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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.

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?

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:

• The Living World: Adaptations and Classification Class 7 Questions And Answers
• Plants: Structure and Function Class 7 Questions And Answers
• Properties of Natural Resources Class 7 Questions And Answers
• Nutrition in Living Organisms Class 7 Questions And Answers
• Food Safety Class 7 Questions And Answers
• Measurement of Physical Quantities Class 7 Questions And Answers
• Motion, Force and Work Class 7 Questions And Answers
• Static Electricity Class 7 Questions And Answers
• Heat Class 7 Questions And Answers
• Disaster Management Class 7 Questions And Answers

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:

1. Churning is the process of shaking up buttermilk to make butter.
2. Butter is essentially the fat of milk.
3. Churning physically agitates the cream until it ruptures the membrane surrounding milk fat
4. 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:

1. Allow sufficient space to work in, working area should be well lit and well ventilated to prevent the accumulation of alcoholic vapours.
2. Keep a fire extinguisher handy.
3. 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:

1. Stopper should be tightly fitted so that the solution does not leak out when the separating funnel is inverted.
2. 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:

1. The salt and water are mixed to give saltwater and can both be separated.
2. It can be separated by boiling saltwater.
3. Water can be obtained by condensation whereas the salt will be leftover.
4. 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:

1. Water is formed by a combination of hydrogen and oxygen but does not help combustion.
2. 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:

1. If a magnet is moved through this mixture all iron filings will stick to the magnet, remove them.
2. Add water to the remaining mixture, all salt will dissolve and then filter through filter paper.
3. Samolina will settle in filter paper.
4. 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:

1. Things are made from only one kind of matter or may be made from more than one kind of matter.
2. When a matter is made up of only one type of atoms it is called an element.
3. We find many elements in our surroundings.
4. But we also see many substances which are made up of two or more elements they are called compounds.
5. 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:

1. Any form of water that falls from the clouds is known as precipitation. Several forms → rain, snow, hail stones.
2. Yes, it is pure as water vapours condense to form rain.
3. 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:

1.  When we boil the water in a tea pot it boils and changes into gaseous state.
2. 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).

1. Sugar is a compound made from these three elements carbon, hydrogen, oxygen.
2. 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:

1. Carbon dioxide is a compound. It is a tasteless, odourless gas. It is a natural product of respiration.
2. Plants use this to produce food.
3. 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:

1. Winnowing
2. Filteration
3. Hand picking
4. Churning
5. 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:

1. A mixture is two or more elements or compounds which are combined physically but no chemical reaction occurs.
2. 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:

1. Cream from buttermilk.
2. Mud from muddy water.
3. Stones from grains.
4. Tea leaves from boiled tea.
5. Salt from water.
6. Kerosene and water.
7. Blood cells and plasma.
8. Ink from water

Answer:

1. Churning
2. Sedimentation and decantation
3. hand picking
4. filtration
5. distillation
6. separating funnel
7. Centrifugation
8. Chromatography

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

7th Std Science Questions And Answers:

• Cell Structure and Micro-organisms Class 7 Questions And Answers
• The Muscular System and Digestive System in Human Beings Class 7 Questions And Answers
• Changes – Physical and Chemical Class 7 Questions And Answers
• Elements, Compounds and Mixtures Class 7 Questions And Answers
• Materials We Use Class 7 Questions And Answers
• Natural Resources Class 7 Questions And Answers
• Effects of Light Class 7 Questions And Answers
• Sound: Production of Sound Class 7 Questions And Answers
• Properties of a Magnetic Field Class 7 Questions And Answers
• In the World of Stars Class 7 Questions And Answers

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:

1. The region around a magnet where the magnetic force acts on an object is called a magnetic field.
2. The magnetic field around a magnet can be shown by means of magnetic lines of force.
3. The intensity of the magnetic field can be obtained from the number of lines of force.
4. 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.
5. A magnetic field is the magnetic effect of electric currents and magnetic materials.
6. The magnetic field at any given point is specified by both the direction and the magnitude.
7. Magnetic fields are produced by electric current.

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

1. The magnetic compass is the most familiar compass type.
2. 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.
3. 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:

1. The region around a magnet where the magnetic force acts on an object is called a magnetic field.
2. The magnetic field around a magnet can be shown by means of magnetic lines of force.
3. The intensity of the magnetic field can be obtained from the number of lines of force.
4. 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.
5. A magnetic field is the magnetic effect of electric currents and magnetic materials.
6. The magnetic field at any given point is specified by both the direction and the magnitude.
7. 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:

1. The merchants of older times used a magnet whose north-south side was known.
2. When the magnet is freely suspended, the north pole of the magnet settles in the direction of the geographic north pole of the earth.
3. This is how the merchants come to know the directions while travelling.
4. The idea for using loadstone in a compass first appeared in China.
5. The first compass were made of loadstone, a naturally magnetised ore of iron.
6. The Chinese used “south pointing spoon” which when thrown upon the ground comes to rest pointing at the south.
7. Then the transition was made from loadstone spoons to iron needles.
8. 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.
9. It was called floating compass.
10. In the twentieth century, liquid filled magnetic compass began to appear.
11. 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:

1. 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.
2. 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:

1. Magnets are made from alloys of iron, cobalt and nickel.
2. 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:

1. 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.
2. 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.
3. 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:

1. A bar magnet kept on the cardboard arranges the iron fillings in line because of the ‘magnetic lines of force’.
2. These magnetic lines gauge the intensity of the bar magnet.
3. 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.
4. 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:

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

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

1. A freely suspended magnet settles in the north- south direction always.
2. Magnets attract objects of iron, cobalt and nickel.
3. The force of attraction of a magnet is greater at its poles than in the middle.
4. Like poles of two magnets repel each other.
5. Opposite poles of two magnets attract each other.
6. 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:

1. Magnetic lines of force start from the north pole and end at the south pole.
2. They are continuous through the body of magnet. These are imaginary lines.
3. Magnetic lines of force can pass through iron more easily than air
4. The number of magnetic lines force determines the strength of the magnetic field at a particular point.
5. Two magnetic lines of force do not intersect each other.
6. 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:

1. Gilbert gave a scientific explanation that earth itself is a gigantic magnet.
2. The north pole of a freely suspended magnet settles in the direction of the geographic north pole of the earth since unlike poles attract.
3. It means that the south pole of some gigantic magnet must be near the geographic north pole of the earth.
4. In other words, the thing we call Earth’s geographic north pole is actually the south pole of the magnet inside the earth.
5. 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:

1. The region around the magnet where the magnetic force acts is known as the magnetic field.
2. It has its influence over a certain distance where these magnetic lines of force act.
3. 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:

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

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

1. 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.
2. Neatly wrap some insulated copper wire around an iron nail.
3. The more wires you wrap around the nail, the stronger will be the electromagnet.
4. Attach a battery to the wire, an electric current will begin to flow and the iron nail will become magnetised.
5. 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:

1. It is a vector quantity. Because a magnetic field is the magnetic effect of electric current and magnetic materials.
2. 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:

1. The magnetic force, is a consequence of the electromagnet force, one of the four fundamental forces of nature.
2. It occurs whenever objects interact in which there is charge in motion, eg. compass, a motor.
3. 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:

1. Magnet has the property to attract things made of iron, cobalt, nickel.
2. A magnet has magnetic field which is invisible but it has the property of attracting, pulling other
3. ferromagnetic material such as iron, cobalt and nickle.
4. So if we bring any iron, nickle objects near it, they will be pulled toward the magnet.
5. The real test is repulsion.
6. 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:

1. Freely suspended magnet does not point to north, but aligns to earth’s magnetic field axially ie – north-south.
2. The magnetic pole of the earth is different from true north (geographic north) because the magnetic north is constantly changing.
3. 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.
4. 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:

• Cell Structure and Micro-organisms Class 7 Questions And Answers
• The Muscular System and Digestive System in Human Beings Class 7 Questions And Answers
• Changes – Physical and Chemical Class 7 Questions And Answers
• Elements, Compounds and Mixtures Class 7 Questions And Answers
• Materials We Use Class 7 Questions And Answers
• Natural Resources Class 7 Questions And Answers
• Effects of Light Class 7 Questions And Answers
• Sound: Production of Sound Class 7 Questions And Answers
• Properties of a Magnetic Field Class 7 Questions And Answers
• In the World of Stars Class 7 Questions And Answers

Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 4 Disaster Management Notes, Textbook Exercise Important Questions and Answers.

Std 6 Science Chapter 4 Disaster Management Question Answer Maharashtra Board

Class 6 Science Chapter 4 Disaster Management Question Answer Maharashtra Board

1. What are the emergency contact numbers of the following:

Question a.
Police Control Room
Answer:
100

Question b.
Fire brigade
Answer:
101

Question c.
Ambulance
Answer:
102

Question d.
National level single emergency number for disaster relief
Answer:
108

2. What first aid will you provide in the following situations?
a. Dog bite
b. Scratches/Bleeding
c. Bums/Scalds
d. Snakebite
e. Sunstroke

Question a.
Dog bite
Answer:
First aid is some immediate aid given to a victim or patient before medical treatment is available.

1. Wash the wound with a soap solution.
2. Cover the wound with a clean and dry cloth.
3. Get a doctor’s help.

Question b.
Scratches / Bleeding
Answer:

1. Make the person sit or lie down comfortably.
2. Clean the bleeding part of the bodywith water.
3. Keep it above the level of the heart.

