When the body is touched, receptors in the skin send messages to the brain causing the release of chemicals such as endorphins.

These solvents, due to their volatility, evaporate into the atmosphere when used.

The cones of the jack pine, for example, do not readily open to release their seeds until they have been subjected to great heat.

When matter is changed chemically, chemical energy is given off.

The sun sends out an incredible amount of heat and light.

Plants give off oxygen as they make food.