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Thursday, 31 October 2013
Sunday, 27 October 2013
Ch 16 : Garbage In Garbage Out
CBSE Class 6 - Science - CH 16 - Garbage In Garbage Out
Q1: Fill in the blanksAnswer:
1. Converting plant and animal waste including that from kitchen, into manure, is called composting.
2. A garbage dump is also used as landfill.
3. The method of making compost from kitchen garbage using redworms is called vermicomposting.
4. Consuming food packed in such plastic bags could be harmful to our health.
Q2: (a) Which kind of garbage is not converted into compost by the redworms?
(b) Have you seen any other organism besides redworms, in your pit? If yes, try to find out their names. Draw pictures of these.
1. Converting plant and animal waste including that from kitchen, into manure, is called composting.
2. A garbage dump is also used as landfill.
3. The method of making compost from kitchen garbage using redworms is called vermicomposting.
4. Consuming food packed in such plastic bags could be harmful to our health.
Q2: (a) Which kind of garbage is not converted into compost by the redworms?
(b) Have you seen any other organism besides redworms, in your pit? If yes, try to find out their names. Draw pictures of these.
 |
| redworms - friends of farmers |
Answer: Non bio-degradable waste like pieces of cloth, polythene bags, broken glass, aluminium wrappers, nails, old shoes and broken toys cannot be converted into compost by the redworms.
(b) Besides redworms there are spiders, small bugs, flies, moulds and small insects etc. can be seen in the pit. Compost is also rich of microbes which can't be seen with unaided eye.
Q3: Discuss:
(a) Is garbage disposal the responsibility only of the government?
(b) Is it possible to reduce the problems relating to disposal of garbage?
Answer:
(a) Garbage Disposal is the responsibility of every citizen. If we continue to generate so much garbage, very soon our beautiful earth will convert into a big garbage-bin. Non-biodegradable waste like plastic is harmful to our environment as well as to our health. We must ensure ways to reduce production of garbage. Wherever possible, we must use recyclable material in our daily use.
(b) Yes it is possible to reduce the problems relating to disposal of garbage to a large extent. We should use those materials which are recyclable. We should avoid or reduce the use of non-biodegradable materials at minimum level. While throwing out garbage in trash can, we should separate biodegradable waste from non-biodegradable and throw them in separate bins.
Q4: (a) What do you do with the left over food at home?
(b) If you and your friends are given the choice of eating in a plastic plate or a banana leaf platter at a party, which one would you prefer and why?
Answer: (a) Left over food can be collected and be converted into compost. We can feed our pet animals with left over food. If enough food is left (e.g. after a party), we may distribute the food to shelter homes.
(b) Banana leaf is a better choice. It is bio-degradable and can be disposed easily. On the other hand, eating in plastic plate is not good. Plastic material may contain harmful substance which can make the contained food toxic. which is harmful to our health. Also plastic is non-biodegradable, it will not dispose off easily.
Q5: (a) Collect pieces of different kinds of paper. Find out which of these can be recycled.
(b) With the help of a lens look at the pieces of paper you collected for the above question. Do you see any difference in the material of recycled paper and a new sheet of paper ?
Answer:
(a) Almost all kinds of paper are recyclable i.e. newspapers, magazines, papers, notebooks, envelopes etc.
(b) The difference between new sheet and recycle paper is subtle. Usually hand made recycled paper is of coarse quality.
Q6: (a) Collect different kinds of packaging material. What was the purpose for which each one was used? Discuss in groups.
(b) Give an example in which packaging could have been reduced?
(c) Write a story on how packaging increases the amount of garbage.
Answer:
(a) Different kinds of packaging materials used commonly are:
- Cardboard - used as shoe boxes
- Plastic Bags - Toys covers, sarees bags
- Wooden Boxes - Fruit baskets
- Jute Bags - School bags, shopping bags
(b) Since plastic is
harmful to our environment and is non-biodegradable. We should avoid using
plastic packaging.
(c) The basic purpose of packaging is to protect the product from tampering and to maintain its freshness. However, most of the packaging material is used to beautify the boxes and make them look attractive on the shelves. Unfortunately a large volume of packaging material goes waste and is thrown into dustbin. For example, if you go to any park, there dustbins are full of potato chips wrappers. It unnecessarily increases the amount of garbage. It also increase the cost of the product due to unnecessary packaging. We should seriously consider how to reduce unnecessary packaging. We should prefer buy products carry less packaging material.
Q7: Do you think it is better to use compost instead of chemical fertilisers? Why?
Answer: No doubt compost is better to use than chemical fertilizers due to following reasons:
(c) The basic purpose of packaging is to protect the product from tampering and to maintain its freshness. However, most of the packaging material is used to beautify the boxes and make them look attractive on the shelves. Unfortunately a large volume of packaging material goes waste and is thrown into dustbin. For example, if you go to any park, there dustbins are full of potato chips wrappers. It unnecessarily increases the amount of garbage. It also increase the cost of the product due to unnecessary packaging. We should seriously consider how to reduce unnecessary packaging. We should prefer buy products carry less packaging material.
Q7: Do you think it is better to use compost instead of chemical fertilisers? Why?
Answer: No doubt compost is better to use than chemical fertilizers due to following reasons:
- Compost is much easier to prepare.
- Compost is environment friendly whereas fertilizers can harm our health and the environment.
- Compost does not pollute our environemnt.
- Compost decomposes bio-degradable waste into natural soil. It conserves our environment.
Q8: How do redworms prepare
vermicompost?
Answer: Red worms have a special structure called gizzards in their bodies with which they grind food material and covert it into manure.
Q9: What will happen if garbage is not disposed off?
Answer: If garbage is not properly disposed off, these garbage dumps turn into breeding grounds for micro-organisms, flies, cockroaches and mosquitoes, that may cause diseases.
Q10: Why is it illegal to burn leaves and other plant wastes?
Answer: Burning of leaves and other plant wastes produces smoke and gases that are harmful to
our health. They may lead to asthma and lung diseases. Instead of burning, these plant wastes must be converted into manure.
Q11: Why should we not throw plastic bags or wrappers carelessly on roads and other places?
Answer: The plastic bags thrown away carelessly on roads and other places get into drains and the sewer system. As a result, drains get choked and the water spills on the roads. During heavy rains,
it might even create a flood like situation.
Sometimes, these bags are eaten by stray animals like cows, dogs etc. These bags are toxic in nature and affect their health.
Answer: Red worms have a special structure called gizzards in their bodies with which they grind food material and covert it into manure.
Q9: What will happen if garbage is not disposed off?
Answer: If garbage is not properly disposed off, these garbage dumps turn into breeding grounds for micro-organisms, flies, cockroaches and mosquitoes, that may cause diseases.
Q10: Why is it illegal to burn leaves and other plant wastes?
Answer: Burning of leaves and other plant wastes produces smoke and gases that are harmful to
our health. They may lead to asthma and lung diseases. Instead of burning, these plant wastes must be converted into manure.
Q11: Why should we not throw plastic bags or wrappers carelessly on roads and other places?
Answer: The plastic bags thrown away carelessly on roads and other places get into drains and the sewer system. As a result, drains get choked and the water spills on the roads. During heavy rains,
it might even create a flood like situation.
Sometimes, these bags are eaten by stray animals like cows, dogs etc. These bags are toxic in nature and affect their health.
Ch 15 : Air Around Us
CBSE class 6 - Science - CH 15 - Air Around Us
Q1: What is the composition of air?
Answer: Air is a mixture gases, water vapours and dust particles. Largely it consists of:
Q2: What are the important properties of air?
Answer: Important properties of air are:
Q3: Which gas in the atmosphere is essential for respiration?
Answer: Oxygen is essential for living organisms.
Q4: How will you prove that air supports burning?
Answer: Place a burning candle in a tray. Cover it with a glass jar. To make it air-tight, fill tray with water. After sometime, burning candle dims and goes off. Water level also rises up in the jar. It shows air support burning.
Explanation: During burning, oxygen is consumed and carbon-dioxide is released. After sometime no oxygen is left inside the jar and flame goes out. Once the candle goes off, the temperature surrounding the candle cools down and volume of air (carbon dioxide) decreases. Thus water rises up little in the jar.
Q5: How will you show that air is dissolved in
water?
Answer: Take some water in a glass vessel or beaker. Heat it slowly on a tripod stand. Well before the water begins to boil, look carefully at the inner surface of the vessel. These bubbles come from the air
dissolved in water.
Q6: Why does a lump of cotton wool shrink in water?
Answer: Air is present in the cotton wool. When dipped in water, air present in wool escape and it shrinks.
Q7: Fill in the blanks:
Answer:
1. The layer of air around the earth is known as _atmosphere_.
2. The component of air used by green plants to make their food, is _carbon dioxide__.
3. Air occupies _space_.
4. Aquatic animals use _dissolved_ air in water for respiration.
Q8: List five activities that are possible due to the presence of air.
Answer:
Q9: How do plants and animals help each other in the exchange of gases in the atmosphere?
Answer: There is the interdependence of plants and animals. Both plants and animals respire i.e. they inhale oxygen and gives out carbon dioxide in the atmosphere. Plants take carbon dioxide from the atmosphere and prepare food. This is called photosynthesis. During this process, plants give out oxygen to the atmosphere. Therefore plants and animals help each other in the exchange of gases in the atmosphere.
Q10:Why do why earthworms come out of the soil, only during heavy rains?
Answer: Most of the small organisms like earth worms, rodents live inside the soil. They usually live in burrows and holes in the soil. These burrows also make spaces available for air to move in and out of the soil. However, when it rains heavily, water fills up all the spaces occupied by the air in the soil. In this situation, animals living in the soil have to come out for respiration.
Q11: What is the use of Nitrogen?
Answer: Nitrogen is used in protein synthesis. Nitrogen is an important constituent of amino-acids which manufacture proteins, Proteins are required by living organisms to grown and repair their body parts.
Q12: How Oxygen is removed from the atmosphere?
Answer:
Q1: What is the composition of air?
Answer: Air is a mixture gases, water vapours and dust particles. Largely it consists of:
- Nitrogen (79%)
- Oxygen (20%)
- Carbon Di-Oxide (1%)
- Other gases like Helium, Hydrogen etc.
