Catalyst Posted April 24, 2005 Share Posted April 24, 2005 I need to make an experiment that proves either Boyle's, Charles, or Gay Lussac's law by tomorrow morning. The simpler the better please as I don't have the time to get any advanced material. Any helped would be extremely appreciated! Link to comment Share on other sites More sharing options...
budullewraagh Posted April 24, 2005 Share Posted April 24, 2005 do you need to actually perform the experiment or do you need to explain it? Link to comment Share on other sites More sharing options...
Catalyst Posted April 24, 2005 Author Share Posted April 24, 2005 I need to actually make it in front of my class. Link to comment Share on other sites More sharing options...
H2SO4 Posted April 24, 2005 Share Posted April 24, 2005 for charles law you can put alittle water in a soda can, bring it to a slight boil, then with tongs quickly upturn it and put it facing down in a bucket of water. The gassses inside will rapidy cool and cause the can to crush instantly as soon as it hits the water. Very dramatic demo. Link to comment Share on other sites More sharing options...
Catalyst Posted April 24, 2005 Author Share Posted April 24, 2005 hey that sounds awesome would you mind explaining it a little more detailed? I also have to give an explanation of why it is happening and make a whole science report on it so info is appreciated Link to comment Share on other sites More sharing options...
jdurg Posted April 25, 2005 Share Posted April 25, 2005 This works even better if you use one of those metal paint thinner containers that you see at hardware stores. (Just make sure you use an empty container. A metal container with a screw on cap works best for this experiment). What you do is take the empty container and put a small bit of water in there. Take the metal container and put it on a hot plate so that you can get the water to boil and form steam. While the water is heating up, you get a big container and fill it with water and ice. Once you see steam coming out of the heating metal container, you quickly screw the cap on to lock the hot water vapor in there. Inside the metal container, you have water in there as a gas at a high temperature. At the elevated temperature, the gas in there fills up the entire volume of the container. If you then take the container and dunk it into the ice-water filled bath, the temperature of the gas inside the container immediately drops. As a result, the volume of that gas drops as well which lowers the pressure inside the container. The external atmospheric pressure is MUCH greater than the low pressure that now exists inside the container, and the container will be crushed almost instantly because of that. At higher temperature, the same amount of gas has a higher pressure than it does at a lower temperature. This experiment shows that fact. Link to comment Share on other sites More sharing options...
Catalyst Posted April 25, 2005 Author Share Posted April 25, 2005 I love you man you just saved me from failing chemistry =D Link to comment Share on other sites More sharing options...
Catalyst Posted April 25, 2005 Author Share Posted April 25, 2005 oh by the way, I will be using normal soda cans will that be fine? Because you said something about screwing a cap and cans dont have caps. Link to comment Share on other sites More sharing options...
akcapr Posted April 25, 2005 Share Posted April 25, 2005 ya that will work fine. quick procedure over view: heat the cans opening in a bunsen burner while holding with tongs, then, dip it into a bowl of ice cold water opening first. Observe the can totally collapse. Link to comment Share on other sites More sharing options...
Bettina Posted April 25, 2005 Share Posted April 25, 2005 for charles law you can put alittle water in a soda can, bring it to a slight boil, then with tongs quickly upturn it and put it facing down in a bucket of water. The gassses inside will rapidy cool and cause the can to crush instantly as soon as it hits the water. Very dramatic demo. That sounds cool...I'm going to try this tommorrow in school...... Bettina Link to comment Share on other sites More sharing options...
jdurg Posted April 25, 2005 Share Posted April 25, 2005 Yeah, an open soda can will work, but you have to move a bit faster to prevent the hot air from leaving the can. Also, inverting the can when you dunk it is a great idea as hot air rises so having the opening on the bottom will keep the hot air in there. When I've done this in the past I've used a screw top container mostly because they were readily available. Plus, this allowed me to put the can in an empty container and just pour ice water over it and watch the can suddenly get crushed by the atmosphere. Link to comment Share on other sites More sharing options...
jdurg Posted April 25, 2005 Share Posted April 25, 2005 I've also seen the experiment done with 55 gallon steel drums that were filled with hot steam and then sealed off. Bags of ice were then thrown on the drums, and almost instantly they imploded due to atmospheric pressure. It was amazing to see. Link to comment Share on other sites More sharing options...
Catalyst Posted April 25, 2005 Author Share Posted April 25, 2005 Thanks guys for your help, but there is another little problem. My teacher said that my experiment had to be measurable and that I need to find a way to measure they pressure inside the heated can and the pressure inside the can once its been crushed. Any ideas? Link to comment Share on other sites More sharing options...
Catalyst Posted April 27, 2005 Author Share Posted April 27, 2005 come on please help all I need to know is a way to make the pressure measurable and that's it. Link to comment Share on other sites More sharing options...
Bluenoise Posted April 27, 2005 Share Posted April 27, 2005 Won't the pressure just be the same as the external pressure for before heating and after? I guess if you used a container with a screw top you could measure the change in volume of the can to determine the drop in pressure caused by the condensation of the steam. And just use Ideal gas law for simplicities sake... It wouldn't be terribly accurate but it would give you something. I don't think accuracy matters too much in a demonstration. Link to comment Share on other sites More sharing options...
Bluenoise Posted April 27, 2005 Share Posted April 27, 2005 Um let me elaborate. Use a can with a screw top, after it's been crused place it in a graduated container and open it upside down, since there will still be a slight vacume in the can some water will get pulled in. Carefully screw it back on and measure the volume of water that got taken into the can. Use this to calculate the pressure difference between the crushed can and the external pressure. Subtract this from the external pressure and that gives you the pressure in the can after being crushed. Then you can use the total change in volume of the can to calculate the pressure change from right as it was cooled till it was opened. Subtract this from your pressure after crushing and you have the pressure once cooled. The pressure in the heated can will just be same as the external pressure. And if you use a pop can without a screw top well then it's an open system and the pressure will pretty much always be the same except for while it's being crushed. By the way I made this up off the top of my head. So if someone who knows better well knows better tell me so and I'll shut up. Link to comment Share on other sites More sharing options...
Catalyst Posted April 28, 2005 Author Share Posted April 28, 2005 thanks for that but it's confusing as hell... it would be great if you could just baby step me through this Link to comment Share on other sites More sharing options...
Bluenoise Posted April 28, 2005 Share Posted April 28, 2005 I'm sorry but I neither have the patients or the will to spend half an hour inventing a procedure. Giving someone suggestions and doing their homework for them are two completely different things. I hope I don't sound rude, I'm willing to answer any questions you have, but if the only reason you'll pass is because of the work of others well maybe you don't deserve to; redoing the course might be good for you. Link to comment Share on other sites More sharing options...
Catalyst Posted April 29, 2005 Author Share Posted April 29, 2005 that's alright blue, is there any other way besides that to calculate the pressure? Maybe using some kind of device? Link to comment Share on other sites More sharing options...
Bluenoise Posted May 1, 2005 Share Posted May 1, 2005 I'm pretty sure there is, but you'd probably have to ask in the Physics forum. And I think it would be alot harder to setup. Using the ideal gas equation would be by far the easiest way to do this. (though not very accurate since steam is far from ideal) PV = nRT Change in pressure = (n x R x T1 / V1) - (n x R x T2 / V2) to give an estimate has to be the easiest way to do this. Link to comment Share on other sites More sharing options...
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