Purpose: To show that if the pressure is reduced enough; water will boil at room temperature, peeps will inflate, sound will not be transmitted.

1. Bell jar, vacuum pump, cup of water. Invite a student to sample the temperature of the water in the beaker by inserting a finger into it. Place the beaker into the bell jar and evacuate. After the water has boiled briefly, ask students to predict the water temperature. Let air into the jar, remove the water, and let the student sample the temperature.

2. Bell jar, vacuum pump, peep. Place a peep inside the bell jar. Evacuate the jar and wactch the peep inflate.

3. Bell jar, vacuum pump, buzzer, microphone, audio amplifier. Since the vacuum pump makes considerable noise, it is best to make certain the apparatus is working and then start the vacuum pump to produce the desired vacuum inside the bell jar. After the container has been evacuated, close the stopcock to the bell jar and turn the pump off. With the buzzer, amplifier, and microphone on, slowly open the stopcock so that a little air will start to enter. With the air slowly coming in, the buzzer should continue to get louder and louder until the inside pressure is the same as atmospheric pressure.

4. Put an inflated balloon inside the bell jar and evacuate the air. Watch the balloon get much larger and explain that the same amount of air is still inside the balloon.

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