Question

Matter undergoes a change. The changes are of two types : Physical and chemical change. A physical change is a change that involves only a change in the physical state of matter.
Its chemical properties remain the same. Usually increasing the temperature of applying pressure or both brings about a physical change. On reversing the condition, i.e., reducing the temperature or reducing the pressure or both, the original state of matter is restored. In other words, physical changes are reversible. A chemical change is a change that involves a change in the chemical composition of matter. A new substance is formed. In a chemical change, the chemical and physical properties of the substance is formed. In a chemical change, the chemical and physical properties of the substance formed will be different from the original substance. When zinc carbonate is heated and cooled, the change(s) that are observed are :

• A. Physical
• B. Nuclear changes
• C. First chemical and then physical
• D. First physical and then chemical

Answer 1

The correct option is C First chemical and then physical

First zinc carbonate decomposes to give zinc oxide and $C{O}_2$ and zinc oxide appears yellow when hot and white when cold. Initially, zinc carbonate under goes chemical change. Cooling of zinc oxide a goes physical change, to change its colour from yellow to white.