Which substances will melt ice better( salt or sugar)?Why?

Question

I need help! It's for a science project! I need a scientist...it's due at January !! I need to get good grades! Give me sites... if your in college or you're in High School and you're not soing anything...please help me!!!

Answer 1

When you dissolve a substance in water, any substance, the freezing point of the solution will become lower than that of pure water. So if you add a substance ice that melts will not re-freeze since the solution formed requires lower temperature to freeze. This way the ice will slowly melt.

Which is best?
The drop of the freezing point is a colligative property. This means that it depends on the number of dissolved particles in the solution.
Salt is NaCl. When it dissolves in water it dissociates according to the reaction NaCl -> Na+ + Cl-. So you see that actually you have twice as many particles in the solution as you would expect according to the molecular formula.

Sugar is the dissaccharide sucrose (C12H22O11). It doesn't dissociate when it dissolves in water.

So if you dissolve 1 mole of NaCl in 1 kg water you will get 2 moles of particles/kg water, whereas dissolving 1 mole of sugar will give 1 mole particles/kg water. Since salt gives more particles it will decrease the freezing point more and thus it is best (twice as good as sugar).

NOTE: I compared here equal amounts expressed into mole as this unit is a measure of the number of particles and thus is the unit of choice for deciding which will bring the strongest decrease. If you compare the same amount of grams, then you need to convert into moles.

Eg if you compare the effect of dissolving 58.5 g salt and sugar into 1kg water, then since the molecular weights are 58.5 and 342.3 respectively you get 1 mole NaCl and 0.17 mole sugar.
Remember that only NaCl will dissociate so you will get 2 mole of particles from salt versus 0.17 mole of particles from the same mass of sugar. Thus salt, when comparing the effect of equal masses, is again much better (approximately 12 times better).

Answer 2

Sugar Melt Ice

Answer 3

i got this off the internet
www.newton.dep.anl.gov/askasci/chem99/chem99504.htm

Dear student,
You have asked many questions, and they do not have very simple
answers, but I will try my best.
First of all, I am afraid I cannot give you sources because it
is not proper to cite sources that you have not yourself read.
So what I am telling you is just basically information from
a supposed expert in this area; I am a physical chemist, and
phase transitions (like melting) is my special area of
research.

Anything that is dissolved in liquid water will tend to
lower the frezing point of the solution as compared to the
freezing point of pure water. There are a number of reasons
for this. A basic reason is that in order for a molecule
of liquid water to freeze onto the surface of an ice crystal,
it must physically run into the ice crystal. However, there
are solute molecules (say, sugar) sometimes in the way,
and so the water molecule sometimes runs into the sugar molecule
instead of running into the ice crystal. So you have to cool
things down more in order to get ice to form. I have
oversimplified things a lot, but this is the basic idea.

Now, sugar and salt dissolve differently. For every molecule
of sugar you dissolve, there is one molecule in solution. But
not so for salt! When you dissolve salt, it changes into ions:
NaCl ----> Na+ + Cl-
so for every molecule of NaCl you dissolve, you make two things
in solution. This makes the solution as if there were twice
as many particles, effectively. So the freezing point changes
twice as much if the number of solute particles is the only
important thing! Of course there are other factors involved,
like the charges on the ions above, and the fact that they
are atoms and not molecules...but these only affect how large
the effect is, not whether it happens.

To learn more, go to a local college's library with a parent
and look up a college general chemistry textbook. I like
Kotz and Treichel's "Chemistry and Chemical Reactivity" but
there are many good books out there.

I hope this helps!
Best regards,
Prof. Robert Topper

Answer 4

The more particles the lower the freezing point. Sugar has one particle. Table salt NaCl dissocoates into 2 particles Na+ and Cl- so has 2 particles. CaCl2 or road salt makes 3 particles, Ca++,and 2 Cl- ions.

Answer 5

Of course it is salt and that is why you only see people spreading salt on the icy road, not sugar.
The salt is great in lowing the freezing point and raising the boiling point of a liquid. Sugar can do that too but just not as great as salt.

Answer 6

salt it works sorta like anti freeze its a somthing somthing i dont remember they wont teach us that until a few years but the awnser is salt