Question

Which of the following experiment proves that dissolving of a substance in a solvent is a physical change?

a- Mixing clay with water, stirring it and noting that it is an unclear solution.
b-Mixing some oil and water in a glass tumbler and noting that a separate layer of oil is formed on water.
c-Suspending alum in dirty water and noting that the dirt particles settle down.
d-Dissolving some salt completely in water and salt getting left behind, after all the water evaporates

Answer 1

Answer:

option D is physical change

Answer 2

According to me, the first 3 options are an example of a physical change because no chemical properties are changing of the solvent. When clay is mixing with water, no chemical properties of water or the clay and water are changing, only the physical appearance and properties (shape, size, etc) are getting changed. When oil is mixing with water, the physical properties of both are changing, no chemical properties as in arrangement of the molecules are changing. When suspending alum in water, no chemical composition of alum or water is changing and only the phyical properties are getting affected with the physical appearance. In the last one, when dissolving salt in water, salt is diffusing into the water molecules, means that it is occupying the space present between two water molecules, which makes it a salt solution resulting in a chemical change. Note that all chemical changes are not irreversible, some are reversible for example we can separate salt from water by boiling the water.