Question

Why is sugar a mixture?
A.Because the composition is not fixed.
B.Because its composition is fixed.
C.Because it is crystalline in nature.
D.Because it is soluble in water.

Answer 1

Sugar is chemically composed of sucrose and has a molecular formula ${{C}_{12}}{{H}_{22}}{{O}_{11}}$. Sucrose is a disaccharide; it contains two monosaccharides. One is Glucose with the molecular formula ${{C}_{6}}{{H}_{12}}{{O}_{6}}$ and the other is fructose with the same molecular formula ${{C}_{6}}{{H}_{12}}{{O}_{6}}$.

Complete answer:
We know that a mixture is a substance that has two or more different compounds. In a mixture, the chemical composition of the substance is not changed.
Sugar mixes with other substances to form a solution mixture. Sugar when dissolved in water forms a sugar solution. The sugar particles still exist in the solution. They do not change their composition. They can be separated later using physical methods. Sugar can be obtained back from the sugar solution by evaporating the water. Boiling the water at $100^oC$ will eliminate the water, and only sugar crystals will be left behind.
We can say that a substance that does not have a fixed proportion is said to be a mixture. Therefore, sugar is a mixture because its composition is not stable.
Final answer: The correct answer is Option A: Because the composition is not fixed.

Note:
Sugar can be consumed in various forms like maple sugar, honey, fruit sugar, etc. However, it breaks down into glucose and gets stored in the body in the form of Glycogen. The glucose and fructose are joined by a condensation reaction. To obtain glucose and fructose from Sucrose, you have to eliminate the water molecule. This is also the reason why sugar is considered a mixture.