Sweating works because liquid water on your skin can evaporate. The fastest-moving water particles are the most likely to escape from the liquid into the air. Those escaping particles carry energy away. The average energy of the particles left behind becomes lower, so the skin cools. Evaporation happens more quickly when air moves past the skin and when the surrounding air is dry. That is why a breeze can make sweat feel especially cooling. Your body is using a change of state to transfer thermal energy to the surroundings.

The effect becomes easier to notice when conditions change. Temperature, pressure and particle motion can alter how quickly processes happen or how matter behaves. Food storage, refrigeration, cooking and weather all give everyday ways to test the same particle ideas without needing specialist equipment.

Temperature is linked to the average kinetic energy of particles, while internal energy includes the energy associated with their motion and interactions. Heating transfers energy into a material, but that energy does not always raise its temperature: during a change of state it can instead alter the arrangement and separation of particles. Conduction, convection and radiation then determine how quickly energy moves to or from the surroundings.