir Isaac Nezvton

Question 7.
Ability to do work is called …………. .
Answer:
Energy

Question 8.
W = …………. × S.
Answer:
F

Question 9.
Unit of work is …………. and …………. .
Answer:
Joule, erg

Question 10.
Unit of force is …………. and …………. .
Answer:
Newton, dyne

Question 11.
Force is a …………. quantity.
Answer:
vector

Question 12.
The velocity at a particular time is called …………. velocity.
Answer:
instantaneous

Question 13.
The …………. of a body is the distance traversed per unit time.
Answer:
speed

Question 14.
Unit of acceleration is …………. and …………. .
Answer:
m/s² and cm/s²

Question 15.
Force is measured by the …………. that it produces.
Answer:
acceleration

Question 16.
Work done by a body with no displacement will be …………. .
Answer:
zero

Say whether True or False, correct the false 1 statements:

Question 1.
Velocity is distance travelled per unit of time.
Answer:
False. Speed is distance travelled per unit of time

Question 2.
In displacement, both distance and direction are taken into account.
Answer:
True

Question 3.
Speed = Distance/time.
Answer:
True

Question 4.
Change in speed per second is acceleration.
Answer:
False. Change in velocity per second is acceleration

Question 5.
Work done depends on the force and the displacement.
Answer:
True

Question 6.
C.G.S. unit of acceleration is m/s².
Answer:
False. C.G.S. unit of acceleration is cm/s².

Question 7.
M.K.S. unit of force is dyne.
Answer:
False. M.K.S. unit of force is Newton

Question 8.
Force is measured by the acceleration that it produces.
Answer:
True

Write the difference between the following:

Question 1.
Speed and Velocity
Answer:

Speed	Velocity
1. Speed is distance travelled per unit of time.	1. Velocity is the distance traversed by a body in a specific direction in unit time.
2. It is a scalar quantity.	2. It is a vector quantity.
3. Formula: Speed = \(\frac{\text { Distance traversed }}{\text { Total time }}\)	3. Formula: Velocity = \(\frac{\text { Displacement }}{\text { Total time }}\)

Question 2.
Distance and Displacement
Answer:

Distance	Displacement
1. The length of the route actually traversed by a moving body, irrespective of the direction is called distance.	1. The minimum distance traversed by a moving body in one direction from the original point to reach the final point is called displacement.
2. It is a scalar quantity.	2. It is a vector quantity.

Solve the following problems!

Question 1.
A bus travelled 200 km in the first 3 hours and then 100 kms for the next one and a half hours and then 120 kms for the next one and a half hours. What is the average velocity of the bus if it has moved in a straight line for the whole journey.
Answer:

Question 2.
See the diagram and calculate the Distance and Displacement travelled by the body from A to I.

Answer:
Distance travelled =
A → B → C → D → E → F → G → H + I
= 5 + 7 + 6 + 3 + 5 + 4 + 6 + 5
= 41 m
Displacement = A → I in a straight line shortest distance
= 1m

Use your brainpower:

Question 1.
The unit of acceleration is m/s², verify this.
Answer:

Question 2.
Acceleration is a vector quantity. Is force a vector quantity too?
Answer:
Yes, acceleration and force both are vector quantities, because both can be expressed completely only when magnitude and direction are given and the quantity which needs direction and magnitude both is called a vector quantity.

7th Std Science Questions And Answers:

Elements, Compounds and Mixtures Class 7 Science Chapter 14 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 14 Elements, Compounds and Mixtures Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 14 Elements, Compounds and Mixtures Question Answer Maharashtra Board

Class 7 Science Chapter 14 Elements, Compounds and Mixtures Question Answer Maharashtra Board

1. Who are my companions?

Question a.

Column ‘A’	Column B’
1. Stainless steel	a. Non-metal
2. Silver	b. Compound
3. Bhajani mixture for milling	c. Mixture
4. Salt	d. Element
5. Coal	e. Alloy
6. Hydrogen	f. Metal

Answer:

Column ‘A’	Column B’
1. Stainless steel	e. Alloy
2. Silver	f. Metal
3. Bhajani mixture for milling	c. Mixture
4. Salt	b. Compound
5. Coal	a. Non-metal
6. Hydrogen	d. Element

2. Write the names of elements from the following symbols:
Zn, Cd, Xe, Br, Ti, Cu, Fe, Si, Ir, Pt.

Question a.
Write the names of elements from the following symbols:
Zn, Cd, Xe, Br, Ti, Cu, Fe, Si, Ir, Pt.
Answer:

Symbol	Element
Zn	Zinc
Cd	Cadmium
Xe	Xenon
Br	Bromine
Ti	Titanium
Cu	Copper
Fe	Iron
Si	Silicon
Ir	Iridium
Pt	Platinum

3. What are the molecular formulae of the following compounds?
(Hydrochloric acid, Sulphuric acid, Sodium chloride, Glucose, Methane)

Question a.
What are the molecular formulae of the following compounds?
(Hydrochloric acid, Sulphuric acid, Sodium chloride, Glucose, Methane)
Answer:

Hydrochloric acid → HCl
Sulphuric acid → H₂SO₄
Sodium Chloride → NaCl
Glucose → C₆H₁₂O₆
Methane → CH₄
Water → H₂O
Carbon dioxide → CO₂
Sucrose (sugar) → C₁₂H₂₂O₁₁

4. Give scientific reasons:

Question a.
Buttermilk is churned to get butter.
Answer:

Churning is the process of shaking up buttermilk to make butter.
Butter is essentially the fat of milk.
Churning physically agitates the cream until it ruptures the membrane surrounding milk fat
Fat droplets can join with each other to form clumps of fat.

Question b.
In Chromatography the ingredients of a mixture rise up to a limited height when water rises up to the upper end of the paper.
Answer:
In Chromatography two properties of substances are used, (a) They are the stability of the substances in the solvent that moves up. The ability of the substance to stick to the stationary filter paper, (b) So all the components of the mixture do not rise all the way to the upper end of the filter paper but remain behind at limited heights.

Question c.
A wet cloth is wrapped around a water storage container in summer.
Answer:
A wet cloth will absorb the heat from the surroundings and it will keep the water in the container, cool for a longer time.

5. Explain the difference.

Question a.
Metals and Non-metals
Answer:

Metals	Non-metals
1. Metals are good conductors of heat and electricity.	1. Non-metals are poor conductors of heat and electricity.
2. Metals are solids at room temperature except for mercury.	2. Non-metals exists in all three states.
3. Metals are lustrous, (shiny)	3. Non-metals are not lustrous, (dull appearance) except graphite.
4. Metals are malleable (can be hammered into sheets)	4. Non-metals are brittle, not malleable.
5. Metals are ductile, can be drawn into wire.	5. Non-metals are not ductile.
6. Metals are very hard and strong.	6. Non-metals are brittle, will break down into pieces except diamond.

Question b.
Mixture and Compound
Answer:

Mixture	Compound
1. The different substances are not chemically joined together to form a mixture but mixed physically.	1. A compound is formed when two or more elements chemically combine together e.g. H₂O → chemical formula of water.
2. Each substance in the mixture retains its own properties	2. Compound has fixed properties.
3. Mixtures are impure substances.	3. Compounds are pure substances.
4. Substances from the mixture can easily be separated by physical methods.	4. The constituents of a compound can be separated only by chemical methods.
5. The constituents of a mixture are present in varying proportions.	5. The constituents of a compound are present in fixed proportion.

Question c.
Atoms and Molecules
Answer:

Atoms	Molecules
1. An atom is the fundamental part of matter.	1. A molecule is a group of chemically bonded atoms.
2. Atoms are basic building blocks of matter.	2. Molecule is the smallest unit of a chemical compound
3. It is foundation of molecules.	3. It is foundation of chemical compound.

Question d.
Separation by distillation and Separation by separating funnel
Answer:

Separation by distillation	Separation by separating funnel
1. Distillation is used for purification of impure liquids, for separating liquid and solids (Separation of mixture containing two miscible liquids) e.g. to separate salt and water from saltwater.	1. This procedure is used for separating two liquids e.g. separating oil and water, (two immiscible liquids)

6. Write answers to the following questions in your own words.

Question a.
How are the components of mixture separated by simple methods?
Answer:
1. Component of mixtures are separated by straining, filtering, sifting, picking, sorting, winnowing, combing with a magnet and sublimation.
2. In a mixture, the constituent substances do not lose their identity, they can be separated easily by physical methods.
a. Sedimentation: (i) It is a process of separating an insoluble solid from a liquid in which it is suspended, by allowing it to settle to the bottom of the container, e.g. Muddy water contains heavier particles like sand and soil, (ii) Leave this muddy water undisturbed for some time, (iii) The heavier soil and sand particles settle down and the clear upper water is poured out by decantation.

b. Filtration: It is used for separating insoluble solids from a liquid, e.g. mixture of chalk and water is poured through a filter paper in a funnel while the water gets

collected in the beaker below, chalk is retained in the filter paper.

c. Evaporation: It is used for recovering dissolved solid substances from solutions by evaporation e.g. sugar can be recovered from sugar-water.

d. Distillation: It is a process of heating a solution containing soluble solids to form vapours of the liquid and then cooling the vapours to get the liquid back. e.g. A mixture of common salt and water is taken in distillation flask and heated. Steam rises up and comes out into condenser.

e. Sublimation: It is a process in which some solids on heating are transformed directly to vapour without passing through the liquid state, (i) It is used to separate a mixture of solids. The vapours are cooled separately, (ii) Used to separate ammonium chloride, iodine, camphor and sulphur from any mixture.

f. Magnetic separation: A mixture with iron fillings as one of the components can be separated using magnet to attract the iron particles away from the mixture.

Question b.
Which elements (metals, non-metals) compounds and mixtures do we use in our day to day life?
Answer:
Elements – non-metal

Oxygen, nitrogen → present in air
Hydrogen → present in water
Silicon → in memory card
Lithium → to make batteries
Neon → in neon signs/lights
Sulphur → used in water treatment, agricultural pesticides

Elements – metals

Calcium → in milk
Silver, gold → used in jewellery
Aluminium, copper, iron → Kitchen vessels
Mercury → in thermometer
Copper → electric wires

Compounds:

Sodium chloride → table salt
Sodium carbonate → washing soda
Sodium bicarbonate → baking soda
Sodium hypochloride → bleaching powder
Sodium hydroxide, Potassium hydroxide → in making soaps
Calcium oxide, Calcium hydroxide → in white washing the buildings.
Hydrochloric acid → in cleaning toilets
Sucrose → sugar used in cooking and baking.

Mixtures:

Bhel → mixture of puffed rice, sev, groundnuts, lemon juice
Concrete → mixture of cement, sand and rocks
Salad → mixture of onion, cucumber, tomato, lettuce, etc.
Sherbet and saltwater are also mixtures.

Question c.
In everyday life, where and for what purpose do we use centrifugation?
Answer:
Centrifugation: It is a process which involves application of centrifugal force.
1. It is used in industrial and laboratory settings. It is used for separation of fluids, gas or liquid based on density. In centrifugation mixture is separated through spinning and the solid settles to the bottom and the solution is clear.

2. Best example of centrifugal force is working of washing machine when it dries the clothes. The wet clothes are moving in circular path and a force acts on water particles in clothes and this force pulls water all outer side. Force involved is centrifugal force which removes the water from the clothes and clothes are dried in this way.

3. Cream separation: When the machine moves, the rod set inside milk moves and milk is pressurised and solid part from this milk goes outside due to centrifugal force and this solid part is cream. In this way the cream is separated from the milk.

Question d.
Where are methods of separation by distillation and by separating funnel used?
Answer:
1. Distillation: It is the process of separating the components or substances from a compound. It is a process of heating a solution containing soluble solids to form vapours of the liquid and then cooling the vapours to get the liquid back.
Distillation method is used in the following:

to separate components of air into oxygen, nitrogen, argon, etc.
to separate salt from saltwater.
to purify impure liquids.
to prepare distilled water.

2. Separating funnel: When a mixture of two immiscible liquids is left undisturbed, two layers are clearly seen to have formed, (a) The heavier of the liquids remain below and the lighter liquid floats on it. (b) So two liquids in a mixture can be separated by making use of this property, e.g.

to separate kerosene and water.
to separate oil and water.

Question e.
Which precaution will you take while using the methods of distillation and separation by separating funnel?
Answer:
In using distillation:

Allow sufficient space to work in, working area should be well lit and well ventilated to prevent the accumulation of alcoholic vapours.
Keep a fire extinguisher handy.
There should be no obstruction in the piping that could cause pressure build-up in the stills and cause it to burst.

In using separating funnel:

Stopper should be tightly fitted so that the solution does not leak out when the separating funnel is inverted.
Never throw any layer away until you are absolutely sure that you isolated the final product.

Project:

Question a.
Visit a jaggery or a sugar factory. Obtain information about the methods that are used to separate the components of the mixture while making jaggery or sugar. Present it in the class.

