Samacheer Kalvi 9th Term II Science Book Back Question and Answers – Unit 1:

Samacheer Kalvi 9th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 9 New Syllabus 2021 to 2022 Book Back Question & Answer solutions available for both English and Tamil Medium. Class 9 Science Book Term 2 Unit 1 – Heat Answers/Solutions are provided on this page. 9th Std Science Book is of Term 1st, 2nd, 3rd, and consists of 9 Units in each Term. All 9 Units of Term 1st, 2nd, 3rd Science Book Back One, and Two Mark Solutions are given below.

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Samacheer Kalvi 9th Science Book Back Unit 1 Term 2 Solutions Guide PDF:

Science Subject 1 Mark and 2 Mark Solutions Guide 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.

Term – 2

Unit – 1

Heat 

I. Choose the correct answer:

1. Calorie is the unit of
a) heat
b) work
c) temperature
d) food

2. SI unit of temperature is
a) Fahrenheit
b) joule
c) Celsius
d) Kelvin

3. The Specific heat capacity of water is
a) 4200 JKg-1K-1
b) 420 Jg-1K-1
c) 0.42J g-1K-1
d) 4.2 Jk g-1K-1

4. Two cylindrical rods of same length have the area of cross section in the ratio 2.1. If both the rods are made up of same material, which of them conduct heat faster?
a) both rods
b) Rod-2
c) Rod-1
d) None of them

5. Two cylinders of equal height and radius are made of copper and aluminium. Which of them conducts heat faster?
a) Copper rod
b) Aluminium rod
c) Both of them
d) None of them

6. In which mode of transfer of heat, molecules pass on heat energy to neighbouring molecules without actually moving from their position.
a) Radiation
b) Conduction
c) Convection
d) Both B and C

7. A device in which the loss of heat due to conduction, convection and radiation is minimized is
a) Solar cell
b) Solar cooker
c) Thermometer
d) Thermos flask

II. Fill in the blanks:

1. The fastest mode of heat transfer is radiation
2. During day time, air blows from sea to land
3. Liquid and gases are generally slow conductors of heat.
4. The fixed temperature at which matter changes state from solid to liquid is called melting point.

III. Assertion and Reason type questions:

Mark the correct choice as:

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

1. Assertion: Food can be cooked faster in copper bottom vessels.
Reason: Copper is the best conductor of heat.
Ans: a. If both assertion and reason are true and reason s the correct explanation of assertion

2. Assertion: Maximum sunlight reaches earth’s surface during the afternoon time.
Reason: Heat from the sun reaches earth’s surface by radiation.
Ans: c. If assertion is true but reason is false

3. Assertion: When water is heated up to 100°C, there is no raise in temperature until all water gets converted into water vapour.
Reason: Boiling point of water is 10°C.
Ans: c. If assertion is true but reason is false

4. Assertion: Aluminium conducts heat faster than copper.
Reason: Specific heat capacity of aluminium is higher than that of copper.
Ans: d. If assertion is false but reason is true.

IV. Short answers questions:

1. Define conduction.
The process of transfer of heat in solids from a region of higher temperature to a region of lower temperature without the actual movement of molecules is called conduction.

2. Ice is kept in a double-walled container. Why?
The double-wall with an insulating material in between is a bad conductor of heat. It prevents heat entering the container from outside. So ice is kept in a double-walled container.

3. How does the water kept in an earthen pot remain cold?
Water in the pot evaporates through the minute holes in the earthen pot. Foe evaporation it takes heat from the water in the pot. So the temperature of water in the pot decreases and the water remains cool.

4. Differentiate convection and radiation.

• In convection heat flows b the movement of the fluid itself but in radiation heat flows by means of electromagnetic waves.
• Radiation takes place even in vacuum but convection needs matter to pass through.

5. Why do people prefer wearing white clothes during summer?
White surface reflects heat but black surface absorbs it. So people prefer wearing white clothes because they reflect the heat of the sun, without absorbing it.

6. What is specific heat capacity?
Specific heat capacity of a substance is defined as the amount of heat required to raise the temperature of 1 kg of the substance by 1oC or 1K.

7. Define thermal capacity.
Heat capacity or thermal capacity is defined as the amount of heat energy required to raise the temperature of a body by 1oC. it is denoted by C’.

8. Define specific latent heat capacity.
Specific latent heat is the amount of heat energy absorbed or liberated by unit mass of a substance during change of state without causing any change in temperature. The SI unit of specific latent heat is J/kg.

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