Heat

Samacheer Book Back Questions And Answers For Science Standard 9 “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. 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

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

5. 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 _____.
2. During day time, air blows from _____ to _____.
3. Liquids and gases are generally _____ conductors of heat.
4. The fixed temperature at which matter changes state from solid to liquid is called _____.

Answers:
1. radiation
2. sea to land
3. poor
4. melting point

III. Assertion and reason type questions:
1. Assertion: Food can be cooked faster in vessels with copper bottom.
Reason: Copper is the best conductor of heat.
(a) If both assertion and reason are true and reason is 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.

2. Assertion: Maximum sunlight reaches earth’s surface during the noon time.
Reason: Heat from the sun reaches earth’s surface by radiation.
(a) If both assertion and reason are true and reason is 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.

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.
(a) If both assertion and reason are true and reason is 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.

Visit Our YouTube Channel For More Free Videos: Click Here