Class 7 Science Chapter 14 Elements, Compounds and Mixtures Important Questions and Answers

Fill in the blanks and rewrite the sentences:

Question 1.
………………, ……………….. and are three states of matter.
Answer:
Solid, liquid, gaseous

Question 2.
Molecules in ……………….. phase of matter are tightly packed together.
Answer:
solid

Question 3.
A ……………….. has a definite volume, but not a definite shape, it takes the shape of its container.
Answer:
liquid

Question 4.
The temperature at which a liquid becomes a solid is called ……………….. .
Answer:
freezing point

Question 5.
Anything that takes up space and has mass is called ……………….. .
Answer:
matter

Question 6.
A ……………….. has no definite shape and no definite volume.
Answer:
Gas

Question 7.
The amount of space that matter occupies is called ……………….. .
Answer:
volume

Question 8.
A ……………….. has a definite shape and definite volume.
Answer:
solid

Question 9.
When a liquid is heated it will ……………….. .
Answer:
expand

Question 10.
A ……………….. is formed by mixing different elements or compounds.
Answer:
mixture

Question 11.
The substance formed by a chemical combination of two or more elements is called a ……………….. .
Answer:
compound

Question 12.
The elements that show some properties of metals and non-metals are called ……………….. .
Answer:
metalloids

Question 13.
Elements are generally classified into ……………….. and ……………….. .
Answer:
metal, non-metals

Question 14.
The smallest particles of substances are called ……………….. .
Answer:
molecules

Question 15.
To date, scientists have discovered ……………….. elements and of these ……………….. elements occur in nature.
Answer:
118, 92

Question 16.
……………….. was the first scientist to use symbols for elements.
Answer:
Berzelius

Question 17.
Symbol for Tungsten is and it is ……………….. and it is derived from its German name ……………….. .
Answer:
W, Wolfram

Question 18.
22-carat gold is an ……………….. of gold.
Answer:
alloy

Question 19.
……………….. of a compound is a short form of its name written using symbols of its constituent elements.
Answer:
Molecular formula

Question 20.
For separating insoluble particles of blood (blood cells) from its liquid part (plasma), ……………….. method is used.
Answer:
centrifugation

Give scientific reason.

Question 1.
Saltwater is a mixture.
Answer:

The salt and water are mixed to give saltwater and can both be separated.
It can be separated by boiling saltwater.
Water can be obtained by condensation whereas the salt will be leftover.
As the salt and water do not react chemically and they are separated by simple processes therefore saltwater is called a mixture.

Question 2.
Classify the following substances according to their properties
(water, thermocol, soil, iron, coal, paper, rubber, copper, coir, plastic)
Answer:

Metals	Mixtures	Compounds
Copper, Iron	Soil, Thermocol	Paper, Coir, Plastic, Rubber, Water

Can you tell?

Answer the following questions:

Question 1.
What are objects made of?
Answer:
An object is made of a certain substance, (i) The term matter is also used as a synonym of substance, (ii) Object is made of matter.

Question 2.
What are these articles of everyday use made of?
Answer:

Electric wire → copper-metal
Kitchen utensils → stainless steel, Brass-alloy (aluminium-metal).
Nails → iron-metal
Tables, chairs → wood, plastic
Sugar → sucrose
Window panes → glass
Salt → NaCl (Sodium chloride) it is a compound.

Question 3.
What do the short-forms Dr, H.M., AC, Adv., C.M., DC stand for?
Answer:
Short forms of Dr. – Doctor, H.M. – Headmaster, AC – Air conditioner, Adv – Advance, C.M. – Chief Minister, DC – Direct current

Question 4.
Which metals do we use in day-to-day life?
Answer:

Gold and silver → used in jewellery, computer and solar cells
Iron, copper, aluminium → used to make utensils
Copper → used in electrical gadgets
Tungsten → used in electric bulbs.
Zinc → for coating on iron to prevent rusting
Tin → for coating on copper and brass vessels
Iron → nails, agricultural equipments, in construction of buildings, to make steel

Question 5.
Are metals elements?
Answer:
Yes, metals are elements.

Question 6.
Which element helps combustion?
Answer:
Oxygen helps combustion.

Question 7.
Does water help combustion?
Answer:

Water is formed by a combination of hydrogen and oxygen but does not help combustion.
It is used to extinguish a fire.

Question 8.
What are the mixtures used in everyday life?
Answer:
Oil and water, lemon juice and sherbet, bhel, honey and tea, milk and chocolate, coffee and cream, salt and water, smog (smoke + fog) air (oxygen + nitrogen), salad, milk.

Question 9.
Are all mixtures useful to us?
Answer:
No, adulterated foodstuff is also a kind of mixture and it is not useful. It is harmful, because when an unwanted and harmful substance is mixed with another substance the resulting mixture no longer remains useful.

Question 10.
How will you separate each component from a mixture of semolina, salt and iron filings?
Answer:

If a magnet is moved through this mixture all iron filings will stick to the magnet, remove them.
Add water to the remaining mixture, all salt will dissolve and then filter through filter paper.
Samolina will settle in filter paper.
The filtrate will be saltwater and salt can be separated by evaporation or distillation.

Use your brainpower!

Answer the following questions:

Question 1.
In day to day life we come across many things in our surroundings. We touch them, we study their properties. Are all these things made from only one kind of matter or from more than one kind of matters?
Answer:

Things are made from only one kind of matter or may be made from more than one kind of matter.
When a matter is made up of only one type of atoms it is called an element.
We find many elements in our surroundings.
But we also see many substances which are made up of two or more elements they are called compounds.
Also we see many substances which are formed by physically mixing two or more elements, they are called mixtures.

Question 2.
Classify the following according to the nature of matter in them – whether it is made from one kind of matter or from more than one kind of matter, and whether it is in solid, liquid or gaseous state: an engraved idol, gold, milk, water, a plank, concrete, salt, soil, coal, smoke, sherbet, cooked khichadi, steam.
Answer:

Question 3.
Which of the following are mixtures?
(water, sharbet, iron, steel, coal, air, salt, copper, brass, soil)
Answer:
Mixtures: sherbet, steel, air, brass and soil

Question 4.
Which elements are present in air?
Answer:
Nearly all of the earth’s atmosphere is made up of gases → Nitrogen, Oxygen, Carbon dioxide, Argon and Neon, Helium and Krypton.

Question 5.
Is carbon dioxide an element?
Answer:
No, carbon dioxide is a compound. A molecule of the compound CO₂ contains one atom of the element carbon and two atoms of the element oxygen.

Question 6.
What are the properties of elements due to?
Answer:
Properties of elements are due to molecules present in it. The molecules are made of one or more atoms which are exactly alike. The mass and volume of atoms of different elements are different.

Question 7.
Are the atoms of different elements similar or dissimilar?
Answer:
The atoms of different elements are dissimilar.

Question 8.
Is the water that falls from clouds naturally pure?
Answer:

Any form of water that falls from the clouds is known as precipitation. Several forms → rain, snow, hail stones.
Yes, it is pure as water vapours condense to form rain.
The same process is used in distillation to obtain the purest water.

Question 9.
Which properties of a liquid are seen in the distillation method?
Answer:
Liquid when boiled turns into gaseous state (e.g. water vapours) and on cooling it condenses to liquid.

Question 10.
For what purposes is distilled water used?
Answer:
Distilled water is used in pharmacy as a solvent, in photography to wash the negatives, in laboratory experiments and in cleaning medical tools.

Answer the following questions:

Question 1.a.
Take a piece of chalk and keep on dividing it in to smaller pieces, what will happen?
Answer:
We will get very tiny particles of chalk.

Question b.
Wipe a drop of ink with a handkerchief what effect does it have on the cloth of the handkerchief?
Answer:
The cloth will absorb the ink drop and cloth will have a stain mark on it.

Question c.
What happens when the lid of a bottle of perfume is opened?
Answer:
The molecules of perfume move out of the bottle and collide with other molecules in the air and eventually perfume spreads throughout the room.

Question 2.
Fill water in a spray pump, spray the water and observe the spray.
Answer:
When we spray the water, spray is composed of small particles of water. They are very tiny that we can not see them.

Question 3.
Take water in a tea pot and cover it, heat the water to a boil. What do you see on the inside of the lid?
Answer:

When we boil the water in a tea pot it boils and changes into gaseous state.
We find vapours (steam) but when we cover it with a lid, the water vapour cools down, condenses into liquid. So we find water droplets on the inside of the lid.

Question 4.a.
Take sugar in a test tube and heat the test tube. Observe what happens. What remains behind?
Answer:
When a test tube containing sugar is heated, the sugar melts and then it loses water leaving behind a black substance. This black substance is carbon.
Sugar is sucrose, a molecule of sugar is composed of 12 atoms of carbon, 22 atoms of hydrogen and 11 atoms of oxygen. (C₁₂H₂₂O₁₁).

Sugar is a compound made from these three elements carbon, hydrogen, oxygen.
It is a Carbohydrate.

Question b.
Using tongs hold a magnesium ribbon in a flame and observe what changes took place?
Answer:
When a magnesium ribbon is ignited, light and heat are produced. Magnesium reacts chemically with oxygen in the air
2Mg_(s) + O_2(g) → 2MgO_(s)
Magnesium oxide is produced.

Question c.
What does the name carbon dioxide imply – how many and which elements is this substance made of?
Answer:

Carbon dioxide is a compound. It is a tasteless, odourless gas. It is a natural product of respiration.
Plants use this to produce food.
Humans breath out the CO₂.

[A molecule of the compound carbon dioxide contains one atom of the element carbon and two atoms of the element oxygen.]

Question d.
Which of these are compound, which are elements?
Answer:

Water → compound H₂O (hydrogen + oxygen), Oxygen → Element
Carbon dioxide → compound CO₂ (Carbon + Oxygen)

Question e.
What is the smallest particle of a compound called?
Answer:
The smallest particle of a compound is called molecule.

Question 5.
From the internet or reference books obtain information about elements and prepare a table according to the format given below:
Answer:

Question 6.
Some methods of separating the components of a mixture.

Answer:

Winnowing
Filteration
Hand picking
Churning
Sieving

Question 7.
What is a molecular formula?
Answer:
Like an element, a compound is also written in an abridged form. A molecule of a compound is formed by a chemical combination of atoms of two or more elements. Therefore a molecular formula is used to represent a compound. Molecular formula of a compound is a short form of its name written with the help of the symbols of constituent elements and the number of their respective atoms, e.g.: Nael – Sodium chloride.

Question 8.
Collect information and prepare table:

Write short notes on:

Question a.
Atoms
Answer:
Atoms are basic building blocks of matter. Desk, chair, air are made up of atoms.

Question b.
Compounds
Answer:
1. A compound is a pure substance that contains two or more elements. Compounds are chemical combination of elements with properties that are different from the elements that formed them.
2. Substance is a compound only if its molecules are made up of atoms of different types e.g. Water, one molecule of water is made of two atoms of hydrogen and one atom of oxygen.

Question c.
Mixtures
Answer:

A mixture is two or more elements or compounds which are combined physically but no chemical reaction occurs.
This means you can separate them again, e.g. air, brass.

Question 9.
Write short notes on:
(1) Distillation (2) Sublimation (3) Magnetic separation (4) Sedimentation (5) Filtration (6) Evaporation
Answer:
1. Distillation: It is a process of heating a solution containing soluble solids to form vapours of the liquid and then cooling the vapours to get the liquid back. e.g. A mixture of common salt and water is taken in distillation flask and heated. Steam rises up and comes out into condenser.

2. Sublimation: It is a process in which some solids on heating are transformed directly to vapour without passing through the liquid state, (i) It is used to separate a mixture of solids. The vapours are cooled separately, (ii) Used to separate ammonium chloride, iodine, camphor and sulphur from any mixture.

3. Magnetic separation: A mixture with iron fillings as one of the components can be separated using magnet to attract the iron particles away from the mixture.

4. Sedimentation: (i) It is a process of separating an insoluble solid from a liquid in which it is suspended, by allowing it to settle to the bottom of the container, e.g. Muddy water contains heavier particles like sand and soil, (ii) Leave this muddy water undisturbed for some time, (iii) The heavier soil and sand particles settle down and the clear upper water is poured out by decantation.

5. Filtration: It is used for separating insoluble solids from a liquid, e.g. mixture of chalk and water is poured through a filter paper in a funnel while the water gets collected in the beaker below, chalk is retained in the filter paper.

6. Evaporation: It is used for recovering dissolved solid substances from solutions by evaporation e.g. sugar can be recovered from sugar-water.

Question 10.
Name the method you will use to separate the following mixtures:

Cream from buttermilk.
Mud from muddy water.
Stones from grains.
Tea leaves from boiled tea.
Salt from water.
Kerosene and water.
Blood cells and plasma.
Ink from water

Answer:

Churning
Sedimentation and decantation
hand picking
filtration
distillation
separating funnel
Centrifugation
Chromatography

Question 11.
Draw the experimental setup of weperation using separating funnel:
Answer:

7th Std Science Questions And Answers:

Properties of a Magnetic Field Class 7 Science Chapter 19 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 19 Properties of a Magnetic Field Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 19 Properties of a Magnetic Field Question Answer Maharashtra Board

Class 7 Science Chapter 19 Properties of a Magnetic Field Question Answer Maharashtra Board

1. Write the appropriate terms in the blanks:

Question a.
The alloys called …………. and …………. are used for making industrial magnets.
Answer:
alnico, Nipermag

Question b.
A magnetic field can pass through ………… and …………. .
Answer:
cardboard, bottle

Question c.
The intensity of a magnetic field is indicated by the lines of …………. .
Answer:
force

Question d.
The real test of a magnet is ……………… .
Answer:
repulsion

2. With whom should I pair up?

Question a.

Column ‘A’	Column ‘B’
1. Compass	a. The highest magnetic force
2. Door of a cupboard	b. Like poles
3. Repulsion	c. A magnet
4. Magnetic pole	d. A magnetic needle

Answer:

Column ‘A’	Column ‘B’
1. Compass	d. A magnetic needle
2. Door of a cupboard	c. A magnet
3. Repulsion	b. Like poles
4. Magnetic pole	a. The highest magnetic force

3. Write answers to the following questions:

Question a.
Distinguish between the two methods of making artificial magnets
Answer:

Single touch method	Double touch method
1. In this method, one magnet is used to magnetise the steel bar.	1. In this method, two magnets are used to magnetise the steel bar.
2. In this method, the magnet is dragged from one end of the steel bar to another end.	2. In this method, two magnets are dragged from the middle of the steel bar to the opposite directions.
3. As only one magnet is used to induce magnetism, this method is called single touch method.	3. As two bar magnets are used to induce magnetism, this method is called double-touch method.
4. The magnetism created by this method is of low strength and lasts for a short time.	4. The magnetism created by this method is of high strength and lasts for a longer time.

