Racing to Win That Checkered Flag: How Do Gases Help?
AbstractWatching professional racing-car drivers compete can be thrilling. The high speeds that racing cars can reach — up to 200 miles per hour (mph) and more! — put some unique demands on the vehicles. For example, to withstand high temperatures, the tires must be inflated with nitrogen gas, instead of air as with normal car tires. This enables the drivers to have better control over steering their cars as they race around the track. In this sports science project, you will inflate balloons to investigate how gases expand and contract due to changes in temperature, and use the results to explain why racing-car tires are filled with nitrogen gas. So get ready to blow up some balloons!
Teisha Rowland, PhD, Science Buddies
- Mylar is a registered trademark of DuPont Teijin Films.
ObjectiveDetermine how gases expand and contract due to changes in temperature, and explain why racing-car tires are inflated with nitrogen gas.
The race for the checkered flag (shown by the racing cars in Figure 1) can be an exciting and thrilling ride. Did you know that a lot of the race is riding on gases? This might sound odd, but the type of gas used to inflate racing-car tires is actually very important. All car tires heat up a bit when you drive the car, due to friction between the tires and the road. Because racing cars go much faster than regular cars, they create even more friction between the tires and the track. Depending on the racing car, it can go 200 mph or faster during a race! This high speed causes the tires to heat up, reaching temperatures of about 120 to 160° Celsius (C) — or about 250 to 325° Fahrenheit (F). Because of these extreme temperatures, racing-car tires need to be inflated with nitrogen gas instead of air, like regular car tires. Why? It comes down to how matter behaves.
Figure 1. Racing-car tires must be filled with nitrogen gas because of the high temperatures they can reach. (Image credit: Todd Ellis)
Everything in the world around you is made up of matter, including a car tire and what is inside of it. We observe matter in everyday life in four different forms, called states. The states, going (generally) from lowest energy to highest energy, are solids, liquids, gases, and plasmas. Gases, like the air inside normal car tires, take the shape of the containers they are in. They spread out so that all the space is filled up evenly with gas molecules. The gas molecules are not connected. They move in a straight line until they bounce into another gas molecule or hit the wall of the container, and then they rebound and continue in another direction until they hit something else. The combined motion energy of all gas molecules in a container is called the average kinetic energy.
This average kinetic energy (energy of motion) changes in response to temperature. When the temperature increases, the average kinetic energy of the gas molecules also increases. This means the molecules move faster and have more frequent and harder collisions inside the tire. Likewise, when the temperature decreases, the kinetic energy of the gas molecules decreases, meaning the molecules move slower and have less frequent and weaker collisions. This is why some specialized vehicles that travel in extremely cold temperatures, such as the Terra Bus (shown in Figure 2), which transports researchers around the McMurdo Station in Antarctica (where it rarely gets above freezing), have special tires that work at abnormally low tire pressures, when the collisions between molecules in the tires are relatively weak and infrequent.
Figure 2. The Terra Bus transports scientific researchers in Antarctica. The Terra Bus is equipped with tires made for low pressures so they can function in the very cold temperatures. (Image credit: Eli Duke)
But what about racing-car tires, which have to deal with very hot temperatures? The important factor for this condition is actually how much water is inside the tires. When water is heated, it vaporizes and turns into a gas. As we mentioned, gas molecules generally have more kinetic energy than liquid molecules. This means that as the tires heat up, any moisture inside of them vaporizes, and because the gas expands (taking up more volume than the liquid water), the tire pressure increases. For normal cars this is not an issue, but because racing-car tires heat up to such extreme temperatures, the increased tire pressure can seriously affect how the car hugs the road. Although it might not feel moist, the air around us, and particularly that which we exhale from our lungs, actually contains small amounts of water (along with different gases, mostly nitrogen and oxygen). Nitrogen gas, however, can be manufactured to be extremely pure, with no water or other gases in it. Because it is a drier gas than air, nitrogen gas is used to fill racing-car tires, giving more control over how the tire pressure builds up during a race, which gives the driver more control steering the car.
