The property of ice which prevents the flow of heat from water of a pond (or lake) to the atmosphere is :

1. conduction
2. insulation
3. low specific heat
4. none of the above

Identify the correct graph showing the variation in the volume of water with temperature :

1.

2.

3.

4.

Two bodies at different temperatures are placed in contact. State the direction in which heat will flow.

Name the S.I. unit of heat. How is it related to the unit calorie?