石けんで汚れが落ちる理由は？油をつかむ小さな尻尾

Why Does Soap Clean Our Hands?

Have you ever tried to wash oil off your hands with only water?

The water just runs off, and your hands still feel oily.

This is because oil and water do not mix.

A lot of the dirt on our skin is oily, too.

Soap solves this problem.

A soap molecule is very small, but it has two different ends.

One end, called the head, likes water.

The other end, called the tail, hates water but likes oil and fat.

When you wash with soap, the tails stick to the oily dirt.

Many soap molecules then form tiny balls called micelles.

The tails are on the inside, and the heads are on the outside.

The outside of each ball likes water, so water can carry it away.

Soap also works on germs.

All bacteria and some viruses are covered with a thin layer of fat.

The tails can push into this layer and break it apart.

In a study from 2010, scientists checked people's hands for bacteria.

When people did not wash at all, bacteria were found on 44 percent of them.

With water alone, the number was 23 percent.

With soap and water, it fell to just 8 percent.

But soap needs time to do its job.

Experts say you should scrub your hands for 20 seconds.

Warm water and cold water remove the same number of germs.

So next time, count to twenty before you rinse.