In this science project, you will compare the kinetic energy changes of air compared to a relatively dry gas when both are exposed to different temperatures. You will not be using racing-car tires in this experiment, but instead will use latex balloons to model the tires. Specifically, you will be filling latex balloons with either air (from your lungs) or helium (from a tank). Like purified nitrogen gas, helium gas is also very pure and dry, but you will be using helium gas because helium gas tanks are much more readily available than nitrogen gas tanks (and pure nitrogen is dangerous to breathe). You will compare the sizes of the balloons at room temperature and after they have spent time in a freezer. How do you expect the shape of the helium-filled balloons to change when they are frozen, compared to when they are warmer, at room temperature? How do you think the changes in the helium-filled balloons will compare to the changes in the air-filled balloons? Here is an opportunity to blow up some balloons and find out!
Note: In this science project you are testing latex balloons at room temperature and in a freezer, but not in hotter temperatures. This is because when heated (such as by exposure to bright sunlight or a hot lamp), latex balloons deflate as the gases escape from the balloon.
Terms and Concepts
- States of matter
- Average kinetic energy
- Tire pressure
- Nitrogen gas
- Helium gas
- Why do car tires heat up when a car moves? Why do racing-car tires heat up even more than the tires on a "normal" car?
- What four different states of matter can you observe in everyday life? How does the amount of energy of each compare to the other?
- Why is it important that the gas inside racing-car tires does not contain moisture?
- How is nitrogen gas similar to helium gas?
To find out more about the different states of matter and gases, check out these resources:
- EDinformatics. (1999). States of Matter. Retrieved December 18, 2013.
- Rader, A. (n.d.). Looking for a Gas. Rader's Chem4Kids.com. Retrieved December 18, 2013.
This webpage has information on elastic and inelastic collisions:
- Nave, C. R. (n.d.). Elastic and inelastic collisions. HyperPhysics. Department of Physics and Astronomy, Georgia State University. Retrieved November 13, 2013.
You can find out more about the Terra Bus, which transports researchers around Antarctica, on this webpage:
- Foremost. (n.d.). Terra Bus. Retrieved December 18, 2013.
Materials and Equipment
- Freezer. It should have enough empty space to easily hold an inflated balloon at least 9 inches in diameter.
- Thermometer. It should have a range of at least -25°C to 30°C. Thermometers like this may be found in stores or through online suppliers such as Amazon.com.
- Helium tank. A helium tank can be purchased at certain grocery stores, or at discount and/or party-supply stores, or through online suppliers such as
- Note: It is important to use a helium tank to inflate the balloons, and not just have them blown up at a store, because you will need to do your tests immediately after the balloons are inflated since helium escapes from latex balloons. You will be doing at least five separate tests, with five separately inflated helium balloons.
- Latex balloons, around 9 to 12 inches inflated size (at least 10). These may be found at discount and/or party-supply stores, or through online suppliers such as Amazon.com.
- String or ribbon (5 pieces, each long enough to tie a balloon to something to hold the balloon down)
- Permanent marker, black or a different dark color
- Cloth tape measure. It should be metric. Metric cloth tape measures can be purchased through online suppliers such as Amazon.com.
- Lab notebook
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Testing the Balloons
- In your lab notebook, make a data table like Table 1. You will record your results and observations in this data table.
|Balloon Number||What the Balloon Is Filled with||Circumference (cm)||Initial Distance (cm)||Distance After Freezing for 1 Hour (cm)||Percentage Change Due to Freezing||Average Percentage Change Due to Freezing|
- Make sure your freezer has enough space to easily fit an inflated balloon inside somewhere. The balloon should not be crushed or squeezed at all.
- If you need to move food in the freezer to make space, be sure to get permission from anybody who is storing food in the freezer.
- Also make sure to avoid pointy objects or parts of the freezer (such as areas covered in sharp ice crystals) that could puncture the balloons.
- Use a thermometer to measure the room temperature. Record this in your lab notebook. Then put the thermometer in the freezer, close the freezer door, and record the freezer's temperature after the thermometer has adjusted to it (this will take about five minutes). Then you can remove the thermometer.
- Use the helium tank to blow up one of the balloons until it is mostly full, but not completely full. Then carefully tie the balloon off with a knot. It should now look similar to Figure 3. Tie a short string or ribbon to the bottom of the balloon so you can hold it and it does not float away.
- Follow the directions on the helium tank (or its packaging) to inflate the balloon.
- Be sure to follow all of the safety precautions that come with the tank.
