Question

When sugar is dissolved in water, why is it not visible?

Answer 1

When sugar is dissolved in water there is no increase in volume as the sugar molecules are surrounded by the molecules of water. The sugar molecules occupy the space between the water molecules.

Complete step by step answer:
When sugar is added to water, sugar molecules interact with the water molecules i.e., when a portion of sugar is poured into a glass of water sugar settles down as the sugar molecules are suddenly exposed to water molecules, the sugar molecules are still attracted to each other. When the solution is mixed the sugar seems to disappear, but it doesn’t disappear but both the sugar molecules and water molecules are still present. The reason that the sugar seems to disappear is that the sugar molecules are now more attracted to water molecules. When the water is stirred the sugar molecules mix with the water molecules. The water molecules insert themselves with the sugar molecules and begin to surround each individual molecule. The sugar molecules are now more attracted towards the water molecules and when all the sugar molecules are surrounded by the molecules of water the sugar is dissolved i.e., the spaces between the water molecules are filled with the sugar particles. The reason why the sugar particles get in the spaces of water molecules is because the intermolecular forces in liquids are lesser than that of solids.

Additional information:
The solubility of sugar is faster in hot water when compared to cold water. The molecules in heated water have more energy and move faster. This gives them more chances to come in contact with the sugar molecules. The molecule that makes up our normal table sugar is nothing but sucrose and sucrose is made up of glucose and fructose molecule. The sucrose has many polar ends as they have many oxygen-hydrogen bonds. These polar ends hold one sucrose molecule to another making up a solid sugar. The polar ends of water molecules attract opposite polar ends of sucrose molecules and separate one sucrose molecule from another. The polar ends of water molecules attract oppositely charged polar areas of sucrose molecules and when the attractions of the water molecules towards sucrose molecules overcome the attractions between the sucrose molecules for one another, the sucrose begins to dissolve

Note: In sweet and salty lemonade, sugar and salt are not visible. Initially the salt and sugar are attracted towards the water molecules and later they are completely surrounded by the water molecules which make them seem disappeared.