- Water Vapours
- Dust particles
Q2: What are the important properties of air?
Answer: Important properties of air are:
- Air occupies space.
- Air is present every where including water and soil.
- Air is transparent.
- Air is colourless.
- Air is essential for life on earth.
Q3: Which gas in the atmosphere is essential for respiration?
Answer: Oxygen is essential for living organisms.
Q4: How will you prove that air supports burning?
Answer: Place a burning candle in a tray. Cover it with a glass jar. To make it air-tight, fill tray with water. After sometime, burning candle dims and goes off. Water level also rises up in the jar. It shows air support burning.
Explanation: During burning, oxygen is consumed and carbon-dioxide is released. After sometime no oxygen is left inside the jar and flame goes out. Once the candle goes off, the temperature surrounding the candle cools down and volume of air (carbon dioxide) decreases. Thus water rises up little in the jar.
Q5: How will you show that air is dissolved in
water?Answer: Take some water in a glass vessel or beaker. Heat it slowly on a tripod stand. Well before the water begins to boil, look carefully at the inner surface of the vessel. These bubbles come from the air
dissolved in water.
Q6: Why does a lump of cotton wool shrink in water?
Answer: Air is present in the cotton wool. When dipped in water, air present in wool escape and it shrinks.
Q7: Fill in the blanks:
Answer:
1. The layer of air around the earth is known as _atmosphere_.
2. The component of air used by green plants to make their food, is _carbon dioxide__.
3. Air occupies _space_.
4. Aquatic animals use _dissolved_ air in water for respiration.
Q8: List five activities that are possible due to the presence of air.
Answer:
- Animals use air for respiration.
- Plants use air to prepare their food. (photosynthesis)
- Power generation by wind mills.
- Burning of fuels and substances.
- Air helps in the scattering of seeds and pollens of plants. (pollination).
- Air helps in the movements of sailing yachts, gliders, parachutes and aeroplanes.
Q9: How do plants and animals help each other in the exchange of gases in the atmosphere?
Answer: There is the interdependence of plants and animals. Both plants and animals respire i.e. they inhale oxygen and gives out carbon dioxide in the atmosphere. Plants take carbon dioxide from the atmosphere and prepare food. This is called photosynthesis. During this process, plants give out oxygen to the atmosphere. Therefore plants and animals help each other in the exchange of gases in the atmosphere.
Q10:Why do why earthworms come out of the soil, only during heavy rains?
Answer: Most of the small organisms like earth worms, rodents live inside the soil. They usually live in burrows and holes in the soil. These burrows also make spaces available for air to move in and out of the soil. However, when it rains heavily, water fills up all the spaces occupied by the air in the soil. In this situation, animals living in the soil have to come out for respiration.
Q11: What is the use of Nitrogen?
Answer: Nitrogen is used in protein synthesis. Nitrogen is an important constituent of amino-acids which manufacture proteins, Proteins are required by living organisms to grown and repair their body parts.
Q12: How Oxygen is removed from the atmosphere?
Answer:
- Through combustion or burning of substances,
- Through respiration by living beings.
- Rusting of iron.
Ch 14 : Water
CBSE Class 6 - Science - CH14 - Water
Q1: Fill up the blanks in the following:(a) The process of changing of water into its vapour is called _________________.
(b) The process of changing water vapour into water is called _________________.
(c) No rainfall for a year or more may lead to _________________ in that region.
(d) Excessive rains may cause _________________.
(e) Water disappears from wet clothes by the process of ___________________.
(f) In winter mornings , __________is formed due to condensation of water vapour near the ground.
(g) The major natural source of water is _________________.
(h) Many tiny water droplets high up in the air, come together and fall down as _____________, __________ and ___________.
Answer:
(a) evaporation
(b) condensation
(c) drought
(d) flood
(e) evaporation
(f) fog
(g) oceans and sea
(h) rain, hail, snow
Q2: State for each of the following whether it is due to evaporation or condensation:
(a) Water drops appear on the outer surface of a glass containing cold water.(b) Steam rising from wet clothes while they are ironed.
(c) Fog appearing on a cold winter morning.
(d) Blackboard dries up after wiping it.
(e) Steam rising from a hot girdle when water is sprinkled on it.
Answer:
(a) Water drops appear on the outer surface of a glass containing cold water. - condensation
(b) Steam rising from wet clothes while they are ironed. - evaporation
(c) Fog appearing on a cold winter morning. - condensation
(d) Blackboard dries up after wiping it. - evaporation
(e) Steam rising from a hot girdle when water is sprinkled on it. - evaporation
Q3: Which of the following statements are “true” ?
Answer:
(a) Water vapour is present in air only during the monsoon. (False ✗)
(b) Water evaporates into air from oceans, rivers and lakes but not from the soil.(False ✗)
(c) The process of water changing into its vapour, is called evaporation.(True ✓)
(d) The evaporation of water takes place only in sunlight.(False ✗)
(e) Water vapour condenses to form tiny droplets of water in the upper layers of air where it is cooler.(True ✓)
(f) Life is possible on earth without water (False ✗)
(g) When water is heated, it changes into ice. (False ✗)
(h) Evaporation of water takes place at all times. (True ✓)
(i) Saline water is fit for drinking and other domestic, agricultural and industrial needs. (False ✗)
(j) About two-thirds of the earth is covered with water. (True ✓)
Q4: Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help? If yes, how?
Answer: Yes, spreading school uniform near anghiti or heater would help dry it quickly. Heater will warm up the surroundings and increase the rate of evaporation. Therefore school uniform will dry up quickly.
Q5: Take out a cooled bottle of water from refrigerator and keep it on a table. After some time you notice a puddle of water around it. Why?
Answer: It is due to condensation of water vapours present in air. The cold surface of the bottle cools the air around it, and the water vapour of the air condenses on its surface.
Q6: To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.
Answer: When we breathe out, moist air comes out which make the glasses wet. Also when we breathe out, we release carbon-dioxide gas which cools the surroundings by absorbing heat from air, thus condenses the water vapours.
Q7: How are clouds formed?
Answer: Clouds are formed due to the process of evaporation and condensation. When air moves up, it gets cooler and cooler. At sufficient height, the air becomes so cool that water vapours present in the air condense. They form tiny droplets and float in air as clouds.
Q8:
When does a drought occur?
Answer: When there is insufficient or no rainfall occurs for more than a year in a region, the scarcity of water happens. Ponds and wells dry up. The soil continues to lose water due to evaporation and transpiration and eventually dry. This leads to drought.
Q9: What is rainwater harvesting? What are the two rainwater harvesting techniques?
Answer: Collecting rain water and storing it for later use is called rainwater harvesting. The two techniques of rainwater harvesting are:
Q10: Explain Water cycle with diagram.
Answer: The continuous journey of water in nature from earth to clouds and back to the earth is called water cycle. The water cycle mainly consists of following processes:
Q11: Explain how floods causes extensive damage to human life and property?
Answer:
Q12(MCQ): What do we see on the surface of the glass containing ice-chilled water ?
(a) dust
(b) water vapour
(c) water droplets
(d) ice
Answer: (c) water droplets
Q13(MCQ): Evaporation of water in shade is
(a) fast
(b) faster
(c) slow
(d) none of these
Answer: (b) faster
Q14(MCQ): The process of changing water into water vapours is called
(a) filtration
(b) condensation
(c) evaporation
(d) sedimentation
Answer: (c) evaporation
Q15(MCQ): How much water is consumed by a city-dweller in washing, bathing, flushing the toilet etc.?
(a) 2-3 litres
(b) 10-15 litres
(c) 100-300 litres
(d) 1000-1500 litres
Answer: (c) 100-300 litres
Q16(MCQ): If tap of your bathroom is leaking drop by drop, how much water is lost per day?
(a) 1 bucket full of water
(b) 2 buckets full of water
(c) 8 buckets full of water
(d) 20 buckets full of water
Answer: (c) 8 buckets full of water
Q1: Fill up the blanks in the following:(a) The process of changing of water into its vapour is called _________________.
(b) The process of changing water vapour into water is called _________________.
(c) No rainfall for a year or more may lead to _________________ in that region.
(d) Excessive rains may cause _________________.
(e) Water disappears from wet clothes by the process of ___________________.
(f) In winter mornings , __________is formed due to condensation of water vapour near the ground.
(g) The major natural source of water is _________________.
(h) Many tiny water droplets high up in the air, come together and fall down as _____________, __________ and ___________.
Answer:
(a) evaporation
(b) condensation
(c) drought
(d) flood
(e) evaporation
(f) fog
(g) oceans and sea
(h) rain, hail, snow
Q2: State for each of the following whether it is due to evaporation or condensation:
(a) Water drops appear on the outer surface of a glass containing cold water.(b) Steam rising from wet clothes while they are ironed.
(c) Fog appearing on a cold winter morning.
(d) Blackboard dries up after wiping it.
(e) Steam rising from a hot girdle when water is sprinkled on it.
Answer:
(a) Water drops appear on the outer surface of a glass containing cold water. - condensation
(b) Steam rising from wet clothes while they are ironed. - evaporation
(c) Fog appearing on a cold winter morning. - condensation
(d) Blackboard dries up after wiping it. - evaporation
(e) Steam rising from a hot girdle when water is sprinkled on it. - evaporation
Q3: Which of the following statements are “true” ?
Answer:
(a) Water vapour is present in air only during the monsoon. (False ✗)
(b) Water evaporates into air from oceans, rivers and lakes but not from the soil.(False ✗)
(c) The process of water changing into its vapour, is called evaporation.(True ✓)
(d) The evaporation of water takes place only in sunlight.(False ✗)
(e) Water vapour condenses to form tiny droplets of water in the upper layers of air where it is cooler.(True ✓)
(f) Life is possible on earth without water (False ✗)
(g) When water is heated, it changes into ice. (False ✗)
(h) Evaporation of water takes place at all times. (True ✓)
(i) Saline water is fit for drinking and other domestic, agricultural and industrial needs. (False ✗)
(j) About two-thirds of the earth is covered with water. (True ✓)
Q4: Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help? If yes, how?
Answer: Yes, spreading school uniform near anghiti or heater would help dry it quickly. Heater will warm up the surroundings and increase the rate of evaporation. Therefore school uniform will dry up quickly.
