Which of the following is not true about chemical changes? a. they form a new substance. b. they can be reversed by physical changes. c. they can be detected by changes such as color. d. they have different properties from their starting materials. select the best answer from the choices provided

Answer : The incorrect option is (b) They can be reversed by physical changes.

Explanation :

Chemical change : It is a change where changes occurs in the chemical composition and thus resulting in the formation of new compound or substance. It is an irreversible reaction.

The indication of chemical changes are :

Formation of gas bubbles.

Formation of precipitate.

Change in color.

Change in temperature.

Change in volume.

Change in smell or taste.

Evolution of heat, light and sound.

Physical change : It is a change in which shape and size of a substance changes. In this there is no change in the chemical composition of the substance and no new substance is forming. It is a reversible reaction.

The indication of chemical changes are :

Change in shape.

Change in form.

Change in size.

Change in phase.

From the given options we conclude that the option (b) is incorrect option while all the options are correct for chemical changes.

Hence, the incorrect option is (b)

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