This week's experiment comes from our dog, Shelby. She is a young, black Labrador, with feet about the size of Nebraska. She loves to run. She would rather run than eat, which for her is saying a lot. After play time, she looks for a place to cool down. At home, we have air conditioning vents in the floor, but in hotels, she has learned a different way to get comfortable. To explore this, you will need:

- bare feet
- a tile floor
- a carpet or rug

If Shelby is hot, she heads for the kitchen floor. She knows that resting on the tile will cool her very quickly. But wait a minute. Why does that work? Take off your shoes and socks. Walk barefoot across a carpeted floor. Notice the temperature. Then step onto a tile or linoleum floor. Do you notice a difference in temperature? Yes. The tile floor feels colder. But is it?

No. Unless the temperature of your room has changed recently, both the carpet and the tile floor are the same temperature. How can that be? If you have a thermometer, you can test it. Don't use the thermometer that you use to check for a fever. Unless your house is very hot, it won't register the temperature. Also, if you used it to check the temperature of the floor, no one would want to put it in their mouth. If you do test, you will find that both the carpet and the tile are the same temperature.

Then why does the tile feel so much cooler? It has to do with the amount of heat that it takes to heat the substances, and how well they conduct the heat. Some things conduct heat better than others. The better it conducts heat, the faster it can transfer that heat. A substance which carries the heat away from your skin quickly will feel cooler than a substance which is slower to carry the heat. The tile is a good conductor of heat, so it feels cooler.

The amount of heat energy that it takes to heat a substance varies a lot. Think about a slice of leftover pizza. If you do not leave it in the oven long enough, you will find that although the crust is hot, the cheese and sauce are still cool. The sauce and cheese have a high specific heat, which means it takes more heat energy to increase their temperature.

The same thing works in reverse. Once the pizza is hot, you have to be careful. You can take a bite of the crust with no problem. It has a low specific heat. It does not have to absorb much heat energy to make it hot, and it does not have to get rid of much heat to cool down. Your mouth can easily absorb that much heat without discomfort. Since the sauce and cheese have a high specific heat, they have to absorb a lot more heat energy to get hot. Once they are hot, they have to get rid of a lot of heat energy to cool down. Moving that much heat to your mouth can hurt, so let the pizza cool a bit before you take a big bite.

Substances with a high specific heat will change temperature slowly, and their temperature will feel more extreme (either hotter or cooler.) Substances with low specific heat will change temperature quickly.

Knowing how specific heat works, and knowing that the tile floor has a higher specific heat than the carpet, we can make some predictions. If you turned on the heat, which would heat up faster? The carpet, right? It takes less heat energy to raise its temperature.

If you spilled hot coffee on both the carpet and the tile floor, which should you clean up first? The coffee on the tile floor. Because the tile has a high specific heat, it will absorb a lot of the heat energy from the coffee. The coffee on the tile will be cool while the coffee on the carpet is still scalding hot.

If you were an overheated puppy, which floor would you pick to rest on? Shelby knows to head straight for that kitchen floor. Besides its cooling properties, it also puts her is a good position to trip someone carrying food, giving her a snack as well. Clever dog!