Fast and Easy Science Fair Projects: Bad Manners

Heat conduction and heat sinking

Purpose: Is there a way to make something cool more quickly, like a drink that is too hot?

Overview: Metal is a good "conductor" of heat. That means it makes an easy path that can travel along. When a metal frying pan is placed on a stove burner, the heat from the burner is conducted (carried) through the bottom of the pan and heats the food inside it.

     Metal is sometimes used to cool things by conducting heat away from an object. In electronics, transistors and integrated circuits ("chips"), which are found in televisions, stereos, and computers, get hot, but heat can damage them. Often metal us made in the shape of fins and attached to transistors and integrated circuits in order to carry the heat away from them. These cooling fins, called heat sinks, help transfer the heat to the surrounding air and keep the transistors and integrated circuits cool. Sometimes a small fan is used to get rid of the heated air. Does your computer have a fan in it?

     Have you ever been served a hot cup of tea or hot chocolate that was too hot to drink and someone told you, "Leave the spoon in. It might be bad manners but it will help cool the drink faster." They are thinking that, since metal conducts heat, the soon will carry some of the heat away from the drink. The spoon is indeed hot to the touch, so it does conduct heat away from the drink.

     However, since the handle of a spoon is not designed like a heat sink, the heat in the spoon doesn't efficiently transfer to the surrounding air so you may want to hypothesize that leaving the spoon in the hot liquid won't male a significant difference.

Hypothesis: Hypothesize that leaving a spoon in a hot drink will not make any noticeable difference in its rate of cooling, reducing the temperature faster.

Procedure: Gather two thermometers. Before we can use them, we must be sure they are calibrated, that is, we may need to adjust the temperature reading of one thermometer so both thermometers correctly read the same. Leave the two thermometers at room temperature for several minutes, then read the temperature on each one. If one reads higher than the other, put a small piece of masking tape on it and make a note of the difference n temperature. If it is 1/2 degree or 1 degree higher, then subtract this much from its readings when comparing the temperature on it to the other temperature on the other thermometer.

     Fill two coffee cups of equal size with equally hot tap water. (Be careful working with and around very hot water.) Place a thermometer in each cup. Put a metal spoon in one of the cups. After one minute, read the temperatures on the two thermometers and write them down. Every minute, write down the temperatures on the two thermometers to make any adjustment of your numbers to calibrate the two thermometers. Continue to make readings until the water in the two cups reach room temperature.

     Did the water in the cup with the spoon in it cool down faster, or wasn't there any noticeable difference.

Results and Conclusion: Write down the results of your experiment. Come toa conclusion as to whether or not your hypothesis was correct.

Something more: Can you find a way that will measurably cool the cup of hot water? Purchase some transistor heat sinks at your local electronics shop and affix them to the cup with the rubber bands.