Chapter 3 Heat Question/Answers With Important Terms to Learn

Celsius scale – A temperature scale where water freezes at 0 degrees and boils at 100 degrees. (सेल्सियस पैमाना)
Conduction – The transfer of heat through direct contact between materials. (चालन)
Conductor – A material that easily allows heat or electricity to pass through it. (चालक)
Convection – The transfer of heat by the movement of fluids like air or water. (संवहन)
Insulator – A material that does not easily allow heat or electricity to pass through it. (रोधक)
Land breeze – A breeze blowing from the land to the sea, usually at night. (स्थलीय पवन)
Radiation – The transfer of energy through space by electromagnetic waves. (विकिरण)
Sea breeze – A breeze blowing from the sea to the land, usually during the day. (समुद्री पवन)
Temperature – A measure of how hot or cold something is. (तापमान)
Thermometer – An instrument used to measure temperature. (थर्मामीटर)

Exercise Question With Answers:👉

1. Similarities and Differences between the Laboratory Thermometer and the Clinical Thermometer

Similarities:

Both are used to measure temperature.
Both contain mercury or alcohol as the thermometric liquid.
Both have a glass tube with a temperature scale.

Differences:

Range:
- Clinical Thermometer: Typically ranges from 35°C to 42°C.
- Laboratory Thermometer: Can measure a wider range of temperatures, often from -10°C to 110°C.
Design:
- Clinical Thermometer: Has a constriction near the bulb to prevent mercury from falling back after reading.
- Laboratory Thermometer: Does not have a constriction; mercury or alcohol falls back into the bulb when not in use.
Use:
- Clinical Thermometer: Used for measuring human body temperature.
- Laboratory Thermometer: Used in scientific experiments to measure the temperature of various substances.

2. Give two examples each of conductors and insulators of heat.

► Conductors: Copper, Aluminum

► Insulators: Wood. Plastic

3. Fill in the Blanks

(a) The hotness of an object is determined by its temperature.

(b) Temperature of boiling water cannot be measured by a clinical thermometer.

(d) No medium is required for transfer of heat by the process of 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 conduction.

(f) Clothes of dark colours absorb more heat better than clothes of light colours.

4. Match the Following

(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.

Wearing more layers of clothing during winter keeps us warmer because the layers trap air between them. Air is a poor conductor of heat, so it acts as an insulating layer, reducing heat loss from our bodies. Multiple layers also allow us to adjust our clothing to maintain a comfortable temperature as conditions change.

6. Look at Fig. 3.13. Mark where the heat is being transferred by conduction, by convection and by radiation.

7. In places of hot climate it is advised that the outer walls of houses be painted white. Explain.

Ans: In hot climates, it is advised to paint the outer walls of houses white because white reflects most of the sunlight and absorbs less heat. This helps in keeping the interior of the house cooler, reducing the need for air conditioning and saving energy.

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

(d) between 30°C and 50°C

Ans: One litre of water at 30°C mixed with one litre of water at 50°C will have a temperature (d) between 30°C and 50°C. The exact temperature will be the average of the two, which is 40°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.

Correct Ans: An iron ball at 40°C dropped in a mug containing water at 40°C will (b) not flow from iron ball to water or from water to iron ball. The temperatures are equal, so there is no heat transfer.

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.

(d) does not become cold.

A wooden spoon dipped in a cup of ice cream (d) does not become cold. Wood is a poor conductor of heat, so the cold does not transfer efficiently along the length of the spoon.

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.

(d) copper is easier to clean than the stainless steel.Ans with Explanation: Stainless steel pans are usually provided with copper bottoms because (c) copper is a better conductor of heat than the stainless steel. This ensures even heating and better cooking performance.

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