Solids, Liquids and Gases

Matter and Its States

Matter is anything that occupies space and has mass, comprised of tiny particles called atoms.
Atoms can exist freely, or they can combine to form molecules.
Matter can mainly be in three states: solid, liquid, or gas.
The state of matter depends on how the atoms or molecules are arranged and the energy they possess.

Solids

In solids, the particles are tightly packed together in a fixed, regular arrangement.
The particles in a solid vibrate in place but don’t move from their fixed positions — this makes solids maintain a fixed shape and volume.
Solids have the strongest intermolecular forces.
Solids do not flow and are not generally compressible.

Liquids

In liquids, particles are in a random arrangement but are still close together.
The particles in a liquid can move around each other but are still in close contact; this allows a liquid to flow and take the shape of its container.
Liquids have medium strength intermolecular forces.
Although liquids can be slightly compressed, they are mostly incompressible.

Gases

In gases, the particles are well separated and in a completely random arrangement.
The particles in a gas move quickly in all directions and have complete freedom of movement; this allows a gas to fill any given space.
Gases have the weakest intermolecular forces.
Gases are highly compressible and always expand to fill their containers.

Changing States

Melting, freezing, evaporation, and condensation are the processes of state changes.
When a solid is heated, it will melt into a liquid at its melting point.
When a liquid is cooled, it will freeze into a solid at its freezing point.
When a liquid is heated, it will evaporate into a gas at its boiling point.
When a gas is cooled, it will condense into a liquid at its condensation point.

The Kinetic Theory of Matter

The Kinetic Theory of matter states that all particles of matter are in constant motion and this motion has consequences that can be studied on a macroscopic level (what we can see) and microscopic (what we cannot see but can imagine or model).
Increasing the temperature of a substance increases the kinetic energy of its particles, making them move more rapidly and irregularly.
The kinetic energy of particles and the attractive forces between particles are what determine the state of the substance - solid, liquid, or gas.