A2 Chemistry OCR - Entropy

Entropy (S)

• quantitative measure of the degree of disorder in a system.

All substances have some degree of disorder because the particles are always in constant motion thus S is always positive

A better description of entropy might be "the dispersal of energy" 

• Nature seems to move from Order to disorder in isolated systems. 

for example Gas molecules spread out over time to fill a space, increasing their entropy over time. 

Entropy helps us to explain things that happen naturally:

• a gas spreading through a room
• heat from a fire spreading through a room 
• …