Understand What Happens When Substances are Heated

Solids, liquids and gases change state when they are heated or cooled.

Melting and boiling are words that we use to describe changes of state - and they happen when a substance is heated. We are going to take a look at what happens when substances are heated, and how heating can cause a change of state. 

So......

A solid will turn into a liquid when heated. This process is called melting.

A liquid will turn into a gas when heated. This process is called boiling. 

Some liquids will also evaporate slowly over time, if heated gently - like a puddle in the sun. The liquid water will slowly evaporate into a gas.

So what do you think is happening to the particles during these changes of state?

Well, when heated, particles in a substance move faster. This means that they can move around more and can move further apart and eventually change state.

Got it? Let's try some questions on heating and the resulting changes of state.