Question b.
Which substances are used for making electromagnets?
Answer:
The substances used for making electromagnets are, an iron nail, insulated copper wire, one or more batteries and a pair of wire strippers.

Question c.
Write a note on magnetic field
Answer:

The region around a magnet where the magnetic force acts on an object is called a magnetic field.
The magnetic field around a magnet can be shown by means of magnetic lines of force.
The intensity of the magnetic field can be obtained from the number of lines of force.
The intensity of a magnetic field is low where the lines of force are sparse and the intensity is high where the lines of force are concentrated.
A magnetic field is the magnetic effect of electric currents and magnetic materials.
The magnetic field at any given point is specified by both the direction and the magnitude.
Magnetic fields are produced by electric current.

Question d.
Why is a magnetic needle used in a compass?
Answer:

The magnetic compass is the most familiar compass type.
It functions as a pointer to magnetic ‘north’ the local magnetic meridian, because the magnetized needle at its heart aligns itself with the horizontal component of the earth’s magnetic field.
A compass is an instrument used for navigation and orientation that shows direction relative to the geographic cardinal direction.

Question e.
Explain with the help of a diagram how the intensity and direction of the magnetic field of a bar magnet can be determined.
Answer:

The region around a magnet where the magnetic force acts on an object is called a magnetic field.
The magnetic field around a magnet can be shown by means of magnetic lines of force.
The intensity of the magnetic field can be obtained from the number of lines of force.
The intensity of a magnetic field is low where the lines of force are sparse and the intensity is high where the lines of force are concentrated.
A magnetic field is the magnetic effect of electric currents and magnetic materials.
The magnetic field at any given point is specified by both the direction and the magnitude.
Magnetic fields are produced by electric current.

4. Give detailed information about how the merchants of olden times used a magnet while travelling.

Question a.
Give detailed information about how the merchants of olden times used a magnet while travelling.
Answer:

The merchants of older times used a magnet whose north-south side was known.
When the magnet is freely suspended, the north pole of the magnet settles in the direction of the geographic north pole of the earth.
This is how the merchants come to know the directions while travelling.
The idea for using loadstone in a compass first appeared in China.
The first compass were made of loadstone, a naturally magnetised ore of iron.
The Chinese used “south pointing spoon” which when thrown upon the ground comes to rest pointing at the south.
Then the transition was made from loadstone spoons to iron needles.
In the medieval period a magnetic needle in the shape of a fish, floating in the bowl of water was used as a compass, pointing south.
It was called floating compass.
In the twentieth century, liquid filled magnetic compass began to appear.
There is a lesser known compass called dry mariners compass.

Project:

Question a.
Obtain information about the function of metal detectors.

Class 7 Science Chapter 19 Properties of a Magnetic Field Important Questions and Answers

Write the appropriate terms in the blanks:

Question 1.
The magnetic lines of force always run from the north pole to the ……………. .
Answer:
south pole

Question 2.
The unit of magnetic field strength is …………….. .
Answer:
A/M (Amperes per metre)

Question 3.
The earth behaves like a giant ………… .
Answer:
barmagnet

Question 4.
The ……………. properties of magnetic field was proposed by scientist
Answer:
Michael Faraday

Question 5.
The region around a magnet where the magnetic force acts on an object is called the …………. .
Answer:
magnetic field

Question 6.
The ……………. of the magnetic field can be obtained from the number of lines of force.
Answer:
strength

Question 7.
The function of the metal detector is based on ………… .
Answer:
electromagnets

Question 8.
The magnetism is ………….. in the case of an electromagnet.
Answer:
temporary

Match the following:

Question 1.

Column ‘A’	Column ‘B’
1. Iron, nickel, cobalt	a. Electromagnet
2. Doorbell magnet	b. Permanent magnet
3. Nickel, cobalt, aluminium	c. Iron, nickel, titanium, aluminium
4. Cupboard magnet	d. Magnetic metals
5. Lodestone	e. Mariner’s compass
6. Nipermag	f. Alnico

Answer:

Column ‘A’	Column ‘B’
1. Iron, nickel, cobalt	d. Magnetic metals
2. Doorbell magnet	a. Electromagnet
3. Nickel, cobalt, aluminium	f. Alnico
4. Cupboard magnet	b. Permanent magnet
5. Lodestone	e. Mariner’s compass
6. Nipermag	c. Iron, nickel, titanium, aluminium

Write True or False correct and rewrite the false statements:

Question 1.
Material alnico is a mixture of aluminium, nickel and iron.
Answer:
False. Alnico is an alloy of aluminium, nickel and cobalt

Question 2.
Nipermag is alloy of iron, nickel, cobalt.
Answer:
False. Nipermag is an alloy of iron, nickel, aluminium and titanium

Question 3.
The magnetic force is concentrated at the centre of the magnet.
Answer:
False. The magnetic force is concentrated at the poles of the magnet.

Question 4.
Magnetism of electromagnet is permanent.
Answer:
False. Magnetism of electromagnet is temporary

Question 5.
Like poles attract each other and unlike poles repel each other.
Answer:
False. Like poles repel each other and unlike poles attract each other

Question 6.
Two poles of a magnet cannot be separated from each other.
Answer:
True.

Answer in one or two sentences:

Question 1.
In which direction does a freely suspended magnet settle?
Answer:
The north pole of a freely suspended magnet settles in the direction of the geographic north pole of the earth. It settles in north-south direction.

Question 2.
Write any two functions of metal detectors.
Answer:

Metal detectors are used in very important places like an airport, bus station, certain temples and buildings to inspect those who are entering these places.
To detect very precious articles.

Question 3.
Which magnetic poles attract each other?
Answer:
Opposite magnetic poles attract each other.

Question 4.
What metals are used for making magnets?
Answer:

Magnets are made from alloys of iron, cobalt and nickel.
Nipermag is an alloy made up of iron, nickel, aluminium and titanium whereas alnico is an alloy made up of aluminium, nickel and cobalt.

Give scientific reasons:

Question 1.
Earth is called as a gigantic magnet.
Answer:

The earth is called as a gigantic magnet because north pole of a freely suspended magnet always settles in the direction of the geographic north pole of the earth.
It means that the South pole of some gigantic magnet must be near the geographic north pole of that magnet, near the geographic south pole of the earth.
Gilbert inferred from this that the earth itself is a gigantic magnet.

Question 2.
A bar magnet kept on the cardboard arranges the iron fillings in line.
Answer:

A bar magnet kept on the cardboard arranges the iron fillings in line because of the ‘magnetic lines of force’.
These magnetic lines gauge the intensity of the bar magnet.
The intensity of the magnetic field is low where the lines of force are sparse and the intensity is high where the lines of force are concentrated.
Therefore, the iron fillings arrange themselves according to intensity of the magnetic lines of force.

Write short note on:

Question 1.
Functions of metal detector.
Answer:

A metal detector is an electronic instrument which detects the presence of metals nearby.
The function of these machines is based on electromagnets.
Metal detectors are useful for finding metal inclusions hidden within objects, or metal objects buried underground.
They often consist of a handheld unit with a sensor probe which can be swept over the ground or other objects.
Metal detectors in the food manufacturing industry are used to detect and eliminate threats of metal contaminants in food.
Metal detectors are used in very important places like an airport, bus station, temples, hospitals, railway stations, theaters, malls.
They are used for inspection of persons entering these places.
In geology, these machines are used to detect the presence and quantity of metals.

Question 2.
Write down the characteristics of magnets.
Answer:

A freely suspended magnet settles in the north- south direction always.
Magnets attract objects of iron, cobalt and nickel.
The force of attraction of a magnet is greater at its poles than in the middle.
Like poles of two magnets repel each other.
Opposite poles of two magnets attract each other.
If a bar magnet is suspended by a thread and if it is free to rotate its south pole will move towards the north pole of the earth.

Question 3.
Characteristic of magnetic lines of force
Answer:

Magnetic lines of force start from the north pole and end at the south pole.
They are continuous through the body of magnet. These are imaginary lines.
Magnetic lines of force can pass through iron more easily than air
The number of magnetic lines force determines the strength of the magnetic field at a particular point.
Two magnetic lines of force do not intersect each other.
They contract longitudinally and expand laterally.

Can you tell?

Answer the following questions:

Question 1.
Why does freely suspended magnet always settle in the north-south direction?
Answer:

Gilbert gave a scientific explanation that earth itself is a gigantic magnet.
The north pole of a freely suspended magnet settles in the direction of the geographic north pole of the earth since unlike poles attract.
It means that the south pole of some gigantic magnet must be near the geographic north pole of the earth.
In other words, the thing we call Earth’s geographic north pole is actually the south pole of the magnet inside the earth.
That is why a freely suspended magnet always settles in geographic north-south attracted by opposite poles of the earth as a great magnet.

Question 2.
Which magnetic poles attract each other?
Answer:
Opposite magnet poles attract each other.

Question 3.
Which pole of a spherical magnet will get attracted towards the south pole of the bar magnet?
Answer:
The north pole of the spherical magnet will get attracted towards the south pole of the bar magnet.

Question 4.
Why does a bar magnet kept at a distance doesn’t attract pins?
Answer:

The region around the magnet where the magnetic force acts is known as the magnetic field.
It has its influence over a certain distance where these magnetic lines of force act.
As these pins are outside this area of influence, a bar magnet does not attract those pins which are at a distance.

Question 5.
What is an electromagnet?
Answer:

A soft metal core made into a magnet by the passage of electric current through a coil surrounding it is called an electromagnet.
An electromagnet is a magnet in which the magnetic field is produced by electricity.
The strength of an electromagnet can easily be changed by changing the amount of electric current that flows through it.
The poles of an electromagnet can even be reversed by reversing the flow of electricity.
An electromagnet works because an electric current produces a magnetic field.
The magnetic field produced by electric current forms circles around the electric current.
The magnetic field disappears when the current is turned off.

Question 6.
How can an electromagnet be made?
Answer:

It is easy to make an electromagnet. To make an electromagnet we needs an iron nail of 10 cm length 1 metre long insulated copper wire, a battery cell, pins.
Neatly wrap some insulated copper wire around an iron nail.
The more wires you wrap around the nail, the stronger will be the electromagnet.
Attach a battery to the wire, an electric current will begin to flow and the iron nail will become magnetised.
When the battery is disconnected the iron nail will lose its magnetism.

Use your brainpower!

Answer the following questions:

Question 1.
Which direction will a magnetic needle show on the geographic north pole?
Answer:
North, all magnetic needle will show north direction.

Question 2.
Is magnetic force a vector or a scalar quantity?
Answer:

It is a vector quantity. Because a magnetic field is the magnetic effect of electric current and magnetic materials.
The magnetic field at any given point is specified by both direction and magnitude as such it is represented by a vector field.

Question 3.
What is meant by magnetic force?
Answer:

The magnetic force, is a consequence of the electromagnet force, one of the four fundamental forces of nature.
It occurs whenever objects interact in which there is charge in motion, eg. compass, a motor.
Magnetic force is an attraction or repulsion that arises between electrically charged particles because of their motion.

Question 4.
How does a magnetic force act without direct contact?
Answer:
Magnetic force acts without even direct contact because of the penetrating ability of the magnetic field.

Question 5.
What is the difference between the gravitational force and magnetic force?
Answer:

Gravitational Force	Magnetic Force
1. Gravitational force acts between any objects with mass.	1. Magnetic force acts between objects with specific properties.
2. It depends on the mass of the objects.	2. It does not depend on the mass of objects.
3. It acts over long-range as a gravitational field is large.	3. It acts over short-range as magnetic field is short.
4. Object are always attracted to each other.	4. Objects are either attracted or repelled.

Question 6.
Why is repulsion the real test for identifying a magnet?
Answer:
A magnet can attract the opposite pole of the magnet as well as magnetic substances (iron, cobalt, nickel).
So if a magnet attracts another object, we cannot say that other object is a magnet or a magnetic substance.
But if the magnet repels the object then we can surely say that the other object is a magnet because like poles of magnets repel each other.

Question 7.
How will you find a magnet from among the various articles given to you?
Answer:

Magnet has the property to attract things made of iron, cobalt, nickel.
A magnet has magnetic field which is invisible but it has the property of attracting, pulling other
ferromagnetic material such as iron, cobalt and nickle.
So if we bring any iron, nickle objects near it, they will be pulled toward the magnet.
The real test is repulsion.
The article which shows repulsion when one of the poles of a magnet is brought near is surely a magnet.

Find out:

Answer the following questions:

Question 1.
Why does the magnetic needle of a compass not settle parallel to the ground but at an angle to it?
Answer:

Freely suspended magnet does not point to north, but aligns to earth’s magnetic field axially ie – north-south.
The magnetic pole of the earth is different from true north (geographic north) because the magnetic north is constantly changing.
It leads to a margin of error called declination in which there is an angle of difference (11.51)° between Magnetic North and True North.
That is the reason the magnetic needle does not settle parallel to the ground.

Observe the diagrams and answer the questions given below:

Question 1.
Name the methods shown.
Answer:
Single touch and Double touch methods of magnetising a steel bar.

