NCERT Solutions for Class 7 Science
Chapter 4 Heat
LearnFatafat offers free NCERT Solutions for Class 7 Science Chapter 4 Heat. Chapter covers the topics like measurement of temperature, laboratory thermometer, heat transfer, conduction, convection, radiation and more. Check video lessons for Class 7 Science Chapter 4 Heat click here to buy.
NCERT Solutions for Class 7 Science Chapter 4 Heat
1. State similarities and differences between the laboratory thermometer and the clinical thermometer.
Answer:
Similarity:
- Both the thermometers have uniform long narrow glass tubes.
- Bulb of both the thermometers have mercury in them.
Difference:
| Clinical thermometer | Laboratory thermometer |
|---|---|
| Temperature range is from 35°C to 42°C | Temperature range is from -10°C to 110°C |
| Used to measure temperature of human body | Cannot be used to measure temperature of human body |
| Has kink near the bulb | Kink is absent near the bulb |
| Can be tilted while reading thermometer | Should be kept straight upright for reading temperature |
2. Give two examples each of conductors and insulators of heat.
Answer:
- Conductors of heat – Copper, Aluminium, Iron.
- Insulators of heat – Wood, Rubber, Plastic.
3. Fill in the blanks :
(a) The hotness of an object is determined by its __________.
Answer: temperature
(b) Temperature of boiling water cannot be measured by a _____________ thermometer
Answer: clinical
(c) Temperature is measured in degree ______________.
Answer: celsius
(d) No medium is required for transfer of heat by the process of __________.
Answer: radiation
(e) A cold steel spoon is dipped in a cup of hot milk. Heat is transferred to its other end by the process of ______________.
Answer: conduction
(f) Clothes of ______________ colours absorb more heat better than clothes of light colours.
Answer: dark
4. Match the following:
| (i) Land breeze blows during | (a) summer |
| (ii) Sea breeze blows during | (b) winter |
| (iii) Dark coloured clothes are preferred during | (c) day |
| (iv) Light coloured clothes are preferred during | (d) night |
Answer:
| (i) Land breeze blows during | (d) night |
| (ii) Sea breeze blows during | (c) day |
| (iii) Dark coloured clothes are preferred during | (b) winter |
| (iv) Light coloured clothes are preferred during | (a) summer |
5. Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.
Answer: More layers of clothing keep us warm during winter, because air gets trapped in these layer, as air is bad conductor of heat, it prevents heat loss from the body. Thus, wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.
6. Look at Fig. 4.13. Mark where the heat is being transferred by conduction, by convection and by radiation.
Answer:
7. In places of hot climate it is advised that the outer walls of houses be painted white. Explain.
Answer: Light colors like white absorb less heat and reflect more heat. Which helps to keep the house temperature cooler than outside. Hence, in places of hot climate it is advised that the outer walls of houses be painted white.
8. One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be
(a) 80°C (b) more than 50°C but less than 80°C
(c) 20°C (d) between 30°C and 50°C
Answer: (d) between 30°C and 50°C
9. An iron ball at 40°C is dropped in a mug containing water at 40°C. The heat will
(a) flow from iron ball to water.
(b) not flow from iron ball to water or from water to iron ball.
(c) flow from water to iron ball.
(d) increase the temperature of both.
Answer: (b) not flow from iron ball to water or from water to iron ball.
10. A wooden spoon is dipped in a cup of ice cream. Its other end
(a) becomes cold by the process of conduction.
(b) becomes cold by the process of convection.
(c) becomes cold by the process of radiation.
(d) does not become cold.
Answer: (d) does not become cold.
11. Stainless steel pans are usually provided with copper bottoms. The reason for this could be that
(a) copper bottom makes the pan more durable.
(b) such pans appear colourful.
(c) copper is a better conductor of heat than the stainless steel.
(d) copper is easier to clean than the stainless steel.
Answer: (c) copper is a better conductor of heat than the stainless steel.
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Chapter 4 – Heat