- Note: The balloon might not float very well because it is not fully inflated with helium, but it does not need to be filled completely to work in this science project. Even if the balloon does not float, however, it should at least be able to stand upright on a surface.
Figure 3. Fill the balloon up so that it is mostly full, but not completely. After tying a knot at the bottom of the balloon, be sure to tie on a string so your helium balloon does not float away.
- Use a permanent marker to write "H1" near the bottom of the balloon. This will be helium balloon number 1; the letter H tells you it is filled with helium.
- With your helper assisting you, measure the circumference of the widest part of the balloon using a cloth tape measure or a piece of string (and then measure the string against a tape measure), as shown in Figure 4. Record the circumference in the data table in your lab notebook.
- Hold the tape measure or string snug on the balloon, but not so tight that it squeezes the balloon and changes its shape.
Figure 4. Measure the circumference of the widest part of the balloon using a cloth tape measure or a piece of string, as shown here. If you use string, you will then need to measure the length of the string using a tape measure.
- Turn the balloon so you can look at the top of it. At the very top, it should have a slightly darker spot, as shown in Figure 5.
Figure 5. The top of the balloon should have a slightly darker spot, as shown here.
- Using the permanent marker, make a small spot in the center of the darker spot at the top of the balloon. This will make it easier for you to identify it later.
- Take a cloth tape measure or some other kind of small, flexible tape measure and make two small lines with the permanent marker at the top of the balloon that are 6 cm away from each other, with the darker spot as the midpoint.
- To do this, center the tape measure so that its 3 cm mark is on the smaller spot you made, and then make a line at the 0 cm and 6 cm points. This is shown in Figure 6.
- You could alternatively use a different part of the tape measure to do this, as long as the lines are 3 cm away from the middle spot, and 6 cm away from each other.
- Once you have finished this step, your balloon should look similar to the one in Figure 7.
- To do this, center the tape measure so that its 3 cm mark is on the smaller spot you made, and then make a line at the 0 cm and 6 cm points. This is shown in Figure 6.
Figure 6. Make two small lines that are 6 cm apart, centered on the small spot you marked in the middle of the dark spot at the top of the balloon.
Figure 7. After making the lines, your balloon should look similar to this one.
- Because it can be difficult to draw lines at exact distances with a thick permanent marker, and because you need precise measurements to do this science project, you will now measure the exact distance between the two lines you just drew. It is important to take careful measurements so that you can determine if the balloon changes sizes by even a tiny amount. Record this as the "Initial Distance (cm)" in the data table in your lab notebook.
- Take your tape measure and measure the distance between the lines and record the exact distance. For example, this might be 5.95 cm or 6.15 cm.
- Do not worry if the distance is not exactly 6.00 cm. You are recording the exact distance in case it is not exactly 6.00 cm.
- Because the lines from the permanent marker are probably thick, you will need to pay attention to where on the marks you are making your measurements. You should always make your measurements from the outside of both marks. For example, in Figure 6, the tape measure is measuring from the outside of both marks.
- Put the balloon in the freezer in the area you cleared out for it. Set a timer for 1 hour (hr) and leave the balloon in the freezer for the entire hour.
- Do not disturb the balloon or open the freezer during this time. Let anybody else who uses the freezer know that you have a science experiment taking place and not to open the freezer.
- After the balloon has been in the freezer for 1 hr, bring your tape measure to the freezer and, with the balloon still in the freezer (but with the freezer door open to let you access the balloon), quickly measure the distance between the two lines, as you did in step 10. Record this as the "Distance After Freezing for 1 Hour (cm)" in the data table in your lab notebook.
- Note: The balloon can quickly change size after taking it out of the freezer, so it is important to do the measurements in the freezer (and not take the balloon out of the freezer), to keep the balloon's temperature as similar to what it had in the closed freezer as possible.
- Again, be sure to make your measurements from the outside of both marks.
- Repeat steps 4–12 but this time blow up the balloon yourself (using air from your lungs).
- When repeating step 4, inflate a new balloon so that it looks about the same size as the first balloon, but do not tie it off yet. Pinch the opening closed between your thumb and finger so the air cannot escape. Have your helper measure the circumference of the balloon, then adjust the air in the balloon until it is within about 2 cm (plus or minus) of the first balloon (by blowing in more air, or letting a little escape). Then tie it off. (You do not need to attach a string.)