Question c.
Bums/scalds
Answer:

a. Minor bums

1. The injured part should be washed with water or held underwater.
2. Give the victim water to drink.
3. Clean the wounds using a cotton swab soaked in an antiseptic solution.
4. Do not apply oily ointments.
5. Cover the wound using dry dressings.

b. Serious bums

1. Give emotional support.
2. Cover the wound with sterilised cloth.
3. Remove jewellery, shoes etc. if easily possible.
4. Do not touch or burst the blisters on the skin.
5. Do not apply oily ointments.
6. Do not try to remove the cloth if it is struck to the burnt skin.
7. If the patient is conscious give water to drink but avoid tea or coffee or other stimulating drinks. Get medical aid at once.

Question d.
Snakebite
Answer:

1. Wash the wound with water.
2. Give emotional support to the patient.
3. Tie a cloth tightly above the wound.
4. Get immediate medical help.

Question e.
Sunstroke
Answer:

1. Take the patient to a cool place or in the shade.
2. Sponge the whole body with cold water.
3. Place a cloth soaked in cold water on the neck.
4. Give plenty of water or liquids like sherbets to drink.
5. If the patient feels like vomiting make him prone i.e. on his/her abdomen with the head turned to one side.
6. Get medical help or shift the patient to a hospital.

3. Write the causes of the following:
a. Floods
b. Forest fires
c. Landslides/building collapse
d. Storms
e. Earthquakes

Question a.
Floods:
Answer:

1. 1. Floods is a frequently occurring natural disaster in all parts of the world.
   2. Due to excessive rains in the same place, a river overflows its banks causing a flood.
   3. The water drainage system in big cities falls short when there is heavy rainfall, resulting in choking of gutters and drainage lines.
   4. Water overflows on to the roads and surrounding houses.

Question b.
Forest fires:

1. Forest fire is an uncontrolled fire in a forest, pasture or grasslands due to natural or man-made causes.
2. Natural causes of forest fire can be lightning, volcanic eruptions, friction amongst branches of trees in extremely hot and dry weather.
3. Man-made causes of forest fires are clearing land by burning which sometimes goes out of control.
4. Campers and hikers sometimes leave behind a potential source of ignition like a lighted cigarette or a campfire.

Question c.
Landslides/building collapse:
Answer:

1. Landslide causes due to erosion, slope movement in the downward direction, prolonged rainfall and seepage, vibration caused by earthquakes, deforestation, river erosion.
2. Building collapses: Bad design, faulty construction, foundation failure or weak foundation, extraordinary loads, earthquakes, rampant and irregular constructions.

Question d.
Storms:
Answer:
The formation of high and low air pressure belts in the atmosphere causes changes in weather resulting in strong winds or storms.

Question e.
Earthquakes:
Answer:

1. Movements in the interior of the earth release tremendous amount of energy.
2. This causes seismic waves leading to movement of the earth’s surface like tremors, shaking, cracking up.
3. Such vibrations or quaking in the earth’s crust is known as earthquake.
4. Man-made causes like mining, construction of big dams can also lead to earthquakes.

4. Answer the following questions.

Question a.
What is meant by ‘disaster’?
Answer:
A sudden event that causes large-scale damage to life, property and social aspects of a nation or society is called a disaster.

Question b.
What are the types of disasters?
Answer:
Disasters are of two types: Natural disasters and man-made disasters.

Question c.
What is meant by disaster management’?
Answer:
Taking steps to prevent disasters, making plans to face disasters and developing the capacity for that is called disaster management.

Question d.
Which are the main components of disaster management?
Answer:
Emergency planning and implementation of disaster management work are the main components of disaster management. Community participation is close, related to disaster management.

5. Find out about the work of a ‘Sarpa-mitra’.

Question a.
Find out about the work of a ‘Sarpa-mitra’.
Answer:

1. A sarpa-mitra is a friend of snakes, a person who is trained to protect, save and safeguard snakes.
2. Whenever there is a phone call from police or citizens informing the sarpa-mitras about snake sightings, they immediately rush to the situation and rescue the snake that would have been killed at the hands of people.
3. Sarpa-mitra are well trained to handle snakes by capturing them, keeping them in baskets or bags before releasing them in the wild.
4. They are in contact with the Police Department and Forest Department for rehabilitation of snakes.
5. Sarpa-mitra are also trained to perform primary first aid to snake bite victims before they are moved to hospitals.
6. Thus, the sarpa-mitra do a commendable job of saving snakes, saving human life without any monetary gains, but for sheer love of snakes.

6. Find out what a first aid kit / box contains.

Question a.
Find out what a first aid kit / box contains.
Answer:
1. First aid kit/box is a necessity at home, workplace, travelling, schools, etc.
2. It contains a cotton roll, sterilized dressing, a pair of scissors, Dettol or Savlon, Dettol soap, adhesive plaster, tablets like Crocin, necessary medicines – painkiller, Tincture iodine, Electrolyte powder, ear/eye drops, Potassium Permanganate crystals, Bumol ointment for cramps.

7. Suggest remedial measures for dealing with natural or man-made disasters.

Question a.
Suggest remedial measures for dealing with natural or man-made disasters.
Answer:

1. Fire: Use a fire extinguisher. Call the fire brigade. Run to a safe exit.
2. Building collapse: Evacuate the building immediately, seek shelter in other safe places. Call the fire brigade or rescue team. First aid should be given to injured people.
3. Road accident: Call the ambulance immediately. Give first aid if possible.
4. Flood: Do not linger in houses or areas near river banks. Seek shelter in other safe places. Move to safer places at a greater height. Do not step into water currents or drive a vehicle into them.
5. War: Take shelter in relief camps. Provide assistance in the rescue mission.
6. Bomb explosions: Take shelter in relief camps/safe place. Immediately call the police. Be alert and do not touch the unattended objects.
7. Earthquakes: Run to a safe place. Hide below a table.and do not use elevators. Use a staircase.
8. Deluge: Take the warnings and signals from the Meteorological Department keep away from river banks and low-lying areas. Take shelter in relief camps.
9. Storm: Remain in a safe place. Unplug all electrical devices. Take instructions given to people by meteorological department do not take shelter in dilapilated structures and under trees.
10. Tsunami: Move to a safer place, stay alert.
11. Drought: Save water, take care of people and cattle.
12. Landslide: Landslide may be caused due to excessive rains or cloudbusrt in hilly areas. Do not take shelter at the foot of a hill.

Activity:

Question 1.
Compile information about measures taken for disaster management in your school.

Question 2.
Make posters, advertisements, banners about disaster management.

Question 3.
Find out the people/organisations that provide aid during a disaster. Obtain their phone numbers, addresses, etc.

Class 6 Science Chapter 4 Disaster Management Important Questions and Answers

Fill in the blanks:

Question 1.
In 1993, many people died due to the earthquake at ……………… in Latur district.
Answer:
Killari

Question 2.
Even today, people of shudder at the memory of ……………… 26 July, 2005.
Answer:
Mumbai

Question 3.
In November 2015, many people died due to flooding caused by heavy rains in ……………… .
Answer:
Tamil Nadu

Question 4.
Movements in the interior of the earth release tremendous amounts of ……………… .
Answer:
energy

Question 5.
Vibrations or ……………… in the earth’s crust is known as earthquake.
Answer:
quaking

Question 6.
Man-made causes like ……………… and construction of big dams can also lead to earthquakes.
Answer:
mining

Question 7.
A frequently occurring natural disaster in all parts of the world is ………………. .
Answer:
floods

Question 8.
Forest fires spread at a ……………… speed.
Answer:
tremendous

Question 9.
Landslides occur in hilly areas due to a ……………… .
Answer:
cloudburst

Question 10.
To get protection from fire, use ……………… .
Answer:
fire extinguisher

Match the following. 

Question 1.

Column ‘A’	Column ‘B’
1. July 2005	a. Floods in Tamil Nadu
2. July 2014	b. Floods in Mumbai
3. November 2015	c. Earthquake in Latur
4. 1993	d. Landslide in Pune

Answer:

Column ‘A’	Column ‘B’
1. July 2005	b. Floods in Mumbai
2. July 2014	d. Landslide in Pune
3. November 2015	a. Floods in Tamil Nadu
4. 1993	c. Earthquake in Latur

State whether the following statements are True or False. If false, correct them.

Disaster Management Class 6  Question 1.
In 1993, many people died due to the earthquake at Malin in Pune district.
Answer:
False: In 1993 many people died due to the earthquake at Killari in Latur district.

Disaster Management Class 6 Exercise Question 2.
Disaster Management Class 6 ExerciseEven today, people of Mumbai shudder at the memory of July 2007.
Answer:
False: Even today people of Mumbai shudder at the memory of July 2005.

Class 6 Science Chapter 4 Disaster Management  Question 3.
Increased risk due to high density of population in a limited area can cause disaster.
Answer:
True

4 Disaster Management Exercise Question 4.
Earthquakes cause huge loss of life and property.
Answer:
True

Question 5.
Forest fire is a controlled fire in a forest, pasture or grassland.
Answer:
False: Forest fire is an uncontrolled fire in a forest, pasture or grassland.

Question 6.
Storms cause no disruption of electric supply.
Answer:
False: Storms cause disruption of electric supply.

Question 7.
Community participation is closely related to disaster management.
Answer:
True

Question 8.
National Disaster Management Authority was established in 2008.
Answer:
False: National Disaster Management Authority was established in 2005.

Question 9.
During a disaster, keep watching movies on TV.
Answer:
False: During a disaster keep watching news bulletin on TV.

Question 10.
In case of a disaster, use the website www. imd.gov.in
Answer:
True

Answer the following in one sentence:

Question 1.
What are man-made causes of earthquakes?
Answer:
Mining, construction of big dams can lead to earthquakes.

Question 2.
What are forest fires?
Answer:
A forest fire is an uncontrolled fire in a forest, pasture or grassland due to natural or man-made causes.

Question 3.
State the website to seek government’s help during disaster.
Answer:
To seek government’s help during a disaster we can log on to xvww.imd.gov.in

Question 4.
Where should we take shelter during floods?
Answer:
We should seek shelter in safe places especially safer places at great heights.

