immediately after.

• You stop shaking them?
• Leave the test tubes undisturbed for sometime and observe. Does the oil layer separate out?
• In which test tube does this happen first? Give your observations.

Suppose that we put dirty cloth in the soap solution. Dirt is mainly greasy matter. The soap molecules are arranged radially with hydrocarbon ends directed inwards into the greasy matter and ionic part directed outwards into water.

When a dirty cloth is inserted in the solution then the hydrocarbon part sticks to the dirt or oil. With a little agitation the dirt particles get entrapped by the soap micelles and get dispersed in water due to which the soap water gets dirty and the cloth gets cleaned.

• What is the action of soap particles on the greasy cloth?

We know that soaps and detergents make oil and dirt present on the cloth come out into water, thereby making the cloth clean.

Soap has one polar end (the end with carboxy) and one nonpolar end (the end with hydrocarbon chain) as shown in the figure.

The polar end is hydrophilic in nature and this end is attracted towards water.

The non-polar end is hydrophobic, in nature and it is attracted towards grease or oil on the cloth, but not attracted towards water.

When soap is dissolved in water, its hydrophobic ends attach themselves to dirt and remove it from the cloth, as shown sequentially in the figure that follows.

• The hydrophobic end of the soap molecules move towards the dirt or grease particle.
• The hydrophobic ends attached to the dirt particle and try to pull out.
• The molecules of soap surround the dirt particle