Ideal Gas QuestionsWatch
A piston is pressed into and open cylinder in the image show above.
Data: Density of air = 1.2 kgm^-3
Atmospheric pressure = 101kPa
1a) Calculate the force needed to reduce the volume in the cylinder if there is no change in temperature.
my answer: I got 5050 N by doing Force = Pressure * Area
1b) Calculate the force needed to reduce the volume in the cylinder if the temperature rises from 17 degrees C to 37 degrees C.
my answer: 5398 N
1c) How many moles of air are there in the piston?
my answer: not sure how to approach this. I know that the number of molecules is constant regardless of the increase of temperature but I'm just stuck on what to do...
2. Explain how the motion of molecules of a gas gives rise to pressure and how this can lead to a definition of absolute zero, 0 K.
my answer: I know that pressure and temperature are directly proportion so one increase with the other. Decrease in pressure causes the temperature to reduce because the motion of the molecules have been slowed down? - am I going down the right lane here with this?
3. A bubble rises from the bottom of a lake at 4 degrees C, to the top at 16 degrees C. The bubble doubles in volume when it reaches the top. Find the the pressure at the bottom of the lake:
Data: Atmospheric pressure = 101 kPa Density of water = 1000 kgm^-3
my answer: I have no idea where to begin but I have a feeling that I need to use some of the data above to calculate this...
Thank you for your time
Regarding the actual answer, I'd say that due to the random motion of molecules in a gas, they can collide with the inner walls of the container which stores the gas. These collisions can occur more frequently with increases in temperature, or less frequently with decreases in temperature, both of which for a fixed volume.