Question 5.
What is sunstroke?
Answer:
When we work in the sun continuously for a long time, the body loses a lot of water and minerals. Hence, the person experiences sunstroke.

Question 6.
Name some poisonous snakes.
Answer:
Some poisonous snakes are cobras, kraits, vipers and sea snakes.

Question 7.
What should we do when we come across a snake?
Answer:
When we come across a snake we should contact a sarpa-mitra.

Question 8.
What is first aid?
Answer:
Immediate aid given even before medical treatment is available on facing a disaster or accident is first aid.

Answer the following questions briefly:

Question 1.
What are the effects of an earthquake?
Answer:
The effects of an earthquake are:

1. Destruction of infrastructure i.e buildings, bridges, roads, railway tracks.
2. Change in the direction of the flow of river.
3. Huge loss of life and property.

Question 2.
What are the effects of floods on people?
Answer:

1. There is a huge loss of life and property.
2. Soil erosion
3. Destruction of standing crops.
4. After-effects of floods, like spread of diseases and epidemics affecting the health of the people.

Question 3.
What are the effects of storms?
Answer:

1. Great damage in the storm affected region.
2. Tremendous losses to life and property.
3. Disruption of electric supply.
4. Disruption of transport and communication.

Question 4.
What are the effects of forest fires?
Answer:

1. Great damage to natural wealth and bio-diversity.
2. Pollution of air.

Question 5.
What preventive measures should we take to protect us from fire?
Answer:
To get protection from fire, use fire extinguishers in public places like schools, hospitals, railway stations.

Question 6.
What first aid can be provided to a person if he is bleeding?
Answer:
If a person is bleeding, first make him sit or lie down comfortably. Clean the bleeding part of the body with water and keep it above the level of the heart.

Give scientific reasons:

Question 1.
Why should a dog bite victim get an injection of the anti-rabies vaccine?
Answer:
In a dog bite, there is a risk of infection of rabies through the blood, hence anti-rabies injection is given to the patient.

Question 2.
During a disaster if possible we should take shelter in relief camps.
Answer:
Relief camps provide medicines, food packets, drinking water and first aid. Since these things help victims to restart, people should take shelter in relief camps during a disaster.

Question 3.
During disaster use battery operated radios and mobile.
Answer:
During disaster, many times there is disruption of electricity, hence battery operated mobiles and radios are convenient.

Can you tell?

Question 1.
What event do you see in these pictures?
Answer:
In this picture we see –
(a) earthquakes
(b) drought
(c) flood
(d) fire
(e) storm
(f) volcanic eruptions.

Question 2.
What would you have done in these situations?
Answer:
In these situations I would have tried to save my life. (Answer:wers may vary)

Question 3.
Have you experienced such a situation yourself?
Answer:
No. (Answer:wers may vary)

Question 4.
Why do these events occur?
Answer:
This events are disasters and some occur naturally and some are man-made.

Question 5.
According to you, what can be done to deal with such a disaster?
Answer:
To deal with such a disaster, take help of some elders or ask for help immediately. Be alert and use first-aid / get some immediate aid even before medical treatment becomes available.

Use your brainpower!

Question 1.
What disaster can occur in school or on the way to school?
Answer:
1. Disasters that can occur in school: Fire in the school building, experience tremors of earthquake, school building collapses, slab in one of the classroom collapses, getting injured while playing, getting an electric shock.
2. Disasters that can occur on way to school: You meet with an accident while crossing the road or school bus meets with an accident. Area near school gets flooded.

Classify the following disasters as man-made or natural.
(fire, earthquake, leakage of chemical gases, storms, floods, tsunami, bomb explosions, collapse of a building, war, forest fire)
Answer:

Man-made disasters	Natural disasters
1. Fire	1. Earthquake
2. Leakage of chemical gases	2. Storms
3. Bomb explosion	3. Floods
4. Collapse of a building	4. Tsunami
5. War	5. Forest fire
6. Forest- fire

Can you tell?

Question 1.
How many children are there in your class at present?
Answer:
There are 50 children in my class at present. (Answers may vary)

Question 2.
What would happen if five times this number sat in your class?
Answer:
If five times this number sat in my class, the classroom would be crowded. There will be utter chaos.

Question 3.
Which kind of disaster can occur in an extremely crowded places?
Answer:
In an extremely crowded place there can be panic in the classroom, stampede while going out of the classroom, breathless among fellow students.

6th Std Science Questions And Answers:

• Natural Resources – Air, Water and Land Class 6 Questions And Answers
• The Living World  Class 6 Questions And Answers
• Diversity in Living Things and their Classification Class 6 Questions And Answers
• Disaster Management Class 6 Questions And Answers
• Substances in the Surroundings – Their States and Properties Class 6 Questions And Answers
• Substances in Daily Use Class 6 Questions And Answers
• Nutrition and Diet Class 6 Questions And Answers
• Our Skeletal System and the Skin Class 6 Questions And Answers
• Motion and Types of Motion
• Force and Types of Force Class 6 Questions And Answers

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:

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

Question b.
Water is a universal solvent.
Answer:

1. 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.
2. 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:

1. It is a fluid substance because it can flow.
2. It does not have its own shape, it takes the shape of a container in which it is kept.
3. It has a definite volume.
4. It is a transparent liquid and it has no colour.
5. It is tasteless and odourless.
6. 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:

1. The properties of the various ingredients of soil can be determined by soil testing.
2. During soil testing, the soil is examined for colour, texture and the proportion of organic matter in it.
3. 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:

1. Air is useful as a medium for the transmission of sound. Density of the air changes with temperature.
2. 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:

1. Due to anomalous behaviour of water, when you cool water below 4°C, the volume of the water increases.
2. 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.
3. 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:

1. 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.
2. As a result, the pressure of the air in the syringe is lowered.
3. 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:

1. Due to the ice cubes in the glass, the air surrounding the glass cools down.
2. As the water vapour in this air cools down, it condenses and gets transformed into water.
3. 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:

1. During the dawn (early morning) when the temperature of air is low, its capacity to hold the vapour is less.
2. 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:

1. In the afternoon, when the temperature of the air is high, the capacity of the air to hold the moisture also increases.
2. 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:

1. The earth receives energy from the sun. This energy is reflected by the earth in the form of heat.
2. 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.
3. 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:

1. The density of air changes due to change in its temperature.
2. 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:

1. When water freezes means it transforms into the soild state therefore its volume increases.
2. When volume increases its density decreases
3. 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:

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

Question 10.
Sandy soil is less fertile.
Answer:

1. Sandy soil is made up of large particles and these particles of sandy soil are made of the mineral called silicon dioxide.
2. 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:

1. Air is a mixture of gases.
2. Air has mass and volume.
3. It spreads in all directions.
4. It exerts pressure.
5. 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.

1. Soil pH less than 6 or higher than 8.
2. Low proportion of organic matter.
3. No proper drainage of water.
4. Repeated cultivation of the same crop.
5. Continuous use of saline water.
6. 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.

1. China clay (Kaolin): (a) It is white in colour, (b) It is used to make crockery, bathroom tiles, tanks, laboratory apparatus, masks, jars etc.
2. Shadu soil: (a) It is whitish in colour, (b) It is used for making statues and idols.
3. Terracotta soil: (a) This soil is red in colour, (b) Decorative articles and pots used for growing plants are made from this soil.
4. 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:

1. Sea water is salty due to minerals in it. Whereas it is absent in well or a lake water.
2. 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:

1. When the temperature increases, the pressure of air also increases.
2. For example, as the air warms up, the molecules in the air become more active.
3. 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:

1. When an uncorked inverted empty bottle is kept slanting in the water container bubbling sound will be heard.
2. Air bubbles come out from the empty bottle and water enters the bottle.
3. Empty bottle is actually not empty but it is occupied by air.
4. 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:

1. Due to anomalous behaviour of water, in cold countries, water changes to ice.
2. Due to this change, its volume increases and density decreases. So ice floats on water.
3. 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:

1. Sandy soil has large sized particles. It has weak structure due to less organic matter and large spaces between them.
2. 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.

1. The particles of silt soil is of medium size.
2. Silt soil is much more ploughable than clayey soil.
3. It contains large proportions of organic material.
4. 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:

• The Living World: Adaptations and Classification Class 7 Questions And Answers
• Plants: Structure and Function Class 7 Questions And Answers
• Properties of Natural Resources Class 7 Questions And Answers
• Nutrition in Living Organisms Class 7 Questions And Answers
• Food Safety Class 7 Questions And Answers
• Measurement of Physical Quantities Class 7 Questions And Answers
• Motion, Force and Work Class 7 Questions And Answers
• Static Electricity Class 7 Questions And Answers
• Heat Class 7 Questions And Answers
• Disaster Management Class 7 Questions And Answers

Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 8 Our Skeletal System and the Skin Notes, Textbook Exercise Important Questions and Answers.

Std 6 Science Chapter 8 Our Skeletal System and the Skin Question Answer Maharashtra Board

Class 6 Science Chapter 8 Our Skeletal System and the Skin Question Answer Maharashtra Board

1. Fill in the blanks with the proper word. 

Question a.
The place where two or more bones are connected is called a …………… .
Answer:
joint

Question b.
Cells of epidermis contain a pigment called ………… .
Answer:
melanin

Question c.
…………… and ……………. are the two layers of the human skin.
Answer:
epidermis, dermis

Question d.
The human skeletal, system is divided into ………….. parts.
Answer:
two

2. Match the pairs.

Question a.

