Question

Which of the following statements is not correct?
(A) In a chemical change, the color of the object may change.
(B) In a chemical change, heat will always be released.
(C) A chemical change always involves a physical change.
(D) Rusting of iron becomes faster when humidity is high.

Answer 1

Hint: We know that the chemical changes happen due to the formation or breaking of bonds. Thus, depending upon the nature of the change, it has been classified into two types which are physical and chemical changes.

Complete Step By Step Answer:
As we know, the changes that occur in the substance such that its chemical properties change, resulting in the formation of a new product. Some of the organic chemical changes occurring in nature are ripening of fruit, blooming of a bud to a flower and many more. Physical changes are the changes occurring in a substance that the change brings about the change in its physical properties such as changing the state of the substance for an ice cube melts into water is a physical change that could be reversed by adjusting the temperature conditions. Similarly, if there is some breakage of chemical bonds the energy is absorbed and when there is formation of bond the energy is released, chemical reactions in one way or the other involves a change of energy between their products and reactants. Thus, heat can be and sometimes may not be released from the reaction. We know that energy can neither be created nor be destroyed.
Therefore, correct answer is option B.

Note:
Remember that the rusting of iron, here if once the iron corrodes to rust due to the action of moisture, then it cannot be changed back to iron. Therefore, one tries to prevent it. Hence, we get to know that chemical changes are irreversible and permanent in nature.