Thermal gas expansion

It’s an easy trick with gas expansion!

Safe­ty pre­cau­tions

Warn­ing! Only un­der adult su­per­vi­sion.

Equip­ment

  • hot wa­ter;
  • cold wa­ter;
  • bal­loon;
  • emp­ty bot­tle.

Step-by-step in­struc­tions

Put a bal­loon on the neck of a bot­tle and sub­merge the bot­tle in hot wa­ter – the bal­loon in­flates! Im­me­di­ate­ly af­ter­wards, im­merse the bot­tle in cold wa­ter – the bal­loon de­flates.

Process de­scrip­tion

When a gas is heat­ed, its mol­e­cules move faster. As the speed of the mol­e­cules in­creas­es, the pres­sure in­side the bal­loon in­creas­es. This caus­es the bal­loon to swell – as its vol­ume in­creas­es, the pres­sure in­side it de­creas­es, and the ten­sion of the bal­loon grows. Even­tu­al­ly, the pres­sure in­side the bal­loon is ad­just­ed to com­pen­sate for at­mo­spher­ic pres­sure and the ten­sion of the bal­loon it­self. When the gas cools, the mol­e­cules slow down, and the pres­sure in­side the bal­loon de­creas­es – it is no longer strong enough to com­pen­sate for at­mo­spher­ic pres­sure and the ten­sion of the bal­loon, so the bal­loon de­flates.

Many more cool ex­per­i­ments are wait­ing for you in the MEL Physics sub­scrip­tion!

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