Physical and Chemical Changes Test - 4

(a) When water is heated to form steam, it can be reversed back. Hence it is a reversible

(b) When the egg is cooked, the egg changes from liquid to solid and there is no way to reverse the change and get back to the reactant. Therefore it is not a reversible change.

(c) Wax can be reversed back on cooling

(d) Cake can also be molten by heating.

According to this question the correct option will be ‘A’ because Layer of zinc is applied on iron surface in galvanization process to save it from rusting.

According to this question the correct option will be ‘C’ as  because in any physical changes one object converted in to other by their physical appearance like shape states etc.

According to this question the correct option will be ‘C’ because  Physical changes are changes in which no new substance is formed, and the chemical composition stays the same. - change in state of matter, e.g. liquid to solid. - change in shape - change in size For example: - freezing water to make ice - molding clay - cutting wood or paper.

According to this question the correct option will be ‘B’ because except the option B that is “cooking of vegetable” in all other reactions, there does not occur  molecule changes and one object does not convert in to other object hence these are physical  changes process while cooking of vegetable is chemical change process.

According to this question the correct option will be ‘C’ because Changing states from a solid to a liquid or a liquid to a gas is a physical change, the chemical composition still remains the same. For example; water, ice and steam all have the same formula H2O.

According to this question the correct option will be ‘C’ because the wax melting is a physical process, while combustion of wax is chemical process.

According to this question the correct option will be ‘A’ because As physical changes do not change the chemical composition of any substance it is known as physical change in the same manner stretching of a rubber is a physical change because it doesn't change its chemical properties or composition.

When a rubber band is stretched, work is done on it , in course of which some amount of energy in the form of elastic potential energy (strain energy) is input into it.  This increases the potential energy of the system. When the rubber band is released, the potential energy is quickly converted to kinetic  energy.