Question 2.
Give 2 points of difference between the methods.
Answer:

Single touch method	Double touch method
1. In this method, one magnet is used to magnetise the steel bar.	1. In this method, two magnets are used to magnetise the steel bar.
2. In this method, the magnet is dragged from one end of the steel bar to another end.	2. In this method, two magnets are dragged from the middle of the steel bar to the opposite directions.
3. As only one magnet is used to induce magnetism, this method is called single touch method.	3. As two bar magnets are used to induce magnetism, this method is called double-touch method.
4. The magnetism created by this method is of low strength and lasts for a short time.	4. The magnetism created by this method is of high strength and lasts for a longer time.

7th Std Science Questions And Answers:

Properties of Natural Resources Class 7 Science Chapter 3 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 3 Properties of Natural Resources Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 3 Properties of Natural Resources Question Answer Maharashtra Board

Class 7 Science Chapter 3 Properties of Natural Resources Question Answer Maharashtra Board

Fill in the blanks with the appropriate term.

Question 1.
The capacity of air to hold moisture depends upon the …………… of the air.
Answer:
temperature

Question 2.
Water does not have a …………… but has definite ………… and ………. .
Answer:
shape, volume, mass

Question 3.
While freezing, the ………….. of water is lowered.
Answer:
density

Question 4.
…………….. soil has pH 7.
Answer:
neutral

2. Why is the said that –

Question a.
Air is a homogeneous mixture of various gases.
Answer:

Air is made of oxygen, nitrogen, carbondioxide, water vapour and dust particles.
All these are in different proportions. Therefore air is a mixture.

Question b.
Water is a universal solvent.
Answer:

Water dissolves more substances than any other liquid. It dissolves solids, other liquids and even gases in it. Therefore, it is called as Universal solvent.
Water is used as a solvent in factories, laboratories, foodstuffs and in various types of biological processes occurring in the body such as digestion, excretion, etc.

Question c.
There is no alternative to water for cleaning purposes.
Answer:
Water is a universal solvent. It dissolves more substances than any other liquid so there is no alternative to water for cleaning purposes.

3. What will happen if……

Question a.
The amount of water vapour in the air increases.
Answer:
We feel the dampness or the humidity.

Question b.
Only one crop is grown repeatedly in the soil.
Answer:
The fertility of the soil decreases.

4. With whom should I pair up?

Question a.

Column ‘A’	Column ‘B’
1. Air	a. Excretion
2. Water	b. Scattering of light
3. Soil	c. Plasticity

Answer:

Column ‘A’	Column ‘B’
1. Air	b. Scattering of light
2. Water	a. Excretion
3. Soil	c. Plasticity

5. State whether the following statements are true or false.

Question a.
Sandy soil has low capacity for holding water.
Answer:
True

Question b.
Sea water is a bad conductor of electricity.
Answer:
False. Sea water is a good conductor of electricity

Question c.
The substance in which a solute dissolves is called a solvent.
Answer:
True

Question d.
The pressure exerted by air is called atmospheric pressure.
Answer:
True

6. Explain the picture in your own words.

Question a.
Explain the picture in your own words.

Answer:

Diagram (a): Water is filled in the crack.
Diagram (b): Water in the crack turns to ice due to decrease in temperature. When it turns to ice the volume increases and it expands. Due to expansion, the size of crack widens more than in diagram (a).

7. Write answers to the following questions in your own words.

Question a.
How is light scattered by the air?
Answer:
Air is a mixture of very fine particles of some gases, dust, smoke and moisture. When rays of light fall on these minute particles, the particles spread the light in all the directions. This natural phenomenon is called scattering of light.

Question b
Explain the various properties of water.
Answer:
Various properties of water are as follows:

It is a fluid substance because it can flow.
It does not have its own shape, it takes the shape of a container in which it is kept.
It has a definite volume.
It is a transparent liquid and it has no colour.
It is tasteless and odourless.
It is a universal solvent.

Question c.
Why is the density of seawater is more than that of rainwater?
Answer:
Seawater has many minerals dissolved in it as compared to rainwater. So due to more dissolved salts, density of seawater is more than that of rainwater.

Question d.
What is the importance of good soil structure?
Answer:
The fertility of soil depends upon soil structure. So importance of good soil structure is as follows: (a) Roots get sufficient supply of oxygen, (b) Water drainage is good therefore the roots of plants grow well.

Question e.
What are the various uses of soil?
Answer:
The uses of soil are as follows:
Plant conservation: To help plants grow. Water conservation: Soil holds water. As a result, by means of bunds and lakes, we can get water for use throughout the year.
Plasticity: (a) Soil can be given any required shape. This property of soil is called plasticity, (b) Because of its plasticity, we can use it to make articles of a variety of shapes, (c) These articles can be baked to make them hard, (d) Water storage earthen pots, earthen lamps, idols, bricks etc. are articles made from soil.

Question f.
What is the need and importance of soil testing from the point of view of farmers?
Answer:

The properties of the various ingredients of soil can be determined by soil testing.
During soil testing, the soil is examined for colour, texture and the proportion of organic matter in it.
Soil is tested to find out if there is a deficiency of any ingredients and to decide what measures should be taken to remove the deficiency. These information would enable the farmers to maintain the fertility of the soil.

Question g.
What is the importance of air in transmission of sound?
Answer:

Air is useful as a medium for the transmission of sound. Density of the air changes with temperature.
If the density of air increases, we can hear the sound more loud and clear.

Question h.
Why should a glass bottle completely filled with water never be kept in a freezer?
Answer:

Due to anomalous behaviour of water, when you cool water below 4°C, the volume of the water increases.
Therefore when the glass bottle completely filled with water is kept in a freezer, water expands on cooling and its volume increases so glass bottle breaks.
To avoid this, completely filled bottle is never kept in a freezer.

Project:

Question a.
Visit a soil testing laboratory. Learn the process of soil testing and share it with others.

Class 7 Science Chapter 3 Properties of Natural Resources Important Questions and Answers

Fill in the blanks with the appropriate term.

Question 1.
Air is a …………… of gases.
Answer:
mixture

Question 2.
Atmospheric pressure is the …………… in all the directions.
Answer:
same

Question 3.
…………… is used to measure atmospheric pressure.
Answer:
Barometer

Question 4.
As we go higher the sea level and the atmospheric pressure …………… .
Answer:
decreases

Question 5.
Pressure of air …………… when its velocity …………… .
Answer:
increases, decreases

Question 6.
…………… an effect of the difference in air pressure.
Answer:
Wind

Question 7.
The level of …………… in the air is determined by its capacity to hold water vapour.
Answer:
humidity

Question 8.
When the temperature of air is low, its capacity to hold the vapour is …………… .
Answer:
less

Question 9.
Air is useful as a …………… for the transmission of sound.
Answer:
medium

Question 10.
Water is a …………… substance.
Answer:
fluid

Question 11.
Ice is …………… than water.
Answer:
lighter

Question 12.
Density of ice is …………… than that of water.
Answer:
less

Question 13.
The space occupied by a substance is its …………… .
Answer:
volume

Question 14.
The storage of matter in a substance is its …………… .
Answer:
mass

Question 15.
The density of water is maximum at …………… °C.
Answer:
4°C

Question 16.
The substance in which the solute dissolves is called …………… .
Answer:
solvent

Question 17.
The particles of sandy soil are made of the mineral called …………… .
Answer:
silicon dioxide (quartz)

Question 18.
…………… soil has a highest water holding capacity.
Answer:
clay

Question 19.
…………… soil is red in colour.
Answer:
Terracotta

Question 20.
…………… soil is used in cosmetics.
Answer:
Multani

Question 21.
…………… is celebrated as World Soil Day.
Answer:
5th December

Question 22.
The excess of water vapour during the night or dawn is transformed into ………….. .
Answer:
dew

Question 23.
Under ordinary conditions atmospheric pressure at sea level is …………… Newtons per square mater.
Answer:
101400

Question 24.
Swedish Scientist …………… put forth the important principle that the pressure of air decreases when its velocity increases.
Answer:
Daniel Bernoulli

Question 25.
When rays of light fall on fine particles of air, the particles spread light in all the directions, this is called …………… of light.
Answer:
Scattering

Question 26.
…………… soil is easy to plough but less fertile.
Answer:
Sandy

Say whether true or false, correct and rewrite the false statements.

Question 1.
Terracotta soil is white in colour.
Answer:
False. Terracotta soil is red in colour

Question 2.
The fertility of soil depends upon soil structure.
Answer:
True

Question 3.
Multani soil is used to make statues and idols.
Answer:
False. Shadu soil is used to make statues and idols

Question 4.
Clay soil has the maximum proportion of small particles.
Answer:
True

Question 5.
Silt soil is not as ploughable as sandy soil.
Answer:
True

Question 6.
The colour of soil near land surface is darker than the colour of the lower layers.
Answer:
True

Question 7.
Kerosene is a universal solvent.
Answer:
False. Water is an universal solvent

Question 8.
The density of substance is the inter-relation between the volume and mass of a substance.
Answer:
True

Question 9.
Water is lighter than ice.
Answer:
False. Ice is lighter than water

Question 10.
Rotation of crops decreases the fertility of the soil.
Answer:
False. Rotation of crop increases the fertility of the soil.

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
1. Concept of pH	a. pH higher than 7.5
2. Acidic Soil	b. pH 6.5 – 7.5
3. Neutral Soil	c. pH less than 6.5
4. Alkaline Soil	d. Sorensen

Answer:

Column ‘A’	Column ‘B’
1. Concept of pH	d. Sorensen
2. Acidic Soil	c. pH less than 6.5
3. Neutral Soil	b. pH 6.5 – 7.5
4. Alkaline Soil	a. pH higher than 7.5

Write short answers.

Question 1.
What is atmospheric pressure?
Answer:
The molecules of the gases in the air are in constant motion. When these molecules strike a body, they create pressure on that body. This pressure of air is called atmospheric pressure.

Question 2.
What is Bernoulli’s principle?
Answer:
Bernoulli’s principle is that the pressure of air ‘ decreases when its velocity increases while the pressure of air increases when its velocity decreases.

Give scientific reasons.

Question 1.
When the piston of a syringe is released, it is immediately pushed in.
Answer:

On pulling the piston of a syringe with the inlet hole of the syringe closed, more space becomes available to the air in the syringe, and it becomes rarified.
As a result, the pressure of the air in the syringe is lowered.
Comparatively the pressure of the outside air is very high. So when the pulled out piston is A released, it is immediately pushed in.

Question 2.
Water droplets are seen on the outer surface of a glass having ice cubes in it.
Answer:

Due to the ice cubes in the glass, the air surrounding the glass cools down.
As the water vapour in this air cools down, it condenses and gets transformed into water.
It is this water that collects on the outer surface of the glass.

Question 3.
Early morning dew drops are found on the grass.
Answer:

During the dawn (early morning) when the temperature of air is low, its capacity to hold the vapour is less.
At such times, the excess vapour is transformed into water droplets and we call them as dew drops.

Question 4.
During the afternoon we feel that the air is dry.
Answer:

In the afternoon, when the temperature of the air is high, the capacity of the air to hold the moisture also increases.
Then, compared to its full capacity to hold water the proportion of moisture in the air is less and we feel that the air is dry.

Question 5.
Earth’s surface remains warm and suitable for the living world on the earth.
Answer:

The earth receives energy from the sun. This energy is reflected by the earth in the form of heat.
The constituents of air surrounding the earth, such as water vapour, carbon dioxide, absorb a part of this heat and give it to the other constituents of air.
So the Earth’s surface remains warm and suitable for the living world on the earth.

Question 6.
We can hear the whistle of a distant train clearly early in the morning in winter.
Answer:

The density of air changes due to change in its temperature.
In winter, temperature is low so the density of the air is more. So we can hear the whistle of a distant train clearly early in the morning in winter.

Question 7.
Ice floats on water.
Answer:

When water freezes means it transforms into the soild state therefore its volume increases.
When volume increases its density decreases
Therefore, density of ice is less than the water, so ice floats on water.

Question 8.
In cold countries aquatic animals remain alive even after the rivers or lakes freeze in water.
Answer:
1. Due to anomalous behaviour of water, in cold countries when water gets cool and turn to ice, its volume increases, so its density decreases
2. Due to less density ice floats on water.
3. (a) Ice is a bad conductor of heat and electricity, (b) It doesn’t allow outside heat to go from the ice to water so water temperature below the ice doesn’t change, (c) It remains as water so aquatic animals remain alive even after the rivers or lakes freeze in winter.

Question 9.
It is easier to swim in the sea than in a well or a lake.
Answer:

Sea water is saline. It contains salt whereas it is not so in well or a lake water.
Due to salts dissolved in sea water, density of sea water is more, so the swijnmer will not sink.
Hence, it is easier to swim in the sea than in a well or a lake.

Question 10.
Sandy soil is less fertile.
Answer:

Sandy soil is made up of large particles and these particles of sandy soil are made of the mineral called silicon dioxide.
These particles do not dissolve in water therefore soil has very little capacity to supply nutrients, so sandy soil is less fertile.

Question 11.
China clay is used for making crockery.
Answer:
China clay is used for making crockery because on heating, this clay acquires a glaze and hardness. It can be moulded into any shape and being a bad conductor of heat, it is easy to handle.

Answer the following:

Question 1.
Write the properties of air.
Answer:

Air is a mixture of gases.
Air has mass and volume.
It spreads in all directions.
It exerts pressure.
It is colourless.

Question 2.
Name the tests for finding out the characteristic of soil. Describe any one method of it.
Answer:
There are two tests for finding out the characteristics of soil: (1) pH (2) electrical conductivity tests.
1. pH tests: The Danish scientist Sorensen put forth the concept of pH, based on the concentration of hydrogen ions. To determine the pH of soil, a mixture of water and soil in the proportion of 1 : 2 is taken and tested using several indicators.
Accordingly, soil may be found to be one of the following types.

