Maybe you've ever felt that it wasn't necessary to use a soap to wash your hands and that with just water you could wash just as well. Most kids think that way. But water can only remove part of the dirt from the surface of the skin, but water and soap together clean better.
If you look under the microscope at a cross section of the skin, you will see that it has many hollow areas or valleys, where particles of grease and dirt can be penetrated. Water alone can get some of that dirt out, but when water hits the grease, there's not much it can do against it.
But if you add soap to that same water it has a totally different action. The action of mixing soap and water sends air into the water and forces it to spread, as it creates bubbles. A bubble is actually an air balloon with a thin outer cover of soap and water.
While the bubbles appear to be very delicate and weak, they actually function as countless powerful magnets. Just as magnets attract metal to them, soap bubbles pick up dirt and pull it out of the skin. The dirty bubbles are then washed away by the stream of water, leaving the skin clean.
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