Which of these represents a chemical change?
a) two compounds combining to form a mixture
b) a mixture being separated into two elements
c) a compound being separated into two elements
d) an element changing state from solid to liquid

Answer : The correct option is, (C) a compound being separated into two elements

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 mixtures are physical combinations.

The indication of chemical changes are :

Change in shape.

Change in form.

Change in size.

Change in phase.

As per question, the option A, B and C is a physical change and option C is a chemical change.

Option C is a chemical change because when a compound being separated into two elements then their chemical compositions are changes and thus resulting in the formation of new compound or substance.

Hence, the option C represents a chemical change.

it's c. elements are placed in rows based on how may valencies electrons have.