Oxygen, which is one of the chemical elements, is necessary for us to breathe.

Understanding chemical equilibrium is very important in understanding chemical reactions.

This substance undergoes a chemical change when heat is applied.

In this experiment, you can observe a chemical reaction.

Unsaturated fatty acids are said to be good for health.

He likes to take a walk in the park at dusk.

The pH of this liquid is 7.

Hydrogen peroxide is often used for disinfecting wounds.

Tritium is one of the radioactive isotopes.

It is reported that North Korea has conducted another underground nuclear test.