Question

Which of the following is always true when a substance undergoes a physical change ?

a. the composition changes.
b. a change in color occurs.
c. no new substance is formed.
d. its specific gravity remains the same.

Answer 1

When a substance undergoes a physical change no new substance is formed.

Answer 2

Answer: c. no new substance is formed.

Step-by-step explanation:

A physical change is defined as a change in which there is alteration in shape, size etc. No new substance gets formed in these reactions.

Example: Melting of ice

`H_2O(s)\righarrow H_2O(l)`

A chemical change is defined as a change in which a change in chemical composition takes place. A new substance is formed in these reactions. Chemical reactions are usually characterized by change in color, heat change, precipitate formation and evolution of bubbles.

Example: Oxidation of magnesium

`2Mg+O_2\rightarrow 2MgO`