During a chemical reaction molecules and atoms (reactants) are rearranged into new combinations that result in new kinds of atoms or molecules (products).

Most animals consume other organisms to survive. Consumers (heterotrophs) are divided into three types, primary, secondary, and tertiary, based on their place in the food chain.

A neutron is a subatomic particle found in the nucleus of an atom. It is neutral as it carries no electric charge.

The speed of light varies based on the material that the waves are passing through. The refractive index of a material indicates how easily light travels through it compared to how easily light travels through a vacuum. For example, the refractive index of water is 1.33, meaning that light travels 1.33 times faster in a vacuum than it does in water.

Food is mixed with gastric acid and pepsin in the stomach to help break down protein.