Samacheer Kalvi 8th Science Unit 4 Book Back Answers:

Samacheer Kalvi 8th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 8 New Syllabus 2021 to 2022 Book Back Question & Answer available for both English and Tamil Mediums. Class 8th Science Book Unit 4 – Heat Answers/Solutions are provided on this page. 8th Std Science Book consists of 23 units, All Science Book Back One, and Two Mark Solutions are given below.

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Samacheer Kalvi 8th Science Book Back Solutions PDF:

8th Science Subject 1 Mark and 2 Mark Solutions PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes. Samacheer Kalvi 8th Science Unit 4 Answers are given below.

Science Book Back Answers

Unit 4 – 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
Answer: (c) thermal energy

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
Answer: (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
Answer: (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
Answer: (c) Gas

5. The process of converting a liquid into a solid is called ……………
(a) sublimation
(b) condensation
(c) freezing
(d) deposition
Answer: (c) freezing

6. Conduction is the heat transfer which takes place in a …………….
(a) solid
(b) liquid
(c) gas
(d) All of them
Answer: (a) Solid

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 1 kg of a substance by 1°C.
3. A thermostat is a device which maintains ……………
4. The process of converting a substance from gas to solid 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 inter atomic distance will ……………

Answer:

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 realized as an increase in the average kinetic energy of the molecules.
Answer: True

2. The dimensions of a substance are increased if the temperature of the substance is decreased.
Answer: False
Correct statement:
The dimensions of a substance are increased if the temperature of the substance is increased.

3. The process of converting a substance from solid to gas is called condensation.
Answer: False
Correct statement:
The process of converting a substance from solid to gas is called sublimation.

4. Convection is the process by which the thermal energy flows in solids.
Answer: False
Correct statement:
Convection is the process by which the thermal energy flows in liquids and gases.

5. The amount of heat gained by a substance is equal to the product of its mass and latent heat.
Answer: True

6. In a thermos flask, the silvered walls reflect and radiate the heat to the outside.
Answer: False
Correct statement:
In a thermos flask, the silvered walls reflect radiated heat back to the liquid in the bottle.

IV. Match the following

1.

Answer:

1. e
2. a
3. d
4. c
5. b

V. Read the directions given below and answer the questions.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true, but reason is not the correct explanation of the assertion.
(c) If the assertion is true, but the reason is false.
(d) If the assertion is false, but the reason is true.

1. Assertion: Radiation is a form of heat transfer which takes place even in vacuum.
Reason: Thermal energy is transferred from one part of a substance to another part without the actual movement of the atoms or molecules.
Answer:
(b) Both assertion and reason are true, but reason is not the correct explanation of the assertion.

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.
Answer:
(a) Both assertion and reason are true and the reason is the correct explanation of the assertion.

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