Column ‘A’	Column ‘B’
1. Ball and socket joint	a. Knee
2. Hinge joint	b. Wrist
3. Gliding joint	c. Shoulder

Answer:

Column ‘A’	Column ‘B’
1. Ball and socket joint	c. Shoulder
2. Hinge joint	a. Knee
3. Gliding joint	b. Wrist

3. Right or wrong? If wrong, write the correct sentence. 

Question a.
Bones are soft.
Answer:
Wrong: Bones are hard.

Question b.
The human skeleton protects the internal organs.
Answer:
Right

4. Put a [✓] mark at the proper places.

Question a.
The system which gives our body. a definite shape to
(a) Excretory system [ ]
(b) Respiratory system [ ]
(c) Skeletal system [ ]
(d) Circulatory system [ ]
Answer:
(c) Skeletal system [✓]

Question b.
The ………… joint is seen in fingers and toes.
(a) Hinge joint [ ]
(b) Ball and socket joint [ ]
(c) Immovable joint [ ]
(d) Gliding joint [ ]
Answer:
(a) Hinge joint [✓]

5. Answer the following questions in your words.

Question a.
What are the functions of your skin?
Answer:
The functions of the skin are :

1. Protects the internal parts of the body like muscles, bones, organ systems etc.
2. Help to preserve the moisture in the body.
3. Synthesizing Vitamin D.
4. Regulates body temperature by releasing sweat.
5. Gives protection from heat and cold.
6. Functions as the sensory organ of touch

Question b.
What should you do to keep the bones strong and healthy?
Answer:
To keep the bones strong and healthy:

1. We should include calcium and phosphrous rich food in our diet.
2. We also include vitamin D rich food in our diet.
3. We get these from milk, milk products, leafy vegetables, meat and exposure to sunlight.
4. We should exercise regularly.

Question c.
What are the functions of human skeletal system?
Answer:
The functions of human skeletal system are:

1. Gives a definite shape to the body.
2. Provides support to the body.
3. Protects the delicate organs inside the body.

Question d.
Which are the various reasons due to which our bones might break?
Answer:
The bones in our body might break due to:

1. Lack of calcium and phosphorous.
2. Due to fracture because of an accident or a fall.
3. Lack of proper nutrition.
4. Due to deficiency of Vitamin D.

Question e.
What are the different types of bones? How many types are there? Give example of each.
Answer:
There are four types of bones in our body:

Types of Bone	Example
1. Flat bones	Sternum in the chest
2. Small bones	Stirrup in each ear
3. Irregular bones	Vertebra posterior (back side) of the body
4. Long bones	Femur or thigh bone

Types of Bone Example

1. Flat bones Sternum in the chest
2. Small bones Stirrup in each ear
3. Irregular bones Vertebra posterior (back side) of the body
4. Long bones Femur or thigh bone

6. What will happen if?

Question a.
There are no joints in our body.
Answer:
If there are no joints in our body, we will be standing like a tree without any movement, we can move only because of joints.

Question b.
There is no melanin pigment in our body.
Answer:
We will not have protection from ultraviolet rays. Our skin will become whitish.

Question c.
Instead of 33 vertebras in our body, we had one single and straight bone.
Answer:
We cannot bend down at our will.

7. Draw diagrams.

Question a.
Types of joints.
Answer:

Question b.
Structure of skin
Answer:

Activity:

Question 1.
Collect pictures of the different parts of the human skeletal system and paste them on chart paper. Write the functions of
each, too.

Question 2.
Collect the pictures, newspaper cuttings, etc. which show the skeletal systems of various animals and observe the differences between them.

Class 6 Science Chapter 8 Our Skeletal System and the Skin Important Questions and Answers

Choose the correct alternative:

Question 1.
The ………………….. protects the brain.
(a) skull
(b) rib cage
(c) spine
(d) none of above
Answer:
(a) skull

Question 2.
X-rays were discovered by …………………..  .
(a) Sir C.V.Raman
(b) Galileo
(c) Sir Isaac Newton
(d) Roentgen
Answer:
(d) Roentgen

Question 3.
The bones of ………………….. are immovable.
(a) hand
(b) leg
(c) spine
(d) skull
Answer:
(d) skull

Question 4.
We can move the bones of ………………….. in a 360° angle.
(a) elbow
(b) knee
(c) shoulder
(d) wrist
Answer:
(c) shoulder

Question 5.
Our body temperature usually remains constant at ………………….. °C.
(a) 32
(b) 35
(c) 37
(d) 40
Answer:
(c) 37

Question 6.
The part of the skin which maintains body temperature is ………………….. .
(a) Epidermis
(b) Dermis
(c) Subcutaneous layer
(d) Network of blood vessels and nerve fibers
Answer:
(c) Subcutaneous layer

Fill in the blanks:

Question 1.
Except for the …………….., none of the bones of the skull can move.
Answer:
lower jaw

Question 2.
The spinal cord originates from the …………… .
Answer:
brain

Question 3.
The longest and the strongest bone in the human body is …………… .
Answer:
femur

Question 4.
…………….. is the smallest bone in our body.
Answer:
stirrup

Question 5.
The vertical, flat bone in the chest is called the ……………… .
Answer:
sternum

Question 6.
The …………… joint moves in a 180° angle.
Answer:
hinge

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
1. Skull	a. 25 bones
2. Rib cage	b. 6 bones
3. Spine	c. 22 bones
4. Both ears	d. 33 bones

Answer:

Column ‘A’	Column ‘B’
1. Skull	c. 22 bones
2. Rib cage	a. 25 bones
3. Spine	d. 33 bones
4. Both ears	b. 6 bones

Question 2.

Column ‘A’	Column ‘B’
1. Lower jaw	a. Movable joint
2. Ears	b. Femur
3. Thigh	c. Movable joint in skull
4. Elbow	d. Smallest bone

Answer:

Column ‘A’	Column ‘B’
1. Lower jaw	c. Movable joint in skull
2. Ears	d. Smallest bone
3. Thigh	b. Femur
4. Elbow	a. Movable joint

Right or Wrong? If wrong, write the correct answers:

Question 1.
The spine is a part of the appendicular skeleton.
Answer:
Wrong: The spine is a part of the axial skeleton.

Question 2.
Ankle joints are gliding joints.
Answer:
Right

Question 3.
All the skull joints are immovable.
Answer:
Wrong: Except lower jaw, all the skull joints are immovable.

Question 4.
The skin maintains normal body temperature.
Answer:
Right

Answer in one word:

Question 1.
The part which protects the heart and lungs.
Answer:
Rib cage

Question 2.
Ali falls down and his elbow is broken.
Answer:
Fracture

Question 3.
The image which spots the broken bone.
Answer:
X-ray

Question 4.
The biotic component of our body.
Answer:
Bone cell

Question 5.
The part which protects the vertebral column.
Answer:
Spine

Question 6.
The part which connects the bone in our body.
Answer:
Ligament

Question 7.
The organ which helps us to sense whether something is hot or cold.
Answer:
Skin

Question 8.
The pigment which gives colour to the skin.
Answer:
Melanin

Can you tell?

Question 1.
What is a fracture? How will you help a friend who has met with an accident and fractured his leg?
Answer:
Fracture is a crack or break in a bone. Fracture may occur due to accident or fall from height or injury. If my friend’s leg is fractured, then. I would –

1. Ask him to prevent any movement of the fractured part.
2. Get immediate medical help.
3. Take the x-ray image of the fractured or swollen part.
4. An x-ray image shows the exact spot where the bone is broken. This will help in providing proper treatment.

Question 2.
What are the properties of bones?
Answer:
The properties of bones are:

1. Bones are hard and not flexible.
2. Bone cells are composed of two main constituents:
   • Bone cells are biotic components.
   • Calcium carbonate, calcium phosphate, minerals and salts are abiotic components.
3. Calcium imparts strength to bones.
4. As we grow the size and length of bones increases upto a certain limit.

Question 3.
What is human skeletal system? How is it divided?
Answer:

1. All the bones together form a framework or a skeleton.
2. All the bones of the body along with cartilage together form the skeletal system.
3. The human skeletal system can be divided into two parts – the axial skeleton and the appendicular skeleton.
4. The axial skeleton consists of the skull, the spine and the rib cage. These are situated symmetrically along the central axis.
5. The appendicular skeleton consists of the bones of arms and legs on either side of the central axis.

Question 4.
What is a joint? What are it’s types?
Answer:
Joints are places where two or more than two bones are connected to each other.

Question 5.
Describe the structure of skin.
Answer:

1. Human skin is made up of two main layers- outermost layer, epidermis and layer below it called dermis.
2. Below dermis there is a network of blood vessels and nerve fibers.
3. Under this layer there is a subcutaneous layer, which maintains body temperature.
4. The epidermis has various layers.
5. There are sweat glands in the skin which secrete sweat.

Question 6.
Write a short note on melanin.
Answer:

1. Melanin is a pigment present in the cells of epidermis.
2. Melanin is synthesized in certain glands in the skin.
3. The percentage of melanin decides the fairness or darkness of the skin.
4. Melanin protects our skin and the inner parts from ultraviolet sunrays.

Use your brain power!

Question 1.
Which colour of the skin will give greater protection from sun’s rays?
Answer:
Darker colour will give greater protection.

Give scientific reasons:

Question 1.
We are able to bend down at our will.
Answer:

1. 33 bones of the spine are placed straight one above the other.
2. They are arranged flexibly.
3. Their flexibility allows us to bend down at our will.

Question 2.
Calcium is an important mineral.
Answer:

1. Calcium imparts strength to our bones.
2. If we are calcium deficient, possibility of bone fracture during a fall or an accident increases.
3. Hence, calcium is an important mineral.

Question 3.
Sweating helps to lower the body temperature.
Answer:

1. In the hot sun, the temperature of the skin rises.
2. The sweat is released.
3. The heat required for the evaporation of sweat is drawn from the body itself.
4. Hence, sweating lowers the body temperature.