Q5: Take out a cooled bottle of water from refrigerator and keep it on a table. After some time you notice a puddle of water around it. Why?
Answer: It is due to condensation of water vapours present in air. The cold surface of the bottle cools the air around it, and the water vapour of the air condenses on its surface.
Q6: To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.
Answer: When we breathe out, moist air comes out which make the glasses wet. Also when we breathe out, we release carbon-dioxide gas which cools the surroundings by absorbing heat from air, thus condenses the water vapours.
Q7: How are clouds formed?
Answer: Clouds are formed due to the process of evaporation and condensation. When air moves up, it gets cooler and cooler. At sufficient height, the air becomes so cool that water vapours present in the air condense. They form tiny droplets and float in air as clouds.
 |
| Drought credits:wikipedia |
Answer: When there is insufficient or no rainfall occurs for more than a year in a region, the scarcity of water happens. Ponds and wells dry up. The soil continues to lose water due to evaporation and transpiration and eventually dry. This leads to drought.
Q9: What is rainwater harvesting? What are the two rainwater harvesting techniques?
Answer: Collecting rain water and storing it for later use is called rainwater harvesting. The two techniques of rainwater harvesting are:
- Rooftop rainwater harvesting.
- Allowing water to into ground directly through roadside drains.
Q10: Explain Water cycle with diagram.
Answer: The continuous journey of water in nature from earth to clouds and back to the earth is called water cycle. The water cycle mainly consists of following processes:
- Evaporation and Transpiration
- Condensation
- Precipitation
- Accumulation
- When the sun heats up the water in rivers, ponds, oceans and lakes, it turns water into vapours. Plants also lose water into air due to transpiration.
- At sufficient heights, the water vapours in the air cool down and condense to form clouds
- Precipitation occurs when too much water vapours condense. The clouds become heavy and begin to fall as rain, hail or snow.
- The water falls on the earth, it goes into lakes, oceans, rivers and ground.
Q11: Explain how floods causes extensive damage to human life and property?
Answer:
- Droughts results in drying up of the crops and vegetation.
- Its leads to scarcity of food and fodder for humans and animal life.
- It leads to malnutrition in humans and animals.
Q12(MCQ): What do we see on the surface of the glass containing ice-chilled water ?
(a) dust
(b) water vapour
(c) water droplets
(d) ice
Answer: (c) water droplets
Q13(MCQ): Evaporation of water in shade is
(a) fast
(b) faster
(c) slow
(d) none of these
Answer: (b) faster
Q14(MCQ): The process of changing water into water vapours is called
(a) filtration
(b) condensation
(c) evaporation
(d) sedimentation
Answer: (c) evaporation
Q15(MCQ): How much water is consumed by a city-dweller in washing, bathing, flushing the toilet etc.?
(a) 2-3 litres
(b) 10-15 litres
(c) 100-300 litres
(d) 1000-1500 litres
Answer: (c) 100-300 litres
Q16(MCQ): If tap of your bathroom is leaking drop by drop, how much water is lost per day?
(a) 1 bucket full of water
(b) 2 buckets full of water
(c) 8 buckets full of water
(d) 20 buckets full of water
Answer: (c) 8 buckets full of water
Ch 13 : Fun With Magnets
Class 6 - Science - CH 13 - Fun with Magnets
Q2: State whether the following statements are true or false.
Answer:
The two ends of the bar magnet represents the two poles.
Magnetic compass works on the same principle. In past it was used by sailors or travellers to find directions.
Q8: You are given an iron strip. How will you make it into a magnet?
Q9: How is a compass used to find
directions?
Answer: The natural magnet is called magnetite.
Q12: Name the place it is believed where natural magnet was found first time.
Q1: Fill in the blanks in the
following:
Answer:
(i) Artificial magnets are made in
different shapes such as _bar-magnet_, _cylindrical_
and _horse-shoe magnet_.
(ii) The Materials which are
attracted towards a magnet are called_magnetic materials_.
(iii) Paper is not a
_magnetic_ material.
(Explanation: Paper does not
attract to magnet. Therefore it is a non-magnetic material).
(iv) In olden days, sailors used to
find direction by suspending a piece of _bar magnet_.
(v) A magnet always has
_two__ poles (i.e. North Pole and South Pole).
Q2: State whether the following statements are true or false.
Answer:
(i) A cylindrical magnet has only
one pole. - False (✗)
(ii) Artificial magnets were
discovered in Greece. - False - (✗)
(iii) Similar poles of a magnet
repel each other. - True - (✓)
(iv) Maximum iron filings stick in
the middle of a bar magnet when it is brought near them.- False - (✗)
(v) Bar magnets always point
towards North-South direction. - True -
(✓)
(vi) A compass can be used to find
East-West direction at any place. - True -
(✓)
(vii) Rubber is a magnetic
material. False - (✗)
Q3: It was observed that a
pencil sharpener gets attracted by both the poles of a magnet although its body
is made of plastic. Name a material that might have been used to make some part
of it.
Answer: The blade of the pencil sharpener is made of
iron. Iron is a magnetic in nature. That's why the sharpener gets attracted by
the poles of a magnet.
Q4: Column I shows different
positions in which one pole of a magnet is placed near that of the other. Column
II indicates the resulting action between them for each situation. Fill in the
blanks.
Answer: | Column I | Column II |
|---|---|
| N-N | Repulsion |
| N-_S_ | Attraction |
| S-N | Attraction |
| _N_-S | Repulsion |
Q5: Write any two properties of
a magnet.
Answer:
- Each magnet has two poles i.e. North Pole(N) and South Pole(P)
- Opposite poles of two magnet attract each other while like poles of two magnet repel each other.
- A freely suspended magnet always aligns in N-S direction.
 |
| Bar Magnet |
Q6: Where are poles of a bar magnet
located?
 |
| Magnetic Compass |
Q7: A bar magnet has no markings
to indicate its poles. How would you find out near which end is its north pole
located?
Answer: Hang up the magnet by a cotton thread so that
it hangs freely. When it comes to rest, we notice that the magnet is lying in a
North - South direction.
Magnetic compass works on the same principle. In past it was used by sailors or travellers to find directions.
Q8: You are given an iron strip. How will you make it into a magnet?
Answer:
- Take a rectangular piece of iron. Place
it on the table. - Take a bar magnet and place one of its poles near one edge of the bar of iron.
- Without lifting the bar magnet, move it along the length of the iron bar till you reach the other end.
- Lift the magnet and bring the pole (the same pole you started with) to the same point of the iron bar from which you began
- Move the magnet again along the iron bar in the same direction as you did
before. Repeat this
process about 30-40 times. - Bring few allpins near to the iron bar and check if it is converted to a magnet or not.
 |
| Compass Directions |
Answer: A magnetic compass consists of a small
pointed magnet which is suspended freely. A freely suspended magnet always
aligns in N-S direction. The red coloured magnetic needle points to North
direction. Once we know North direction, we can easily find out the other
directions.
E.g. If North is upwards, South is
downward side, East will be on right hand side and West shall be on left hand
side.
Q10: A magnet was brought from
different directions towards a toy boat that has been floating in water in a
tub. Affect observed in each case is stated in Column I. Possible reasons for
the observed affects are mentioned in Column II. Match the statements given in
Column I with those in Column II.
Answer:
| Column I | Column II |
|---|---|
| Boat gets attracted towards the magnet | Boat is made of magnetic material |
| Boat is not affected by the magnet | Boat is made up non-magnetic material |
| Boat moves towards the magnet if
north pole of the magnet is brought near its head |
Boat is fitted with a magnet with
south pole towards its head |
| Boat moves away from the magnet
when north pole is brought near its head |
Boat is fitted with a magnet with
north pole towards its head |
| Boat floats without changing its direction. | Boat has a small magnet fixed along
its length |
Q11: What is
magnetite?
Answer: The natural magnet is called magnetite.
Q12: Name the place it is believed where natural magnet was found first time.
Answer: Magnesia in Ancient Greece.
Q13: How magnets were
discovered?
Answer: There was a shepherd called Magnes who lived
in Ancient Greece. He used to carry a stick with iron piece attached to it while
taking his sheep for grazing to nearby mountains. One day he found his stick was
attracted to a rock. This was the way he discovered natural magnet.
Q14: What are magnetic
materials? Give two examples.
Answer: The materials which get attracted to magnets
are known as
magnetic materials.
magnetic materials.
Examples are: Iron, Nickel,
Cobalt
Q15: What are non-magnetic
materials? Give examples.
Answer: The materials which do not get attracted to
magnets are called non-magnetic materials.
Examples: Plastic, wood,
paper
Q16: How do magnets loose their
magnetic property?
Answer: Magnets lose their property on heating, hammering and dropping.
Q17: If a bar magnet is cut lengthwise into three parts, how many number of Poles will form?
Answer: Six (Three North and three south)
Answer: Magnets lose their property on heating, hammering and dropping.
Q17: If a bar magnet is cut lengthwise into three parts, how many number of Poles will form?
Answer: Six (Three North and three south)
Ch 12 : Electricity and Circuits
CBSE Class 6 - Science - CH 12 - Electricity and Circuits
Q1. Fill in the blanks :(a) A device that is used to break an electric circuit is called _______________.
(b) An electric cell has _______________ terminals.
(c) Electric cell is a device which converts energy of chemicals into ________________energy.
(d) The electric energy which is supplied in our home comes from electric _______________houses.
(e) An electric ______________ is a continuous path along which the current flows.
(f) If the filament of a bulb breaks, it is said to be ______________.
(g) Rubber is a good example of electric ______________.
Answer:
(a) switch
(b) two terminals
(c) electrical
(d) poles nearby
(e) circuit
(f) fused
(g) insulator
Q2: Mark 'True' or 'False' for following statements:
Answer:
(a) Electric current can flow through metals. (✓ True)
(b) Instead of metal wires, a jute string can be used to make a circuit. (✗ False)
(c) Electric current can pass through a sheet of thermocol. (✗ False)
(d) When current flows through a circuit, the circuit is called open circuit. (✗ False)
(e) An electric bulb has one terminal (✗ False)
Q3: What is an electric cell?
