The Eye Wonder team discovers how art glass is made. D.V. visits an art glass studio and watches a piece being made in real time. He learns that glass is made from silica, and there are many tools required to make unique shapes, styles and colors.
Design an experiment that reduces the rate at which a substance melts.
Type of Activities: Post-video lab
Introduction: This lab relates to the statement in the video segment where the glass blower says that they add ash to the silica to help reduce the temperature at which the sand melts.
Background: Glass blowers add ash to the silica that is melted in order to make glass. This helps reduce the temperature at which the mixture melts. This means that they do not have to get the kiln as hot in order to work the glass. Other substances also affect the melting or freezing rates of different substances. For example, when it snows or when there is the danger of ice on the roads, road crews will often pour salt over the road in an effort to reduce the amount of ice that forms. The salt lowers the freezing point of the water, making it stay as a liquid at lower temperatures. This is the same reason that in deep underwater, at temperatures near freezing, the water at the bottom of the ocean never freezes.
Another application of this is in making homemade ice cream. When you use an ice cream maker, you pack ice around the container with the ice cream mixture in it. You then add water and salt to the ice. A motor on the top of the maker spins the container. If the water with the ice froze too quickly, then the container would not be able to rotate and it could damage the motor. With the added salt, the water will not freeze as quickly, allowing the temperature to get lower to freeze the ice cream mixture without freezing the water on the outside of the container, jamming the motor.
Activity: Liquid Water below 0° C.
This lab shows another example of how something added to a substance can affect the rate at which melting or freezing occurs, like the ash added to the silica to make glass. You may need to have the class involved in some other activity while waiting for the water to reach 0° C.
Materials: 4 Beakers (two large, two small), ice, water, 2 thermometers, timer, salt, insulation (newspaper), aluminum foil
Procedure:
1. Put the smaller beakers in the larger beakers and surround them with ice.
2. Add a small amount of water to the small beakers, enough to cover the thermometers.
3. Add salt to one of the small beakers so that the solution becomes supersaturated (salt will no longer dissolve).
4. Surround the larger beakers with insulation. Cover the tops with aluminum foil, leaving a tight-fitting hole for the top of the thermometer to poke through.
5. Begin timer, periodically checking every five minutes to see if the water has begun to freeze yet. Record and graph the temperatures versus time with each check.
Modification: If you have an ice cream maker, you may want to use it as an extra.