Question 4.
Some people have jet black hair, while others have brown or reddish hair.
Answer:

1. It is melanin that determines the colour of our hair.
2. Jet black hair is due to pure melanin.
3. Brown hair is due to sulphur in the melanin.
4. Reddish hair is due to iron in the melanin.

Question 5.
Observe and discuss:
Your grandmother has wrinkles on her skin.
Answer:

1. As we grow older, the proportion of fat beneath the skin reduces.
2. However, previously tout skin does not shrink.
3. This causes wrinkles on the face of older people.

What will happen if:

Question 1.
If skin had no sweat glands.
Answer:
Skin regulates body temperature by releasing sweat. If skin had no sweat glands then we will not be able to maintain our body temperature at a constant 37°C.

Can you recall?

Question 1.
Which organ help us to sense whether something is hot or cold, rough or smooth, etc?
Answer:
The skin functions as the sensory organ of touch.

Question 2.
What happens when we walk or play in the hot sun?
Answer:
When we walk or play in the sun, we get tired, our skin secrete sweat.

Observe the figure and label as directed.

Question 1.

In the above figure label the parts marked a, b, c, d, e and hence show axial and appendicular
skeleton.
Answer:
(a) Skull
(b) Rib cage
(c) Spine
(d) Arm
(e) Leg
Axial skeleton: skull, the spine and rib cage
Appendicular: legs, arms

Question 2.

In the given figure, name the type of bones marked a, b, c, d. State where they are seen in our body.
Answer:
(a) Flat bones – rib cage and gliding joint
(b) small bones – finger
(c) Irregular bones – vertebal column
(d) Long bones – legs, arms

6th Std Science Questions And Answers:

• Natural Resources – Air, Water and Land Class 6 Questions And Answers
• The Living World  Class 6 Questions And Answers
• Diversity in Living Things and their Classification Class 6 Questions And Answers
• Disaster Management Class 6 Questions And Answers
• Substances in the Surroundings – Their States and Properties Class 6 Questions And Answers
• Substances in Daily Use Class 6 Questions And Answers
• Nutrition and Diet Class 6 Questions And Answers
• Our Skeletal System and the Skin Class 6 Questions And Answers
• Motion and Types of Motion
• Force and Types of Force Class 6 Questions And Answers

Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 16 The Universe Notes, Textbook Exercise Important Questions and Answers.

Std 6 Science Chapter 16 The Universe Question Answer Maharashtra Board

Class 6 Science Chapter 16 The Universe Question Answer Maharashtra Board

1. Name these.

Question a.
Birthplace of stars.
Answer:
Nebulae

Question b.
The biggest planet in the Solar System.
Answer:
Jupiter

Question c.
The galaxy which is our neighbour.
Answer:
Andromeda

Question d.
The brightest planet in the solar system.
Answer:
Venus

Question e.
Planet with the largest number of satellites.
Answer:
Jupiter

Question f.
Planet without a single satellite.
Answer:
Venus and Mercury

Question g.
Planet with a rotation different from other planets.
Answer:
Venus

Question h.
A celestial body that carries a tail along.
Answer:
Comet

2. Fill in the blanks.

Question a.
The group of galaxies of which our Milky Way is a part is called ………….. .
Answer:
Local group

Question b.
Comets are made of ………… .
Answer:
ice and dust particles

Question c.
The planet ……………… appears as if it is rolling along its orbit.
Answer:
Uranus

Question d.
…………….. is a stormy planet.
Answer:
Jupiter

Question e.
The pole star is the best example of a ………………. type of star.
Answer:
variable

3. Say if the statements given below are right or wrong. Rewrite the statements after correcting them.

Question a.
Venus is the planet closest to the sun.
Answer:
Wrong: Mercury is the planet closest to the sun.

Question b.
Mercury is called a stormy planet.
Answer:
Wrong: Jupiter is called a stormy planet.

Question c.
Jupiter is the biggest planet.
Answer:
Right

4. Answer the following.

Question a.
What is a special characteristic of the planet Mars?
Answer:
The highest and the longest mountain in the solar system ‘Olympus Mons’ is located on Mars.

Question b.
What are the type of galaxies?
Answer:
The different types of galaxies identified according to their shapes are spiral, elliptical, barred spiral, irregular.

Question c.
Which celestial bodies does a galaxy include?
Answer:
Galaxy includes stars, their planetary system, cluster of stars, nebulae, clouds of gases, clouds of dust, dead stars, newly bom stars etc.

Question d.
Name the different types of stars.
Answer:
The different types of stars are

1. Sun-like stars e.g. stars like Sirius, Alpha Centauri
2. Red Giants Stars
3. Super Nova
4. Binary or Twin Stars
5. Variable Stars e.g. Polaris (pole star)

Question e.
What are the types of comets and on what basis are they classified?
Answer:

1.  Comets are of two types: Long-period comets and short-period comets.
2. Classification of comets is based on the time (period) taken by the comets to complete one revolution around the sun.

Question f.
What is the difference between meteors and meteorites?
Answer:

1. Meteors are rocky pieces originating from the asteroid belt. Smaller rocky pieces get completely burnt due to friction with air after they enter the earth’s atmosphere.
2. Meteors which do not bum completely and fall to the surface of the earth are called meteorites.

Question g.
What are the characteristics of the planet Neptune?
Answer:
Neptune is the eighth planet in the solar system. A season on Neptune lasts for about 41 years. On this planet winds blow with extremely high speed.

5. Match the following.

Question a.

Group ‘A’	Group ‘B’
1. Galaxy	(a) From east to west
2. Comet	(b) 33 satellites
3. Sun-like star	(c) Spiral
4. Saturn	(d) Sirius
5. Venus	(e) Halley

Answer:

Group ‘A’	Group ‘B’
1. Galaxy	(c) Spiral
2. Comet	(e) Halley
3. Sun-like star	(d) Sirius
4. Saturn	(b) 33 satellites
5. Venus	(a) From east to west

Activity:

Question 1.
Using the material you can find in your house, prepare a model of the solar system.

Question 2.
Collect information about different aspects of each planet such as its distance from the sun, its diameter, its volume, etc. and present it in a science exhibition.

Class 6 Science Chapter 16 The Universe Important Questions and Answers

Fill in the blanks.

Question 1.
The Milky Way is known as ………….. .
Answer:
Mandakini

Question 2.
The ………….. is a galaxy in which our solar system is located.
Answer:
Milky Way

Question 3.
The galaxy that is closest to our Milky Way is ………….. .
Answer:
Andromeda

Question 4.
The universe includes innumerable galaxies, the space between them and also ………….. .
Answer:
energy

Question 5.
The Milky Way is a part of the ………….. of galaxies.
Answer:
Local group

Question 6.
Generally, the surface temperature of stars ranges from 3500° C to ………….. .
Answer:
50000°C

Question 7.
The colour of stars changes according to their ………….. .
Answer:
temperature

Question 8.
Red giants stars are ………….. in colour.
Answer:
red

Question 9.
Super Nova stars are ………….. and ………….. than the red giant stars.
Answer:
brighter, larger

Question 10.
More than ………….. of the stars in the sky are ………….. stars.
Answer:
half, binary

Question 11.
The ………….. and ………….. of variable stars is not stable.
Answer:
luminance, shape

Question 12.
When a star contracts, its surface temperature ………….. and the star emits ………….. energy and appears ………….. .
Answer:
increases, greater, brighter

Question 13.
The sun which is at the centre of the solar system is a ………….. coloured star.
Answer:
yellow

Question 14.
The diameter of the sun is approximately ………….. km.
Answer:
13, 92, 000

Question 15.
………….. is the fastest moving planet.
Answer:
Mercury

Question 16.
………….. is the brightest planet in the solar system.
Answer:
Venus

Question 17.
………….. is the hottest planet.
Answer:
Venus

Question 18.
As the earth is a ………….. there is a magnetic field around the earth.
Answer:
magnet

Question 19.
Mars is also called the ………….. .
Answer:
Red planet

Question 20.
As the soil on Mars contains ………….. its colour is reddish.
Answer:
iron

Question 21.
………….. planets of the size of the earth can get accommodated on Jupiter.
Answer:
1397

Question 22.
Jupiter is called as ………….. .
Answer:
The stormy planet

Question 23.
Saturn mass is ………….. times that of the earth.
Answer:
95

Question 24.
………….. cannot be seen without a telescope.
Answer:
Uranus

Question 25.
Winds blow with extremely high speed on ………….. .
Answer:
Neptune

Question 26.
………….. is the satellite of the earth.
Answer:
The moon

Question 27.
The moon’s period of ………….. and ………….. are both of 27.3 days.
Answer:
rotation, revolution

Question 28.
………….. is classified as a dwarf planet.
Answer:
Pluto

Question 29.
Pluto takes ………….. years to complete its revolution around the sun.
Answer:
248

Question 30.
………….. are formed out of ice and dust particles.
Answer:
Comets

Question 31.
………….. lake in Maharashtra has been formed by the impact of such a meteorite.
Answer:
Lonar

Can you tell?

Question 1.
Which celestial bodies form the solar system?
Answer:
Sun, the eight planets – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, their satellites, Dwarf planets, asteroids, meteors and comets all together form our solar system.

Question 2.
What is the difference between stars and planets?
Answer:

Stars	Planets
1. Stars are the celestial bodies which can emit heat and light continuously.	1. The celestial bodies which revolve around the sun in certain orbit are called planets.
2. Stars twinkle in the sky.	2. Planets do not twinkle in the sky.
3. They have their own light.	3. They do not have their own light.
4. They are fixed at a point.	4. They revolve around the sun.
5. They are very big in size.	5. Planets are small as compared to

Question 3.
How many planets are there in our solar system?
Answer:
There are 8 planets in our solar system.