Answer: An electric cell is a device which converts chemical
energy into electric energy. It has two different metal plates:
Q4: Explain why the bulb would not glow in the arrangement shown in Fig. below:
Answer: The handle of the screw driver acts as an insulator. It does not allow current to flow and circuit is still open. Therefore the bulb does not glow in the arrangement.
Q5: Complete the drawing shown in Fig below to indicate where the free ends of the two wires
should be joined to make the bulb glow.
Answer: The bulb
will glow when circuit is complete i.e. one end of the wire from clip is
connected to positive terminal. Second end of the wire from the clip is
connected to the bulb.
Q6:
Would the bulb glow after completing the circuit shown in Fig. above (Q5) if
instead of safety pin we use an eraser?
Answer: No. An eraser is made of rubber which is a poor conductor of electricity. Therefore, bulb would not glow.
Q7:
What is the purpose of using an electric switch? Name some electrical gadgets
that have switches built into them.
Answer: An electric switch is a simple device which is used to break or complete an electric circuit. Switches are widely used in different electrical or electronic gadgets. A few are:
Answer: No.
Q9: Would the bulb glow in the circuit shown in Fig. below?
Answer: The electric bulb has two terminals, both the
wires are connected to the one terminal of the bulb. Current will not flow from
the bulb and it will not glow. To make glow, the two wires should be connected
to each terminal of the bulb, as shown below.
Q10:
What are the components of an electric circuit?
Answer: In general a circuit has the following components:
Q11: How many terminals are there in an electric cell?
Answer:An electric cell has two terminals; positive and negative. The metal cap is the positive terminal of the cell. The metal disc is the negative terminal.
Q12: Using the "conduction tester" on an object it was found that the bulb begins to
glow. Is that object a conductor or an insulator? Explain.
Answer:Since the object allows current to flow and completes the circuit. Due to this bulb begins to glow. It means the object is a conductor of electricity.
Q13: What are conductors? Give examples.
Answer: The materials which allow electric current to pass through them are called conductors.
Examples are: All metals (copper, silver, iron) are good conductors. Water usually contains impurities and traces of salt is also a good conductor. Human body is also a conductor.
Q14: What are insulators? Give examples.
Answer: Materials that do not allow electricity to pass through them are called insulators. Insulators oppose electric current and so they are used as protection from the dangerous effects of electricity.
Examples of insulators are glass, air, plastic, cotton, thermocol, wood and rubber.
Q15: Why should an
electrician use rubber gloves while repairing an electric switch at your home?
Explain
Answer: Electricians need to touch copper wires or they may accidentally come in contact with live wires (wires carrying current). Since human body is also a good conductor, electricians may get shock. Rubber is good insulator. To prevent themselves from electric shock or flow of current, the electricians use rubber gloves while repairing.
Q16: The handles of the tools like screwdrivers and pliers used by electricians for repair work usually have plastic or rubber covers on them. Can you explain why?
Answer: Without the help of insulators, the use of electrical tools like pliers and screwdrivers is impossible. Wood and plastics are insulators and help in avoiding direct contact with electric current. When electricians touch these live electric wires with the tools covered with plastic and wood, current does not flow in their body avoid any accident.
Q17(MCQ): In an electric bell, the electric energy is transformed into ____________energy.
(a)Mechanical energy
(b) Magnetic energy
(c) Sound energy
(d) Light energy
Answer: (b) Magnetic energy
Q18(MCQ): The tiny coiled metal wire present inside the bulb is called____________.
(a) Element
(b) Conductor
(c) Filament
(d) None of these
Answer: (c) Filament
Q19(MCQ): Which of the following is NOT a good conductor of electricity?
(a) Mercury
(b) Copper
(c) Plastic
(d) Aluminum foil
Answer: (c) Plastic
Q20(MCQ): Which of the following is a good conductor of electricity?
(a) Wood
(b) Paper
(c) Glass
(d) Graphite
Answer: (d) Graphite
Q21: What will happen if you join the two terminals of a cell without connecting them through a switch or a bulb?
Answer: By doing so, the chemicals in the electric cell get used up very fast and the cell will no longer produce electric current. It will stop working.
Q22: Why do an electric bulb and an electric cell have two terminals?
Answer: Because the two terminals (positive and negative) can be connected to form an electric circuit.
Q23: Is Distilled water a conductor of electricity?
Answer: No. The distilled water is the purest water and it acts as an insulator. Therefore, it used in batteries as an insulator. The tap water, sea water contains some traces of salts and impurities, due to which it becomes good conductor of electricity.
Q1. Fill in the blanks :(a) A device that is used to break an electric circuit is called _______________.
(b) An electric cell has _______________ terminals.
(c) Electric cell is a device which converts energy of chemicals into ________________energy.
(d) The electric energy which is supplied in our home comes from electric _______________houses.
(e) An electric ______________ is a continuous path along which the current flows.
(f) If the filament of a bulb breaks, it is said to be ______________.
(g) Rubber is a good example of electric ______________.
Answer:
(a) switch
(b) two terminals
(c) electrical
(d) poles nearby
(e) circuit
(f) fused
(g) insulator
Q2: Mark 'True' or 'False' for following statements:
Answer:
(a) Electric current can flow through metals. (✓ True)
(b) Instead of metal wires, a jute string can be used to make a circuit. (✗ False)
(c) Electric current can pass through a sheet of thermocol. (✗ False)
(d) When current flows through a circuit, the circuit is called open circuit. (✗ False)
(e) An electric bulb has one terminal (✗ False)
Answer: An electric cell is a device which converts chemical
energy into electric energy. It has two different metal plates:
- one is the positive terminal
- the other is the negative terminal
Q4: Explain why the bulb would not glow in the arrangement shown in Fig. below:
Answer: The handle of the screw driver acts as an insulator. It does not allow current to flow and circuit is still open. Therefore the bulb does not glow in the arrangement.
Q5: Complete the drawing shown in Fig below to indicate where the free ends of the two wires
should be joined to make the bulb glow.
Answer: No. An eraser is made of rubber which is a poor conductor of electricity. Therefore, bulb would not glow.
Answer: An electric switch is a simple device which is used to break or complete an electric circuit. Switches are widely used in different electrical or electronic gadgets. A few are:
- Toggle switches used in houses.
- Pushbutton switches used in microwaves, water pump, mixer etc.
- Joystick switches used in Video Games Controllers, Toy Cars etc.
Answer: No.
Q9: Would the bulb glow in the circuit shown in Fig. below?
Answer: In general a circuit has the following components:
- A cell or battery : source of electricity.
- Connecting wires
- Bulb or electric device
- Key or switch.
Q11: How many terminals are there in an electric cell?
Answer:An electric cell has two terminals; positive and negative. The metal cap is the positive terminal of the cell. The metal disc is the negative terminal.
Q12: Using the "conduction tester" on an object it was found that the bulb begins to
glow. Is that object a conductor or an insulator? Explain.
Answer:Since the object allows current to flow and completes the circuit. Due to this bulb begins to glow. It means the object is a conductor of electricity.
Q13: What are conductors? Give examples.
Answer: The materials which allow electric current to pass through them are called conductors.
Examples are: All metals (copper, silver, iron) are good conductors. Water usually contains impurities and traces of salt is also a good conductor. Human body is also a conductor.
Q14: What are insulators? Give examples.
Answer: Materials that do not allow electricity to pass through them are called insulators. Insulators oppose electric current and so they are used as protection from the dangerous effects of electricity.
Examples of insulators are glass, air, plastic, cotton, thermocol, wood and rubber.
Answer: Electricians need to touch copper wires or they may accidentally come in contact with live wires (wires carrying current). Since human body is also a good conductor, electricians may get shock. Rubber is good insulator. To prevent themselves from electric shock or flow of current, the electricians use rubber gloves while repairing.
Q16: The handles of the tools like screwdrivers and pliers used by electricians for repair work usually have plastic or rubber covers on them. Can you explain why?
Answer: Without the help of insulators, the use of electrical tools like pliers and screwdrivers is impossible. Wood and plastics are insulators and help in avoiding direct contact with electric current. When electricians touch these live electric wires with the tools covered with plastic and wood, current does not flow in their body avoid any accident.
Q17(MCQ): In an electric bell, the electric energy is transformed into ____________energy.
(a)Mechanical energy
(b) Magnetic energy
(c) Sound energy
(d) Light energy
Answer: (b) Magnetic energy
Q18(MCQ): The tiny coiled metal wire present inside the bulb is called____________.
(a) Element
(b) Conductor
(c) Filament
(d) None of these
Answer: (c) Filament
Q19(MCQ): Which of the following is NOT a good conductor of electricity?
(a) Mercury
(b) Copper
(c) Plastic
(d) Aluminum foil
Answer: (c) Plastic
Q20(MCQ): Which of the following is a good conductor of electricity?
(a) Wood
(b) Paper
(c) Glass
(d) Graphite
Answer: (d) Graphite
Q21: What will happen if you join the two terminals of a cell without connecting them through a switch or a bulb?
Answer: By doing so, the chemicals in the electric cell get used up very fast and the cell will no longer produce electric current. It will stop working.
Q22: Why do an electric bulb and an electric cell have two terminals?
Answer: Because the two terminals (positive and negative) can be connected to form an electric circuit.
Q23: Is Distilled water a conductor of electricity?
Answer: No. The distilled water is the purest water and it acts as an insulator. Therefore, it used in batteries as an insulator. The tap water, sea water contains some traces of salts and impurities, due to which it becomes good conductor of electricity.
Ch 11 : Light,Shadows & Reflections
CBSE Class 6 - Science - CH 11 - LIGHT, SHADOWS AND REFLECTIONS
Q1(MCQ): A body which emits light by itself is
(a) Luminous body
(b) Non luminous body
(c) Shadow
(d) Opaque body
Answer: (a) Luminous body
Q2: Fill in the Blanks
(i) Object like the sun that give out or emit light of their own are called ______________ Object.
(ii) Light travels in ______________ line.
(iii) _________________ are formed when an opaque object comes in the path of light
(iv) Polished surfaces produce ____________________ reflection which causes glare in our eyes.
(v) ______________________objects allow light to pass through them completely.
(vi) ______________________ objects do not allow the light to pass through it at all.
(vii) _______________________ objects allow the light to pass through them partially.
(viii) Stars are ________________ sources of light.
