Resource Blog-Balloon Morphing: How Gases Contract and Expand

Balloon Morphing: How Gases Contract and Expand

Experimental Procedure

Preparing for the Balloon Tests

1. Blow up one of the balloons until it is quite full, but not close to popping, and tie it off.
2. Mark the balloon with the number 1.
3. Measure the circumference of this first balloon with the cloth tape measure, selecting the fullest part of the balloon to measure, as shown in Figure 1 on the right. Hold the tape measure snug on the balloon, but not so tight that the balloon is being squeezed by the tape measure and changing its shape. In your lab notebook, make a data table like Table 1, below, and record this starting circumference in millimeters (mm) in the data table.
   
   Figure 1. This drawing shows where to measure the circumference of the balloons.
4. Blow up the second balloon so it looks about the size of the first balloon, but do not tie it off yet. Pinch the opening closed between your thumb and finger so the air can not escape. Have your helper measure the circumference of the second balloon, just as you measured the first balloon. Adjust the air in the second balloon until its circumference is within 0.5 cm of the starting circumference of the first balloon, as follows:
   • If the circumference of the second balloon is smaller than the starting circumference of the first balloon, then blow up the second balloon some more.
   • If the circumference of the second balloon is larger than the starting circumference of the first balloon, then let some air out of the second balloon.
5. Tie off the second balloon and mark it with the number 2. Record the balloon's circumference in your data table.
6. Repeat step 4 for the third balloon, adjusting the circumference until it is within 0.5 cm of the starting circumference of the first balloon, then tying it off, marking it with the number 3, and recording its circumference in your data table.

Table 1: Circumference Data Table

Temperature (°C)	Balloon 1 Circumference (mm)	Balloon 2 Circumference (mm)	Balloon 3 Circumference (mm)	Average Circumference (mm)	Average Circumference Cubed (mm3)

Testing Your Balloons at Room Temperature

1. Measure the temperature of the room with the thermometer and record your measurement in the data table.
2. Measure the circumference of each balloon with the tape measure, selecting the fullest part of each balloon to measure, as shown in Figure 1. Hold the tape measure snug on the balloon, but not so tight that the balloon is being squeezed by the tape measure and changing its shape. Record your measurements in the data table.

Testing Your Balloons in the Cold Area

1. Place the thermometer and all three balloons—one at a time, if necessary—in the area where you have chosen to do your cold-temperature testing; such as in the freezer.
2. Wait approximately 1 hour. If you can only put one balloon in at a time, this step will take 3 hours.
3. Remove the balloon(s) from the freezer and immediately measure the circumference(s) and record your measurements in the data table.
4. Record the temperature inside your cold area in the data table.
5. Repeat steps 1–3, if necessary, until all three balloons have been tested in the cold area.

Testing Your Balloons in the Hot Area

1. Wait 20 minutes to allow your balloons to come to room temperature.
2. Place the thermometer and the balloons—one at a time, if necessary—in the area you have chosen to do your hot-temperature testing; such as inside a car on a hot day.
   1. Note: Do not put the balloons in direct sunlight or under a heat lamp because this causes the gas to escape from the balloons and will deflate them due to losing gas. This will not let you determine whether the gas contracted or expanded.
3. Wait approximately 5–10 minutes, or until you can see obvious changes. If you can only put one balloon in the hot area at a time, this step will take up to 30 minutes.
4. Remove the balloon(s) from the hot area and immediately measure the circumference and record your measurements in the data table(s).
5. Record the temperature inside your hot area in the data table.
6. Repeat steps 1–4, if necessary, until all three balloons have been tested.

Analyzing Your Data Table

1. For each temperature, calculate the average circumference and enter your calculations in the data table.
2. For each temperature, cube the average circumference by multiplying the average circumference by itself three times. For example, if the average circumference is 60 mm, then the average circumference cubed is 60 X 60 X 60, or 216,000 mm³.
3. Plot the temperature on the x-axis (in °C) and the average circumference cubed on the y-axis (in mm³). You can make the line graph by hand or use a website like Create a Graph to make the graph on the computer and print it.
4. Assuming the balloon is a sphere, the volume is proportional to the circumference cubed, meaning there is a linear relationship between volume and circumference if you plot them on a graph. In your graph, is there a linear relationship between the circumference cubed and the temperature? If not, was there a greater change in circumference cubed in going from room temperature to a cooler temperature, or in going from room temperature to a warmer temperature? As the temperature increases, what do you think happens to the space between the gas molecules inside the balloon? What do think happens to the space between the gas molecules inside the balloon as the temperature decreases?

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