Question 4.
What is to be found between Mars and Jupiter?
Answer:
A belt of celestial bodies called as asteriods is found between the planets Mars and Jupiter.

Question 5.
Have you ever seen in the evening or in the pre-dawn hours a large celestial body with a long tail? What is it called?
Answer:
Yes, it is a comet – a large celestial body with a long tail. I have not seen it, but heard that in 1986 there was a Halley’s comet seen in the Indian sky.

Use your brain power!

Question 1.
Why do we see only one side of the moon?
Answer:
As the moon revolves around the earth it also rotates around itself. The moon takes 27.3 days to complete one revolution around the earth. It takes the moon the same time to complete one rotation around itself. Therefore, only one side of moon is visible.

Question 2.
Which planet has a day longer than its year?
Answer:
A planet’s day is how long it takes to complete one rotation on its own axis. Venus takes 243 earth days to complete one rotation because of its slow rotation around its axis. A year is the time taken by the planet to complete one revolution around the sun. Venus completes one revolution around the sun in 225 days. This makes a day longer than a year on Venus.

Answer in one sentence.

Question 1.
What is the Milky Way?
Answer:
Milky way is the galaxy in which our solar system is located.

Question 2.
What is a galaxy?
Answer:
A group of innumerable stars and their planetary systems are together known as galaxy.

Question 3.
What does the Universe include?
Answer:
The universe includes innumerable galaxies, the space between them and also energy.

Question 4.
What different colours do the stars radiate?
Answer:
The stars radiate different colours such as blue, white, yellow and red.

Question 5.
Where are stars bom?
Answer:
The birth place of stars are the huge nebulae, made of dust particles and gases.

Question 6.
What is the surface temperature of the sun?
Answer:
The surface temperature of the Sim is around 6,000°C.

Question 7.
What is the size of the sun?
Answer:
The size of the sun is so huge that around 13 lakh planets of the size of the earth can be easily placed within it.

Question 8.
How does the sun balance the other celestial bodies?
Answer:
Due to the gravitational force of the sun, the celestial bodies in the solar system revolve around it.

Question 9.
How does the sun move in the Milky Way?
Answer:
The sun rotates around its axis and while doing so, it revolves around the centre of the Milky Way taking the solar system along with it.

Question 10.
Which planet doesn’t have atmosphere?
Answer:
Mercury doesn’t have atmosphere.

Question 11.
How much time does the earth take to complete one rotation and one revolution?
Answer:
The earth completes one rotation in 24 hrs and one revolution in 365 days i.e. 1 year.

Question 12.
Which planets have rings around them?
Answer:
Jupiter, Saturn, Uranus, Neptune have rings around them.

Question 13.
Which planet do not have rings around them?
Answer:
Mercury, Venus, Earth and Mars do not have rings around them.

Question 14.
State two properties of planet Mercury.
Answer:
Mercury is the closet planet to the Sim. Mercury is the fastest moving planet.

Question 15.
When is the Mercury visible to us?
Answer:
Mercury is visible in the morning and in the evening if it is away from the sun.

Question 16.
What is seen on the surface of the mercury?
Answer:
A number of depressions which are actually caused by meteoric falls are seen on the surface of mercury.

Question 17.
When is Venus seen in the sky?
Answer:
Venus is seen in the sky in the east before the sunrise and in the west after the sunset. It rotates around itself from east to west.

Question 18.
How does earth protect us from harmful rays of Sun?
Answer:
As the earth is a magnet there is a magnetic field around the earth. It diverts the harmful rays from the sun towards the polar regions of the earth.

Question 19.
What is Olympus Mons?
Answer:
Olympus Mons is the highest and longest mountain in the solar system located on Mars.

Question 20.
Which is the largest planet of the solar system?
Answer:
The Jupiter is the largest planet of the solar system.

Question 21.
Why is Saturn considered a peculiar planet?
Answer:
Saturn considered a peculiar planet because of the rings around it.

Question 22.
How is the axis of Uranus?
Answer:
Uranus axis is so greatly inclined that it appears as if it is rolling along on its axis.

Question 23.
How are seasons on Neptune?
Answer:
The seasons on Neptune last for about 41 years.

Question 24.
What is a satellite?
Answer:
The celestial bodies that revolve around a planet , without independently revolving around the sun are called Satellite.

Question 25.
What is an Asteroid?
Answer:
A great number of small sized bodies could not turn into planets when the solar system was formed, but continued to revolve around the sun. This bodies are known as asteroids.

Question 26.
What is a Dwarf Planet?
Answer:
A small sized celestial body that revolves independently around the sun is called the dwarf planet.

Question 27.
What is a comet?
Answer:
A comet is a celestial body that revolves around sun. Comets are formed out of ice and dust particles.

Question 28.
What are meteors?
Answer:
Meteors are rocky pieces originating from the asteroids belt.

Question 29.
What are meteorites?
Answer:
Meteors which do not bum completely and fall to the surface of the earth are called meteorites.

Give reasons for the following.

Question 1.
Comets came to be called ‘dirty snowballs’.
Answer:
Comets consist of an icy cluster of various constituents like dust particles. Hence it is called dirty snowballs.

Question 2.
Comets are visible when they are close.
Answer:
Comets are formed out of ice and dust particles. They appear like points when they are far away from the sun, but when they are close to the sun they become easily visible to us because of the shorter distance and the heat of the sun.

Question 3.
Comets appear to have a long feathery tail.
Answer:
Comets are made up of frozen matter and dust particles. When they are close to the sun this frozen matter gets converted into gas due to the solar heat. These gases get thrown in a direction away from the sun. As a result comets appear to have a long feathery tail.

Question 4.
Pluto is called as a dwarf planet.
Answer:
Pluto is a small sized celestial body that revolves independently around the sun.

Question 5.
Moon is a satellite of the earth.
Answer:
Moon revolves around the earth without independently revolving around the sun. Hence moon is a satellite of the earth.

Question 6.
Mars is called the Red Planet.
Answer:
As the soil on the Mars contains iron its colour is reddish. Hence Mars is also called the RedPlanet.

Question 7.
Jupiter is called the Stormy Planet.
Answer:
Jupiter revolves around itself with a great speed. Hence Jupiter is called the Stormy planet.

Question 8.
Uranus appears rolling along on its orbit.
Answer:
Uranus axis is so greatly inclined that it , appears as if it is rolling along on its orbit.

Question 9.
Saturn is considered to be a peculiar planet.
Answer:

1. Saturn is considered as peculiar planet because of its rings around it.
2. Though its mass is 95 times that of the earth, its density is very low.
3. If it were dropped into a large sea enough to hold it, it would float in it.

6th Std Science Questions And Answers:

• Work and Energy Class 6 Questions And Answers
• Simple Machines Class 6 Questions And Answers
• Sound Class 6 Questions And Answers
• Light and the Formation of Shadows Class 6 Questions And Answers
• Fun with Magnets Class 6 Questions And Answers
• The Universe Class 6 Questions And Answers

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:

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

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

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

Question c.
Storm:
Answer:

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

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

1. Shift people to safe places with the help of airplane, helicopter and army.
2. Supply them food, clothes, water and medicines.
3. Give time to time weather report.
4. Open more helpline centres.
5. 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:

1. Waves generated by an earthquake or volcano occurring on the ocean floor is called ‘tsunami’. ‘Tsunami’ is a Japanese word which means ‘harbour wave’.
2. As on land, earthquakes and volcanic eruptions occur, at the bottom of the sea, too.
3. 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.
4. These waves are not very high near the source, but they start spreading very fast to long distances.
5. 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:

1. 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.
2. As a result the amount of vapour in those clouds becomes very high.
3. 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:

1. 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
2. The atmosphere gets polluted due to the ash and gases ejected by the volcano.
3. Often, it rains as a result of a volcanic eruption.
4. The temperature rises due to hot gases.
5. 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:

1. Do not stand on open ground, below a tree, on high location, near an electric pole, near a telephone pole or a tower etc.
2. Do not lean on wire fences around a farm, a compound, a garden or a house.
3. If you are on two-wheeler, a bicycle, a tractor or a boat, get off immediately and go to safe place.
4. Do not gather all together in one place.
5. Take care to keep a distance of 15 feet between any two persons.
6. Do not use plugged in electrical appliances. Do not use a mobile or telephone.
7. Stand on dry wood, a plastic sheet, sack or jute cloth or dry leaves.
8. Keeping your feet together support yourself on the soles of your feet placing your hands on your knees and crouch low.
9. Swimmers and fishermen should immediately come out of the water.
10. 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.

1. The plan deals extensively with the emergency, and evacuation measures to be taken up in cases of flood and landslide.
2. The district-level disaster management plan has detailed information about geographical details, population, flood-prone areas, villages and other macro details.
3. 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.
4. 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.
5. The administration through radio jingles, public advertisements and other measures is informing people about how to react at times of flood and landslide.
6. 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.

1. Keep proper first aid kit at a handy place.
2. Keep all the electric connections in proper condition.
3. Keep the gas line or tube connection proper.
4. Keep self-powered flashlights and self-powered radios.
5. Keep non-perishable food which will last for a week.
6. Keep a fire extinguisher handy and in proper condition.
7. 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:

1. Grow more trees near the bunds.
2. Grow grass strips.
3. Make stone lines near the bunds.
4. 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:

1. 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.
2. 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:

1. 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.
2. 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.
3. 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:

• The Living World: Adaptations and Classification Class 7 Questions And Answers
• Plants: Structure and Function Class 7 Questions And Answers
• Properties of Natural Resources Class 7 Questions And Answers
• Nutrition in Living Organisms Class 7 Questions And Answers
• Food Safety Class 7 Questions And Answers
• Measurement of Physical Quantities Class 7 Questions And Answers
• Motion, Force and Work Class 7 Questions And Answers
• Static Electricity Class 7 Questions And Answers
• Heat Class 7 Questions And Answers
• Disaster Management Class 7 Questions And Answers

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:

1. 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.
2. When people would put their ear to the rail they could hear vibration caused by the wheels moving over the joints. ,
3. 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:

1. In tabla where leather is fitted, sound gets generated when the leather surface is thumped by fingers or palm.
2. The waves thus created travel in two dimensions. Sitar is having strings attached to pumkin box called sound box.
3. 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.

