(B) Very Short Answer Type Questions
1. What is heat? Write its S.I. unit.
Heat is a form of energy transferred due to temperature difference. SI unit: joule (J).
2. Two bodies at different temperatures are placed in contact. State the direction in which heat will flow.
Heat flows from the body at higher temperature to the body at lower temperature.
3. Name the SI unit of heat. How is it related to the unit calorie?
SI unit: joule (J). Relation: 1 cal = 4.186 J.
4. Define temperature and write its SI unit.
Temperature is the measure of degree of hotness or coldness of a body. SI unit: kelvin (K).
5. Why does a piece of ice when touched with hand, appear cool? Explain.
It is because heat flows from the hand (warmer) to the ice (colder).
6. Name two substances which expand on heating.
Iron, Aluminium.
7. Name two substances which contract on heating.
Water between 0°C and 4°C, Silica below - 80⁰C
8. What do you mean by anomalous expansion of water?
Water expands when cooled from 4°C to 0°C . This is anomalous expansion.
9. At what temperature is the density of water maximum? State its value.
At 4°C, maximum density is 1 g/cm³.
10. A deep pond of water has its top layer frozen during winter. State the expected temperature of water layer (i) just below ice, (ii) at the bottom of pond.
(i) 0°C (ii) 4°C.
(C) Short Answer Type Questions
1. Distinguish between heat and temperature.
1. Heat is a form of energy transferred from one body to another due to a temperature difference. 1. Temperature is the measure of the degree of hotness or coldness2.Heat depends on the mass, material, and temperature of the body.2. Temperature depends only on the average kinetic energy of the molecules of the body.3. The SI unit of heat is joule (J). 3. The SI unit of temperature is kelvin (K).4. Heat flows from a body at higher temperature to one at lower temperature. 4. Temperature determines the direction of flow of heat.5. Two bodies at the same temperature may contain different amounts of heat energy. 5. Two bodies at the same temperature are said to be in thermal equilibrium.6. Heat is measured by a calorimeter. 6. Temperature is measured by a thermometer.
2. What do you understand by thermal expansion of a substance?
The increase in the size (length, area or volume) of a substance when its temperature increases.
3. State the three kinds of thermal expansion. Out of solids, liquids and gases, which expands more?
Linear, Superficial and Cubical expansion. Gases expand the most.
4. State the volume changes observed when a given mass of water is heated from 0°C to 10°C.
From 0°C to 4°C, water contracts. From 4°C to 10°C, it expands.
5. Explain why water pipes burst in colder countries during winter.
It is so because water expands when cooled from 4⁰C to 0⁰C, exerting high pressure inside pipes.
