Question

The specific heat capacity is the property of a substance which determines the change in temperature of the substance due to exchange of heat energy with the surrounding. It is defined as the amount of heat energy absorbed or released per unit mass of the substance to change its temperature by one unit. Its SI unit is given by J kg-1K-1. Specific heat capacity of some substances at room temperature and atmospheric pressure is given by the table shown.

Suppose an amount of heat ΔQ supplied to a substance changes its temperature from T to T + ΔT. Heat capacity of a substance to be S = ΔQ/ΔT. We expect ΔQ and, therefore, heat capacity S to be proportional to the mass of the substance. Further, it could also depend on the temperature, i.e., a different amount of heat may be needed for a unit rise in temperature at different temperatures. To define a constant characteristic of the substance and independent of its amount, we divide S by the mass of the substance m in kg: s = S/m = (1/m) ΔQ/ΔT, s is known as the specific heat capacity of the substance. It depends on the nature of the substance and its temperature. The unit of specific heat capacity is J kg-1 K-1

(a) What are the differences between the centre of gravity and the centre of mass? (b) A square plate of mass 120 g and edge 5.0 cm rotates about one of edges. If it has a uniform angular acceleration of 0.2rad/s², what torque acts on the plate?

ASSERTION: If two different substances of equal mass at different temperature are mixed with each other equilibrium temperature is always different from their mean temperature. REASON: Two substances have different specific heat capacity.