Exploratories

Canister Entropy

Problem:

What is the natural tendency of a system in which interactions occur?

Materials:

40 to 50 empty 35 mm film canisters or ping pong balls or crumpled balls of paper

Procedure:

1. Divide the students into two groups, those with canisters, balls, or paper balls and those without.
2. Have students with canisters stand on one side of the classroom and those without stand on the other side of the room.
3. When told to begin, students with the canisters are to begin throwing them across the room at those who do not have canisters. As soon as a canister lands on the other side of the room, it is to be picked up and thrown back across the room.
4. Continue this process for 2 to 3 minutes. Then stop and count the number of canisters on each side of the room.
5. Record the number of canisters on each side
6. Repeat the above procedure 2 to 3 times.

Summing Up:

1. What were your observations as to the number of canisters on each side of the room following the energy exchange that occurs with the tossing of the canisters?
2. What happened to the internal energy of the system?
3. Where was there more order prior to or after the exchange?

Teacher's Notes:

This activity is designed to demonstrate the process of entropy. This system goes from order, a divided room with canisters on one side only, to disorder. If you refer to the side of the room with canisters as a hotter body and the side without canisters as a colder body, thermal equilibrium is reached. There are normally an equal number of canisters on each side following the exchange.

As an application for entropy you can have students list examples of systems that
demonstrate the concept of entropy. For most high school students their bedrooms are often a viable example. No matter how often they clean them, they tend to achieve a heightened degree of clutter. Another example is to have students place and open container of perfume in the front of the room and discuss the process that allows it to travel to the back of the room without the aid of fans or other currents. Ask students why they tend to place cologne on pulse points.