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[latine]

I NEED HELP WITH CHEMISTRY, I WOULDN'T BE POSTING THIS IF I WEREN'T DESPERATE. I HAVE TO DESIGN A LAB REPORT/EXPERIMENT TO THIS PROBLEM:

As an energy conservation method you decide to turn your water heater to 55ºC. The only thermometer available is unmarked above 40ºC. Using your 40ºC thermometer and any other materials on your lab, determine the

Comments

[zazenica]

Do you have any chemicals in the lab you know will precipitate in and out of solution at temperatures between forty and fifty-five degrees C, or any combinations of chemicals that will precipitate at known temperatures and concentrations?

And what about measuring vapor pressure above the surface of the water? Phase changes always occur at constant temperatures, right? Even if the water isn't boiling, there'll still be a phase change occurring at the surface. So under ideal conditions we can assume the steam is the same temperature as the water. In which case...use the ideal gas law, and set up your station so that you can control for volume and measure the gas pressure inside a closed container. (I know there's a way to do it, but I can't remember exactly how to set it up - something involving rubber tubes connectng airtight flasks, one of which is sitting on a hot plate. In any case, I'm sure you'll be able to find a resource on this...)

Hope this helped, if in no other way than to make you look for an easier way of solving the problem. Good luck! :)

[potterchick958]

I'm guessing that you wanted this to go to Sharon. lol

[zazenica]

Eek. Yes. :P Sorry, I just clicked on the first "reply" link I saw...

[potterchick958]

lol no worries. :D

[zazenica]

...Now that I think about it, that second suggestion is pretty sketchy, and I'm assuming you guys are allowed to treat water vapor as an ideal gas (if you weren't, they'd have to provide you with about fifty different tables of thermodynamic data)...

[twinsuns]

There's the science that I lacked! ♥

[zazenica]

Except I just realized there's one problem with the gas law suggestion...the mass of the vapor is unknown if you use PV = nRT. O_o If you use a specific version of the gas law, you can correct for that...but I'm wondering how much ideal gas stuff anyone does before they get to college and take thermo. Heh.

[zazenica]

Haha, Sharon, you could also try a calorimetry experiment...at this point I don't know how good any of my suggestions are, but what if you had a cup of water of known mass and temperature (make it cold so you don't get any thermometer readings above 40C later on), a cup of water of known mass and the unknown temperature, and then measured the heat transfer between the two of them using q=mc(T2-T1) as the two cups approached equilibrium? As long as there's enough water in the first cup, you'd be able to measure the temperature change of the first cup of water with a thermometer. This will give you the amount of energy lost from the water in the water heater, which will allow you to determine the temperature change. Use the equilibrium temperature of the cups as one of your temperature values for the water in the heater, plug the energy value (q) into the equation, and solve for your second temperature value. This will be the temperature of the water being heated.

[latine]

Jenna! Wow. Thank you so much. It's horrible that I saw this after I have handed the work in (worst I've ever done), but yes, you were right. The easiest way was the Q = m.cw.change in T but I forgot about that.

Many thanks, anyway!

[zazenica]

Eek. Sorry I didn't comment sooner...? Haha. Well, good luck with everything, and I'm sure you'll do fine. :) Cheers!