Question

1. Define the terms ‘Kraft temperature’ and ‘Critical micelle concentration’.

2. Explain the cleansing action of soap.

Answer 1

1. Kraft temperature (T_k ) – The temperature above which micelle formation occurs.

Critical micelle concentration (CMC) – The concentration above which micelle formation occurs.

2. Soap is sodium or potassium salt of higher fatty acids. At a particular concentration the soap molecules will rearrange in such a way that its polar end is towards water and non-polar end towards oil.

These molecules aggregate to form ionic micelles around the oil/dirt particles. Since the polar groups can interact with water, the micelles are pulled in water and are removed from the dirty surface. Thus soap helps in emulsification and washing away of oils and fats.