States of Matter

Matter Everything around us is made up of matter. Matter can be weighed, and this is called its mass. Matter takes up space - the amount of space occupied by something is called its volume. So matter is anything that takes up space, and can be weighed. That is… has a mass and a volume.

The Particle Model All matter is made up of invisible particles. Particles have kinetic energy and are constantly moving Spaces exist between particles As temperature increases, the kinetic energy of particles increases. Particles are attracted to each other by forces of attraction. The strength of these forces, along with the temperature determine the state of the matter (solid, liquid, gas)

States of Matter Matter can be classified into three main groups: solids, liquids and gases. These are called the three states of matter.

Solids Solids include such things as your desk, and most objects around you. They occupy space and can be weighed. The volume of a solid cannot easily be changed, nor can the shape. Substances will be solids because either: The attractive forces between them are strong enough to hold them tightly; or The temperature is low and the particles have very little kinetic energy – easily held tightly together even by weak attractive forces (is frozen)

Liquids Water, milk and oil are examples of matter in liquid form. The volume of a quantity of liquid does not change, but its shape may. The molecules are not as close together as they were in the solid and the particles can move around slightly. Substances will be liquids because either: The attractive forces between them are not strong enough to hold them tightly, but still hold them together; or The temperature is high and the particles have too much kinetic energy to be held tightly, but not enough to separate completely

Gases As the temperature increases the liquid changes to a gas. The attractive forces between molecules are very weak and the particles are therefore not held together. The particles are very far apart. Substances will be gases because either: The attractive forces between them are very weak and not strong enough to hold the particles together; or The temperature is very high and the particles have too much kinetic energy to be held together, even by strong attractive forces.

Changes in State When a liquid is heated and turns into a gas it is said to have evaporated 9or vapourised). When a gas cools and turns into a liquid it is said to have condensed. Freezing is when a liquid turns into a solid. Melting is when a solid turns into a liquid. Boiling is when the vapour pressure of a liquid is equal to the external air pressure (chem defn) – or it is rapid evaporation