What is entropy? and what does it do?

Entropy by the modern definition is the amount of energy dispersal in a system. Therefore, the system entropy will increase when the amount of motion within the system increases. For example, the entropy increases when ice (solid) melts to give water (liquid). It will even increase more when water is evaporated to steam (gas).    

(from wiki)

when heated, the valance electrons increased their speed and transferred the heat from electron to electron.   i just took the test.