(ix) Shadows are of two kinds named _________ and ____________.
Answer:
(i) luminuous
(ii) straight
(iii) Shadows
(iv) regular
(v) Transparent
(vi) Opaque
(vii) Translucent
(viii) natural
(ix) umbra, penumbra
Q3(NCERT): Rearrange the boxes given below to make a sentence that helps us understand opaque objects.
Answer: OPAQUE
OBJECTS MAKE SHADOWS
Q4: What are luminous objects? Give two examples.
Answer: Objects that emit their own light are called luminous objects. Stars, Sun, candle, torch are examples of luminous objects. The light emitted by luminous objects enables us to see things.
Q5: What are non-luminous objects? Give two examples.
Answer: The objects which do not emit light are called non-luminous objects. Table, chair, trees, moon are examples of non-luminous objects.
Q6: To see an object what do we need?
Answer: To see any non-luminous object we need the following:
Q7: Moon appears bright at night. Is it a luminous or non-luminous body?
Answer: Moon is a non-luminous body, it does not emit its own light. It reflects the sun light that falls on it.
Q8(NCERT): Classify the objects or materials given below as opaque, transparent or translucent and luminous or non-luminous:
Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the flame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of cellophane, a wire mesh, kerosene stove, sun, firefly, moon.
Answer:
Q9: How shadows are formed? What are different types of shadows?
Answer: When some objects are placed in the path of light, a dark portion is formed on the opposite side of the objects. This dark portion is called shadow.
There are two types of shadows:
The penumbra is formed where some light reaches and it is grey in color.
Q10: Do all objects cast shadow?
Answer: No. Only opaque objects cast shadow.
Q11: Which type of surfaces produce clear images?
Answer: Polished and plane reflecting surfaces produce clear image.
Q12(NCERT): Can you think of creating a shape that would give a circular shadow if held in one way and a rectangular shadow if held in another way?
Answer: A cylinder object can cast shadows in two ways. When the top circular view faces the sun, a circular shape shadow is formed. When its horizonatal side faces the sun, it casts a rectangular shadow.
Q13(NCERT): In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror?
Answer: To see the reflection, source of light is required We can only in the presence of light.
Q14:
What is lateral inversion?
Answer: When an object is placed in front of a plane mirror, the right side of the object appears to be on the left side of image and left side of the object appears to be on the right side of image. This is called lateral inversion.
Q15: State the principle behind the working of a pinhole camera.
Answer: Light travels in straight line. This principle is behind the working of pinhole camera.
Q16: What are transparent objects?
Answer: The objects which allow light to pass through them are called transparent objects.
Q17: What are opaque objects?
Answer: The objects which do not allow light to pass through them are called opaque objects.
Q18: What are translucent objects?
Answer: The objects which partially allow light to pass through them are called translucent objects.
Q19: What types of objects do not cast shadows?
Answer: Transparent objects and few translucent objects, because light passes through them.
Q20(MCQ): The image formed in pinhole camera is
(a) Inverted
(b) Erect
(c) Both a and b
(d) None of the above
Answer: (a) Inverted
Q1(MCQ): A body which emits light by itself is
(a) Luminous body
(b) Non luminous body
(c) Shadow
(d) Opaque body
Answer: (a) Luminous body
Q2: Fill in the Blanks
(i) Object like the sun that give out or emit light of their own are called ______________ Object.
(ii) Light travels in ______________ line.
(iii) _________________ are formed when an opaque object comes in the path of light
(iv) Polished surfaces produce ____________________ reflection which causes glare in our eyes.
(v) ______________________objects allow light to pass through them completely.
(vi) ______________________ objects do not allow the light to pass through it at all.
(vii) _______________________ objects allow the light to pass through them partially.
(viii) Stars are ________________ sources of light.
(ix) Shadows are of two kinds named _________ and ____________.
Answer:
(i) luminuous
(ii) straight
(iii) Shadows
(iv) regular
(v) Transparent
(vi) Opaque
(vii) Translucent
(viii) natural
(ix) umbra, penumbra
Q3(NCERT): Rearrange the boxes given below to make a sentence that helps us understand opaque objects.
Q4: What are luminous objects? Give two examples.
Answer: Objects that emit their own light are called luminous objects. Stars, Sun, candle, torch are examples of luminous objects. The light emitted by luminous objects enables us to see things.
Q5: What are non-luminous objects? Give two examples.
Answer: The objects which do not emit light are called non-luminous objects. Table, chair, trees, moon are examples of non-luminous objects.
Q6: To see an object what do we need?
Answer: To see any non-luminous object we need the following:
- source of light
- an object
- eyes
Q7: Moon appears bright at night. Is it a luminous or non-luminous body?
Answer: Moon is a non-luminous body, it does not emit its own light. It reflects the sun light that falls on it.
Q8(NCERT): Classify the objects or materials given below as opaque, transparent or translucent and luminous or non-luminous:
Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the flame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of cellophane, a wire mesh, kerosene stove, sun, firefly, moon.
Answer:
| Object | Transparent /Translucent /Opaque |
Luminous/ Non-luminous |
|---|---|---|
| Air, Water | Transparent | Non-luminous |
| Piece of Rock, Sheet of Aluminium, Mirror, Wooden Board, CD, Umbrella, Wall, Sheet of Carbon Paper, Sheet of cardboard, Moon |
Opaque | Non-luminous |
| A sheet of polythene, Smoke, Fog, Sheet of cellophone, Wire-mesh, |
Translucent | Non-luminous |
| A piece of Red hot iron, Light fluorescent tube, Lighted torch, Kerosene stove, Sun, firefly |
Opaque | Luminous |
| Flame of gas burner | Translucent | Luminous |
Q9: How shadows are formed? What are different types of shadows?
Answer: When some objects are placed in the path of light, a dark portion is formed on the opposite side of the objects. This dark portion is called shadow.
There are two types of shadows:
- umbra
- penumbra.
The penumbra is formed where some light reaches and it is grey in color.
Q10: Do all objects cast shadow?
Answer: No. Only opaque objects cast shadow.
Q11: Which type of surfaces produce clear images?
Answer: Polished and plane reflecting surfaces produce clear image.
Q12(NCERT): Can you think of creating a shape that would give a circular shadow if held in one way and a rectangular shadow if held in another way?
Answer: A cylinder object can cast shadows in two ways. When the top circular view faces the sun, a circular shape shadow is formed. When its horizonatal side faces the sun, it casts a rectangular shadow.
Q13(NCERT): In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror?
Answer: To see the reflection, source of light is required We can only in the presence of light.
Answer: When an object is placed in front of a plane mirror, the right side of the object appears to be on the left side of image and left side of the object appears to be on the right side of image. This is called lateral inversion.
Q15: State the principle behind the working of a pinhole camera.
Answer: Light travels in straight line. This principle is behind the working of pinhole camera.
Q16: What are transparent objects?
Answer: The objects which allow light to pass through them are called transparent objects.
Q17: What are opaque objects?
Answer: The objects which do not allow light to pass through them are called opaque objects.
Q18: What are translucent objects?
Answer: The objects which partially allow light to pass through them are called translucent objects.
Q19: What types of objects do not cast shadows?
Answer: Transparent objects and few translucent objects, because light passes through them.
Q20(MCQ): The image formed in pinhole camera is
(a) Inverted
(b) Erect
(c) Both a and b
(d) None of the above
Answer: (a) Inverted
Ch 10 : Motion And Measurements
Class 6 - Science - CH10 - Motion and Measurement of Distances
Q1: Give two examples each, of modes of transport used on land, water and
air.Answer:
- On Land: Bicycle, Car, Bus
- On Water: Ship, Boat, Ferry
- On Air: Helicopter, Aeroplane, Glider
Q2: Fill in the blanks:
Answer:
(i) One metre is ____100_ cm.
(ii) Five kilometre is ___5000_ m. (1 Km = 1000m)
(iii) Motion of a child on a swing is ___periodic motion__.
(iv) Motion of the needle of a sewing machine is __periodic motion_.
(v) Motion of wheel of a bicycle is__circular motion_.
Q3: Why can a pace or a footstep not be used as a standard unit of length?
Answer: A pace or a footstep not be used as a standard unit of length because the size of pace and footstep vary from person to person. This will lead to confusion while measuring the lengths by different persons. We should use standard units like International System of Units (SI Units).
Q4: Arrange the following lengths in their increasing magnitude:
1 metre, 1 centimetre, 1 kilometre,1 millimetre
Answer: 1 millimetre < 1 centimetre < 1 metre < 1 kilometre
Q5: The height of a person is 1.65 m. Express it
into cm and mm.
Answer: 1m = 100cm and 1cm = 10mm
∴ 1.65 m = 1.65 x 100cm = 165cm
Also, 1.65m = 165cm = 165 x 10mm = 1650 mm
Q6: The distance between Radha's home and her
school is 3250 m. Express this distance into km.
Answer: Since 1 m = 1 ÷ 1000km
∴ 3250m = 3250 ÷ 1000 = 3.250 km
Q7: While measuring the length of a knitting needle, the reading of the scale at one end is 3.0 cm and at the other end is 33.1 cm. What is the length of the needle?
Answer: Length of the needle = Final reading -
Starting Reading
= 33.1 cm - 3.0 cm =
30.1 cm
Q8: Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.
Answer: Similarity: Both ceiling fan and bicycle exhibit circular motion.
Difference: Bicycle shows rectilinear motion while ceiling fan does not.
Q9:Why could you not use an elastic measuring tape to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with an elastic tape?
Answer: Since the tape is stretchable, its measurements will be inaccurate. Therefore we cannot use it as measuring tape. While measuring a distance, we need to tell someone how much tape has been stretched which is difficult to measure. It leads to incorrect measurements.
Q10: Give two examples of periodic motion.
Answer: Pendulum, Guitar String, Needle of Sewing Machine.
Q11: Which invention lead to a great change in modes of transport?
Answer: Invention of Wheel
Q12: Before 19th century which power was used in transportation?
Answer: Till the beginning of 19th century, people reply on animal power to transport them from one place to another.
Q13: Which invention as new source of power lead to development of railroads?
Answer: Steam engine.
Q14: Name the 20th century inventions in the field of transportation.
Answer: Electric train, monorail, supersonic aeroplanes and spacecraft.