Acidic soil – pH less than 6.5
Neutral soil – pH 6.5 – 7.5
Alkaline soil – pH higher than 7.5

2. By Electrical conductivity tests we come to know how many nutrients are present in the soil.

Question 3.
Write the causes of diminished soil fertility.
Answer:
Following are the causes of diminished soil fertility.

Soil pH less than 6 or higher than 8.
Low proportion of organic matter.
No proper drainage of water.
Repeated cultivation of the same crop.
Continuous use of saline water.
Excessive use of chemical fertilizers and pesticides.

Question 4.
Which crops reduce the fertility of soil and Which crops increase the fertility of soil?
Answer:
Wheat reduces the fertility of soil and leguminous crops like peanut, moong, moth bean, pea, lentil, Bengal gram, soyabean increase the fertility of soil.

Question 5.
Name and explain some useful types of soil.
Answer:
Following are some useful types of soil.

China clay (Kaolin): (a) It is white in colour, (b) It is used to make crockery, bathroom tiles, tanks, laboratory apparatus, masks, jars etc.
Shadu soil: (a) It is whitish in colour, (b) It is used for making statues and idols.
Terracotta soil: (a) This soil is red in colour, (b) Decorative articles and pots used for growing plants are made from this soil.
Multani soil: This soil is used in cosmetics.

Question 6.
Explain the types of soil on the basis of its texture.
Answer:
There are 3 types of soil on the basis of its texture.
1. Sandy soil: (a) Large particles are high in sandy soil, (b) Water drains rapidly through sandy soil, (c) It is easy to plough this soil, (d) It is less fertile because the particles of sandy soil are made of the mineral called silicon dioxide (quartz), (e) These particles do not dissolve in water and therefore the soil has very little capacity to supply dissolved nutrients.

2. Silt soil: (a) The particles of silt soil are of medium size, (b) Silt soil is not as ploughable as sandy soil but is much more ploughable than clay soil, (c) This soil contains a large proportion of organic materials, (d) Its capacity to supply nutrients is much greater, (e) Silt soil is also called sedimentary soil.

3. Clay soil: (a) The proportion of small particles is maximum, (b) The particles of clay soil feel smooth to touch, (c) Clay soil has a high water holding capacity.

Explain the given picture in your own words.

Question 1.

Answer:
1. The potato will sink in water as potato’s density is more than water.
2. This is the effect of density. The potato will float in salt solution as the density of salt solution is more than potato. The density of the water becomes greater due to the dissolved salt. That is why it is easier to swim in sea than in a well or a lake.

Can you tell?

Answer the following questions.

Question 1.
What change takes place in a balloon on filling air in it?
Answer:
On filling air in balloon, the shape of the balloon changes. Its size increases due to expansion.

Question 2.
Why is it easier to swim in the sea than in a well or a lake?
Answer:

Sea water is salty due to minerals in it. Whereas it is absent in well or a lake water.
Due to presence of salts, density of seawater is more than well or lake water, so it is easier to swim in the sea than in a well or lake.

Use your brain power!

Answer the following questions.

Question 1.
What is the effect of increased temperature on the pressure of air?
Answer:
Condition for closed environment:

When the temperature increases, the pressure of air also increases.
For example, as the air warms up, the molecules in the air become more active.
They use up more individual space even though there is same number of molecules. T1 s causes an increase in the air pressure.

Question 2.
Dip an uncorked inverted empty bottle in a slanting position into the water in a wide container. What do you observe?

Answer:

When an uncorked inverted empty bottle is kept slanting in the water container bubbling sound will be heard.
Air bubbles come out from the empty bottle and water enters the bottle.
Empty bottle is actually not empty but it is occupied by air.
When this air comes out, its place is taken by water. This shows that air occupies space.

Question 3.
In cold countries how do aquatic animals remain alive even after the rivers or lakes freeze in winter.
Answer:

Due to anomalous behaviour of water, in cold countries, water changes to ice.
Due to this change, its volume increases and density decreases. So ice floats on water.
Ice is a bad conductor of heat so it doesn’t allow heat to go inside so the water below ice remains as it is. So aquatic animals remain alive even after the rivers or lakes freeze in winter.

Question 4.
Why is it difficult to plough clay soil?
Answer:
It is difficult to plough clay soil because in clay soil the proportion of small particles is maximum. The particles of clay soil feel smooth to touch and has high water holding capacity, making it very difficult to penetrate through it.

Question 5.
Why is it easy to plough sandy soil?
Answer:

Sandy soil has large sized particles. It has weak structure due to less organic matter and large spaces between them.
The water also drains quickly through it making it dry and allows the plough to penetrate through it.

Question 6.
What is the water holding capacity of silt soil?
Answer:
Silt occurs as a deposit in riverbeds. The size of silt particles is between those of sand and clay. This soil also has humus in it which makes it the best soil to hold the right amount of water.

Question 7.
Which soil is suitable for cultivation? Why?
Answer:
The silt soil is suitable for cultivation.

The particles of silt soil is of medium size.
Silt soil is much more ploughable than clayey soil.
It contains large proportions of organic material.
This helps the soil in retention of water for a proper amount of time and makes it suitable for crops to grow.

7th Std Science Questions And Answers:

Disaster Management Class 7 Science Chapter 10 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 10 Disaster Management Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 10 Disaster Management Question Answer Maharashtra Board

Class 7 Science Chapter 10 Disaster Management Question Answer Maharashtra Board

1. Find the odd man out:

Question a.
Famine, earthquake, cloudburst, railway accident.
Answer:
Railway accident.

Question b.
Drought, heavy rains/storm, tsunami.
Answer:
Drought.

Question c.
Lava, hot mud, ash, locusts.
Answer:
Locusts.

Question d.
Washing away of crops, attack of pests on crops, volcano, singeing of crops.
Answer:
Volcano.

2. What are the remedial measures for the following calamities?

Question a.
Famine:
Answer:
Following are the remedial measures for famine:

Supply food and water to the people those who are dying due to hunger.
Give medicines to the people those who are suffering from malnutrition.
Government should start helping centres for the people those who are suffering from famine.
Give them temporary shelter in some other places where water and food are available.
Shift the animals to safer places.
Do proper planning so that region doesn’t get famine again and again.
Reuse water
grow more trees.

Question b.
Lightning strike:
Answer:
Following are the remedial measures for lightning strike:

Give immediate treatment to the lightning affected persons so their life can be saved.
Keep the people away from the open ground and swimming pool.
Provide them proper guidelines to cure for the lightning strike.

Question c.
Storm:
Answer:

Supply food, water and medicines to the people
Shift them to safe places.
Maintain peace, and advice the people not to panic.
Give time to time report on T.V. and radio.

Question d.
Cloudburst:
Answer:
Following are the remedial measures for cloudburst:

Shift people to safe places with the help of airplane, helicopter and army.
Supply them food, clothes, water and medicines.
Give time to time weather report.
Open more helpline centres.
Government should immediately send the help in terms of money and army to the people.

3. True or false? Give reasons for your answer.

Question a.
Information about a forthcoming storm is to be kept secret.
Answer:
False. Information about a forthcoming storm is not to be kept secret because, with this information we can take immediate steps for disaster management. Large scale damage of property and loss of life can be avoided.

Question b.
You should not swim when there is lightning in the sky.
Answer:
True. Lightning carries some electric charges which causes electric current in it. Water catches this current so if any person is swimming pool during lightning in the sky, then there are more chances that lightning may strike in water and the person may die due to it.

Question c.
It is possible to prevent the eruption of a volcano.
Answer:
False. It is not possible to prevent the eruption of a volcano because it is a natural event. However, by means of science and technology, it is possible to predict an eruption in advance and to take immediate steps for disaster management.

Question d.
Heavy rains result in famine.
Answer:
True. Heavy rains result in flood so crops get washed away or damaged in the flood and results in famine.

Question e.
A loud crashing sound follows a lightning.
Answer:
True, Friction and brushing happens between two clouds making them charged and lightning is produced between two clouds or one cloud and earth. The temperature increases and air pressure also increases to high amount and produces a loud sound of thunder.

4. Write answers to the following questions in our own words.

Question a.
What is a tsunami? What gives rise to a tsunami?
Answer:

Waves generated by an earthquake or volcano occurring on the ocean floor is called ‘tsunami’. ‘Tsunami’ is a Japanese word which means ‘harbour wave’.
As on land, earthquakes and volcanic eruptions occur, at the bottom of the sea, too.
If an earthquake occurs at the bottom of ocean, the energy released pushes the water upwards. As a result of this particular type of waves are formed.
These waves are not very high near the source, but they start spreading very fast to long distances.
The velocity of these waves is 800 to 900 km/hr. When they reach a coastal area, their velocity is reduced, but their height is found to have increased tremendously even to about 30 m. These are tsunami waves.

Question b.
What is cloudburst?
Answer:

Sometimes the water coming down from rain clouds does not reach the land in the form of rain. Instead, due to very high temperature near the land, it vaporizes and goes back into the same clouds.
As a result the amount of vapour in those clouds becomes very high.
Due to rapid condensation, it rains suddenly over a specific and small region at a rate of 100 mm per hour or more. This is known as a cloudburst.

Question c.
Explain the effects of a volcano.
Answer:
Following are the effects of a volcano:

The chemical substances such as lava, vapour, hot mud, sulphur etc. get collected on the surface of the earth and thereby mountains and hills are created
The atmosphere gets polluted due to the ash and gases ejected by the volcano.
Often, it rains as a result of a volcanic eruption.
The temperature rises due to hot gases.
Forests and settlement get buried under the hot mud.

Question d.
What are the measures to prevent loss of life due to lightning?
Answer:
Following are the measures to prevent loss of life due to lightning:

Do not stand on open ground, below a tree, on high location, near an electric pole, near a telephone pole or a tower etc.
Do not lean on wire fences around a farm, a compound, a garden or a house.
If you are on two-wheeler, a bicycle, a tractor or a boat, get off immediately and go to safe place.
Do not gather all together in one place.
Take care to keep a distance of 15 feet between any two persons.
Do not use plugged in electrical appliances. Do not use a mobile or telephone.
Stand on dry wood, a plastic sheet, sack or jute cloth or dry leaves.
Keeping your feet together support yourself on the soles of your feet placing your hands on your knees and crouch low.
Swimmers and fishermen should immediately come out of the water.
A pucca house is the safest place. Find out if there is a lightning conductor on any tall building near your house. If necessary get a lightning conductor fitted on your house.

5. What measures have been taken to deal with calamities such as floods and landslides under the disaster management programme in Maharashtra?

Question a.
What measures have been taken to deal with calamities such as floods and landslides under the disaster management programme in Maharashtra?
Answer:
In Maharashtra, all districts have their own disaster management plan to deal with calamities such as floods and landslides.

The plan deals extensively with the emergency, and evacuation measures to be taken up in cases of flood and landslide.
The district-level disaster management plan has detailed information about geographical details, population, flood-prone areas, villages and other macro details.
Nearly 14 such key departments are engaged in disaster mitigation measures and each one has been assigned a specific task to do at times of natural disasters.
The administration is now training master trainers at the district level who in turn will train key persons at village and taluka levels to deal with a natural disaster.
The administration through radio jingles, public advertisements and other measures is informing people about how to react at times of flood and landslide.
Currently, the Indian Meteorological Department (IMD) gives weather forecast on daily basis and for the next 5 days with advice to farmers on when to start crop sowing and harvesting etc.

6. With reference to disaster management what are the things in your house that you will check?

Question a.
With reference to disaster management what are the things in your house that you will check?
Answer:
With reference to disaster management, we should keep the following things at home and check regularly.

Keep proper first aid kit at a handy place.
Keep all the electric connections in proper condition.
Keep the gas line or tube connection proper.
Keep self-powered flashlights and self-powered radios.
Keep non-perishable food which will last for a week.
Keep a fire extinguisher handy and in proper condition.
Keep updated telephone diary which should have emergency phone numbers.

Project:

Question 1.
With the help of the Internet, collect information about the places where a calamity has occurred.

Question 2.
Collect information from the Internet about how cyclonic storms are named.

Class 7 Science Chapter 10 Disaster Management Important Questions and Answers

Fill in the blanks:

Question 1.
………… and ………… disasters are related to each other.
Answer:
Natural manmade.

Question 2.
………… implemented a canal scheme for drinking water in Aurangabad.
Answer:
Malik Ambar.

Question 3.
………… has turned out to be the most famine-affected contents of the world.
Answer:
Asia

Question 4.
The government of India established the ………… in 1976.
Answer:
National Flood Commission

Question 5.
The ………… that occurred in Mumbai on 26th August 2005 was extraordinary and unforgettable.
Answer:
cloudburst.

Question 6.
A cloudburst occurred at ………… on 6th August, 2010.
Answer:
Ladakh (Leh)

Question 7.
About ………… lightning flashes occur per second in the atmosphere.
Answer:
40.

Question 8.
The temperature generated by ………… is higher than that of the sun.
Answer:
lightning

Question 9.
When some substances comes out of the earth’s crust in an eruption and start flowing is called a ………… .
Answer:
volcano

Question 10.
Some islands are created due to the eruption, of ………… in the sea.
Answer:
volcano

Question 11.
………… is a Japanese word which means ‘harbour wave’.
Answer:
Tsunami.

Question 12.
About ………… nations from all over the world are members of the UNDP.
Answer:
177.

Question 13.
………… established a standing international organization UNDP in 1965.
Answer:
United Nations.

Question 14.
………… is celebrated as International Day for Disaster Reduction.
Answer:
13th October

Question 15.
The condition that arises due to long term and severe scarcity of food grains and water is called………. .
Answer:
famine

Can you tell?

