Describe one way to prove that a mixture of sugar and water is a solution and that a mixture of sand and water is not a solution.

The solution is always homogeneous mixture and transparent through which the light can travel. The mixture of water and sugar is a solution because sugar is soluble in water and form homogeneous mixture while the sand can not dissolve in water and sand particles scatter the light.

Explanation:

Solution:

"The solution is always homogeneous mixture and transparent through which the light can travel"

The mixture of water and sugar is a solution because sugar is soluble in water and form homogeneous mixture. The solubility of sugar is high as compared to the sand in water because the negative and positive ends of sucrose easily dissolve into the polar solvent i.e, water

Suspension:

"Suspension is the heterogeneous mixture, in which the solute particles settle down but does not dissolve"

The mixture of water and sand is suspension. The sand can not dissolve in water because it is mostly consist of quartz. The nonpolar covalent bonds of  sand are too strong and cannot be break by water molecules.