Why Does Balloon Volume Decrease with Liquid Nitrogen?

[TheLil'Turkey]

50 minutes into this video the professor puts a balloon into liquid nitrogen that's about 1/4 of the room temperature, but its volume decreases to much less than 1/4 of its original volume. Why?

Right after the balloon demo, he talks about tennis balls. Why if you open up a can of tennis balls, don't play with them for a few days, do they become useless? And how does this relate to whether the pressure in the sealed can of tennis balls was less than or greater that 1 atm?

 

[TheLil'Turkey]

50 minutes into this video the professor puts a balloon into liquid nitrogen that's about 1/4 of the room temperature, but its volume decreases to much less than 1/4 of its original volume. Why?

Right after the balloon demo, he talks about tennis balls. Why if you open up a can of tennis balls, don't play with them for a few days, do they become useless? And how does this relate to whether the pressure in the sealed can of tennis balls was less than or greater that 1 atm?

I figured out the bolded! It's because a large percentage of the air in the balloon condenses at such a low temperature.

I still have no idea about the 2nd question though. Please watch the video starting at the 51:30 mark to hear it.

 

[James Leighe]

some tennis balls are pressurized and the pressure leaks causing them to lose bounce

see: http://www.livestrong.com/article/402536-do-pressureless-tennis-balls-hit-the-same-as-regular-balls/

 

[TheLil'Turkey]

Thanks James. I now understand all the puzzles that are given at the end of the 1st semester MIT physics lectures. I highly recommend the lectures to other beginners.

 

[pmacias]

The decrease in volume of the balloon when placed in liquid nitrogen can be explained by the principles of thermal expansion and gas laws. When the balloon is placed in liquid nitrogen, it is exposed to extremely low temperatures. This causes the air molecules inside the balloon to lose energy and move closer together, resulting in a decrease in volume. This phenomenon is known as thermal contraction.

In addition, the pressure inside the balloon also decreases due to the decrease in temperature. As per the ideal gas law, pressure and volume are inversely proportional, meaning that as pressure decreases, volume increases and vice versa. Therefore, the combination of thermal contraction and decrease in pressure results in a significant decrease in the volume of the balloon.

The example of tennis balls is related to the concept of pressure. When tennis balls are manufactured, they are filled with a certain amount of gas at a specific pressure. As they sit unused for a few days, the pressure inside the can decreases due to the leakage of gas molecules through the walls of the can. This decrease in pressure leads to a decrease in the volume of the gas inside the tennis balls, making them lose their bounce and become useless.

This decrease in pressure can also be related to the concept of atmospheric pressure. If the pressure inside the sealed can of tennis balls is less than 1 atm, then the pressure of the surrounding atmosphere will be higher and will push against the walls of the can, causing the gas inside to escape. On the other hand, if the pressure inside the can is greater than 1 atm, then the pressure of the atmosphere will be lower and the gas will not escape. This is why it is important to maintain a certain level of pressure inside the can to keep the tennis balls usable.

In conclusion, the decrease in balloon volume when placed in liquid nitrogen and the loss of bounce in tennis balls after being unused for a few days can both be explained by the principles of thermal expansion, gas laws, and atmospheric pressure. These concepts are fundamental in understanding the behavior of gases and how they are affected by changes in temperature and pressure.