Ch 9 : The Living Organisms and Their Surroundings
Class 6 - Science - CH9 - The Living Organisms and Their Surroundings
Q1: What is a habitat?Answer: The surroundings where plants and animals live, is called their habitat. A habitat provides suitable climatic conditions like food and shelter so that plants and animals can live there.
Q2: Do all organisms live in same habitat?
Answer: No all organisms do not live in same habitat. Some may share the habitat e.g. lion and deer. For example camel can live in deserts only while frogs can survive in fresh/rain water.
Q3 Are all forests habitats of tigers or lions?
Answer: No all forest are not habitats of tigers and lions. For example, tigers can live in forests which have thick forests, water (ponds and streams) and rich supply of food (e.g. deer).
Q4: How are cactus adapted to survive in a desert?
Answer: Cactus survive in deserts due to following adaptations:
Q5. Fill up the blanks
Answer:
(a) The presence of specific features, which enable a plant or an animal to live in a particular habitat, is called adaptation.
(b) The habitats of the plants and animals that
live on land are called terrestrial habitat.
(c) The habitats of plants and animals that live in water are called aquatic habitat.
(d) Soil, water and air are the abiotic factors of a habitat.
(e) Changes in our surroundings that make us respond to them, are stimuli called.
(f) Fish have streamline shaped body that help them to move inside water.
(g) Dolphins and whales breathe through nostrils or blowholes.
(h) In the mountain regions, the trees are normally cone shaped and have sloping branches.
Q7: Name two plants and two animals of mountain regions.
Answer: Animals:
Yak, Snow leopard, mountain goat.
Q9: Which of the non-living things listed below, were once part of a living thing?
Butter, Leather, Soil, Wool, Electric bulb, Cooking oil, Salt, Apple, Rubber
Answer: Following are the things which were once part of living beings:
Q10: List the common characteristics of the living things.
Answer:
Q11: Explain, why speed is important for survival in the grasslands for animals that live there. (Hint: There are few trees or places for animals to hide in grasslands habitats.)
Answer: In the grassland there are less number of trees and places to hide. The animals are vulnerable to predators (e.g. lions, tigers, wolves etc.). They can only survive and escape if they run very fast. Therefore speed is important for survival in the grasslands for animals (e.g. deer) that live there.
Q12: Give examples of animals which give birth to young ones.
Answer: Humans, dogs, cats (mammals) give birth to young ones.
Q13: Give examples of Terrestrial habitats.
Answer: Deserts, forests, grasslands, coastal region, mountain regions.
Q14: Give examples of aquatic habitats.
Answer: Aquatic habitat includes rivers, ponds, lakes, ocean and swamps.
Q15: What is Acclimatization? How it is different from adaptation?
Answer: The small adjustments by the body to overcome small changes in the surrounding atmosphere for a short period of time are called acclimatization. While in adaptation, it takes thousands of years for a livings being to adapt to its habitat.
Q16: What are the two components of habitat?
Answer:
Q17: Why is adaptation necessary? What does happen to those animal who do not adapt to the environment?
Answer: Over thousands of years, the abiotic factors of a region change. To survive animals and plants must adapt to these changes. Those animals which cannot adapt to these changes die out, and only the adapted ones survive.
Q18: Do animals have the same kind of
adaptations? Explain with an example.
Answer: Animals adapt to different abiotic factors in different ways. For example, to survive in deserts, camels have long legs and padded feet. While desert animals like snakes and rats do not have long legs, but they stay in burrows deep in the sand and come out during night, when it is cooler.
Q19: Name four important abiotic factors needed for growth of plants.
Answer:
Q1: What is a habitat?Answer: The surroundings where plants and animals live, is called their habitat. A habitat provides suitable climatic conditions like food and shelter so that plants and animals can live there.
Q2: Do all organisms live in same habitat?
Answer: No all organisms do not live in same habitat. Some may share the habitat e.g. lion and deer. For example camel can live in deserts only while frogs can survive in fresh/rain water.
Q3 Are all forests habitats of tigers or lions?
Answer: No all forest are not habitats of tigers and lions. For example, tigers can live in forests which have thick forests, water (ponds and streams) and rich supply of food (e.g. deer).
Q4: How are cactus adapted to survive in a desert?
Answer: Cactus survive in deserts due to following adaptations:
- It has flat green stem to store water and prepare food by photosynthesis.
- The stem is also covered with a thick waxy layer, which helps to retain water.
- Its roots that go very deep into the soil for absorbing water.
- Leaves are turned into spines to prevent loss of water.
Q5. Fill up the blanks
Answer:
(a) The presence of specific features, which enable a plant or an animal to live in a particular habitat, is called adaptation.
(c) The habitats of plants and animals that live in water are called aquatic habitat.
(d) Soil, water and air are the abiotic factors of a habitat.
(e) Changes in our surroundings that make us respond to them, are stimuli called.
(f) Fish have streamline shaped body that help them to move inside water.
(g) Dolphins and whales breathe through nostrils or blowholes.
(h) In the mountain regions, the trees are normally cone shaped and have sloping branches.
Q6: Which of the things in the following list
are nonliving?Plough, Mushroom, Sewing machine, Radio, Boat, Water hyacinth,
Earthworm
Answer:
Non-living Things: Plough, Sewing machine, Radio, Boat, Q7: Name two plants and two animals of mountain regions.
Plants: Pines, Spruce, Fir, Cedar
Q8: Give an example of a non-living thing,
which shows any two characteristics of living things.
Answer: A bus or
a car which shows movement and consume energy (petrol). Q9: Which of the non-living things listed below, were once part of a living thing?
Butter, Leather, Soil, Wool, Electric bulb, Cooking oil, Salt, Apple, Rubber
Answer: Following are the things which were once part of living beings:
- Butter: Obtained from milk from dairy animals.
- Leather: From animal skin of buffaloes, cows etc.
- Wool: From hair of sheep and goat
- Cooking oil: seeds of plants (e.g. mustard) or by grinding whole plant (e.g. olive),
- Apple: fruit from apple tree
- Rubber: Latex of rubber tree.
Q10: List the common characteristics of the living things.
Answer:
- Movement: All organisms show movement of one kind or another. Animals can move from one place to another. While plants also show movement e.g. bend towards light.
- Respiration: All organisms breathe and respire. They intake oxygen and release carbon di-oxide.
- Feeding: They consume food to stay fit and grow.
- Growth and Death: All living beings grow i.e. with age they become larger in size and eventually die.
- Excretion: They remove waste material their bodies.
- Reproduction: Living being bear children.
- Stimuli or Sensitivity: All living beings react to external changes around them.
Q11: Explain, why speed is important for survival in the grasslands for animals that live there. (Hint: There are few trees or places for animals to hide in grasslands habitats.)
Answer: In the grassland there are less number of trees and places to hide. The animals are vulnerable to predators (e.g. lions, tigers, wolves etc.). They can only survive and escape if they run very fast. Therefore speed is important for survival in the grasslands for animals (e.g. deer) that live there.
Q12: Give examples of animals which give birth to young ones.
Answer: Humans, dogs, cats (mammals) give birth to young ones.
Q13: Give examples of Terrestrial habitats.
Answer: Deserts, forests, grasslands, coastal region, mountain regions.
Q14: Give examples of aquatic habitats.
Answer: Aquatic habitat includes rivers, ponds, lakes, ocean and swamps.
Q15: What is Acclimatization? How it is different from adaptation?
Answer: The small adjustments by the body to overcome small changes in the surrounding atmosphere for a short period of time are called acclimatization. While in adaptation, it takes thousands of years for a livings being to adapt to its habitat.
Q16: What are the two components of habitat?
Answer:
- Biotic component
- Abiotic component
Q17: Why is adaptation necessary? What does happen to those animal who do not adapt to the environment?
Answer: Over thousands of years, the abiotic factors of a region change. To survive animals and plants must adapt to these changes. Those animals which cannot adapt to these changes die out, and only the adapted ones survive.
Answer: Animals adapt to different abiotic factors in different ways. For example, to survive in deserts, camels have long legs and padded feet. While desert animals like snakes and rats do not have long legs, but they stay in burrows deep in the sand and come out during night, when it is cooler.
Q19: Name four important abiotic factors needed for growth of plants.
Answer:
- Soil
- Air
- Water
- Sunlight
Ch 8 : Body Movements
CBSE-Class 6 - Science - Ch8 - Body Movements
Q1:
Fill in the blanks:
Answer:
(a) Joints of the bones help in the _movement_ of the body.
(b) A combination of bones and cartilages forms the _skeleton_ of the body.
(c) The bones at the elbow are joined by a _hinge_ joint.
(d) The contraction of the _muscle_ pulls the bones during movement.
Q2: Indicate true (T) and false (F) among the following sentences.
Answer:
(a) The movement and locomotion of all animals is exactly the same. (False)
(b) The cartilages are harder than bones. (False)
(c) The finger bones do not have joints. (False)
(d) The fore arm has two bones. (True)
(e) Cockroaches have an outer skeleton. (True)
Q3: Match the items in Column I with one or more items of Column II.
Answer:
Q4:What is a ball and socket joint?
Answer: A ball and socket joint is a moveable joint. It has a rounded end of one bone fit into the cavity (hollow space) of the other bone. It allows movement in all directions. Example: shoulder joints.
Q5: Which of the skull bones are movable?
Answer: Only the lower jaw in skull bones is movable.
Q6: Why can our elbow not move backwards?
Answer: Elbow joint is an example of hinge joint which allows movement back and forth. Therefore, we cannot move our elbow backwards.
Q7: What are joints?
Answer: The place where two bones meet in a skeleton is called a joint.
Q8: How do animals move from place to place? Fill the table.
Answer:
Q9: What are bones made up of?
Answer: Bones are made up of Calcium, Phosphorus, and other minerals.
Q10: What is a skeleton?
Answer: The framework of the body formed by the bones and cartilages is called skeleton.
Q11: What are the functions of skeleton?
Answer:
Answer: The longest bone in the human body is the thigh bone or femer. It is about 45cm long.
Q13: Name the smallest bone in the human body.
Answer: Stapes is the smallest bone present inside the ear.
Q14: How many bones usually a human body has?
Answer: Human body has 206 bones.
