Question

why sugar dissolves easily in water, but sand does not?

Answer 1

When sugar dissolves, these whole sucrose molecules separate from one another. The molecule itself doesn't come apart: The atoms that make up each molecule stay together as a sucrose molecule.

Sand will not dissolve in water because the "bond" of water is not strong enough to dissolve the sand. However, some strong acids can dissolve sand. Dissolution will proceed faster in warmer water, because it has more room for the molecules of the salt to “fit” between the molecules of water.