Question 1.
Is it possible to prevent the loss of life caused by lightning?
Answer:
Yes, it is possible to prevent the loss of life caused by lightning, by taking precautions.

Question 2.
What should be done to prevent the bunds on a farm from getting washed away in the rainy season?
Answer:

Grow more trees near the bunds.
Grow grass strips.
Make stone lines near the bunds.
Use contour ploughing and tillage network method to prevent the bunds on a farm from getting washed away in the rainy season.

Question 3.
Why do we experience water scarcity?
Answer:
Lessor no rain leads to water scarcity.

Question 4.
What causes rain?
Answer:

Due to heat of the sun, water from the sea, lake and river gets evaporated and this water vapour is light in weight so it goes higher and higher and forms the cloud.
At a certain level the amount of vapour in those clouds becomes very heavy and it burst and rain occurs.

Question 5.
Have you seen a flash of lightning in the sky? When?
Answer:
Students will answer this question based on their experience.

Question 6.
What causes lightning?
Answer:

Where air and clouds rub against each other in the sky, the upper part of some clouds on the upper side becomes positively charged and the lower sides become negatively charged.
When this negative charge on the bottom of the cloud becomes much larger than the charge on the ground it starts flowing towards the ground in stages.
This happens very fast, in much less than a second and heat, light and sound energy are produced along with the electric current.

Use your brainpower!

Answer the following questions:

Question 1.
We should not wait at the foothill while it is raining heavily.
Answer:
During heavy rain there are chances of landslide and flood, so we should not wait at the foothill while it is raining heavily.

7th Std Science Questions And Answers:

Sound: Production of Sound Class 7 Science Chapter 18 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 18 Sound: Production of Sound Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 18 Sound: Production of Sound Question Answer Maharashtra Board

Class 7 Science Chapter 18 Sound: Production of Sound Question Answer Maharashtra Board

1. Fill in the blanks:

Question a.
Sound is generated by the rhythmic ……………. of any object.
Answer:
vibrations

Question b.
The frequency of sound is measured in …………….. .
Answer:
Hertz (Hz)

Question c.
If …………….. of sound is decreased its loudness also decreases.
Answer:
intensity

Question d.
A medium is necessary for …………… of sound.
Answer:
generation

2. Match the pairs.

Question a.

Column ‘A’	Column ‘B’
1. Flute	a. Frequency less than 20 Hz
2. Frequency	b. Frequency more than 20,000 Hz
3. Sound level	c. Vibrations in the air
4. Ultrasonic sound	d. Measured in Hz
5. Infrasonic sound	e. Decibel

Answer:

Column ‘A’	Column ‘B’
1. Flute	c. Vibrations in the air
2. Frequency	d. Measured in Hz
3. Sound level	e. Decibel
4. Ultrasonic sound	b. Frequency more than 20,000 Hz
5. Infrasonic sound	a. Frequency less than 20 Hz

3. Give scientific reasons.

Question a.
In earlier times, people used to listen for the arrival of a distant train by putting their ear to the rails.
Answer:

It was a technique that worked better in those days when train speed were slower than they are today and when there were more rail joints.
When people would put their ear to the rail they could hear vibration caused by the wheels moving over the joints. ,
Metal being a solid is an efficient medium for the sound to travel and so the sound can propagate further in the rail than would in air as speed of sound is faster in solids than in air.

Question b.
The sounds generated by a tabla and sitar are different.
Answer:

In tabla where leather is fitted, sound gets generated when the leather surface is thumped by fingers or palm.
The waves thus created travel in two dimensions. Sitar is having strings attached to pumkin box called sound box.
Sounds generated by tabla and a sitar are different because they have different pitch and frequencies.

Question c.
If you were both on the moon your friend will not be able to hear you call.
Answer: Yes, your friend will not be able to hear your call because sound needs a medium for transmission since it is a mechanical wave it cannot travel through vaccum.

As there is no air on the moon and sound is actually vibration in air.
So astronauts communicate to each other by signals or microphones in space even when they are closer.

Question d.
We can hear the movement of a mosquito wings but we cannot hear the movement of our hands.
Answer:

Humans cannot hear frequency less than 20 Hz. In the movement of hands oscillations does take place but is less than frequency that humans can hear.
Mosquitos wings flap in air.
When they fly in air it produces buzzing sound in our ears.
The movement of mosquito wings produces sound greater than 20 Hz.
Sound is the reception of such waves and their perception by the brain.

4. Write answers to the following questions.

Question a.
How is sound produced?
Answer:

Sound is generated due to the vibration of an object, e.g. bell, string or diaphragm of a musical instrument.
Vibrations are imparted to the molecules in the air. These vibrations reach our ears through the air and sound is heard.
Vibrations of an object is necessary for generation of sound.
These vibrations in air are called travelling longitudinal waves which we can hear.

Question b.
What does the intensity of sound depend upon?
Answer:

The intensity of sound is proportional to the square of the amplitude of vibration, e.g. If the amplitude is doubled the intensity of sound becomes four times.
Therefore the loudness or softness of sound is dependent on the intensity of sound and sound level.

Question c.
Explain how the frequency of oscillation is related to the length of a pendulum and the amplitude of its oscillation.
Answer:

1. Given an oscillatory motion to the pendulum, the maximum distance between the original position A of the pendulum and extreme position B or C is called the amplitude of oscillation. AB, AC is the amplitude of oscillation.
2. The number of oscillations completed by an oscillator in one second is called the frequency of oscillation.

Relation between frequency and length of a pendulum: If the length of the pendulum increases the period of oscillations also increases.
We know time period of oscillations = \(\frac{1}{\text { Frequency }}\)
If time period increases, frequency decreases, therefore, if the length of the pendulum increases frequency will decrease.
Relation between frequency and amplitude: Frequency of oscillation is independent of its amplitude of oscillation.

Question d.
Explain the two ways by which the pitch of the sound generated by a stretched string can be changed?
Answer:
1. A string vibrates with a particular fundamental frequency. It is however possible to produce pitches with different frequencies from the same string.

2. The two properties of the string that affect its frequency are length and diameter.

3. When the length of a string is changed, it will vibrate with a different frequency. Shorter strings have higher frequency and therefore higher pitch.

4. When a musician presses her finger on a string, she shortens its length. The more fingers she adds to the string, the shorter she makes it, higher will be the pitch.
Diameter: Thick strings with large diameter vibrate slower and have lower frequency than the thin ones.

Project:

Question a.
The bat, a mammal, flies during the night manoeuvering with the help of the ultrasonic sounds it produces. Find out more about this.

Class 7 Science Chapter 18 Sound: Production of Sound Important Questions and Answers

Fill in the blanks:

Question 1.
Bats detect the obstacles in their path by receiving the reflected ………….. .
Answer:
ultrasonic waves

Question 2.
An object that moves back and forth is called ……………. .
Answer:
an oscillator

Question 3.
If the length of a pendulum is increased the time period of oscillation ………………. .
Answer:
increases

Question 4.
The …………… of a wave is the maximum distance moved by the object on either side of the mean position.
Answer:
amplitude

Question 5.
Sound waves do not travel through ……………… .
Answer:
vaccum

Question 6.
The frequency above which sound is not audible to the human ear is …………….. .
Answer:
50,000 Hz

Question 7.
Number of vibrations in a second is called …………….. .
Answer:
frequency

Question 8.
Higher the frequency greater will be the ………….. .
Answer:
Pitch

Question 9.
The loudness of sound depends on ………….. .
Answer:
amplitude

Question 10.
Loudness of sound is measured in units of ………………. .
Answer:
decibel dB

Question 11.
100 hertz is equal to hundred oscillations in ………………. .
Answer:
one second

Name the following:

Question 1.
The sound frequencies above 20,000 Hz.
Answer:
ultrasonic

Question 2.
The medium through which sound is most clearly propagated.
Answer:
solids

Question 3.
The range of frequency in which humans can hear sound.
Answer:
20 – 20,000 Hz

Question 4.
The sound level physically painful to humans.
Answer:
above 100 dB

Question 5.
The technique used by bats to find their way.
Answer:
echolocation

Question 6.
The unit of frequency of sound.
Answer:
Hertz

Question 7.
The unit of sound level or intensity.
Answer:
Decibel

Question 8.
The scientist in whose honour was the unit decibel named for intensity of sound.
Answer:
Alexander graham Bell

Question 9.
Bats and dolphins can hear these sound frequencies.
Answer:
Ultra sonic sound

Question 10.
The sound frequencies used in RADAR systems.
Answer:
Ultra sonic sound

Answer in one or two sentences:

Question 1.
How is sound produced?
Answer:
Sound is produced by vibration of an object.

Question 2.
What produces sound in human beings ?
Answer:
The vibration of the vocal chords in our larynx or voice box produces sound.

Question 3.
What is oscillatory motion?
Answer:
To and fro motion of an object (oscillator) on either side of a central position is called oscillatory motion.

Question 4.
What is periodic motion?
Answer:
The motion of an object repeated again and again at fixed intervals of time is called periodic motion.

Question 5.
What is frequency of oscillation?
Answer:
The number of oscillations completed by an oscillator in one second is called the frequency of oscillation.

Question 6.
How is intensity of sound and amplitude of vibration related?
Answer:
The intensity of sound is proportional to the square of the amplitude of vibration. For example, if the amplitude is doubled the intensity becomes four times as much.

Question 7.
What happens if the frequency of sound is greater than 1000 Hz or 100 dB?
Answer:
If frequency of sound is increased more than 100dB, the hearing can be temporarily affected which can result in temporary deafness.

Question 8.
What is infrasonic sound?
Answer:
A sound with a frequency less than 20Hz is called infrasonic sound.

Question 9.
What is application of ultrasonic sound?
Answer:
Ultrasonic sound is used in ships as a system known as ‘SONAR’ to detect the obstacle beneath the ocean as well as the depth of an ocean.

Question 10.
What is the difference between pitch and frequency?
Answer:
Pitch is directly proportional to the frequency of a sound whereas frequency is the repeating vibrations per unit time.

Question 11.
What happens when the rubber band is stretched with a greater force and released?
Answer:
When a rubber is stretched with a greater force and released, the amplitude increases which in turn result in a louder sound being generated.

Question 12.
What happens to frequency if the amplitude is changed?
Answer:
The frequency remains the same even if the amplitude is increased or decreased.

Define:

Echo: It is a repetition of sound due to the reflection of original sound by a large and hard obstacle.
Frequency: It is defined as the number of vibrations per unit time.
Hertz (Hz): One hertz is one vibration per second.
Ultrasonic vibration: Sounds of frequency higher than 20,000 Hz are called the ultrasonic.
Time period: The time taken by an object to complete one oscillation is called time period.
Amplitude: The distance between the mean or central position to the extreme position of an oscillator on either side is called amplitude.

Say True or False with explanation:

Question 1.
Sound cannot travel in vacuum.
Answer:
True. Sound needs a medium to travel through. Since vacuum does not provide any medium, sound cannot travel through it.

Question 2.
If the amplitude of vibration is large, sound is feeble.
Answer:
False. When the amplitude of vibration of a sound is large, the sound is very loud. The sound is feeble, when the amplitude is small. Loudness of a sound is proportional to the square of the amplitude of its vibration.

Question 3.
For human ears, the audible range is 2 Hz to 20,000 Hz.
Answer:
True. Human being can hear sounds only within the range of 20-20,000 Hz. We cannot hear the sound having frequency out of this range.

Question 4.
The lower the frequency of vibrations the higher is the pitch.
Answer:
False. Pitch of sound increases when the frequency of vibration increases. The pitch of a sound is directly proportional to its frequency.

Question 5.
Unwanted or unpleasant sound is termed as music.
Answer:
False. Unwanted, or unpleasant sounds are termed noise. Sounds which are melodious, and pleasing to ears are called music.

Question 6.
Noise pollution may cause partial hearing impairment.
Answer:
True. Unwanted, unpleasant sounds are called noise. If one is subjected to noise continuously for a long time, one may suffer from partial hearing impairment.

Question 7.
Time taken by an object to complete one oscillation is called time period.
Answer:
True. Time taken by an object to complete one oscillation is called time period.

Solve the following problems:

Question 1.
A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.
Answer:
Frequency is the number of oscillations per second of a vibrating body.

The time taken to complete one oscillation (to and fro) is known, as time period.

Question 2.
The sound from a mosquito, is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the time period of the vibration?
Answer:
The time taken to complete one oscillation (to and fro) is know as time period.

Give scientific reasons:

Question 1.
Loud speakers should not be put in congested areas.
Answer:

The loudness or softness is indicated by the intensity of sound and sound level.
By putting loud speakers in congested areas, the intensity of sound being more than 100 dB will cause ill effects like temporary deafness and a prolonged exposure can lead to permanent damage.

Answer the following:

Question 1.
Why are the ceilings of concert halls curved?
Answer:
The ceilings of concert halls are curved because sound after reflection from the ceiling it reaches all the comers of the hall and is audible to each person in the hall.

Question 2.
Have you ever heard the sound of movement of hands and falling of leaves from a tree?
Answer:

The term infrasonic refer to sound waves below the frequencies of audible sound i.e. under 20 Hz.
Humans cannot hear infrasonic sound.
Movement of hands and falling of leaves comes below this audible range. Therefore we cannot hear these sounds.

Question 3.
How can dogs perceive in advance the signals of an impending earthquake?
Answer:
Dogs can hear sounds upto about 65,000 Hz. That’s why dogs can receive ultrasonic sound signals produced by the vibration of the earth and start barking in advance before the actual earthquake is felt.