1. As there is no air on the moon and sound is actually vibration in air.
2. 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:

1. 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.
2. Mosquitos wings flap in air.
3. When they fly in air it produces buzzing sound in our ears.
4. The movement of mosquito wings produces sound greater than 20 Hz.
5. 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:

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

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

1. 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.
2. 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:

1. Echo: It is a repetition of sound due to the reflection of original sound by a large and hard obstacle.
2. Frequency: It is defined as the number of vibrations per unit time.
3. Hertz (Hz): One hertz is one vibration per second.
4. Ultrasonic vibration: Sounds of frequency higher than 20,000 Hz are called the ultrasonic.
5. Time period: The time taken by an object to complete one oscillation is called time period.
6. 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:

1. The loudness or softness is indicated by the intensity of sound and sound level.
2. 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:

1. The term infrasonic refer to sound waves below the frequencies of audible sound i.e. under 20 Hz.
2. Humans cannot hear infrasonic sound.
3. 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:

1. To clean delicate ornaments and the tiny parts of a watch.
2. To observe internal organs of the body.
3. To detect tumors in the brain.
4. To detect faults in a metal.
5. In RADAR systems
6. To Kill certain microbes and insects.
7. 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:

1. No, If the ruler kept on the table is only a little part off the table, it will not vibrate with a greater force.
2. 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:

1. When two pupils talk to each other, the sounds of two frequencies produced can be heard clearly.
2. When all the children talk to one another sounds of many frequencies produced can not be heard clearly.
3. Sound level will be more creating loud noise.

7th Std Science Questions And Answers:

• Cell Structure and Micro-organisms Class 7 Questions And Answers
• The Muscular System and Digestive System in Human Beings Class 7 Questions And Answers
• Changes – Physical and Chemical Class 7 Questions And Answers
• Elements, Compounds and Mixtures Class 7 Questions And Answers
• Materials We Use Class 7 Questions And Answers
• Natural Resources Class 7 Questions And Answers
• Effects of Light Class 7 Questions And Answers
• Sound: Production of Sound Class 7 Questions And Answers
• Properties of a Magnetic Field Class 7 Questions And Answers
• In the World of Stars Class 7 Questions And Answers

Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 12 Simple Machines Notes, Textbook Exercise Important Questions and Answers.

Std 6 Science Chapter 12 Simple Machines Question Answer Maharashtra Board

Class 6 Science Chapter 12 Simple Machines Question Answer Maharashtra Board

1. Classify the following as a lever, a pulley and an inclined plane:
(A wedge, a needle, a staircase, a slide, the wheel of a flagpole, nutcrackers, scissors, an opener, an axe, a crane, a knife)

Question a.
Classify the following as a lever, a pulley and an inclined plane:
(A wedge, a needle, a staircase, a slide, the wheel of a flagpole, nutcrackers, scissors, an opener, an axe, a crane, a knife)
Answer:

Inclined plane	Pulley	Lever
Wedge	Wheel of flagpole	Nutcracker
Needle	Crane	Scissors
Staircase		Opener
Slide
Axe
Knife.

2. Fill in the blanks using the proper word and complete the statements.

Question a.
The ………….. in the centre, the ………….. on one side and the on the ………….. other side make a lever of the first order.
Answer:
Fulcrum, load and effort

Question b.
The ………….. in the centre, the ………….. on one side and the ………….. on the other side make a lever of the second order.
Answer:
Load, fulcrum, effort

Question c.
The ………….. in the centre, the ………….. on one side and the ………….. on the other side make a lever of the third order.
Answer:
Effort, fulcrum, load

3. Which machines will you use to do the following work? Write their types.

Question a.
To remove the lid of a tin. Opener Lever of the second order
Answer:

• Work: To remove the lid of a tin.
• Machine: Opener
• Machine: Lever of the second order

Question b.
To lift bricks to the top of a tall building Crane Complex machine
Answer:

• Work: To lift bricks to the top of a tall building
• Machine: Crane
• Machine: Complex machine

Question c.
To cut vegetable Knife Wedge – Simple machine
Answer:

• Work: To cut vegetable
• Machine: Knife
• Machine: Wedge – Simple machine

Question d.
To draw water from a well Pulley Simple machine
Answer:

• Work: To draw water from a well
• Machine: Pulley
• Machine: Simple machine

Question e.
To hold a papad for roasting it. A pair of tongs Lever of the third order
Answer:

• Work: To hold a papad for roasting it.
• Machine: A pair of tongs
• Machine: Lever of the third order

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

Question a.
What is meant by a simple machine?
Answer:

1. Machines which have only one or two parts and a simple and easy structure are simple machines.
2. Example: the bottle opener, nail cutter.
3. Simple machines can be handled easily.
4. We use many simple machines in our day to day life.

Question b.
Mention the advantages of using a machine.
Answer:

1. Machines, simple or complex, are used to get more work done in less time and with less effort.
2. Machines are used to accomplish certain tasks more easily.
3. Use of simple or complex machines depends upon the task to be carried out and the time and the efforts required to do it.

Question c.
What is meant by a complex machine?
Answer:

1. Complex machines have many parts which carry out many processes for completing a task.
2. For this purpose the parts are joined to one another.
3. Therefore, these machines are called complex machines.
4. Some of the parts of such complex machines are actually simple machines.
5. The structure of complex machine is complicated.

Question d.
What is a lever? How is the order of the lever determined?
Answer:

1. Lever is a simple machine made up of 3 parts: Load, effort and fulcrum.
2. Order of the lever are determined on the position of the effort, the fulcrum and the load.

5. Why is this so?

Question a.
Traveller’s bags have wheels.
Answer:

1. Combination of wheel and axle is a simple machine.
2. When the axle starts rotating due to force applied, the wheel fitted to it also starts rotating.
3. This makes easier for travellers to carry heavy load.
4. Instead of lifting heavy bag, to drawing it on wheels require less energy. Therefore, traveller’s bag have wheels.

Question b.
Machines have to be maintained.
Answer:

1. Parts of machines rub against one another when they are used.
2. Soiled, dusty parts create more friction. Some parts are affected by the weather, rust and corrosion.
3. Machines get damaged or become useless due to such wear and tear. Hence to avoid this, machines should be maintained properly to keep them in good working condition.

Question c.
A bicycle is said to be a complex machine.
Answer:

1. Bicycle has a complicated structure.
2. Bicycle has many parts which carry out many processes for completing a task.
3. Many parts of bicycle such as pedals, wheels, axle, handle are actually simple machines.
4. The parts of a bicycle are joined to one another – making it a complex machine.

6. Name the levers mentioned in the following passage. Identify the fulcrum, load and effort of each and say which type of lever it is.

Ravi and Savita sit on a sea-saw in a garden. In the mean time, a gardener is trimming trees in the garden. He puts the leaves and other garbage in the wheelbarrow. Later, Ravi gets thirsty and he buys lemon sherbet. The sherbet seller cuts the lemon and squeezes it using a lemon squeezer. He puts small pieces of ice in the glass with the help of the tongs.

Question a.
Name the levers mentioned in the following passage. Identify the fulcrum, load and effort of each and say which type of lever it is.

Ravi and Savita sit on a sea-saw in a garden. In the mean time, a gardener is trimming trees in the garden. He puts the leaves and other garbage in the wheelbarrow. Later, Ravi gets thirsty and he buys lemon sherbet. The sherbet seller cuts the lemon and squeezes it using a lemon squeezer. He puts small pieces of ice in the glass with the help of the tongs.
Answer:
Levers:

1. See – saw – lever of the first order.
   Load – fulcrum – effort.
2. Wheelbarrow – lever of the second order.
   Fulcrum – load – effort.
3. Lemon squeezers – lever of the second order.
   Fulcrum – load – effort.
4. Tongs – lever of the third order.
   Fulcrum – effort – load.

Activity:

Question 1.
Make a list of the various machines used in your home and neighborhood and write their types.

Question 2.
Go to a bicycle repair shop, observe how a bicycle is repaired, and note down the information.

Class 6 Science Chapter 12 Simple Machines Important Questions and Answers

Fill in the blanks.

Question 1.
Simple machines can be handled ………….. .
Answer:
easily

Question 2.
The structure of complex machine is ………….. .
Answer:
complicated

Question 3.
The more gradual the the ………….. lesser is the we bear. But, such an inclined plane is ………….. .
Answer:
slope, weight, longer

Question 4.
The steeper the ………….. , the ………….. is the inclined plane. But we have to bear a …………. weight.
Answer:
slope, shorter, greater

Question 5.
A screw is like a rolled up inclined plane made of an ………….. strip.
Answer:
iron

Question 6.
A wedge is used for ………… an object into two pieces or to ………….. the objects stuck together.
Answer:
breaking, separate

Question 7.
A farmer uses a strong …………. to remove the big stone bogged down in the farm.
Answer:
crow-bar

Question 8.
A device with a grooved wheel and thread designed to lift weights is called a …………. .
Answer:
pulley

Question 9.
When we use a pulley, force is applied in the downward direction for lifting the weight in an …………. direction.
Answer:
upward

Question 10.
Combination of an axle and a wheel is a …………. machine.
Answer:
simple

Question 11.
A needle and a nail are also kind of …………. .
Answer:
wedge

Question 12.
Machines are covered when not in use to prevent …………. settling on them.
Answer:
dust

Question 13.
In Archimedes’ screw, the pipe was placed at an angle of …………. with one end inside the …………. and the rod resting on a …………. .
Answer:
45°, water, flat surface.

