Charles Law Balloon Experiment

In this experiment we will learn,

  • How to inflate the balloon by simply changing the temperature of the gas?
  • What is Charles’ law?
  • Why does gas expand on heating?

Materials Required (What Do I Need?)

  • Two large balloons
  • Coldwater
  • Hot water
  • Glass vessel
  • Conical flask
  • Laboratory Burner or hot plate

Procedure (What to do?)

  1. Add a half cup of cold water in the conical flask
  2. Attach balloon over the mouth of the conical flask
  3. Place the conical flask on the hot plate or lab burner and start heating it
  4. Now observe the balloon. You will notice that the balloon will inflate in some time.
  5. Remove the flask from the heat and allow it to cool down.


Be careful while handling hot items

Science Behind This Experiment (What’s Going On?)

You will notice that the balloon will start inflating as we heat the conical flask.

This expansion of the balloon is due to the expansion of the air molecules present in the flask. However, the conversion of liquid water into water vapors is also responsible for the inflation of the balloon.

Now try to understand what Charles’ law is and how it is related to the above experiment?

Charles’ law states that the volume of an ideal gas at constant pressure is directly proportional to the absolute temperature. Basically it describes how gases expand on heating. Whenever we heat a gas, the energy in the form of heat gets converted to the kinetic energy of the gas molecules. This increase in kinetic energy causes an increase in the space between these air molecules. Due to which the volume of the gas increases and hence gas expands.

In the above experiment, on heating the kinetic energy of air molecules inside the flask increases and hence the volume of the gas. Due to the fixed volume of the conical flask, these gas molecules try to escape the flask and occupy the space inside the balloon and hence the balloon starts to inflate as we heat the conical flask.


From the above experiment, we can conclude that the gas expands as we increase the temperature of the gas.

Professor Atom

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Professor Atom is a science enthusiast and alumni of IIT Bombay. According to him, every question can be solved with curiosity and mind mapping. ( Curiosity = Asking Questions = Learning )

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