Green Eggs??

Have you ever noticed the green film that sometimes forms around the yolk in a hard-boiled egg? It doesn't look very yummy - what is that stuff? Eggs don't start out with anything green in them! The green film is iron sulfide (chemical formula, FeS), and it forms during cooking when iron in the yolk combines with some of the egg's proteins. You can't taste it, and it's not dangerous to eat.

How can you avoid forming this green film? You need to cool the eggs quickly after they are done cooking. As soon as the eggs are finished, pour off the hot water and cover them with cold water. The reaction happens at high temperature, and by cooling the eggs, you stop it from occurring!

Chemical Heat

Here's an experiment that shows how a common chemical reaction creates heat. See if you can figure out what the reaction is.

You'll need a good-sized jar with a lid, a small thermometer that will fit in the jar, some steel wool (plain steel wool, not the scrubbing pads that contain soap), and vinegar.

First, take a handful of steel wool, and place it in the jar. Put the thermometer in, making sure that the bulb (temperature-sensing part) in surrounded by steel wool. Record the temperature. Wait a few minutes, then check again. Boring, huh? The temperature shouldn't change very much.

Now for some chemistry! Take the thermometer and steel wool out of the jar. Soak the steel wool in vinegar for a few minutes, then remove it and squeeze the vinegar out (wear a rubber glove when doing this). Quickly put the steel wool and thermometer back in the jar the way it was before. Watch the thermometer for several minutes. Does anything happen? Check back a few times over the next hour or so. What happens to the temperature? Does the steel wool look the same? What do you think happened to it? Here's a hint: don't get distracted by the vinegar - it's not involved in the reaction.