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
1. Pair of Scissors	a. Third order of lever
2. Tongs	b. Second order of lever
3. Opener	c. First order of lever

Answer:

Column ‘A’	Column ‘B’
1. Pair of Scissors	c. First order of lever
2. Tongs	a. Third order of lever
3. Opener	b. Second order of lever

Question 2.

Column ‘A’	Column ‘B’
1. Inclined plane	a. Needle
2. Pulley	b. Screw
3. Wedge	c. Crane

Answer:

Column ‘A’	Column ‘B’
1. Inclined plane	b. Screw
2. Pulley	c. Crane
3. Wedge	a. Needle

State whether the following statements are ‘true’ or ‘false’.

Question 1.
Lever helps big vehicle to climb up and down the mountain easily.
Answer:
False

Question 2.
Combination of wheel and axle is a simple machine.
Answer:
True

Question 3.
In pulley, force can be applied in upward direction.
Answer:
False

Question 4.
Screw is an example of wedge.
Answer:
False

Question 5.
In Archimedes screw, the rod rests on flat surface.
Answer:
True

Question 6.
A slanting plank is used to lift a weight.
Answer:
True

Question 7.
A winding road or ghat is an example of lever of first order.
Answer:
False

Answer the following questions in one sentence.

Question 1.
What is a machine?
Answer:
Devices which are used to get more work done in less time and less effort are called machines.

Question 2.
What is a simple machine?
Answer:
Machines which have only one or two parts and a simple and easy structure are called simple machines.

Question 3.
What is a complex machine?
Answer:
Some machines have many parts and they carry out many processes for completing a task. For this purpose, the parts are joined to each other. They are called complex machines.

Question 4.
List the properties of simple machines.
Answer:
Properties of simple machine are:

1. They are made up of only one or two parts.
2. They have a simple and easy structure.
3. They can be handled easily.
4. There are less chances of simple machines breaking down or getting damaged.

Question 5.
List properties of complex machines.
Answer:
Properties of complex machine are:

1. These machines have many parts to carry out many processes.
2. The parts are joined to one another.
3. The structure of complex machines is complicated.
4. Some parts of complex machines are actually simple machines.

Question 6.
What is an inclined plane?
Answer:
A slanting plank which is used to lift a weight on which we bear less weight and lifting becomes easier is an inclined plane.

Question 7.
What is a screw?
Answer:
A screw is like a rolled up inclined plane made up of iron strip.

Question 8.
What is a wedge?
Answer:
A wedge is used for breaking an object into two pieces or to separate objects stuck together.

Question 9.
State examples of wedges.
Answer:
An axle, a knife, a chisel, a needle and a nail are different kinds of wedges.

Question 10.
What is a lever?
Answer:
A lever is a machine made up of 3 parts: effort, load and fulcrum.

Question 11.
What is a fulcrum?
Answer:
The support at which the rod of a lever is rested is called fulcrum of a lever. The lever rotates about the fulcrum.

Question 12.
What is a load?
Answer:
The weight lifted by a lever or the force against which the lever acts is called a load.

Question 13.
What is a load arm?
Answer:
The arm of the lever from the fulcrum to the load is called a load arm.

Question 14.
What is an effort?
Answer:
The force applied on the other end of the rod to lift the load is called an effort.

Question 15.
What is an effort arm?
Answer:
The part of the lever from the fulcrum to the effort is called an effort arm.

Question 16.
What is lever of the first order?
Answer:
The fulcrum is in the centre, the load is at one end while effort is at other end.

Question 17.
What is lever of the second order?
Answer:
The load is in the centre, the fulcrum on one side, and the effort on the other side.

Question 18.
What is lever of the third order?
Answer:
The effort is in the centre, the fulcrum on one side, and the load on the other side.

Question 19.
What is a pulley?
Answer:
A pulley is a device with a grooved wheel and thread designed to lift weights.

Question 2.
How does a pulley help us?
Answer:
If we use a pulley, force can be applied in the downward direction for lifting the weight in an upward direction. It is convenient and easy.

Give scientific reasons:

Question 1.
We use many simple machines in our day-to-day life.
Answer:
Simple machines can be handled easily and there are less chances of these machines breaking down or getting damaged. Hence, we use many simple machines in our day-to-day life.

Question 2.
Less force is required to fit a screw than to hammer a nail.
Answer:

1. A screw is like a rolled-up inclined plane of an iron strip.
2. When a screw is fitted in wood it goes in as if it is going down an inclined plane.
3. Therefore, less force is required to fit a screw than hammer a nail.

Question 3.
Big vehicles easily climb up and down the mountains than a pathway.
Answer:
A winding road or ghat that goes up a mountain is like an inclined plane wrapped around the mountain. It helps big vehicles to climb, up and down the mountain easily.

Question 4.
Oil or lubricant is released between parts of machine.
Answer:
Oil or lubricant is released between parts that rub against each other so that there is less friction between them and wearing is reduced.

Question 5.
Machines are covered when not in use.
Answer:
Machines are covered when not in use to prevent dust settling on them.

Question 6.
How are machines protected from the effect of weather?
Answer:
To prevent the effect of weather, metallic parts in a machine are painted externally and the machines are always kept dry.

Draw the neat and labelled diagram of following:

Question 1.
The screw as an inclined plane.
Answer:

Question 2.
Archimedes’ screw
Answer:

Observe the following diagram and identify the order of lever.

Question 1.
Removing the lid.
Answer:

Question 2.
Picking up an object.
Answer:

Question 3.
Lifting a paper weight.

Answer:

1. Lever of the second order
2. lever of third order
3. Level of first order.

Answer each of the question in brief:

Question 1.
With the help of the diagram explain lever of the 1st, 2nd, 3rd order.
Answer:
1. Lever of the First order: The fulcrum is in the centre, the load is at one end, while the effort is at the other end. e.g. scissors

2. Lever of the Second order: The load is in the centre, the fulcrum on one side, and the effort on the other side. e.g. lid opener

3. Lever of the Third order: The effort is in the centre, the fulcrum on one side, and the load on the other side. e.g. Tongs

Question 2.
How can machines be maintained?
Answer:

1. To maintain machines, all its parts are wiped clean.
2. Oil or lubricant is released between parts that rub against each other.
3. Machines are covered, painted externally and always kept dry.

Question 3.
What is an inclined plane? Explain longer and shorter inclined plane.
Answer:

1. A slanting plank used to lift a weight, is called an inclined plane. Because of inclined plane we will experience less weight and weight lifting become easier.
2. Longer inclined plane: When the inclined plane is longer, the slope is more gradual and lesser is the weight we bear.
3. Shorter inclined plane: When the inclined plane is shorter, the slope is steeper and greater is the weight we bear.

Question 6.
Explain the working of a giant wheel.
Answer:

1. The giant wheel is fitted to a rod at its centre. This rod is called an axle.
2. When the axle starts rotating with the help of electricity the wheel fitted to it starts rotating.
3. This combination of an axle and a wheel is a simple machine.

Observe and discuss:

Question 1.
Name the devices and discuss how they help.

Answer:

1. Needle and thread – Stitching of clothes
2. Wheelbarrow – To carry materials.
3. Opener – To open the lids of bottles.
4. Pulley – To lift bucket
5. Nail cutter – To cut nails
6. Axe – To cut wood into small pieces

Can you tell?

Question 1.
Observe the machines shown in the following pictures. For what purposes are they used? Can you name some other machines of this kind?

Answer:

1. Mixer grinder – To grind the foodstuffs
2. Scooter – To ride and reach places
3. Bicycle – To ride and reach places
4. Sewing machine – To stitch clothes
5. Wheel chair – Specially designed for handicapped patients to move around.

Question 2.
Compare the pathway and a road, available to climb the mountain, the time and strength and your convenience, required to reach the mountain top.
Answer:
We can reach the mountain top by climbing the pathway early than by the road. The time required is less but the strength required is more. The road is easy to walk and more time consuming.

Question 3.
If the point of a needle or the edge of a knife become blunt, then the needle does not penetrate the cloth and the knife does not cut into the fruit. Why is this so?
Answer:
The tip of the needle or the edge of a knife becomes blunt due to regular use. Both the knife and the needle lose their sharpness.

Use your brain power!

Question 1.
Which task can be done using a lever?
Answer:
Task such as using a nut cracker, cutting paper with scissors, can be done using a lever.

Question 2.
Some machines we use in our day to day life are shown in picture. What is the type in each of these?

Answer:

• Wheelbarrow – Lever of the third order
• Pair of tongs – Lever of the first order
• See – saw – Lever of the first
• order Cutter – Lever of the second lever
• Pair of Scissors – Lever of the first order.

Question 3.
When the pedal of the bicycle is rotating, the wheel starts rotating. How does this happen?
Answer:
Pedals of the bicycle are connected to the wheels through the axle, when the axle starts rotating, the wheels also start rotating.

Question 4.
Examples of pulley.
Answer:

1. A simple pulley is used to hoist a flag, to draw water from a well.
2. The crane which is used to lift heavy loads is an example of application of pulleys and levers working together.

6th Std Science Questions And Answers:

• Work and Energy Class 6 Questions And Answers
• Simple Machines Class 6 Questions And Answers
• Sound Class 6 Questions And Answers
• Light and the Formation of Shadows Class 6 Questions And Answers
• Fun with Magnets Class 6 Questions And Answers
• The Universe Class 6 Questions And Answers