Wood & Metal – Cool or Hot?

EQUIPMENTS:

1. A piece of wood
2. A piece of metal
3. A large piece of Styrofoam
4. A large piece of cardboard
5. Four liquid crystal thermometer cards (Try a science equipment store)

INSTRUCTIONS:

1. At first, place the pieces of wood, metal, Styrofoam and cardboard on a tabletop.
2. Now place the palm of your hand on one object and the other hand on another object. Do this with all four of the objects. Feel the warmth of each object and try to figure out which one is the warm and which one is the cold.
3. After that, arrange the objects in order from the one that feels the coldest to the one that feels the hottest!
4. Now use the liquid crystal thermometer cards to check out the temperature of those objects. To do that, lay a thermometer card flat on each object and wait for about 15 to 20 seconds for the temperature to register. The color of the thermometer card will change when the temperature of the adjacent object registers.

RESULTS:

Even though the palms of your hands are telling you that the four objects have different temperature, all the four objects actually have the same temperature according to the liquid crystal thermometer cards!

EXPLANATIONS:

The nervous system of our skin is detects temperature differently than a thermometer. It is designed to detect temperature by determining whether our body heat is being taken away or whether it is being held in place when we touch something. When we touch a heat conductor such as a piece of metal, our body heat is easily conducted away then. So these heat conductors feel cold when we touch them. On the other hand when we touch a heat insulator, our body heat is then held up in one place because the insulator prevents the heat from escaping. Examples for such materials are wood, Styrofoam, cardboard etc. These heat insulator materials feel a lot warmer than the heat conductors when we touch them. In reality, when all these materials are at the same temperature, some feel warmer or colder is actually based on their ability to conduct or insulate heat. Difference is the rate at which a conductor carries heat away or at which an insulator keeps the heat in place explains why even different conductors or/insulators with same temperature might feel as if they are different temperature.

MORE EXPERIMENTS FOR YOU:

1. Try using different thicknesses of the same materials and see if there is any difference?
2. Try using other kinds of materials.