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Boiling in a Balloon
Conservation of Energy SCIENTIFIC
Introduction
A perfect demonstration that dramatically shows the tremendous heat capacity of plain, ordinary water.
Concepts
• Heat transfer
Materials
Water, 20 mL
Balloons, 129 round, 3, 1 opaque
Safety Precautions
• Specific heat
Wear chemical splash goggles, chemical-resistant gloves, and a chemical-resistant apron. Please consult current Material Safety Data Sheets for additional safety, handling, and disposal information.
Procedure
1. Prepare three balloons for the demonstration. Add 20 mL of water to an opaque balloon and another 20 mL to a semi-transparent balloon. Blow up these balloons to a diameter of about 5 inches and tie them off. Take a third balloon and inflate it to the same size and tie it off.
2. Place the two candles on the bench top. Put the semi-transparent balloon with the water inside under the desk and place the other two balloons next to the candles.
3. Light the candles. Tell your students to predict how long these two balloons can remain inflated when placed in the flame.
4. Holding each balloon by the tied end, gently place each balloon just above the yellow flame of the candle. (Try not to flinch when the one balloon pops.)
5. After 5 to 10 seconds, take the opaque balloon out of the flame. Ask the students to hypothesize the reason behind this discrepant event.
6. After a bit of class discussion, show the students the semi-transparent balloon and the water it contains.
Discussion
The heat capacity of water is the amount of heat energy that must be transferred to raise the temperature of one gram of water one degree. This value is 4.18 J/g. For the 20 mL of water in the balloon, this means that the water absorbs 83.6 J of heat energy for every degree of increased temperature. If the temperature is raised 40oC, this translates to 3344 J or
3.344 kJ of absorbed heat energy. This heat transfer prevents the balloon from bursting in the low heat flame of the candle.
© 2016 Flinn Scientific, Inc. All Rights Reserved. Publication No. 91085 1 061616
Candles, 59 5 11⁄49, 2 Lighter or matches
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