Ice melting experiment

[alext87]

My chemistry master has asks me to do an experiment to find out the how to change the melting point of ice, up or down. What i need to do is write a complete report on how i intent to show that i can increase the melting point of ice by adding salt and i also need to show the sensivity eg. number of degrees melting point increased compared to the concentration change of salt.

 

After this i have to try and get the value degrees per concentration for other salts. LiCl,KCl,MgCl,CaCl. I am guessing this with all increase the melting point.

 

Can anybody suggest a plan for the experiment and estimate how much change in concentrations i will need to make a noticable melting point change.

 

 

Also is there any salt or compound that will actually decrease the melting point of ice?

[budullewraagh]

After this i have to try and get the value degrees per concentration for other salts. LiCl,KCl,MgCl,CaCl. I am guessing this with all increase the melting point.

adding a solute will decrease the melting point and increase the boiling point actually.

 

search for "colligative properties"

 

for your experiment, i would recommend cooling your solutions and noting the freezing points for each. same thing works with boiling

[YT2095]

are you allowed to use Oraganic chems, such as 1-2-3 propan triol

or ethylene Glycol for instance ?

[swansont]

A well-mixed ice/water mixture will stay at the freezing point because of the latent heat. As long as the ice starts out colder than that, a simple measurement of the temperature of the water should suffice.

 

So freeze the solution and then let it melt in a bath of the same concentration.

[Silencer]

The K_f value for water is 1.853 C/m. This means that the boiling point depression is equal to 1.853 * m, m being the molality of the substance. Molality is the moles of solute divided by the kilograms of solvent.

 

Thus, if you have a .5m aqueous solution, the freezing point depression will be 0.9265 degrees, the freezing point being -0.9265.

 

The same thing goes for boiling point elevation (K_b). This contstant is 0.515 for water, so with that same aqueous solution the boiling point will be 100+(0.515*.5) = 100.2575 C.

 

Each solvent has a different constant value, which you can look up. Realize that it has nothing to do with the solute, just the molality of the solution. Your results should be the same for any salt you use.

[Silencer]

are you allowed to use Oraganic chems' date=' such as 1-2-3 propan triol

or ethylene Glycol for instance ?[/quote']

 

Probably not, since he said salt. Plus, the K values only work for a nonvolatile solute.

 

We recently made ice cream in chemistry class, with the excuse being that we were studying freezing point depression.

[budullewraagh]

Probably not, since he said salt

there are organic salts

 

We recently made ice cream in chemistry class, with the excuse being that we were studying freezing point depression.

i remember that from last year

[swansont]

We recently made ice cream in chemistry class, with the excuse being that we were studying freezing point depression.

 

Using liquid Nitrogen is more fun than salting the ice, and actually makes better ice cream (colder = smaller ice crystals = better, smoother flavor. or so I'm told. It was tasty)

[budullewraagh]

ive actually had ice cream made that way before. it's incredibly good and far better than normal ice cream...altho liquid nitrogen is significantly more expensive to keep cold

[Gilded]

"Using liquid Nitrogen is more fun than salting the ice, and actually makes better ice cream (colder = smaller ice crystals = better, smoother flavor. or so I'm told. It was tasty)"

 

Yeah, liquid nitrogen doesn't really let time for big crystals to form.

http://www.theodoregray.com/PeriodicTable/Stories/SacksVisit/index.html <- three movie clips of making ice cream with N2(aq)

[budullewraagh]

aqueous nitrogen???

[ed84c]

aqueous nitrogen???

 

It says liquid N in the article, read it again.

[Gilded]

Hmmh, I don't know why I even had to put the (aq) in there. ) Of course, I didn't meant dissolved in water but similar to water (by being a liquid).

[budullewraagh]

ah, so N2(l)

 

It says liquid N in the article, read it again.

i read it again...whoops i still dont think it's accurate. (aq) means aqueous, or dissolved in water. he meant (l) which means liquid.

[ed84c]

sorry i thought you meant it said aqueos N2 in the article