Balloons! Some Float! Some Sink! How does the Temperature of a Gas Affect its Density?

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Updated on Feb 11, 2012

Grade Level: 7th - 8th; Type: Physics


To determine how the temperature of a gas affects its density.

Research Questions

  • What is the Kinetic Theory of Matter?
  • What is Charles’s Law?
  • How does the temperature of a gas affect its volume?
  • How does the density of a gas affect its volume?
  • What are some practical applications of the effects of temperature, density and volume
  • interactions?

On the information level, this experiment serves to acquaint students with basic information as to the affect of temperature on the density of a gas, such as air. In this specific case, this project serves to illustrate how specific kinds of balloons such as hot air balloons will remain floating in the air while the ordinary balloons we blow up do not. Given the fact that warm air rises, that warm air is lighter than cool or cold air due to its lowered density, a balloon containing warm air will float. In short, hot air is lighter than cool air because it has less mass per unit volume. This science fair experiment also serves to acquaint students with the essential processes of sciencing such as the importance of the use of a control, of identifying dependent and independent variables, of data collection, of pictorial and or graphic presentation of data and of being able to make better judgments as to the validity and reliability of their findings. They take on the role of scientists and in the process they learn to act as one.


  • balloons
  • a medium sized beaker
  • a cm ruler
  • a hot plate
  • aluminum pans ice water
  • safety gloves.

Experimental Procedure

  1. Gather all the materials that you require for this project. These include balloons, a medium sized beaker, a cm ruler, a hot plate, aluminum pans ice water and safety gloves. Put on the safety glasses. You may wish to include a camera and take photos of the procedure and the observations of this experiment to include in your final report and your display at the Science Fair.
  2. Copy the chart on the next page so that you can readily record your observations and /or draw the results.
  3. Take your aluminum pan and fill it with about 5 cm of water. Place on stove and heat.
  4. Take your second aluminum plate and fill it with 5 cm of ice water.
  5. Place a balloon into your medium sized beaker. You are going to blow the balloon up to a specific size, not to exceed the volume that the beaker can accommodate.
  6. Now, holding the balloon in the beaker, blow into the balloon filling it up to beaker capacity.
  7. Tie the balloon keeping it in the beaker.
  8. Now, place the beaker with the balloon into the ice water. Observe. What happened to the balloon?
  9. Take the beaker and balloon out of the ice water. Let them stand for about 4 to5 minutes. Observe and record your observations.
  10. Put on your heat resistant gloves. Check your first aluminum pan. Is the water hot? Fine. Now, put the beaker and balloon into the hot. Water. Wait for a few minutes. Observe the results and record. You may want to draw what you observed.
  11. Turn off the stove. Carefully discard the hot water.
  12. Review your observations. Write up your experiment. What were your conclusions? Do a “So what?” How can these conclusions be applied to daily life? Include your armchair research in your report.

Charting Observations and or Drawing the Data

Balloon in Cold Water Water Balloon in Hot Water Water “Cold “Sketch “Hot” Sketch

Terms/Concepts: Mass, volume, density, temperature.


Masterton, W, Slowinski, E. Walford, E., Chemistry, Holt, Rinehart and Winston, New York, 1980

Dr. Muriel Gerhard (Ed.D.) is a retired educator with fifty seven years of experience in all aspects of public education. She has been a teacher, principal, administrator, college professor, researcher, grants writer, change agent and science editor. She is the author of several books on education used as college texts. These include the best selling Effective Teaching Strategies with the Behavioral Outcomes Approach and The Behavioral Outcomes Handbook for Teachers and Administrators. Presently she is a consultant in science education and curriculum development, a marriage and family therapist, a newspaper columnist and an author. Her latest book, recently published, is a memoir of sixty vignettes entitled âNow That I`m Dead, I Decided to Write this Bookâ.

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