States of Matter

Solid

Atoms in a solid are closely packed together in a regular pattern.
The atoms in solids vibrate about their fixed positions, the higher the temperature the greater the vibration.
Solids have definite shape and volume.
Fixed shape and volume in solids is due to strong forces of attraction between particles, allowing minimal movement.
Solids can’t flow and are difficult to compress.

Liquid

In a liquid, atoms are still close together but can move around each other.
Liquids have a definite volume but can flow and change shape, filling the bottom of a container.
The particles in a liquid are in more chaotic arrangement than those in a solid.
Liquids are almost incompressible and density is usually lower than that of a solid.

Gas

Atoms in a gas are far apart and move randomly at high speeds.
Gases fill containers, taking both the shape and volume of the container.
Gases are easily compressed due to the large spaces between particles.
The density of gases is lower than liquids and solids because the gas particles are spread out.
Gases can flow and diffuse into each other.

Transition from one state to another

Melting, evaporating, and sublimating are transitions that require an input of energy.
Freezing, condensing, and depositing are transitions that release energy.
Melting point and boiling point are specific temperatures where phase transitions occur.
Sublimation is when a substance goes directly from a solid to a gas and deposition is when it goes from a gas to a solid.
The specific latent heat is the amount of energy needed to change the state of a 1kg substance without changing its temperature.

Brownian Motion

Brownian motion provides evidence of the continuous random motion of particles.
It was observed by Robert Brown in 1827, who saw pollen grains in water jigging about erratically.
This motion is due to the pollen grains constantly being hit by the water molecules.

The particle model can be used to explain the various states and properties of matter.
It assumes all substances are made of tiny particles and these particles are in constant random motion.
The model can further explain expansion and contraction of materials, pressure in gases and differences in density.

The model assumes particles are solid spheres.
It doesn’t account for the forces between particles.
It assumes there’s no space between particles in solids and liquids, which isn’t the case.
The model doesn’t mention that particles themselves can be broken down into even smaller components (protons, neutrons, electrons etc.)