3. What is foam

3.1 Definition of foam

We encounter foams in many aspects of our daily lives, as we use them cosmetically in products such as shaving foam and shampoos, or consume them for food use in products such as chocolate mousse. From a fundamental point of view, these products are called "liquid foams", since they correspond to a set of gas bubbles dispersed in a continuous liquid phase. A foam is therefore a two-phase system comprising a gaseous phase and a liquid phase containing agents stabilizing the air/water interface. The main characteristic of a liquid foam is its stability. Foams are intrinsically unstable systems from a thermodynamic point of view. This is because...