Foam is a substance that is formed when pockets of gas are trapped in liquids or solids. Therefore, foam is found in various forms around us.
Forms can be solid, like the bath sponge we use to clean ourselves, or it can be airy liquidy like the froth on top of a mug of cappuccino or even in the sea.
In most cases, the amount of gas is more than the volume of liquid or solid.
Solid forms are of two types; open cell foams and closed cell foams. In closed cell foams the gas forms separate pockets that are surrounded by the solid material. In open cells, the gas pockets connect to each other.
A bath sponge is an open cell foam because water can easily flow through the entire structure releasing air, yet not damaging it.
For form to be produced and for it to remain stable there needs to be mechanical work and surfactants (surface active components that reduce surface tension). These two together help foam form faster than it can breakdown.
For the foam to remain stable there needs, to be a certain force that is created between the foam molecules, a certain electrical charge between the surfactants, and a chemical that is able to keep the balance.
Liquid foams are used for many purposes such as to extinguish fires, to make bread, and other chemical processes.
The fire extinguishers that are found in buildings and factories are full of pressurized foam, so that when the cap is released, the foam is shot out at high speeds.
The open cell solid foams are found in many forms around our homes and schools. Foam rubber is an excellent open cell solid foam because it soaks up any liquid around it.
Other types of foam are syntactic foam (made from glass or ceramic), and integral skin foam (found in baby seats, shoe soles, armrests and mattresses).
Car cushions and pillows are made from a soft material called foam rubber, which is firm, yet spongy.