An atom is the smallest unit of matter that retains all the chemical properties of an element.

The three states of matter are solid, liquid, and gas.

Evaporation is the process by which water changes from a liquid to a gas.

Condensation is the process by which water changes from a gas to a liquid.

Freezing is the process by which water changes from a liquid to a solid.

Melting is the process by which water changes from a solid to a liquid.

Gravity is the force that pulls objects towards the center of the Earth.

Friction is the force that causes objects to move when they are pushed or pulled.

Magnetism is the force that causes objects to stick together.

Electricity is the force that causes objects to move when they are connected to a battery.

Nitrogen is the name of the gas that makes up most of the Earth's atmosphere.

Oxygen is the name of the gas that we breathe in.

Carbon Dioxide is the name of the gas that we breathe out.

Oxygen is the name of the gas that is produced by plants during photosynthesis.

Carbon Dioxide is the name of the gas that is produced by animals during respiration.