An atom is the smallest component of an element that still retains the properties of the element.

The heart is the organ that drives the circulatory system. In humans, it consists of four chambers with two that collect blood called atria and two that pump blood called ventricles. The heart's valves prevent blood pumped out of the ventricles from flowing back into the heart.

The liver produces bile which emulsifies (separates) fat.

A substance undergoes a phase transition when it moves from one state of matter to another, for example, when water freezes or boils.

A warm front is the boundary between warm and cool (or cold) air when the warm air is replacing the cold air. Warm air at the surface pushes above the cool air mass creating clouds and storms.