Matter is anything that has weight and occupies space.
Is air also a matter? Yes because it has weight and also occupies space.
Matter can exist in three state, it is called three states of matter.
These are the three state of matter:
Solid state of matter
In a solid particles are packed tightly together so they don’t move much. The electrons of each atom are constantly in motion, so the atoms have a small vibration, but they are fixed in their position. Because of this, particles in a solid have very low kinetic energy.
Solids have a definite shape, as well as mass and volume, and do not conform to the shape of the container in which they are placed. Solids also have a high density, meaning that the particles are tightly packed together.
Liquid state of matter
In a liquid, the particles are more loosely packed than in a solid and are able to flow around each other, giving the liquid an indefinite shape. Therefore, the liquid will conform to the shape of its container.
Gaseous state of matter
In a gas the particles have a great deal of space between them and have high kinetic energy. A gas has no definite shape or volume. If unconfined, the particles of a gas will spread out indefinitely; if confined, the gas will expand to fill its container. When a gas is put under pressure by reducing the volume of the container, the space between particles is reduced and the gas is compressed.
Matter can change from one state of matter to another.
Example: Ice water which is in solid state can change to liquid when heat is applied, the liquid also can change to gas when more heat is applied.
That is, ICE +heat = liquid + heat = gas
Gas can also change to liquid when heat is removed, and liquid to ice when heat is further removed.
That is, Gas minus heat = liquid minus heat = ice.
Example of matter are many, they are, air, water, Stone, television, cars, iron, cloth, atom and many more.
Matter is made up of molecules, which is made up atoms, though a molecule, or an atom can also be called matter, since they have weight and in the same hand occupies space.
Matter can undergo physical or chemicals change.
For example, when a liquid change to ice or gas, by removal of heat or addition of heat respectively is called physical change. This is because the change is reversible. That is a liquid that change to ice by removal of heat can as well reverse back to liquid when heat is added.
Example, when wood is burnt, it change to another thing which can never reverse back to wood again by any means. This kind of change is called chemical change, because is not reversible.