Why does water dissolve table salt so effectively?
AWater is hot enough to melt the salt
BWater's polar molecules attract the positive and negative ions in salt
CWater chemically reacts with salt to destroy it
DWater physically crushes the salt crystals
Water molecules are polar — they have a partially negative oxygen side and a partially positive hydrogen side. These partial charges attract the Na+ and Cl- ions in salt, pulling them away from the crystal lattice and surrounding them, which is the process of dissolving.
Question 2 True / False
Water dissolves most substances because it is the universal solvent.
TTrue
FFalse
Answer: False
The term 'universal solvent' is an exaggeration. Water dissolves many substances, especially ionic and polar ones, but it does not dissolve nonpolar substances like cooking oil or wax. The rule 'like dissolves like' means polar solvents dissolve polar solutes, and nonpolar solvents dissolve nonpolar solutes.
Question 3 Short Answer
Explain the phrase 'like dissolves like' in terms of water and oil.
Think about your answer, then reveal below.
Model answer: Water is polar and oil is nonpolar, so they do not dissolve in each other because polar and nonpolar substances are not attracted to each other strongly enough.
Polar molecules have uneven charge distributions that attract other polar molecules. Nonpolar molecules have even charge distributions and attract each other through weaker forces. Water (polar) strongly attracts other polar or ionic substances but cannot attract nonpolar oil molecules strongly enough to pull them into solution, so oil and water separate.