Question

If you place a teaspoon of sugar in the bottom of a glass of water, it will dissolve completely over time. Left longer, eventually the water will disappear and the sugar crystals
will reappear. Explain these observations in terms of entropy.

Answer 1

Answer:

It is known that entropy is the degree of randomness. More is the speed of molecules of a substance more will be its degree of randomness. Hence, more will be the entropy of substance.

When we place a teaspoon of sugar in the bottom of a glass of water, it will dissolve completely over time. This dissolution will cause the sugar molecules to spread out in the water.

And, with time water will evaporate and this will lead to the formation of crystals again. This reappearance of sugar crystals will cause a decrease in entropy as there occurs decrease in randomness.

But this decrease in entropy is balanced by increase in the entropy of water molecules as they are evaporating.