Which of the following indicates a chemical change? question 7 options: a. an exploding firecracker b. a freezing ice cube c. wood breaking into splinters d. a wire conducting electricity

Option (A) is the correct answer.

Explanation:

Chemical changes are defined as the change which tend to show difference in chemical composition of a substance.

For example, toxicity, reactivity, combustion etc are all chemical properties.

A chemical change will always lead to the formation of a new compound and this change is irreversible in nature by any physical means.

When we explode a fire cracker then it is a chemical change.

On the other hand, a change which is unable to bring any difference in chemical composition of a substance is known as a physical change.

For example, change in shape, size, mass, volume etc are all physical properties.

Physical changes are reversible in nature.

Thus, we can conclude that out of the given options an exploding firecracker indicates a chemical change.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.