additional research

Salt water is an example of a chemical solution. In a solution, there is a solvent (the water in this example), and a solute (the salt in this example). A molecule of the solute will dissolve (go into solution) when the force of attraction between solute molecule and the solvent molecules is greater than the force of attraction between the molecules of the solute. Water (H₂O) is a good solvent because it is partially polarized. The hydrogen ends of the water molecule have a partial positive charge, and the oxygen end of the molecule has a partial negative charge. This is because the oxygen atom holds on more tightly to the electrons it shares with the hydrogen atoms. The partial charges make it possible for water molecules to arrange themselves around charged atoms (ions) in solution, like the sodium (Na₊) and chloride (Cl⁻) ions that dissociate when table salt dissolves in water. Other substances that dissolve in water also lower the freezing point of the solution. The amount by which the freezing point is lowered depends only on the number of molecules dissolved, not on their chemical nature. This is an example of a colligative property.--- i don't understand that. someone tell me? it doesn't make sense :S

And also, I change my last post:

the independent variables are
soluble substances : salt, sugar
insoluble substances: pepper, sand

What Makes Ice Melt Fastest?

this is what i have decided to do my experiment on.
I will do this experiment by adding substances (pepper, salt, sugar, sand, nothing added) to ice cubes and determine which one melts the fastest. This experiment will be repeated 3 times for each substance.

independent variables:
the substances i.e. salt, pepper, sugar, sand, compared to when nothing is added

dependent variables:
percentage of the ice cube remaining
percentage of the ice cube that melted

controlled variables:
same size ice cube (volume)
same water, tap
time in which the ice melts (10 minutes)
same place for each experiment
same amount of the substance added (1 teaspoon)
use same scales to measure