Materials
Two identical glasses
Ice
A cooler
Clear plastic baggies that are big enough to hold one of the glasses.
Preparation
A few hours before doing the lesson, be sure one of the glasses is cold. The best effect is when you can keep it in a freezer for an hour or so. It still works well inside a classroom just covered with ice. Another way it works well and quickly is in the shade on a warm and humid day as long as the glass is under ice before starting.
Ask the students how we usually check if something is hot or cold. We should emphasize dangerous locations, such as stoves, or ovens. But most often if we are sure something is harmless, we usually touch it to find out the temperature. But today I will ask you to tell if something is hot or cold by just looking and not touching.
One glass is left at room temperature, the other glass is placed inside the plastic bag, and covered with ice in the cooler for a few hours before the lesson begins.
Show student the glass that is room temperature. Pull the other glass out of the ice and out of the bag and place it right next to the warm glass. In less than 5 minutes the condensation will appear on the cold glass and nothing will appear on the other glass. Comparing these two makes the difference and constitutes proof.
Students can have a turn touching both glasses at the same time. Students should only use one finger on each hand. Any person holding the glass warms it up and the condensation stops.
We agree that the cold glass has the condensation.
After students have done this, they talk about what we saw and what we learned. Write down the important things they say, Students write about what they saw and what they learned in their notebooks. When finishing, students read what they wrote to three other students.
