Foam
![Soap foam bubbles](/Images/godic/202501/20/Foam_-_big4041.jpg")
![Cappuccino is topped with a layer of steamed-milk foam.](/Images/godic/202501/20/Classic_Cappuccino4042.jpg")
![Order and disorder of bubbles in a surface foam.](/Images/godic/202501/20/lossy-page1-220px-Order_and_Chaos.tif4042.jpg")
![Rising bubble from orifice](/Images/godic/202501/20/Rising_Bubble_from_Orifice4042.png")
A foam is a substance that is formed by trapping pockets of gas in a liquid or solid. A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions of gas.