A story told by a chemistry professor:

A student wished to make some potassium hydroxide solution (aqueous) and decided to throw a large lump of potassium into a bucket of water.

Out of the corner of his eye, the professor observed what the student was about to do and hurried over.  After confirming this was what was intended, he asked the student to first to stir the water in the bucket for five minutes before adding the potassium.

Puzzled, the student asked the purpose of this action.

“It will give me time to run away,” said the professor.

One Liner
One good turn gets most of the blankets.