Foam is a substance made by trapping pockets of gas in a liquid or solid. The gas can be air, carbon dioxide, or another gas, while the liquid can be water, oil, or a solvent. Examples of foams include a bath sponge and the head on a glass of beer. In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions. Foam can be formed when the physical characteristics of the water are altered by the presence of organic materials in the water. There are different types of foam, including:
- Memory foam: This is a type of foam that is used in mattresses, pillows, and other furniture. It conforms to the shape of the person or object that is lying on it, and it returns to its original shape when the weight is removed.
Foams can be classified as solid or liquid foams. Solid foams are materials that are composed of gas-filled bubbles dispersed in a solid, while liquid foams are materials that are composed of gas-filled bubbles dispersed in a liquid. The size of the bubbles ranges from a few micrometers to a few millimeters. The mechanical properties of solid foams depend on the size and shape of the bubbles, the properties of the solid matrix, and the volume fraction of the gas. Liquid foams are sometimes made relatively long-lasting by adding some substance, called a stabilizer, that prevents or retards the coalescence of the gas bubbles.
