| A | B | 
| average kinetic energy | temperature | 
| internal energy of a system | heat | 
| an instrument to measure heat exchange | calorimeter | 
| heat + work | enthalpy | 
| to go from the solid to the liquid phase | melt | 
| to go from the liquid to the solid phase | freeze | 
| to go from a liquid to the gas phase | evaporate | 
| to go from the gas phase to the liquid phase | condense | 
| a reaction which puts heat out into the environment | exothermic | 
| a reaction that takes heat into the environment | endothermic | 
| the amount of heat needed to raise the temperature of one gram of substance by 1 degree C | specific heat | 
| amount of heat needed to raise the temperature of 1 g of water by 1 degree C | calorie | 
| the official system internationale (SI) unit for energy | Joule | 
| How heat flows | from hot to cold | 
| absolute zero | O K - the temperature at which all molecular motion stops |