Salt in water Vs Sugar in water

[C_l_e_0..Q_c]

How different is salt in water from sugar in water, from a chemical point of view? Of course they would taste differently. I'm asking from a chemistry point of view.

 

My son has the following question to answer, and the solution manual just skips over that specific question.

Predicting : If you added salt instead of sugar to a pitcher of lemonade, how would this change the properties of the lemonade?

 

I vaguely remember that there was a chemical difference between the two, but last time I studied this was 25 years ago!

[mysterious_jedi]

Table salt is NaCl (sodium chloride). It is an ionic bond. This makes it dissolve very well in water, because H20 is polar. The positive sodium ions are attracted to the partially negative oxygens in the H20, while the negative chloride ions are attracted to the partially positive Hydrogens in H20.

 

Table sugar is sucrose, which is made up of carbons and hydrogens. Since carbons and hydrogens are about equally electronegative, it is a nonpolar covalent bond, meaning the charge on the atoms within the molecule are negligible. Nonpolar solutes do not dissolve well in water, because water is polar. The water will exhibit hydrogen bonding, meaning the partial positive Hydrogens will be attracted to the partially negative Oxygens in the other water molecules. The sugar will be excluded.

 

So if you want to make lemonade, you should heat the water when you dissolve the sugar in it. Otherwise, you'll just have lemon water with clumps of sugar at the bottom of the pitcher!

 

This is probably a more detailed answer than you wanted, but I can't help it, I'm a chemistry minor!

[C_l_e_0..Q_c]

Thanks Jedi.

(you can always count on a Jedi for help :001_smile: )

 

Your explanation does go with what I remember from so long ago. However, my son isn't that far yet into his studies. Basically the choices are:

 

homogeneous mixture

heterogeneous mixture

solution

suspension

colloid

 

My (faulty) memory would have said that salt+water is a solution, and sugar+water is a suspension or colloid, but the book mentions sugar+water as a solution, and makes no reference whatsoever to salt+water.

[mysterious_jedi]

I suppose some sugar would technically dissolve, making it a solution, but not all the sugar would dissolve. Some would just be percipitate. If there were clumps at the bottom, I suppose that would make it a heterogeneous mixture. So basically, it's a confusing question!

[C_l_e_0..Q_c]

Ah! Ah!

I checked the manual again and this is what it says:

If you place a spoonful of sugar in a glass of hot water and stir, the sugar dissolves in the water

 

It mentions HOT water, which isn't standard lemonade temperature. Ok, now I can have DS in the kitchen and try a few things out.

 

Thanks again Jedi! Now I can see the salt+water is a solution, and sugar+water at room temperature is a heterogeneous mixture.

[mysterious_jedi]

Ah! Ah!

I checked the manual again and this is what it says:

If you place a spoonful of sugar in a glass of hot water and stir, the sugar dissolves in the water

 

It mentions HOT water, which isn't standard lemonade temperature. Ok, now I can have DS in the kitchen and try a few things out.

 

Thanks again Jedi! Now I can see the salt+water is a solution, and sugar+water at room temperature is a heterogeneous mixture.

You're welcome. Have fun making lemonade!