Question 4.
State the uses of Ultrasonic sound.
Answer:
Uses of Ultrasonic sound are:

To clean delicate ornaments and the tiny parts of a watch.
To observe internal organs of the body.
To detect tumors in the brain.
To detect faults in a metal.
In RADAR systems
To Kill certain microbes and insects.
SONAR (Sound navigation and ranging) is used to locate the seabed or the position of a ship.

Use your brainpower!

Answer the following questions:

Question 1.
Will a sound be generated no matter how the ruler is kept on the table.

Answer:

No, If the ruler kept on the table is only a little part off the table, it will not vibrate with a greater force.
On the contrary if the ruler is kept with a larger portion off the table it will vibrate with a greater force generating louder sound.

Question 2.
Is there any correlation between the length of the free part of the ruler and the sound generated?
Answer:
Yes, vibrating ruler pushes the molecules in the air producing sound waves. More the length of free part of ruler less will be the vibrations and less will be the frequency and pitch of the sound. If the length of free part of ruler is shorter it vibrates more quickly producing sound of higher frequency and pitch.

Question 3.
If the ruler is plucked while it is held with 25 cm of it off the table, does it makes any sound? If there is no sound, look for the reason why it is so?
Answer:
No, the ruler vibrates very slowly, which has frequency which is not audible.

Question 4.
What would be the difference perceived between hearing only two pupils in the class talking to each other and all the children talking to one another at the same time?
Answer:

When two pupils talk to each other, the sounds of two frequencies produced can be heard clearly.
When all the children talk to one another sounds of many frequencies produced can not be heard clearly.
Sound level will be more creating loud noise.

7th Std Science Questions And Answers:

Measurement of Physical Quantities Class 7 Science Chapter 6 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 6 Measurement of Physical Quantities Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 6 Measurement of Physical Quantities Question Answer Maharashtra Board

Class 7 Science Chapter 6 Measurement of Physical Quantities Question Answer Maharashtra Board

1. Write answers to the following questions in your own words:

Question a.
Why is the weight of the same object different on different planets?
Answer:
The weight of the same object is different on different planets because weight depends on the gravitational force of the planet and gravitational force on every planet is different so the weight also differs from planet to planet.

Question b.
What precautions will you take to make accurate measurements in day-to-day affairs?
Answer:
Following precautions will be taken to make accurate measurements in day to day affairs:

The balance should carry the stamp of standardisation by the department of weights and measures.
Balance should be stable and the pointer of the balance should be upright.
The underside of the pan should not be tampered with any other weight or layers of other metal.
The weight should be made of metal.

Question c.
What is the difference between mass and weight?
Answer:

Mass	Weight
1. The amount of matter present in a substance is called mass.	1. The gravitational force that acts on this mass is called its weight.
2. It is a scalar quantity.	2. It is a vector quantity.
3. Mass remains same everywhere on the earth.	3. Weight changes from place to place on the ‘ earth.

2. Who is my companion?

Class 7 Science Chapter 6 Measurement Of Physical Quantities Exercise Question 1.

Column ‘A’	Column ‘B’
1. Velocity	a. Litre
2. Area	b. Kilogram
3. Volume	c. metre/second
4. Mass	d. kilogram/cubic metre
5. Density	e. square metre

Answer:

Column ‘A’	Column ‘B’
1. Velocity	c. metre/second
2. Area	e. square metre
3. Volume	a. Litre
4. Mass	b. Kilogram
5. Density	d. kilogram/cubic metre

3. Explain giving examples.

Question a.
Scalar quantity:
Answer:
A quantity that can be completely expressed by its magnitude alone is called a scalar quantity, e.g. length, breadth, area, mass, temperature, density, time, work. In all these examples a value with a unit is used to express quantities. Thus, we say that the length of a tunnel is 2 km.

Question b.
Vector quantity:
Answer:
The quantity that is expressed completely only.’ v when magnitude and direction are both given is called a vector quantity. Displacement, velocity are vector quantities e.g. a displacement of 20 km towards north, the aeroplane flying at a velocity of 500 km/hr towards Mumbai.

4. Explain, giving examples, the errors that occur while making measurements.

Question a.
Explain, giving examples, the errors that occur while making measurements.
Answer:
Major causes of errors in measurement are:

Not using the appropriate device.
Not using the device properly.

Example: While buying things at grocery shops and the vegetable market remember to look out for the following:

The balance should carry the stamp of standardisation by the department of weights and measures.
Balance should be stable. The pointer of the balance should be upright.
No changes should be done on the underside of the pan of the balance.
Weight should be made up of metals and it has to be standardized.

5. Give reasons:

Question a.
It is not proper to measure quantities by using body parts as units.
Answer:
It is not proper to measure quantities by using body parts as units because length of the body parts changes from person to person, so accurate measurement can not be found with the body parts as units.

Question b.
It is necessary to get the weights and measures standardized at regular intervals.
Answer:
It is necessary to get the weights and measures standardized at regular intervals because of that accurate weight and measurement can be taken. Errors will be avoided.

6. Explain the need for accurate measurement and the devices to be used for that.

Question a.
Explain the need for accurate measurement and the devices to be used for that.
Answer:

Measurement of substances that are precious or of great importance and used in very small quantities is done meticulously and accurately.
Due to advancements in technology, devices that measure very small magnitudes of quantities like distance, mass, time and temperature are available now.
e.g. distance and time in connection with very important sports competitions, mass of gold, body temperature etc.
Devices to be used for this are thermometer, digital balance (Analytical balance) etc.

Project:

Class 7 Science Chapter 6 Measurement Of Physical Quantities Question 1.
Collect information about various physical quantities used in day-to-day life and the devices used for their measurement.

Class 7 Science Chapter 6 Measurement of Physical Quantities Important Questions and Answers

Fill in the blanks:

Std 7 Science Chapter 6 Measurement Of Physical Quantities Question 1.
The amount of matter present in a substance is called ………………. .
Answer:
mass

Measurement Of Physical Quantities Class 7 Exercise Question 2.
…………. is the qualitative measure of the inertia of an object.
Answer:
mass

6. Measurement Of Physical Quantities Question 3.
The larger the mass, the ……………. is the inertia.
Answer:
greater

6.Measurement Of Physical Quantities Question 4.
Mass is a …………… quantity.
Answer:
scalar

Physical Quantities And Measurement Class 7 Question 5.
…………… does not change from place to place anywhere in the world.
Answer:
mass

Measurement Of Physical Quantities Class 7 Question 6.
The gravitational force that acts on a mass is called its ……………. .
Answer:
weight

6 Measurement Of Physical Quantities Question 7.
Wright is a …………… quantity.
Answer:
vector

Question 8.
System International (SI) is also called ………….. .
Answer:
metric system

Question 9.
In Egypt in ancient times, the distance from a man’s elbow to the tip of his middle finger was called a ………… .
Answer:
cubit

Question 10.
Gold was weighed in a unit called …………… .
Answer:
gun

Who is my companion?

Question 1.

Column ‘A’	Column ‘B’
1. Gold	a. Hour glass
2. Time	b. Vector
3. Distance	c. Gunj
4. Weight	d. Cubit

Answer

Column ‘A’	Column ‘B’
1. Gold	c. Gunj
2. Time	a. Hour glass
3. Distance	d. Cubit
4. Weight	b. Vector

Say whether true or false. Correct and rewrite the false statements:

Question 1.
The standards of the six fundamental units are kept in the National Physical Laboratory at New Delhi.
Answer:
True

Question 2.
Matter has a natural tendency to resist a change in its state, which is called inertia.
Answer:
True

Question 3.
Weight and mass are both equal quantities.
Answer:
False. Weight and mass are both different quantities

Question 4.
Work is a vector quantity.
Answer:
False. Work is a scalar quantity

Question 5.
Velocity is a scalar quantity.
Answer:
False. Velocity is a vector quantity

Question 6.
Unit of time in both the systems is second.
Answer:
True

Question 7.
Unit of mass in C.G.S. system is kilogram
Answer:
False. Unit of mass in C.G.S. system is gram

Question 8.
Symbol of unit of second is sec.
Answer:
False. Symbol of unit of second is ‘s’

Question 9.
1 cubic foot means 28.317 ml
Answer:
False. 1 cubic foot means 28.317 litres.

Question 10.
Vector quantity requires magnitude only.
Answer:
False. Vector quantity required magnitude and direction both.

Give scientific reasons:

Question 1.
Weight of our body on the moon is less than that on the earth.
Answer:

Gravitational power of moon is less than the earth.
Weight depends on the gravitational power of that place.
Since the gravitational power of the moon is less than that of the earth, the weight on moon is less than that on the earth.

Question 2.
Mass is a scalar quantity
Answer:
Mass is a scalar quantity because it can be completely expressed by its magnitude alone, so it is scalar quantity.

Question 3.
Weight is a vector quantity.
Answer:
Weight can be expressed completely only when magnitude and direction are both given so weight is a vector quantity.

Distinguish between the following:

Question 1.
Scalar quantity and Vector quantity
Answer:

Scalar quantity	Vector quantity
1. A quantity that can be completely expressed by its magnitude alone is called a scalar quantity.	1. The quantity that is expressed completely only when magnitude and direction are both given is called a vector quantity.
2. e.g. mass, length, area, breadth, density, time, work etc.	2. e.g. velocity displacement

Question 2.
M.K.S. system and C.G.S. system
Answer:

M.K.S. system	C.G.S. system
1. In this system distance is measured in metres, mass in kilograms and time in seconds.	1. In this system distance is measured in centimetres, mass in grams and time in seconds.
2. e.g. Unit of velocity is m/sec, Unit of area is square metre.	2. e.g. Unit of velocity is cm/sec, Unit of area is square centimetre.

Define the following:

Mass: The amount of matter present in a substance is called mass.
Inertia: Matter has a natural tendency to resist a change in its state, which is called Inertia.
Weight: The gravitational force that acts on the mass is called its weight.
Physical Quantities: The quantities in day to day life which can be measured are called physical quantities.
Standardization: The process of checking things against a standard measure from time to time is called standardization.

Write answers to the following questions in your own words.

Question 1.
What is an atomic clock?
Answer:
An extremely accurate type of clock which is regulated by the vibrations of an atomic or molecular system such as caesium atom or ammonia is called atomic clock. It is used to maintain standard times of countries accurately.

Answer the following questions:

Question 1.
Why would the weight of an object be; maximum at the poles and minimum at the equator?
Answer:

The gravitational force that acts on the mass is called the weight.
The earth is not exactly spherical, it flattens at the poles.
As the distance increases the gravitational force decreases.
Therefore due to reduced distance at the poles compared to the equator, the weight is maximum at the poles than equator.

Question 2.
Why is the weight of an object at a high altitude less than its weight at the sea-level?
Answer:

The gravitational force that acts on the mass is called the weight.
The gravitational force is always inversely proportional to the distance.
So as the distance increases between the earth and the object, the gravitational force decreases.
The gravitational force by which the earth attracts an object towards its centre is called weight.
The weight at the sea-level is higher than at higher altitude, as the object is at a greater distance at higher altitudes compared to sea-level.

7th Std Science Questions And Answers:

Plants: Structure and Function Class 7 Science Chapter 2 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 2 Plants: Structure and Function Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 2 Plants: Structure and Function Question Answer Maharashtra Board

Class 7 Science Chapter 2 Plants: Structure and Function Question Answer Maharashtra Board

1. Give examples of 3 plants that have:

Question a.
Spiny fruits
Answer:
Jack fruit, Pineapple, Lychee (litchi), Datura

Question b.
Spiny stem
Answer:
Cactus, Wild rose, Catclaw acacia, Silk, Cotton

Question c.
Red flowers
Answer:
Rose, Dahlia, Hibiscus, Tulips,

Question d.
Yellow flowers
Answer:
Marigold, Daffodil, Sunflower, Daisy

Question e.
Leaves which close at night
Answer:
Mimosa plant, Tallwood, Prayer plant, Gulmohar

Question f.
Single seeded fruits
Answer:
Mango, Lychee, Jamun

Question g.
Many seeded fruits
Answer:
Custard apple, Papaya, Watermelon.

2. Observe any one flower and its various parts and describe it in your own words.

Question a.
Answer:

A flower has following parts:
1. Pedicel: (a) Flower may have a long or a short stalk called pedicel, (b) One end of the pedicel is attached to the stem, (c) The other end of the pedicel is expanded and swollen. It is called the receptacle, (d) Petals and other parts of the flower are supported on the receptacle.
2. Calyx: In the bud condition, the petals are covered by leaf like parts called sepals which are green in colour. They form the calyx.
3. Corolla: This is made up of colourful parts called petals.
4. Androecium: (a) This is the male reproductive part of the flower, (b) It consists of stamens, (c) Each stamen is made up of anther and filament.
5. Gynoecium: (a) This is the female reproductive part of the flower, (b) This is made up of carpels, (c) A carpel consists of stigma, style and ovary.

3. What are the similarities and differences between?

Question a.
Jowar and Moong
Differences:

Jowar	Moong
i. It has fibrous root.	i. It has tap root.
ii. It is a monocotyledonous seed.	ii. It is a dicotyledonous seed.
iii. It is a rabi crop.	iii. It is a kharif crop

Similarities:
Jowar and Moong both are angiosperms.

Question b.
Onion and Coriander
Differences:

Onion	Coriander
i. It is a biennial plant.	i. It is an annual plant.
ii. It has monocotyledonous seed.	ii. It has dicotyledonous seeds.
iii. It has fibrous root.	iii. It has tap root but later on changes to fibrous root system.

Similarities:

Both are used in cooking.
Both are edible.
Both belongs to kingdom plantae.

Question c.
Leaves of banana and Leaves of mango
Answer:

Leaves of banana	Leaves of mango
i. It has parallel venation.	i. It has reticulate venation.
ii. It is very large in size.	ii. It is small in size.
iii. It is a monocotyledonous plant.	iii. It is a dicotyledonous plant.

