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The Brownian motion is the motion of the pollen grains theory (Robert Brown). It developed the theory because all molecules behave the same wayl. Therefore, developed a theory of heat and temperature for solids, liquid and gases.
Solids: have a definite shape, maintain that shape, are difficult to compress as teh particles are already packed closely together, are often dense because the spaces between the particles are closely packed.
Liquids: do not have a definite shape, flow and fill a bottom of a container/maintain the same volume unless the temperature changes, are difficult to compress because there are quite a lot of particles, are often dense because there are quite a lot of particles in a small volume
Gases: do not have a definite shape, are easily compressed because there are only a few particles in a large volume, are often low density as there large spaces in between the particles.

The particle theory of matter states that:
1. All matter is made up of molecules/particles.
2. The particles are always moving in constants motion.
3. When heating the particles, the spaces between the particles are farther apart and the particles move in different directions quicker.
Expansion and Contraction:
At high temperatures, particles have more energy, move more quickly, and have more collisions. As a result, they take up more space, and the substance expands. At lower temperatures, particles have less energy, move more slowly and have fewer collisions. They take up less space, and the substance contracts. Gain in heat is called endothermic change and a loss in heat is called an exothermic change.
Sublimation: Solid to gas; endothermic change; eg. moth crystals disappear when left in a closet for several days.
Sublimation: Gas to solid; exothermic change; eg. frost forms on a car's windshield.
Evaporation: Liquid to gas; endothermic change; eg. rain dries up when the sun heats it up.
Melting/liquefaction: Liquid to gas; endothermic change; eg. ice cube melts into water.
Freezing/solidification: Liquid to solid; exothermic change; eg. water freezes into ice.
Condensation: Gas to liquid; exothermic change; eg. drops of water form on the mirror when taking a hot shower.
Physical change means that there is no new substance produced, substance remains teh same even with a change of stsate, may require addition of energy and release of energy may occur; outside may look different, inside remains the same, particles may be rearranged, forces of attraction between particles may be weaker or stronger; mixing sugar and water, ice melts into water, solid wax into liquid wax.
A physical change remains with its physical features.
Chemical change means that there is a final substance substantially different than the initial substance, new substance is produced, energy is usually released but may be required to get the change going; a new substance is produced, the particles of the new substance do not resemble those of the old substance, internally, the substance produced is different than the old substances; vinegar and baking soda mix to form carbon dioxide, hydrochloric acid reactes with magnesium metal to form hydrogen gas.
A chemical change changes its internal elements/substances.