The most general definition of foam is a substance that is formed by trapping many gas bubbles in a liquid or solid. Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of A solid' object is in the States of matter characterized by resistance to Deformation and changes of Volume. It can also refer to anything that is analogous to such a phenomenon, such as quantum foam. Quantum foam, also referred to as spacetime foam, is a concept in Quantum mechanics, devised by John Wheeler in 1955. Often people mean polyurethane foam (foam rubber), Styrofoam or some other manufactured foam when they are using the term. A polyurethane, commonly abbreviated PU, is any Polymer consisting of a chain of organic units joined by urethane links Styrofoam is a trademark for polystyrene Thermal insulation, a material manufactured by Dow Chemical Company. It can be considered a type of colloid. A colloid is a type of mechanical Mixture where one substance is dispersed evenly throughout another

From the early 20th century, various types of specially manufactured solid foams came into use. The low density of these foams made them excellent as thermal insulators and flotation devices, and their lightness and compressibility made them ideal as packing materials and stuffings. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different The term thermal insulation can refer to materials used to reduce the rate of Heat transfer, or the methods and processes used to reduce heat transfer Some liquid foams, called fire retardant foams, found use in extinguishing fires, especially oil fires. Fire Retardant Foam, or fire suppression foam, is a Foam used for fire suppression. Oil well fires are Oil gushers that have caught on Fire, and burn uncontrollably

Foam, in this case meaning "bubbly liquid", is also produced as an often unwanted by-product in the manufacture of various substances. A by-product is a secondary or incidental product deriving from a Manufacturing process a Chemical reaction or a biochemical pathway and is not the primary product For example, foam is a serious problem in the chemical industry, especially for biochemical processes. The chemical industry comprises the companies that produce industrial chemicals Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as Many biological substances, for example proteins, easily create foam on agitation and/or aeration. Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Aeration is the Process by which Air is circulated through mixed with or dissolved in a Liquid or substance Foam is a problem because it alters the liquid flow and blocks oxygen transfer from air (therefore preventing microbial respiration in aerobic fermentation processes). Cellular respiration is the set of the metabolic reactions and processes that take place in Organisms cells to convert biochemical energy from Fermentation is the process of deriving energy from the oxidation of organic compounds such as carbohydrates using an endogenous electron acceptor which is For this reason, anti-foaming agent compounds, like silicone oils, are added to prevent these problems. An antifoaming agent is a chemical additive that inhibits the formation of Foam. Silicones are largely inert compounds with a wide variety of forms and uses

If foaming is desired, a foaming agent may help. A foaming agent is a surfactant which when present in small amounts facilitates the formation of a Foam, or enhances its colloidal stability by inhibiting the coalescence of

Foaming around the mouth can be a symptom of rabies in animals. Rabies (from rabies “madness rage fury” Also known as “ hydrophobia ” is a viral Zoonotic neuroinvasive disease that The term sea foam is used to describe the foam that forms on top of seawater from the action of waves. In some ways, leavened bread is a foam, as the yeast causes the bread to rise by producing tiny bubbles of gas in the dough. Bread is a Staple food prepared by Baking a Dough of Flour and Water. Yeasts are a growth form of eukaryotic Microorganisms classified in the kingdom Fungi, with about 1500 Species currently described

Structure of foams

Real-life foams are typically disordered and have a variety of bubble sizes. The study of idealised foams is closely linked to the mathematical problems of space-filling and minimal surfaces. In Mathematics, a Minimal surface is a surface with a Mean curvature of zero The Weaire-Phelan structure is believed to be the best possible (optimal) unit cell of a perfectly ordered foam, while Plateau's laws describe how the soap-films form structures in foams. Kelvin structure In 1887, Lord Kelvin asked how space could be partitioned into cells of equal volume with the least area of surface between them i In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. Plateau's Rules describe the structure of soap films in foams

Solid foams form an important class of lightweight cellular engineering materials. These foams can be classified into two types based on their pore structure. The first type of foams are called open cell structured foams. These foams contain pores that are connected to each other and form an interconnected network which is relatively soft. The second type of foams do not have interconnected pores and are called closed cell foams. Normally the closed cell foams have higher compressive strength due to their structures. Closed cell foams are also generally denser, requiring more material though and consequentially are more expensive to produce. The closed cells can be filled with a specialized gas to provide improved insulation. This is in contradistinction to the open cell foam which will fill with whatever it is surrounded with. While filled with air - this could be a relatively good insulator, however, if the open cells fill with water, insulative properties would be reduced.

A special class of closed cell foams is known as syntactic foam, which contains hollow particles embedded in a matrix material. Syntactic foams are Composite materials synthesized by filling a Metal, Polymer or Ceramic matrix with hollow particles called Microballoons

The closed cell structure foams have higher dimensional stability, low moisture absorption coefficient and higher strength compared to open cell structured foams. All types of foams are widely used as core material in sandwich structured composite materials. A Sandwich structured composite is a special class of Composite materials that is fabricated by attaching two thin but stiff skins to a lightweight but thick core

See also

• Beijing National Aquatics Centre
• Bubble
• Nanofoam
• Metal foam

External links

• Beer foam
• Aqueous foam technology
• Fomaco Foam production
• The strange physics of foam

The Beijing National Aquatics Center ( also known as the National Aquatics Center (国家游泳中心 better known as the Water Cube (水立方 or the "Ice Nanofoams are a class of nanostructured porous materials Foams containing a significant population of pores with diameters less than 100 nm. A metal foam is a cellular structure consisting of a solid Metal - frequently Aluminum - containing a large volume fraction of gas-filled Pores The pores

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