an oil in water emulsion consisting of water, oil and water-soluble surfactant exist in equilibrium. How many intensive variables must be fixed to describe the emulsion completely.

To describe the emulsion completely, we need to fix the values for all the intensive variables that can affect its properties.

Intensive variables are properties that are independent of the size or amount of the system, such as temperature, pressure, and concentration. In this case, the main intensive variables that need to be fixed are:

1. Temperature: The emulsion's properties, such as stability, viscosity, and phase behavior, can change with temperature. Fixing the temperature helps to define its behavior.

2. Pressure: Pressure can also affect the stability and phase behavior of the emulsion. Fixing the pressure helps to define its behavior under specific conditions.

3. Concentration: The concentration of water, oil, and surfactant in the emulsion can determine its stability, droplet size, and other properties. Fixing the concentrations helps to describe the relative amounts of each component.

Therefore, at least three intensive variables must be fixed (temperature, pressure, and concentration) to describe the emulsion completely.