CBSE Class 6 Science Question Paper Set 24 with Solutions

Answer: 4000 metres, because 1 km = 1000 m, so 4 × 1000 = 4000 m.

Teacher's Note:
1. Multiply by 1000 when you change kilometres into metres.
2. Do not mix this up with 100, which is used for metres and centimetres.

Answer: standard. A hand span differs from person to person, so it cannot be used as a standard unit.

Teacher's Note:
1. A standard unit has the same value for everyone, everywhere.
2. Units based on body parts such as hand span, foot and cubit give different values for different people.

Answer: True. Evaporation is the change of liquid water into water vapour, which happens at any temperature from the surface of the liquid.

Teacher's Note:
1. Evaporation takes place only from the surface of the water.
2. Remember it as liquid to gas, and the opposite change, gas to liquid, is condensation.

Answer: False. Excessive rain may cause floods; drought is caused by too little or no rain for a long time.

Teacher's Note:
1. Drought means a shortage of water, while flood means too much water.
2. Read the key word 'excessive' carefully before deciding.

Answer: Atmosphere.

Teacher's Note:
1. The atmosphere is held around the Earth by gravity.
2. It contains gases such as nitrogen and oxygen, which living things need.

Answer: Habitat.

Teacher's Note:
1. A habitat gives an organism food, water, shelter and air.
2. Examples are a forest, a desert, a pond and a mountain.

Answer: (b) repel. Like poles (N and N, or S and S) push each other away.

Teacher's Note:
1. Remember the rule: like poles repel and unlike poles attract.
2. Repulsion is the only sure test to find whether an object is a magnet.

Answer: (a) rectilinear motion. The apple moves along a straight line downwards.

Teacher's Note:
1. Rectilinear motion means motion along a straight line.
2. Do not choose rotatory motion, which needs spinning about a fixed axis.

Answer: (a) 250 mm. 1 cm = 10 mm, so 25 × 10 = 250 mm.

Teacher's Note:
1. Going from a bigger unit to a smaller unit means you multiply.
2. Check that the answer in millimetres looks bigger than the number of centimetres.

Answer: 1. Turn off taps when not in use and repair leaking taps and pipes.
2. Use a bucket and mug for bathing instead of a shower, and do not let water run while brushing teeth.
3. Reuse water, for example use water used for washing vegetables or rice to water plants.
4. Harvest rainwater and avoid wasting water in gardens and while washing vehicles.

Teacher's Note:
1. Write at least four practical points from daily life.
2. Mention both saving water and reusing water for full marks.

Answer: 1. Animals breathe in oxygen and breathe out carbon dioxide.
2. Plants take in this carbon dioxide and, during photosynthesis, release oxygen into the air.
3. Animals use this oxygen again, so the amounts of oxygen and carbon dioxide in the air stay balanced.

Teacher's Note:
1. Show that the gas given out by one is the gas taken in by the other.
2. Mention photosynthesis to link the plant side of the exchange.

Answer: 1. Periodic motion (repeats after a fixed interval of time): the swing of a pendulum, or the movement of a swing.
2. Rotatory motion (spinning about a fixed axis): a spinning top, a ceiling fan, or a wheel of a moving cycle spinning about its axle.

Teacher's Note:
1. In periodic motion the same movement repeats again and again after equal times.
2. In rotatory motion the object turns about a fixed line called the axis.

Answer: Earlier, people used different units in different places, such as hand span, cubit and foot, which gave different results and caused confusion in trade and science. So the International System of Units (SI) was developed in 1960.
Advantages:
1. The same units are used by everyone across the world, so measurements can be compared easily.
2. They are based on multiples of 10, so changing from one unit to another is easy.
3. They are accurate and have fixed values, for example the metre is the SI unit of length.

Teacher's Note:
1. Give the reason first (confusion due to different units) and then the advantages.
2. Name at least one SI unit, such as metre for length, to make the answer complete.

Answer: Activity:
1. Fix a small candle on a table and light it.
2. Cover the burning candle with a glass jar or tumbler.
3. The candle burns for a short time and then goes out, because the oxygen inside the closed jar gets used up.
4. If the jar is lifted and a fresh supply of air reaches the candle, it burns again when relit.
Conclusion: Burning needs air (its oxygen), so air supports burning.

