Asubstance with a ph of 4.0 will
a. change red litmus paper to blue.
b. change blue litmus paper to red.
c. not change red or blue litmus paper.
d. not be testable using litmus paper.

The correct option is B

Explanation:

pH is a measure of acidity of a substance. A typical pH scale ranges from 0 - 14. When a substance has a pH less than 7, it is said to be acidic while a substance having a pH greater than 7 is said to be basic. A substance that has the pH of 7 is said to be neutral.

The closer the pH of a substance is to 0, the more acidic it is and the closer the pH of a substance is to 14, the more basic it is.

When the pH of a substance is 4.0, it is clear from the above that the substance is an acid and one of the properties of an acid is that it turns blue litmus paper to red.

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e