Q15: Why do doctors use X-Ray images?
Answer: Sometimes when we are hurt, or have an accident, doctors use these X-ray images to find out if there is any injury to the bones. The Xrays show the shapes of the bones in our bodies.
Q16: List some important parts of the skeleton.
Answer:
Q17: What is a Ribcage? How does it help to our body?
Answer: Ribcage is box like structure which is a part of our skeletal system. It consists of 12 pairs of curved bones called ribs. They join the chest bone and the backbone together to form a box. Ribcage protects the internal organs of the body like heart, lungs.
Q18: What is a skull? What is its function?
Answer: The bony part of head is called skull. The skull is made up of many bones joined together. Only the lower jaw bone is movable. It protects the brain.
Q19: How does human body perform its movement activities?
Answer: Human body perform all these activities with the help of the movements of the bones and muscles.
Q20: Do muscles push and pull both?
Answer: No, muscles can pull only. That;s why to move a bone, a pair of muscles act in opposite directions.
Q21: What is the difference between bone and cartilage?
Answer: Bone is hard and inflexible. E.g. femur (thigh bone). While cartilage is soft and flexible. E.g. Ear and nose bones are actually cartilage.
 |
| Bones help in movement |
Answer:
(a) Joints of the bones help in the _movement_ of the body.
(b) A combination of bones and cartilages forms the _skeleton_ of the body.
(c) The bones at the elbow are joined by a _hinge_ joint.
(d) The contraction of the _muscle_ pulls the bones during movement.
Q2: Indicate true (T) and false (F) among the following sentences.
Answer:
(a) The movement and locomotion of all animals is exactly the same. (False)
(b) The cartilages are harder than bones. (False)
(c) The finger bones do not have joints. (False)
(d) The fore arm has two bones. (True)
(e) Cockroaches have an outer skeleton. (True)
Q3: Match the items in Column I with one or more items of Column II.
Answer:
| Column I | Column II |
|---|---|
| Upper jaw | is an immovable joint |
| Fish | have fins on the body have a streamlined body |
| Ribs | protect the heart |
| Snail | shows very slow movement |
| Cockroach | has an outer skeleton can fly in the air |
Q4:What is a ball and socket joint?
Answer: A ball and socket joint is a moveable joint. It has a rounded end of one bone fit into the cavity (hollow space) of the other bone. It allows movement in all directions. Example: shoulder joints.
Q5: Which of the skull bones are movable?
Answer: Only the lower jaw in skull bones is movable.
Q6: Why can our elbow not move backwards?
Answer: Elbow joint is an example of hinge joint which allows movement back and forth. Therefore, we cannot move our elbow backwards.
Q7: What are joints?
Answer: The place where two bones meet in a skeleton is called a joint.
Q8: How do animals move from place to place? Fill the table.
Answer:
| Animal | Body part used for moving from place to place |
How does the animal move? |
|---|---|---|
| Cow | Legs | Walk |
| Humans | Legs | Walk |
| Snake | Whole body | Slther |
| Bird | Feather | Fly |
| Insect | Wings, Legs | Fly, Hop |
| Fish | Fins, Whole Body | Swim |
Q9: What are bones made up of?
Answer: Bones are made up of Calcium, Phosphorus, and other minerals.
Q10: What is a skeleton?
Answer: The framework of the body formed by the bones and cartilages is called skeleton.
Q11: What are the functions of skeleton?
Answer:
- Skeleton provides framework and shape to the body.
- It protects the internal organs (like heart, lungs, brain etc.) of the body.
- Bone marrow (present in long bones) produces red blood cells and platelets.
- It acts as lever and helps in movement and locomotion.
Answer: The longest bone in the human body is the thigh bone or femer. It is about 45cm long.
Q13: Name the smallest bone in the human body.
Answer: Stapes is the smallest bone present inside the ear.
Q14: How many bones usually a human body has?
Answer: Human body has 206 bones.
Q15: Why do doctors use X-Ray images?
Answer: Sometimes when we are hurt, or have an accident, doctors use these X-ray images to find out if there is any injury to the bones. The Xrays show the shapes of the bones in our bodies.
Q16: List some important parts of the skeleton.
Answer:
- Skull
- Ribcage
- Backbone
- Pelvic bones
- Shoulder bones
- Arms bones and leg bones
Q17: What is a Ribcage? How does it help to our body?
Answer: Ribcage is box like structure which is a part of our skeletal system. It consists of 12 pairs of curved bones called ribs. They join the chest bone and the backbone together to form a box. Ribcage protects the internal organs of the body like heart, lungs.
Q18: What is a skull? What is its function?
Answer: The bony part of head is called skull. The skull is made up of many bones joined together. Only the lower jaw bone is movable. It protects the brain.
Q19: How does human body perform its movement activities?
Answer: Human body perform all these activities with the help of the movements of the bones and muscles.
Q20: Do muscles push and pull both?
Answer: No, muscles can pull only. That;s why to move a bone, a pair of muscles act in opposite directions.
Q21: What is the difference between bone and cartilage?
Answer: Bone is hard and inflexible. E.g. femur (thigh bone). While cartilage is soft and flexible. E.g. Ear and nose bones are actually cartilage.
Ch 7 : Getting To Know Plants
Class 6 - Science - Ch7 - Getting to Know Plants
Q1: Correct the following statements and rewrite them in your notebook.
(a) Stem absorbs water and minerals from the soil.
(b) Leaves hold the plant upright.
(c) Roots conduct water to the leaves.
(d) The number of petals and sepals in a flower is always equal.
(e) If the sepals of a flower are joined together, its petals are also joined together.
(f) If the petals of a flower are joined together, then the pistil is joined to the petal.
Wheat, tulsi, maize, grass, coriander (dhania), China rose
Answer: Tulsi, Coriander,China rose.
Q6: If a plant has fibrous root, what type of venation do its leaves likely to have?
Answer: Parallel venation.
Q7: Is it possible for you to recognize the leaves without seeing them? How?
Answer: Yes. You can identify the type of leaves by looking at its roots. Plants having leaves with reticulate venation have tap roots while plants having leaves with parallel venation have fibrous roots.
Q8: Write the names of the parts of a flower.
Answer: The parts of a flower are sepals, petals, stamens and pistil.
Q9: Which of the following plants have you seen? of those that you have seen, which one have flowers?
Grass, maize, wheat, chilli, tomato, tulsi, pipal, shisham, banyan, mango, jamun, guava, pomegranate, papaya, banana, lemon, sugarcane, potato, groundnut
Answer: Flower bearing plants are: tomato, tulsi,mango, jamun, guava, pomegranate,papya banana,lemon.
Q10: Name the part of the plant which produces its food. Name this process.
Answer: Leaves produce food with an help of process called photosynthesis.
Q11: In which part of a flower, you are likely to find the ovary?
Answer: Ovary lies in the lowermost and swollen part of the pistil of the flower.
Q12: Name two flowers, each with joined and separated sepals.
Answer: Plants with joined sepals: Hibiscus, Tomato flowers, Datura, Cotton
Plants with separated sepals: Jasmine, Lostus, Lily, Rose
Q13: What is transpiration?
Answer: Leaves give out water vapours through the process called transpiration.
Q14: What do you mean by venation? What are its types?
Answer: the pattern of veins on the leaf is called venation. It can be reticulate or parallel.
Q15: Identify the following plants as herbs shrubs and trees
(a) rice
(b) tomato
(c) blueberry
(d) eucalyptus
(e) mango
(f) china rose
(g) Lavendar
Answer:
(a) rice - herb
(b) tomato - herb
(c) blueberry - shrub
(d) eucalyptus - tree
(e) mango - tree
(f) china rose - shrub
(g) Lavendar - herb
Q16: What are the functions of roots.
Answer:
Answer: Turnip, carrot, sugar-beet, beet root.
Q1: Correct the following statements and rewrite them in your notebook.
(a) Stem absorbs water and minerals from the soil.
(b) Leaves hold the plant upright.
(c) Roots conduct water to the leaves.
(d) The number of petals and sepals in a flower is always equal.
(e) If the sepals of a flower are joined together, its petals are also joined together.
(f) If the petals of a flower are joined together, then the pistil is joined to the petal.
Answer:
(a) Root absorbs water and minerals from
the soil.
(b) Stem holds the plant upright.
(c) Stem conducts water to the
leaves.
(d) The number of petals and sepals in a flower
is not always equal.
(e) If the sepals of a flower are joined together,
its petals are separate and are not joined together.
(f) If the petals of a flower are joined together,
then the pistil is not necessary joined to the petal.
Q3: Can you find a plant in your house or in
your neighborhood, which has a long but a weak stem? Write its name. In which
category would you classify it?
Answer: Money
plant which has long and weak stem. It is a climber.
Q4: What is the function of a stem in a
plant?
Answer: Following
are the functions of a stem in a plant:
- The stem holds the branches, leaves, fl owers and fruits.
- The stem transports water and minerals from roots to the upper parts.
- It also transports the prepared food from leaves to other parts.
Wheat, tulsi, maize, grass, coriander (dhania), China rose
Answer: Tulsi, Coriander,China rose.
Q6: If a plant has fibrous root, what type of venation do its leaves likely to have?
Answer: Parallel venation.
Q7: Is it possible for you to recognize the leaves without seeing them? How?
Answer: Yes. You can identify the type of leaves by looking at its roots. Plants having leaves with reticulate venation have tap roots while plants having leaves with parallel venation have fibrous roots.
Q8: Write the names of the parts of a flower.
Answer: The parts of a flower are sepals, petals, stamens and pistil.
Q9: Which of the following plants have you seen? of those that you have seen, which one have flowers?
Grass, maize, wheat, chilli, tomato, tulsi, pipal, shisham, banyan, mango, jamun, guava, pomegranate, papaya, banana, lemon, sugarcane, potato, groundnut
Answer: Flower bearing plants are: tomato, tulsi,mango, jamun, guava, pomegranate,papya banana,lemon.
Q10: Name the part of the plant which produces its food. Name this process.
Answer: Leaves produce food with an help of process called photosynthesis.
Q11: In which part of a flower, you are likely to find the ovary?
Answer: Ovary lies in the lowermost and swollen part of the pistil of the flower.
Q12: Name two flowers, each with joined and separated sepals.
