To investigate the effects of hot water on the expansion of balloons submerged in water.
Inside a balloon is air, and when the surrounding temperature of the balloon is increased, the air inside the balloon receives more energy and thus expands. This can be seen when a balloon is submerged in water and then the water is heated, giving energy to the air inside the balloon and thus expanding it. Also, when salt is added to water, this increases the boiling point of water, allowing it to be at a higher temperature before boiling. This experiment aims to measure the expansion of the balloon using a motion sensor submerged in hot water, using salt so as to increase the boiling point to prevent the water from boiling under high temperatures.
The measurement of the expansion of the balloon is done with the motion sensor as it also measures the position, and since when the balloon expands in the water, the water level would rise and would register in the motion sensor.

5x balloons
 1x stand-clamp
 1x motion-sensor

1x hot-plate
 1x 250-ml beaker
 1x thermometer

Water

Salt
 Spoon

100-gram cylindrical weights
 Laptop

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Larger volumes of water would require more salt to increase the boiling point
Surrounding temperature could affect the rate of which the temperature of the water would cool.
By measuring the amount of times the beaker is poured with water, heated, and poured in the basin.
By setting a fixed airconditioning temperature.

1.
Inflate the balloon using the mouth
2.
Enclose the balloon and attach the 100-gram weights under the balloon
3.
Turn on the hot-plate and set it to maximum
4.
Pour water into the beaker and heat it
5.
Place the thermometer on the beaker
6.
Once heated (up to the maximum desired temperature, using the thermometer), pour the water to the basin
7.
Add salt into the basin depending on the amount of water poured
Note* The balloon is not yet submerged
8.
If required, repeat steps 4-6 to add more hot water to the basin
9.
Attach the thermometer to the stand-clamp and adjust the stand-clamp so it is now measuring the temperature in the basin
10.
Connect the motion sensor with the data-logger, and place the motion sensor so it is facing the balloon and the water
11.
Submerge the balloon into the basin

12.
Use the laptop to record data – allow for about 5 minutes for each temperature (using the datalogger)
13.
After 5 minutes, wait until the water to cool down to the next desired temperature a.
(if the temperature range was 100, 90, 80, 70, heat the water to 100, then wait until it drops to 90, then until 80, etc.)
14.
After the temperature has dropped, re-inflate another balloon
15.
From the previous balloon, remove the weights and add it to the new balloon.
16.
Submerge the new balloon into the basin
17.
Record data using laptop and datalogger for about 5 minutes
18.
Repeat steps 11-15 for the other temperatures

The use of this particular basin might not be very thermally insulated and thus could affect the rate at which the water cools, as the basin would determine how much heat is lost over time.

As the water cools down, the expansion rate should go down and thus the balloon’s expansion measurements does not exactly result from the fact that the water is kept at a constant, predetermined temperature, but only initially, and that the temperature (whilst measuring the expansion) would be gradually cooling.
Temperature of Water (Celsius)
100
90
80
70
60
Expansion of balloon (change in size)
(centimetres)
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