Heat is a form of energy which transfers from high temperature body to low temperature body. The temperature of a body determines whether or not the body is in thermal equilibrium with the neighboring systems. Thermometer is the instrument to measure the temperature. When heat is supplied to the body the internal energy increases.
Heat energy(Q)S=Mass (m)× temperature difference
The average kinetic energy of molecules of the body is directly proportional to the absolute temperature. The amount of heat energy absorbed by substances depends on the Mass of the body, temperature of the body and specific heat of the substances. The specific heat of a substance gives us an idea of the degree of reluctance of a substance to change its temperature. The specific heat of a body determines with the principle of “Method of Mixtures”. When a liquid is exposed to air, the molecules at the surface keep on escaping the surface till the entire liquid disappears in air. This process is called evaporation. The reverse process of evaporation is condensation. The amount of water vapor present in air is called humidity. In the winter when temperature goes down, the water vapor condensed on the grass and flowers.
The water droplets condense on such surfaces is known as dew. If the temperature falls further, the water molecules condense on the dust particles in air forms fog. The liquid state matter converts into gases state at a temperature. This temperature is known as boiling temperature and the processed is called boiling. The temperature is kept at constant during this process. The heat energy required to convert the liquid state matter into gases state at constant temperature is called “Latent heat of vaporization”. The process in which the solid phase changes to liquid phase at a constant temperature is called melting.
This constant temperature is called melting point. The heat energy required to convert “1gram” of solid completely into liquid at a constant temperature is called Latent heat of fusion. Freezing is the process to convert liquid to solid. In this process internal energy of the system decreases.