Fact 1: Boiling means change from a liquid into a gas by adding heat energy.

Fact 2: Heat is Energy and is measured in Joules.

Given the two facts above, answer the question "boiling is changing from a liquid to a gas by adding what?" with the following options: 
- Joules
 - ice
 - warmth
 - air
 - water
 - forces
 - light
 - digestion


 

 Joules        