posted by josh on .
1. What will happen to the pressure in your tires if the temperature drops 40 degrees over the night?
a) Pressure will increase
b) Pressure will decrease
c) Pressure will not change
d) Cannot determine
2. Explain, on a molecular level, why this happens.
these questions are just a part of my study guide for my test in 3 days and these are one of the only ones i cannot get. they were meant to be challenging. I just cant get them and i don't want to guess and do it wrong.
1. The ideal gas law says that PV = nRT.
In this case n (the number of moles), R and V (the tire's inside volume) are constant. Therefore Pressure (P) is proportional to absolute temperature (T). When T drops, so does P.
(2) At lower temperature, the air molecules inside the tire nove move more slowly, and hit the surface less frequently and with less average momentum. Pressure is caused by these collisions, and increases in proportion to the average velocity squared. The absolute temperature T is also a measure of the average velocity squared. That is why P is proportional to T.