Question

Which of the following is not a physical change?
A. Dissolution of sugar or salt in water
B. Powdering of sugar
C. Mixing of iron particles and sand
D. Burning of paper

Answer 1

Hint: Combustion is a chemical process in which a substance reacts rapidly with oxygen and gives off heat. During combustion a new chemical substance is created from the fuel and the oxidizer. The products of a combustion reaction are called oxides.

Complete step by step answer:
First, let us understand what physical change is!
So, basically physical change is a type of change in which the form of matter is altered but one substance is not transformed into another. The size or shape of matter may be changed, but no chemical change occurs.
Physical changes are usually reversible. Contrast this with a chemical change, in which chemical bonds are broken or formed so that the starting and ending materials are chemically different. Most chemical changes are irreversible.
For Example, Crumpling a sheet or paper, Freezing water into ice etc,

Now, let us see chemical change!
Chemical reaction, a process in which one or more substances, nothing but the, reactants are converted to one or more different substances. Substances are either chemical elements or compounds. In a chemical change the chemical bonds are broken or formed so that the starting and ending materials are chemically different. Most chemical changes are irreversible.
For Example, Burning of wood, souring milk, digesting food etc,

Therefore, Burning of paper is a chemical change not a physical change!
Option D is your answer!

Note: Remember that whether a process is reversible or not is not truly a criterion for being a physical change. Example, smashing a rock or shredding paper are physical changes that cannot be undone.