[cindy]

1. Why can you smell gasoline a block away from a gas station?
2. Why will a pop can explode if heated?
3. Would a column of mercury be longer or shorter at the top of a mountain? (I don't know what a "column" of mercury is) and why?
4. What will happen to the size of a balloon containing helium when it rises to the atmosphere? why?


thanks to anyone who can help me out on any of these questions!   Chem's just now what i do best  

[Mitch]

2.) PV = nRT and when you raise the Tmeperature you also raise the pressure. Once the pressure is high enough, it will explode out of the can.

What science class are you doing this HW for?

[cindy]

thanks! this is all for chemistry.. the questions seem kinda weird to me though.. How am i supposed to know why you can smell gas a block away? COME ON NOW! lol

[Mitch]

1.) Well the answer is actually somewhat sophisticated dealing with vapor pressures. But, since this is high school, the answer should just be diffusion.

What chapter are you in, in Chemistry?

[cindy]

wow, you guys are so amazing    

ps. the unit is called "the behaviour of gases"

[Donaldson Tan]

1. pure gasoline is odourless. certain pungent additives are added to give gasoline that characterisitc smell, so that we can detect its presence with our nose easily.

3. attached is a diagram of a mercury barometer from http://erkki.kennesaw.edu/GCII1/gc00002.htm
The higher the pressure acting on the mercury, the higher will be the column. At high altitudes (such as mountain top), the atmospheric pressure is much lower than that at sea level, thus the mercury column would be shorter.

4. There are 2 factors that can account for the size of balloon, excluding leakage. The temperature and the external pressure (aka atmospheric pressure) acting on the balloon.  That u can decipher on your own already.

[hmx9123]

"pure gasoline is odourless. certain pungent additives are added to give gasoline that characterisitc smell, so that we can detect its presence with our nose easily."

I think that you're thinking of methane, a.k.a., natural gas.  Gasoline (the stuff that goes in cars) has it's own odor--due to a lot of different chemicals going into it--like benzene, for instance.  Gasoline is a pretty wide mix of chemicals, and even pure octane smells like something.  However, natural gas does not.  Methyl mercaptain is added to it (IIRC) to give it the characteristic odor.