Railway Science (Chemistry-Ideal Gas Law)

Evaporation is the process by which molecules in a liquid state spontaneously become gaseous due to energy input. This can occur at any temperature, not just at the boiling point. Even at temperatures below the boiling point, water molecules can gain enough kinetic energy to escape the liquid surface and enter the gaseous phase.

Evaporation is a surface phenomenon. If the surface area is increased, the rate of evaporation increases. The rate of evaporation depends on temperature, the presence of wind velocity and the humidity. Condensation is the process through which the physical state of matter changes from the gaseous phase into the liquid phase.

In the ideal gas law, R is the ideal gas universal constant. This constant quantifies the relationship between the properties of a gas, namely pressure, temperature, volume and gas quantity. It is valid for an ideal gas, which is one that has low pressure.

On increasing the temperature, the most probable speed increases. Also, the speed distribution curve broadens at higher temperatures. Broadening of the curve shows that the number of molecules moving at higher speed increases. Speed distribution also depends upon mass of molecules. At the same temperature, gas molecules with heavier mass have slower speed than lighter gas molecules.