gas and temperature

[vinson16]

does gas expand and contract with temperature

I just though this would be interesting to debate

[TL chris]

No, but the gas vapors do when in a sealed container.

[maniacmedia]

It is for this reason that manufacturers strongly suggest that you never top off the tank on your motorcycle. There should always be room in the tank for another half gallon or so.

[vinson16]

It is for this reason that manufacturers strongly suggest that you never top off the tank on your motorcycle. There should always be room in the tank for another half gallon or so.

so you are saying yes they do expand and contract.
like when water expands when frozen

[TL chris]

Yes, the vapors do. Not the liquid gasoline.

[Drake]

Water is an odd compound. Unlike most elements and compounds which contract as they go from gas to liquid to solid. Water actually contracts from gas to liquid and then expands from liquid to solid. So, nothin really behaves like water that way (well maybe some other manmade compounds). So.. expansion would be the gasoline going from liquid to gas.

[TL chris]

Yes we all took chemistry in high school. Thread Done.

[Drake]

Originally Posted by TL chris

Yes we all took chemistry in high school. Thread Done.

Ya never know Chris.... Either vinson was trying to cheaky or he/she didn't really grasp the concept. I don't see how there's anything to debate though....

[The Chad]

if you all think that you are so smart, why is it that gas pumps across northamerica are temturature corrected. It's because gasoline DOES expand when heated and contract when cold. there is a built in safty procaution in all D.O.T approved gas tanks, they are designed so that you can't put more than 80% of the entire volume of the tank in. This is done so that when heated, the liquid gasoline hase somewhere to go without spilling causing an enviromental concern.

[Drake]

Originally Posted by The Chad

if you all think that you are so smart, why is it that gas pumps across northamerica are temturature corrected. It's because gasoline DOES expand when heated and contract when cold. there is a built in safty procaution in all D.O.T approved gas tanks, they are designed so that you can't put more than 80% of the entire volume of the tank in. This is done so that when heated, the liquid gasoline hase somewhere to go without spilling causing an enviromental concern.

Chad,
The expansion you are allowing for is the vapor expansion. Gasoline is stored at your gas station, in underground tanks whose temperature is typically around 55 to 60 degrees F. Now, you put that cold fuel into your nice warm gas tank, and there will be a lot of liquid gasoline going to vapor and building up pressure. If you topped up your tank completely with this cold fuel, and then sealed it, you could get quite a nasty surprise of pressure buildup in your fuel tank due to the physics of it all. Due to gasoline's low viscocity (it really likes to flow anywhere and everywhere), this pressure increase will likely cause a certain amount of fuel to seep out of that cap. It's not that the level of fuel in your tank has risen and is now level with the lip of the fuel tank, it's the low viscocity and the vapor pressure that's pushing that thin slick of fuel out. Case and point would be your little plastic gasoline container for your lawn-mowers. You may fill it near the top, but leave your air-vent unscrewed, or even the lid unscrewed, and you will likely see some fuel (very thing shine) spreading. Yet, your fuel level in the container is below that lip.

This is also part of the reason they came up with those cute little accordian type nozzles on the fuel hoses. These nozzles allow the fuel pump to more accurately measure the backpressure from your tank, and is the reason they shut off at times (which confound us all) when the tank isn't "full" yet. That is because it has reached a predefined limit of pressure in your gas tank, and it won't let you exceed that by adding more fuel (and thus risking explosion). Hope that helps.

[md2lgyk]

I'm sorry, but The Chad is correct. I'm an engineer, and can tell you that gasoline (and other liquids) DO expand with temperature. You can see the coefficient for gasoline at http://www.ac.wwu.edu/~vawter/Physic...hermExpan.html

[Drake]

I stand corrected... I just found conflicting reasonings, and I'm inclined to believe the chevron one....

The first one talks of vapor expansion.

http://www.shrinershq.org/prevention.../gasoline.html

This one talks of gasoline expansion. I only found it after doing search on gasoline expansion instead of gasoline vapor expansion.

http://www.chevron.com/prodserv/fuel...ling-gasoline/

However, after seeing my 5 gallon gas-tank for my mower start pushing gas out the air vent at the top when it wasn't even full to the top, lead me agree with the first statement of vapor expansion not liquid expansion.... could be a combo of the 2 of em.

Alls I know is it's a stinky (and dangerous) mess to get on ya.

[md2lgyk]

No problem. Fluid mechanics is complicated. That's why we get the big bucks LOL.

[TL chris]

Guess it did turn into a debate. Now, why does Coor's Light not fill you up and never let you down?

[Drake]

Originally Posted by TL chris

Guess it did turn into a debate. Now, why does Coor's Light not fill you up and never let you down?

Cause it's water with a little alcohol in it. So, there's no beer in the can (hence no carbs) to fill you up.

GJ Water that tries and fails to taste like beer.

[The Chad]

I thought that "every" liquid expands when heated, I know that petrolium based ones do, does anyone know if there is a liquid out there that doesn't.

P.S. I'm surprised that any one would belive anything that an oil company tells them LOL

[Drake]

Gasoline is a tricky one because even at temperatures below freezing, certain components of its mixture will be (for want of a better word) evaporating off. The fact of all this vapor coming off affects the expansion effect. You're losing liquid volume at a certain rate just as your trying to gain liquid volume from thermal expansion. In an enclosed/sealed container, you would reach an equilibrium point, but in the open, you'd just keep on evaporating and expanding... the whole thing has so many variables (airflow, temp, surface area exposed etc).

I don't think anyone discussed a liquid not expanding when heated... I'd be interested if there were such a compound... Water is just the odd one where it is at it's most contracted point at about 40 degrees F, and then starts expanding both as it is heated from there or cooled further from there...

[Clint]

Another example of too many people speculating. Don't answer a question unless you either 1. Know what the heck you're talking about, or 2. Broadly proclaim your post to be AN OPINION OR GUESS. Just because you've read one answer more often than another on the 'net doesn't mean it's correct. It's your responsibility to scrutinize your sources.

{in best RoboCop voice}YOU HAVE 15 SECONDS TO COMPLY...{end RoboCop voice}

[Drake]

But Forum Spam is where it's at... Just look at the Purple Hippo.

[TL chris]

At least I didn't try to hijack this thread.