- When repeating step 5, label the balloon "A1" because this will be air balloon number 1. The "A" means it is filled with air.
- Do not forget to write your results in the data table in your lab notebook.
- Repeat steps 4–13 until you have tested five helium balloons and five air balloons.
- Use a new balloon each time, so you go through a total of ten balloons.
- For each helium balloon, try to make the same-numbered air balloon have about the same circumference (as described in step 13a.).
- For example, if you inflate helium balloon number 2 to have a circumference of 50 cm, then you could blow up air balloon number 2 to have a circumference of 48.5 cm. Similarly, if helium balloon number 3 has a circumference of 54 cm then air balloon number 3 could have a circumference of 55 cm.
- If you want, you could try to make all of your balloons have about the same circumference, but this can be challenging to do when filling balloons from the helium tank, and may result in wasted helium.
- Use each balloon immediately after inflating it. This is important because the gases will escape from the balloons over time.
- Note that this testing might take more than one day to do, because each balloon requires 1 hr in the freezer. If you can fit more than one balloon in the freezer at a time, then you could test more than one at once, but you still will need to take your measurements quickly. Be sure to plan accordingly.
- After you have finished testing all ten balloons, you can move on to the next section to analyze your results.
Analyzing Your Results
- Calculate the percentage change in the distance (between the lines) from the initial distance at room temperature to the freezing distance for each balloon and record this in the data table in your lab notebook. Use Equation 1 to do this.
- For example, if the initial distance for a balloon was 6.05 cm and after freezing it was 5.35 cm, the percentage change due to freezing would be 11.6% (because 6.05 cm minus 5.35 cm is 0.70 cm, and 0.70 cm divided by 6.05 cm is 0.116, which is the same as 11.6%).
- Next calculate the average percentage change in the distance for all of the helium balloons and all of the air balloons and record this in your data table.
- For example, if the percentage change in the distance for the five helium balloons was 9.5%, 11.6%, 12.3%, 10.2%, and 9.2%, the average would be 10.6% (because this is the sum of those five numbers divided by five).
- Note: The percentages listed are made up and should not be compared to the data you collect.
- Make a bar graph of your results. Put the average percentage change due to freezing on the y-axis (the vertical axis) and what the balloons were filled with (helium or air) on the x-axis (the horizontal axis). Make one bar for the helium balloons and one bar for the air balloons.
- If you want, you could make another bar graph that shows the results for each of the ten balloons you tested. If you do this, put the percentage change in the distance on the y-axis. On the x-axis put the balloon's number. Make the bars for the helium balloons one color, and the bars for the air balloons a different color. Try to pair up the same-numbered balloons.
- Look at your data and your graph(s) and analyze your results.
- How did the helium balloons change size after freezing them? What about the air balloons?
- Do you see a difference in the percentage change between the helium balloons and the air balloons? In other words, did one type of balloon change size more than another type?
- Do your results make sense to you? Can you use your results to help explain why tires on racing cars are filled with nitrogen instead of air? Hint: If you are stumped, try rereading the Introduction.
Ask an Expert
- What are other ways you can measure how the presence of water affects how much tires expand when their temperature changes? For example, you could repeat this experiment, using five balloons filled with air (or helium) and five balloons filled with some air and water. Design your experiment and then try it out.
- Does the entire surface of a balloon expand by the same amount when you inflate it? To find out, try drawing several lines from top to bottom on an uninflated balloon, making all of the lines the same length, and then blow the balloon up. Do the lines remain the same length once the balloon is inflated, or are they different lengths? Do you see any patterns in your results? If so, can you explain them?
- For a similar science project idea to this one, check out Balloon Morphing: How Gases Contract and Expand.
- How does the amount of space a piece of ice takes up compare with the space that same piece of ice takes up once it has melted? Did it take up more space when it was ice compared to water? Design an experiment to investigate this and then try it out.
- How much space does vaporized water take up compared to water in liquid form? Design a safe way to test this. Be sure to ask an adult to help you if you use a stove or some other method to create boiling water.
- In this science project, you used latex balloons, but there are many other types of balloons available from different suppliers, such as Mylar® balloons, foil balloons, and tiny water balloons. Try this experiment using different types of balloons. How do your results compare to latex balloons?
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