The volume of a gas is directly related to the heat and pressure. If temperature increases, volume increases. If pressure increases, volume decreases. You can do an experiment for yourself: take a balloon and put it in the freezer, if what I said above is true, it should shrink, because it gets colder.

If you are interested in the math, we describe this relationship with the equation:
PV=nTR which means:
pressure x volume = amount of atoms x temperature x a constant “R”
The constant R is just a number we add so that the equation is actually equal.

Have you ever opened a warm soda and took a sip? It probably didn’t taste very good, and one of the reasons might be because it’s not very bubbly anymore. To make a soda bubbly, the factory will use a high-pressure tank to pump in lots and lots of carbon dioxide (the same stuff that we breathe). Then, they seal the can or bottle so that none of the carbon dioxide escapes. If we keep the soda cold, we can keep most of the carbon dioxide in for a tasty, fizzy drink.

But what does that have to do with the volume of gas in a balloon? Well, whether a gas is trapped in a balloon or dissolved in a soda, it won’t change too much how the gas behaves. So, when soda gets warm, the carbon dioxide gets warm, and it can travel faster and escape your drink. If you had gas in a balloon and you heat it up, the gas molecules would start traveling faster in the same way. This time though the fast gas molecules strike the balloon walls harder than before, and the balloon will have to get bigger and bigger.

This observation resulted in what is now called Charles’s Law, which says that the ratio of temperature and volume of a gas should remain the same. If you add heat, you should increase the volume.

There is a law in science called Charles’s Law which states that as temperature increases in a gas, its volume will increase. When the temperature of a gas increases, each molecule generally gets more energy and moves faster. One way to think about this is that the faster moving molecules need more room to move about, so if nothing is stopping the volume of the container from expanding, the container will get larger. Since a balloon is not a fixed container, as heat is added, it will expand.

How pressure and temperature interact in a closed system can be understood with one simple equation, PV=nRT, or the ideal gas law. Pressure multiplied by volume is equal to the amount of gas “n”, multipled by the gas constant “R” and temperature. If you increase temperature, pressure and volume will also increase.

Temperature is proportional to volume in a gas, so the higher the temperature for a given number of gas molecules in a balloon, the larger the volume of the balloon.

The more heat a gas has, the more kinetic energy its particles have.That kinetic energy generally means how fast particles are moving. So, since, the particles of the gas are moving quickly and bumping into each other more when hot, a heated balloon will expand. A cooled balloon will shrink.

Air expands when it is hot, so heating the air in a balloon will puff up the balloon.