Heat

Samacheer Book Back Questions And Answers For Science Standard 8 “Heat“

I. Choose the best answer:
1. Heat is a form of ________.
a. Electrical energy
b. Gravitational energy
c. Thermal energy
d. None of these

2. If you apply some heat energy to a substance, which of the following can take place in it?
a. Expansion
b. Increase in temperature
c. Change of state
d. All the above.

3. Which of the following substances will absorb more heat energy?
a. Solid
b. Liquid
c. Gas
d. All the above

4. If you apply equal amount of heat to a solid, liquid and gas individually, which of the following will have more expansion?
a. Solid
b. Liquid
c. Gas
d. All of them

5. The process of converting a liquid into a solid is called _____.
a. sublimation
b. condensation
c. freezing
d. deposition

6. Conduction is the way of heat transfer which takes place in a _____.
a. solid
b. liquid
c. gas
d. all of them

II. Fill in the blanks:
1. A calorimeter is a device used to measure the _____.
2. _____ is defined as the amount of heat required to raise the temperature of 1kg of a substance by 1°C.
3. A thermostat is a device which maintains _____.
4. The process of converting a substance from gaseous state to solid state is called _____.
5. If you apply heat energy, the temperature of a system will _____.
6. If the temperature of a liquid in a container is decreased, then the interatomic distance will _____.

Answers:
1. Heat capacity of water
2. Specific heat capacity
3. Temperature of an object constant
4. Deposition
5. Increase
6. Decrease

III. State True or False. If false, correct the statement:
1. The applied heat energy can be realised as an increase in the average kinetic energy of the molecules.
2. The dimensions of a substance are increased if the temperature of the substance is decreased.
3. The process of converting a substance from solid state to gaseous state is called condensation.
4. Convection is the process by which the thermal energy flows in solids.
5. The amount of heat gained by a substance is equal to the product of its mass and latent heat.
6. In a thermos flask, the silvered walls reflect and radiate the heat outside.

Answers:
1. True
2. False (The dimensions of a substance are increased if the temperature of the substance is increased)
3. False (The process of converting a substance from solid to gas is called sublimation)
4. False (Convection is the process by which the thermal energy flows in liquids and gases)
5. True
6. False (In a thermos flask, the silvered walls reflect radiated heat back to the liquid in the bottle)

IV. Match the following:
1. Conduction            A. Liquid
2. Convection            B. Gas to liquid
3. Radiation               C. Solid to gas
4. Sublimation           D. Vacuum
5. Condensation        E. Solid

Answers:
1. E
2. A
3. D
4. C
5. B

V. Consider the statements given below and choose the correct option:
1. Assertion: Radiation is a form of heat transfer which takes place only in vacuum.
Reason: The thermal energy is transferred from one part of a substance to another part without the actual movement of the atoms or molecules.
a. Both assertion and reason are true and reason is the correct explanation of assertion.
b. Both assertion and reason are true, but reason is not the correct explanation of assertion.
c. Assertion is true, but the reason is false.
d. Assertion is false, but the reason is true.

2. Assertion: A system can be converted from one state to another state.
Reason: It takes place when the temperature of the system is constant.
a. Both assertion and reason are true and reason is the correct explanation of assertion.
b. Both assertion and reason are true, but reason is not the correct explanation of assertion.
c. Assertion is true, but the reason is false.
d. Assertion is false, but the reason is true.

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