Have you ever seen your mom pour boiling water into a drinking glass? Did the glass break? Sometimes they do.

There is a way to prevent that, and it isn't a secret. Many people know about it. They put a silver spoon into the glass before pouring boiling water into the glass. The secret is the reason the silver spoon keeps the glass from breaking. How can it be?

We'll do an experiment to find out. We will do it a little differently, by pouring very hot (not boiling) water into a coffee cup. Coffee cups are made to withstand very high
temperatures. After pouring in the very hot water, we'll put a silver spoon into the cup. (We'll do this several times, so that each student can have a turn putting in the spoon.) Hold onto the spoon, and see what happens. The spoon gets pretty hot, doesn't it?

So what? Why is that a big deal? It is a big deal, because it teaches us a little bit about transfer of heat. The heat is transferred from the water to the spoon, and the spoon conducts the heat out of the water.

I think we could check on this. We can put very hot water into two cups. We put a thermometer into each cup. We put a spoon into one cup, but not into the other. Let's watch the thermometers, and see if the water cools faster in the cup with the spoon in it.

Let's put other things into the water to see if they conduct heat as well as the silver spoon. We can try a copper spoon, a pencil, a plastic toothbrush, and a celery stalk.

What will happen to the celery stalk?