Like the respiratory system, the circulatory system serves to transport oxygen throughout the body while removing carbon dioxide. In addition, the circulatory system transports nutrients from the digestive system.

If no oxygen is present, cellular respiration is anaerobic and will result in fermentation where either lactic acid or alcohol is used instead of oxygen.

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

Velocity is the rate at which an object changes position. Rate is measured in time and position is measured in displacement so the formula for velocity becomes \(\vec{v} = { \vec{d} \over t } \)

The water (hydrologic) cycle describes the movement of water from Earth through the atmosphere and back to Earth. The cycle starts when water evaporates into a gas from bodies of water like rivers, lakes and oceans or transpirates from the leaves of plants.