You fill a balloon with gas on a warm summer day. The balloon seems to be stretched to its limit. You put the balloon inside a freezer. What do you predict will happen?

Question

Options:

1. The balloon bursts from the added pressure caused by the cold temperatures
2.  The balloon stays the same size. Temperature does not affect it.
3.  The balloon shrinks due to the colder temperature.
4.  The gas molecules are slowed down by the cooler temperature, but that effect is balanced by the force of the balloon pulling on the gas.
5.  None of the above

Answer 1

Here, a good explanation is the ideal gas law! Keep in mind this law applies under certain conditions.

PV=nRT

where P is pressure, V is volume, n is typically the moles of gas, R is the ideal gas constant, and T is temperature.

In the equation, what is the relationship between pressure, temperature, and volume?

P ~ T: pressure is proportional to temperature (P and T are on opposite sides of the equals sign); meaning, if temperature increases then pressure increases. Also, if temperature decreases then pressure decreases.

P is ~ (1/V): pressure is inversely proportional to volume (P and V are on the same side of the equals sign); meaning, if volume increases then pressure decreases (and vice versa).

V ~ T: volume is proportional to temperature (V and T are on opposite sides of the equals sign).

In addition, look into Gay-Lussac's law (or Amontons's law) which expresses the same relationship between pressure and temperature; they are directly proportional to each other. Also, Charles' Law expresses the same relationship between volume and temperature; they are directly proportional to each other.

Apply this to your question:

If the balloon is placed in cooler temperatures, what happens to the gas? The gas particles do not have as much kinetic energy, so they slow down and do not exert as much pressure against the elastic balloon. The elastic balloon still has tension, and will not remain expanded, it will get smaller.

Since temperature decreases, what happens to the volume of the gas? It decreases! Therefore, the balloon gets smaller. The balloon shrinks due to the colder temperature.