Question d.
Coconut tree and Jowar stalk plant
Answer:
Differences:

Coconut tree	Jowar stalk plant
i. It is tall and has a thick stem	i. It is small and has a thin stem.
ii. It has strong root system.	ii. It has weak root system.
iii. Each and every part of tree is useful.	iii. Only seeds are useful.

Similarities:

Both are from same kingdom plantae.
Both are autotrophic.
Both are monocotyledonous plants.

4. Explain the following images in your own words.

Question a.

Answer:

Diagram A is of maize seed. It is a monocotyledonous seed and does not divide into two equal parts. The plant has fibrous root system.
Diagram B is of bean seed. It is a dicotyledonous seed and it divides into two equal parts. The plant has tap root system.

5. Describe the functions of various parts of a plant.

Question a.
Describe the functions of various parts of a plant.
Answer:
The functions of various parts of a plant are as below.
1. Root: (a) Fixation: It anchors the plant body to the soil, so helps in fixation, (b) Absorption: It absorbs water and nutrients from the soil, so helps in absorption, (c) Conduction: The root translocates water and mineral salts into the stem. (d) Storage: A certain amount of food is stored in the root which is utilized as it grows.
(e) Preventing soil erosion: It helps to bind the soil particles and prevent them from being blown away by wind or water.
2. Stem: (a) It supports and holds leaves, flower and fruits, (b) The stem conducts the water and minerals from roots to leaves and fruits, (c) It stores the food.
3. Leaves: (a) It synthesizes food for the plant, (b) Stomata, the tiny openings in the leaf help in gaseous exchange and are responsible for the process of transpiration.
4. Flower: It helps in pollination.
5. Fruit: (a) It protects the seed, (b) It helps in seed dispersal.
6. Seed: A new plant develops from it.

6. Certain properties are mentioned below. Find a leaf corresponding to each property and describe those plants.

Question a.
Certain properties are mentioned below. Find a leaf corresponding to each property and describe those plants.
leaves with smooth surface, leaves with rough surface, fleshy leaf, spines on leaf.
Answer:

Leaves with smooth surface: e.g. Banana leaf. It is large in size. It is closely rolled up one over the other. Together they look like a trunk but they form only an apparent trunk. It has parallel venation.
Leaves with rough surface: e.g. Hibiscus leaf. It has reticulate venation. Leaf margin is toothed.
Fleshy leaf: e.g. Jade plant, water hyacinth. It has fleshy, glossy and smooth leaves. They are coloured jade green and having a slightly red tinge towards the edge of leaves when exposed to higher level of light.
Spines on leaf: e.g. Opuntia, Ci/cas, kevda. Opuntia is a desert plant. Leaf is thick, fleshy and having spines on it.

7. Find the plant parts.

Question a.

Answer:

ROOT, ROOT CAP, ROOT HAIR, BUD, PETALS, STEM, RADICLE, FLOWER, LEAF, VEIN, CALYX, NODE, OVUM.

Class 7 Science Chapter 2 Plants Structure And Function Question Answer Activity:

Sketch various types of leaves in Paintbrush on the computer and save the sketches in a folder of your own name.

Class 7 Science Chapter 2 Plants: Structure and Function Important Questions and Answers

Plants Structure And Function Exercise Fill in the blanks:

Plants Structure And Function Class 7 Questions And Answers Question 1.
The part that grows from inside the seed towards the soil is called the …………….. .
Answer:
radicle

Plants Structure And Function Class 7 Question 2.
The part that grows above the soil from the seed is called the …………….. .
Answer:
plumule

Plants Structure And Function Question And Answer Question 3.
The part of the plant growing below the soil from radicle for support is called …………….. .
Answer:
root

Plants Structure And Function Class 7 Exercise Question 4.
The …………….. protects the root-tip from injuries.
Answer:
root cap

Plants Structure And Function Exercise Question 5.
Roots bearing hair like processes near the root tips are called …………….. .
Answer:
root hairs

Class 7 Science Chapter 2 Plants Structure And Function Question Answer Question 6.
Thread-like or fibre like roots arising from the stem are called ……………. .
fibrous roots

Question 7.
The stem grows above the soil from the …………….. of the sprouting seed.
Answer:
plumule

Question 8.
Leaves come out at the …………….. .
Answer:
nodes

Question 9.
The part of the stem between two nodes is called …………….. .
Answer:
inter node

Question 10.
The tip or the apical end of the stem is called a …………….. .
Answer:
bud

Question 11.
The broad, spread out part of the leaf is called the …………….. or …………….. .
Answer:
leaf blade, lamina

Question 12.
The tip of the leaf is called the …………….. .
Answer:
leaf apex

Question 13.
Leaves of some plants have a stalk called a …………….. .
Answer:
petiole

Question 14.
The portion of the leaf attached to the stem is called the …………….. .
Answer:
leaf base

Question 15.
Small leaf like structures near the leaf base is called …………….. .
Answer:
stipides

Question 16.
Flowers may have a long or a short stalk called …………….. .
Answer:
pedicel

Question 17.
One end of the pedicel is attached to the …………….. .
Answer:
stem

Question 18.
…………….. is a male reproductive organ of the flower.
Answer:
Androecium

Question 19.
…………….. is a female reproductive organ of the
Answer:
gynoecium

Question 20.
Androecium consists of …………….. .
Answer:
stamens

Question 21.
Gynoecium consists of …………….. .
Answer:
carpels

Question 22.
Seeds which get divided into two equal parts are called …………….. seeds.
Answer:
dicotyledonous

Question 23.
Seeds which do not divide into two equal parts are …………….. called seeds.
Answer:
monocotyledonous

Question 24.
Petals and other parts of the flower are supported on the …………….. .
Answer:
receptacle

Question 25.
Sepals are …………….. in colour.
Answer:
green.

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
1. Peepal	a. carpels
2. Maize	b. stamen
3. Androecium	c. parallel venation
4. Gynoecium	d. reticulate venation

Answer:

Column ‘A’	Column ‘B’
1. Peepal	d. reticulate venation
2. Maize	c. parallel venation
3. Androecium	b. stamen
4. Gynoecium	a. carpels

Question 2.

Column ‘A’	Column B’
1. Tap roots	a. stem
2. Fibrous roots	b. root
3. Radicle	c. monocotyledonous plants
4. Plumule	d. dicotyledonous plants

Answer:

Column ‘A’	Column B’
1. Tap roots	d. dicotyledonous plants
2. Fibrous roots	c. monocotyledonous plants
3. Radicle	b. root
4. Plumule	a. stem

Question 3.

Column A’	Column B’
1. Leaf-tip	a. petiole
2. Edge of leaf blade	b. leaf margin
3. Portion of leaf attached to stem	c. lamina
4. Stalk of leaf	d. leaf apex
	e. leaf base

Answer:

Column A’	Column B’
1. Leaf-tip	d. leaf apex
2. Edge of leaf blade	b. leaf margin
3. Portion of leaf attached to stem	e. leaf base
4. Stalk of leaf	a. petiole

Say whether True or False Correct and rewrite the false statements:

Question 1.
Stem grows from radicle.
Answer:
False. Stem grows from the Plumule

Question 2.
Leaf margins may be entire, dentate or lobed.
Answer:
True

Question 3.
The leaf blade of leaves in some plants is divided into many small parts called leaflets.
Answer:
True

Question 4.
Maize plant has reticulate venation.
Answer:
False. Maize plant has parallel venation

Question 5.
A carpel consists of stigma, style and ovary.
Answer:
True.

Question 6.
A stamen is made up of nodes and internodes.
Answer:
False. A stamen is made up of anther filament

Question 7.
The ovary develops into a fruit.
Answer:
True

Question 8.
Fertilized ovules form the seeds.
Answer:
True

Question 9.
A mango fruit contains many seeds.
Answer:
False. A mango fruit contains only one seed

Question 10.
A fruit like cashew have seed outside the fruit.
Answer:
True.

Question 11.
Leaves of some plants do not have a petiole.
Answer:
True

Question 12.
The peepal leaf has parallel venation.
Answer:
False. It has reticulate venation.

Find the odd one out:

Question 1.
Pea, Moong, maize, groundnut
Answer:
Maize – Its seed is monocotyledonous, while others have dicotyledonous seeds.

Question 2.
Cashew, apple, mango, chikoo
Answer:
Cashew – Its seed is outside the fruit, others have internal seeds.

Question 3.
Stigma, anther, style, ovary
Answer:
Anther – It is a part of androecium, while others are a part of gynoecium.

Question 4.
Petiole, vein, calyx, apex
Answer:
Calyx – It is a part of flower, whereas others are parts of leaf.

Question 5.
Aerial, stilt, runner, lobed
Answer:
Lobed – It is a type of leaf margin, while others are types of modified roots.

Answer the following in one or two sentences:

Question 1.
Which types of roots do the fenugreek, spinach and onion plants have?
Answer:

Fenugreek and spinach have tap roots with a few secondary roots whereas onion has fibrous root.
Fenugreek roots also have some nodules which contain nitrogen fixing bacteria.

Question 2.
What are called prop roots?
Answer:
Roots emerging from the trunk and branches of a banyan tree grow towards the soil. These roots are called prop roots.

Question 3.
What is called reticulate venation?
Answer:

A leaf is divided into two equal parts by a single mid-vein which lies along the midline of the leaf blade.
Secondary veins arise from the mid-vein. They are branched and form a network or reticulum. Such a type of venation is called reticulate venation.

Question 4.
What is called parallel venation?
Answer:
In a leaf all the veins are parallel, running from the leaf base to the leaf apex. Such a venation is called parallel venation.

Question 5.
What is pollination?
Answer:
After maturity, anthers burst and the pollen grains which are released fall on the stigma. This process is called pollination.

Question 6.
Why are the underground parts of plants like radish, carrot, beet and sweet potato thick, fleshy and swollen? Which parts of the plant are they?
Answer:
The underground parts of plants like radish, carrot, beet and sweet potato are thick, fleshy and swollen because they store food in the form of starch. These are the root part of the plant.

Distinguish between:

Question 1.
Tap roots and fibrous roots.
Answer:

Tap roots	Fibrous roots
1. Roots of some plants produce secondary roots that grow obliquely and spread far and wide in the soil. This type of root is called a tap root.	1. Thread like or fibre roots arising from the stem are called fibrous roots.
2. It is found in dicotyledonous plant.	2. It is found in monocotyle-donous plant.

Question 2.
Dicotyledonous seeds and monocotyledonous seeds.
Answer:

Dicotyledonous seeds	Monocotyledonous seeds
1. Seeds which get divided into two equal parts are called dicotyledonous seeds.	1. Seeds which do not divide into two equal parts are called monocotyledonous seeds.
2. Dicotyledonous seeded plants have tap root system.	2. Monocotyledonous seeded plants have fibrous root system.

Draw neat and labelled diagram for the following:

Question 1.
Tap root
Answer:

Question 2.
Parts of a leaf.
Answer:

Question 3.
Parts of stem
Answer:

Do as directed:

Question 1.
Certain properties are mentioned below. Find a leaf corresponding to each property and describe those plants.
Answer:

Leaves with smooth surface: e.g. Banana leaf. It is large in size. It is closely rolled up one over the other. Together they look like a trunk but they form only an apparent trunk. It has parallel venation.
Leaves with rough surface: e.g. Hibiscus leaf. It has reticulate venation. Leaf margin is toothed.
Fleshy leaf: e.g. Jade plant, water hyacinth. It has fleshy, glossy and smooth leaves. They are coloured jade green and having a slightly red tinge towards the edge of leaves when exposed to higher level of light.
Spines on leaf: e.g. Opuntia, Cycas, kevda. Opuntia is a desert plant. Leaf is thick, fleshy and having spines on it.

Use your brainpower!

Answer the following questions:

Question 1.
What would have happened if plants like tamarind, banyan and mango had fibrous roots?
Answer:
If plants like banyan, mango, tamarind had fibrous roots they would get uprooted and fall even with a little strong wind as the roots would not be able to support and anchor the trees firmly.

Question 2.
What will happen if the root-tip is injured?
Answer:

Root cap helps the root to grow downward It protects the sensitive part of the root and eases the movement of the root through the soil.
Injury of the root tip causes the root to grow randomly and it also may lead to injury of the sensitive part of the root.

Question 3.
Which types of roots do the fenugreek, spinach and onion plants have?
Answer:

Fenugreek and spinach have tap roots with a few secondary roots whereas onion has fibrous root.
Fenugreek roots also have some nodules which contain nitrogen-fixing bacteria.

Question 4.
Of what use to a plant are the insects flitting about around its flowers?
Answer:

The insects try to suck the nectar from the flowers and in that process the pollen grains stick to their legs.
When they sit on another flower the pollen grain stick to the stigma and the pollination takes place. Thus, these insects help in the pollination.

Observe the figure and answer the questions given.

Question a.
What is shown in the picture?
Answer:
The picture shows the arrangement of leaves on the stem.

Question b.
What arrangement is shown in (A), (B), and (C)?
Answer:
(A) Alternate (B) Opposite (C) Whorled

Question a.
Lable parts 1 to 6.
Answer:

Gynoecium or carpel
Corolla
Androecium (Stamen)
Ovary
Corolla
Pedicel

Question b.
Name the female reproductive part.
Answer:
Gynoecium

Question c.
Name the colourful part of the flower.
Answer:
Corolla

Question d.
Which part develops into fruit?
Answer:
Ovary

Question e.
Which pa pollination?
Answer:
The transfer of pollen grains from the anther to the stigma of flower is called pollination.

7th Std Science Questions And Answers: