Define Kraft temperatuer.

Explanation

### Step-by-Step Text Solution:

1. **Definition of Kraft Temperature**: The Kraft temperature (often denoted as \( T_K \)) is defined as the minimum temperature above which the formation of micelles occurs in a soap solution.

2. **Understanding Micelle Formation**: Micelles are aggregates of surfactant molecules, such as soap, that form when the concentration of the surfactant exceeds a certain threshold at a specific temperature. Below this temperature, surfactants exist primarily as individual molecules.

3. **Role of Surfactants**: Surfactants, like soaps, have a dual nature; they possess both a hydrophilic (water-attracting) part and a hydrophobic (water-repelling) part. This structure allows them to reduce surface tension and form micelles in solution.

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