Moldy Cheese

Let's try a little experiment to see if temperature really does affect rates of reaction. Cut two small pieces of cheese about the same size. Place one in the freezer and one on a countertop, both uncovered on a paper plate. Observe any changes you might see during the course of the next few days.

What you need

• A few pieces of cheese (you may choose to try different types of cheeses to see if that makes a difference)
• Time
• A countertop where your guardians won't be upset to find moldy cheese

What's going on here

You should notice that the cheese on the countertop gets moldy much faster than the cheese in the refrigerator. The mold is caused by bacteria from the air and from the cheese growing on the cheese itself. The colder the temperature, the slower the molecules are moving. The slower hte molecules move around, the slower the reactions can proceed. We know this because for molecules to react, they must come in contact with one another. For bacteria to grow quickly on the cheese, it must be at a high enough temperature to proceed at a quick rate. Bacteria are still growing on the cheese in the freezer, but at a rate so slow that you won't be able to see the mold growing until much later. The freezer does not kill the bacteria, it only slows them down.

If you want, try doing this experiment with other kinds of cheese. Make sure you cut the cheeses about the same size - you wouldn't want to introduce any more factors into this experiment than are already present!

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