Question

When a hot concentrated sugar syrup is kept in freeze, on cooling crystals of sugar get separated, this indicates that:
A. Physical change is reversible.
B. The chemical change is reversible.
C. Physical change is irreversible.
D. The chemical change is irreversible.

Answer 1

Hint: Physical change is a change that occurs in a compound which does not change their chemical composition like their weight, color etc whereas chemical change is a change that occurs in compounds which changes the chemical composition by breaking or combining it to form new compounds. So first find whether cooling hot concentrated sugar syrup is a physical change or a chemical change. Sugar in solid form is available in crystals. So use this information to answer the given question.

Complete answer:Scientifically sugar is called sucrose which is a combination of glucose and fructose which is found in many plants and fruits.
So naturally sugar is available in the form of crystals. A hot sugar syrup is a mixture of sugar and water which is heated to form a concentrated liquid. We know that converting solid to liquid is called melting.
And to cool this hot sugar syrup, it is then kept in the fridge. On cooling, crystals of sugar get separated from the mixture which is the solid form of sugar. Now this conversion of liquid to solid is called freezing.
As we can see, from solid to liquid state of sugar syrup and vice-versa, sugar did not change into any new compounds and no change in color or weight can be seen. So this is a physical change. And a physical change is reversible as we can see the above process.

Hence, the correct option is Option A.

Note:Physical change is reversible whereas chemical change is irreversible. Generally Option D is also correct but in the question the given change is a physical change. So we had to answer in terms of physical change. In physical changes only the appearance of the compounds change whereas in chemical changes, there will be a change in the formulas and it can also be called a chemical reaction.