Answer: Plants with joined sepals: Hibiscus, Tomato flowers, Datura, Cotton
Plants with separated sepals: Jasmine, Lostus, Lily, Rose
Q13: What is transpiration?
Answer: Leaves give out water vapours through the process called transpiration.
Q14: What do you mean by venation? What are its types?
Answer: the pattern of veins on the leaf is called venation. It can be reticulate or parallel.
Q15: Identify the following plants as herbs shrubs and trees
(a) rice
(b) tomato
(c) blueberry
(d) eucalyptus
(e) mango
(f) china rose
(g) Lavendar
Answer:
(a) rice - herb
(b) tomato - herb
(c) blueberry - shrub
(d) eucalyptus - tree
(e) mango - tree
(f) china rose - shrub
(g) Lavendar - herb
Q16: What are the functions of roots.
Answer:
- Absorbs water and minerals from soil and transports to stem.
- Stores food.
- Provides support and fixes plant to the soil.
- Prevents Soil Erosion.
Answer: Turnip, carrot, sugar-beet, beet root.
Ch 6 : Changes Around Us
CBSE Class 6 Science - CH6 - Changes Around Us
Q1: To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?
Answer: Yes, by unfolding the dress we can reverse this change.
Q2: What are the various types of changes?
Answer: Changes can be categorised as:
Q3: You accidentally dropped your favourite toy and broke it. This is a change you did not want. Can this change be reversed?
Answer: No, it cannot be reversed. It is an irreversible change.
Q4: Some changes are listed in the following table. For each change, write in the blank column, whether the change can be reversed or not.
Answer:
Q5: A drawing sheet changes when you draw a picture on it. Can you reverse this change?
Answer: By erasing the drawing we can undo the change. For example, if we draw with the help of pencil, we can erase the drawing by using an eraser. Then, it is a reversible change.
If we draw using a pen, we cannot erase the drawing. Then this change cannot be reversed.
Q6: Bursting of cracker is a/an
(a) reversible change
(b) irreversible change
(c) both reversible and irreversible
(d) None of these
Answer: (b) irreversible change
Q7: Give examples to explain the difference between changes that can or cannot be reversed.
Answer:
Examples of Reversible Changes:
Answer: When water is added to POP, it undergoes a chemical change. Its composition changes and is converted into another substance. Since it is a chemical change, it cannot be reversed.
Q9: A bag of cement lying in the open gets wet due to rain during the night. The next day the sun shines brightly. Do you think the changes, which have occurred in the cement, could be reversed?
Answer: Due to water, cement hardens and its composition changes. Chemical changes, in general, are irreversible changes. Since it is a chemical change which cannot be reversed.
Q10: What is a change?
Answer: An object may undergo different look, composition, colour, position, size or shape due to some factor (external or internal). It is called a change. Change may be permanent or temporary.
Q11: What are reversible changes? Give examples.
Answer: Those changes which can be reversed to obtain original form by removing the cause of change are called reversible changes.
Examples are:
Q12: What is irreversible change? Give examples of irreversible change.
Answer: The change in a substance which cannot be converted back to its original form is called irreversible change.
Examples are:
Q13: What are slow and fast changes? Give examples also.
Answer:
Slow Changes: Changes that take place in longer duration i.e. few hours, days, months or years are called slow changes. Rusting of iron, growth of a baby, cooking of food, formation of coal etc. are examples of slow changes.
Fast Changes: Changes that take place in a short duration (instant or nick of time) are called fast changes. Bursting of cracker, burning of paper etc. are examples of fast changes.
Q14:
Identify from the following list of changes which are fast or slow. Also mention
the duration that take place in happening the change.
(a) Curdling of milk
(b) Switching on light bulb in a dark room
(c) Formation of Petrol
(d) Bursting a balloon
(e) Turning of a child into an adult.
(f) Burning a matchstick.
Answer:
Q15: What are periodic changes? Give examples of periodic changes.
Answer: Those changes that occur at periodic intervals of time are called periodic changes. It is easy to periodic changes.
Examples are:
Q16: What are non-periodic changes? Also list two examples of non-periodic changes.
Answer: Changes that do not occur at fixed intervals of time are termed as non-periodic changes. Such changes may be unpredictable.
Examples are:
Q17: Differentiate between physical changes and chemical changes.
Answer:
Q18: Explain how iron rim is fixed over a wooden wheel. Which type of change is associated with this activity?
Answer: The iron rim taken, has slightly smaller diameter than the wooden wheel The iron rim is fixed over the wooden wheel by heating the rim first. On heating, the iron expands and becomes slightly bigger than the wheel. Once mounted, water is poured on the rim to cool it down. On cooling the iron rim contracts to its original size. As a result it becomes fixed on the wooden wheel.
Iron expands on heating and contracts on cooling, this physical change is associated with this activity.
Q1: To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?
Answer: Yes, by unfolding the dress we can reverse this change.
Q2: What are the various types of changes?
Answer: Changes can be categorised as:
- Slow and fast changes.
- Reversible and irreversible changes.
- Natural and man-made changes.
- Periodic and non-periodic changes.
- Physical and chemical changes.
Q3: You accidentally dropped your favourite toy and broke it. This is a change you did not want. Can this change be reversed?
Answer: No, it cannot be reversed. It is an irreversible change.
Q4: Some changes are listed in the following table. For each change, write in the blank column, whether the change can be reversed or not.
Answer:
| S. No. | Change | Can be reversed (Yes/ No) |
|---|---|---|
| 1. | The sawing of a piece of wood | No |
| 2. | The melting of ice candy | Yes |
| 3. | Dissolving sugar in water | Yes |
| 4. | The cooking of food | No |
| 5. | The ripening of a mango | No |
| 6. | Souring of milk | No |
Q5: A drawing sheet changes when you draw a picture on it. Can you reverse this change?
Answer: By erasing the drawing we can undo the change. For example, if we draw with the help of pencil, we can erase the drawing by using an eraser. Then, it is a reversible change.
If we draw using a pen, we cannot erase the drawing. Then this change cannot be reversed.
Q6: Bursting of cracker is a/an
(a) reversible change
(b) irreversible change
(c) both reversible and irreversible
(d) None of these
Answer: (b) irreversible change
Q7: Give examples to explain the difference between changes that can or cannot be reversed.
Answer:
Examples of Reversible Changes:
- Melting of Ice into water. By freezing the water we can obtain ice again.
- Folding a paper: By unfolding it, we can undo the change.
- Hot milk to cold milk: By boiling milk, we can make it warm.
- Bursting a balloon.
- Bud to flower
- Cutting a paper into pieces
Answer: When water is added to POP, it undergoes a chemical change. Its composition changes and is converted into another substance. Since it is a chemical change, it cannot be reversed.
Q9: A bag of cement lying in the open gets wet due to rain during the night. The next day the sun shines brightly. Do you think the changes, which have occurred in the cement, could be reversed?
Answer: Due to water, cement hardens and its composition changes. Chemical changes, in general, are irreversible changes. Since it is a chemical change which cannot be reversed.
Q10: What is a change?
Answer: An object may undergo different look, composition, colour, position, size or shape due to some factor (external or internal). It is called a change. Change may be permanent or temporary.
Q11: What are reversible changes? Give examples.
Answer: Those changes which can be reversed to obtain original form by removing the cause of change are called reversible changes.
Examples are:
- melting of ice
- folding of paper
- evaporation of water
Q12: What is irreversible change? Give examples of irreversible change.
Answer: The change in a substance which cannot be converted back to its original form is called irreversible change.
Examples are:
- burning of candle
- germination of seed
- bursting a balloon
- rusting of iron
Q13: What are slow and fast changes? Give examples also.
Answer:
Slow Changes: Changes that take place in longer duration i.e. few hours, days, months or years are called slow changes. Rusting of iron, growth of a baby, cooking of food, formation of coal etc. are examples of slow changes.
Fast Changes: Changes that take place in a short duration (instant or nick of time) are called fast changes. Bursting of cracker, burning of paper etc. are examples of fast changes.
(a) Curdling of milk
(b) Switching on light bulb in a dark room
(c) Formation of Petrol
(d) Bursting a balloon
(e) Turning of a child into an adult.
(f) Burning a matchstick.
Answer:
| Changes | Fast or Slow | Duration |
|---|---|---|
| (a) Curdling of milk | Slow | Few hours |
| (b) Switching on light bulb in a
dark room |
Fast | Instant |
| (c) Formation of Petrol | Slow | Million years |
| (d) Bursting a balloon | Fast | Instant |
| (e) Turning of a child into an adult. | Slow | 20 years |
| (f) Burning a matchstick. | Fast | less than a minute |
Q15: What are periodic changes? Give examples of periodic changes.
Answer: Those changes that occur at periodic intervals of time are called periodic changes. It is easy to periodic changes.
Examples are:
- Occurence of day and night
- Phases of moon
- Heartbeat
Q16: What are non-periodic changes? Also list two examples of non-periodic changes.
Answer: Changes that do not occur at fixed intervals of time are termed as non-periodic changes. Such changes may be unpredictable.
Examples are:
- Earthquake
- Eruption of volcano
- An accident
- Sneezing
Q17: Differentiate between physical changes and chemical changes.
Answer:
| S.No. | Physical Changes | Chemical Chnages |
|---|---|---|
| 1. | Composition of substance remains
same No new substances are formed. |
Composition of substance changes. New substance os formed. |
| 2. | Change in shape, size or physical state occurs. Chemical properties of substance remain same. | New substance have new shape, physical state, different physical and chemical properties. |
| 3. | Physical changes are reversible. | Chemical changes are irreversible. |
| 4. | e.g.: Melting of ice, expansion of iron on heating | Burning of wood, rusting of iron |
Q18: Explain how iron rim is fixed over a wooden wheel. Which type of change is associated with this activity?
Answer: The iron rim taken, has slightly smaller diameter than the wooden wheel The iron rim is fixed over the wooden wheel by heating the rim first. On heating, the iron expands and becomes slightly bigger than the wheel. Once mounted, water is poured on the rim to cool it down. On cooling the iron rim contracts to its original size. As a result it becomes fixed on the wooden wheel.
Iron expands on heating and contracts on cooling, this physical change is associated with this activity.
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