Teacher's Note:
1. Always describe what you do, what you observe and the conclusion.
2. Say that it is the oxygen in air that supports burning, not the whole air.

Answer: 1. The leaves of a cactus are reduced to spines, which reduce loss of water by transpiration and protect it from animals.
2. The stem is thick, green and fleshy; it stores water and carries out photosynthesis.
3. The stem is covered with a waxy coating, and the roots go deep or spread wide to absorb as much water as possible.

Teacher's Note:
1. Link each feature with its use, such as spines with less water loss.
2. Do not forget that the green stem makes food in the absence of normal leaves.

Answer: 1. Magnets are used in compasses to find directions.
2. They are used in refrigerator doors, cupboard doors and pencil boxes to keep them closed.
3. They are used in toys, magnetic hooks and holders, and to separate iron objects from a mixture of materials.
4. They are used in electric bells, loudspeakers, motors, cranes lifting iron scrap and in credit/debit cards and other devices.

Teacher's Note:
1. Write at least three uses with an example for each.
2. Include the compass, since it uses a freely suspended magnet to show north and south.

Answer: Camel (desert):
1. It has long legs that keep its body away from the hot sand and wide, padded feet that do not sink into the sand.
2. It stores fat in its hump, which gives it energy and lets it live for many days without food and water.
3. It has long eyelashes and can close its nostrils to keep out sand, and it loses very little water in sweat and urine.
Mountain animals (such as yak, snow leopard, mountain goat):
1. They have thick fur or woolly coats and a layer of fat to keep them warm in the cold.
2. They have strong hooves or claws and strong legs for climbing steep rocky slopes.
Difference: desert animals are adapted to heat and shortage of water, while mountain animals are adapted to cold and steep, rocky land.

Teacher's Note:
1. Divide your answer into two parts so the difference is clear.
2. Give the reason for each feature, for example thick fur for cold or padded feet for sand.

Answer: Air pollution is the addition of harmful substances such as smoke, dust and poisonous gases to the air, which makes it unclean and harmful to living things.
Causes:
1. Smoke from vehicles, factories and power plants burning fuels.
2. Burning of wood, coal, crop residue and garbage.
3. Dust from construction and from roads, and gases from chemicals and sprays.
4. Natural causes such as forest fires and volcanic eruptions.

Teacher's Note:
1. First define air pollution in one clear sentence, then list the causes.
2. Mention both human causes and natural causes to score full marks.

Answer: Magnetite (also called lodestone) is the natural magnet.

Teacher's Note:
1. The case study itself gives the name of the rock.
2. Natural magnets are rare; most magnets we use are man-made.

Answer: 1. A magnet attracts objects made of iron, cobalt and nickel.
2. It has two poles, north and south, and a freely suspended bar magnet rests in the north-south direction. (Also: like poles repel and unlike poles attract.)

Teacher's Note:
1. Give two different properties, one word each is not enough.
2. Properties about poles and about direction are the most commonly asked.

Answer: Each piece becomes a smaller magnet with its own north and south poles. A magnet's poles cannot be separated.

Teacher's Note:
1. Think of the poles as a pair that always comes together.
2. A common mistake is to say one piece will have only a north pole.

Answer: A magnet loses its magnetism when it is heated, hammered, dropped from a height, or kept near another strong magnet in the wrong way. (Any two ways.)

Teacher's Note:
1. Think of anything that shakes up or disturbs the tiny magnetic parts inside.
2. Keeping magnets with unlike poles together in pairs with soft iron keepers helps to protect them.

Answer: The continuous movement of water between the oceans, air and land is called the water cycle.
1. Evaporation: The heat of the Sun changes water of oceans, rivers, lakes and ponds into water vapour, which rises up. Plants also give out water vapour (transpiration).
2. Condensation: At higher places the air is cold, so the water vapour cools and changes into tiny droplets of water, which form clouds.
3. Precipitation: When the droplets become big and heavy, they fall as rain, snow or hail.
4. Collection: Rainwater flows into rivers and streams that reach the sea, and some seeps into the ground as groundwater. Then the cycle starts again.

Teacher's Note:
1. Write the steps in the correct order: evaporation, condensation, precipitation, collection.
2. If you draw a diagram, label the Sun, clouds, rain, river and sea.