When you pour a heap of hot chocolate powder into a glass of hot water, it dissolves. Once dissolved, the water and powder become one liquid called hot chocolate. The solution of hot chocolate becomes one mixture rather than powder and water.
The substance that is being dissolved in another substance is called the solute. In this example, the hot chocolate powder is the solute.
The substance that is dissolving another substance is called the solvent. In this example, the hot water is the solvent that dissolves the powder.
If too much powder is added to a glass of hot water, the powder will be unable to dissolve. Solvents have a maximum amount of solute that they are able to dissolve called the solubility limit. One cup of hot water would not be able to dissolve 4 pounds of hot chocolate powder.