Heat capacity or thermal capacity is defined as the amount of heat energy required to raise the temperature of a body by 1°C.

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 1^oC.

Water has the highest specific heat capacity. So water absorbs a large amount of heat for unit rise in temperature. Thus water is used as a coolant in car radiators and factories to keep engine and other machinery parts cool. So water is a bad conductor of heat. Specific heat capacity of water is 4200J/kg^oC. So it is easy to raise the temperature. So it is possible to heat water easily while cooking.

Hot air balloons:
Air molecules at the bottom of the balloon get heated by a heat source and rise. As the warm air rises, cold air is pushed downward and it is also heated. When the hot air is trapped inside the balloon, it rises.
Breezes:
During day time, the air in contact with the land becomes hot and rises. Now the cool air over the surface of the sea replaces it. It is called sea breeze. During night time, air above the sea is warmer. As the warmer air over the surface of the sea rises, cooler air above the land moves towards the sea. It is called land breeze.
Winds:
Air flows from area of high pressure to area of low pressure. The warm air molecules over hot surface rise and create low pressure. So, cooler air with high pressure flows towards low pressure area. This causes wind flow.
Chimneys:
Tall chimneys are kept in kitchen and industrial furnaces. As the hot gases and smoke are lighter, they rise up in the atmosphere.

Mass (m) = 2 kg
Specific heat capacity (c) = 4200 Jkg^-1 K^-1
Temperature variation (\(\triangle \)t) = 20^oC -0^oC = 20^oC
Specific latent heat (L) = 3,34,000 J/kg
Heat energy required = mc\(\triangle \)t + ml
= (2 x 4200 x 20) + (2 x 3, 34,000)
= 168000 + 668000
= 836000 J

Mass of water = 25 grams
\(\triangle\)T = (100^oC - 0^oC) =100^oC
C = 4.18 J/g^oC
Heat energy required Q = M x C x \(\triangle\)T
= 25 x 4.18 x 100^oC
= 10450 J