He is an expert in planetary science.

Humanities is an academic field that studies human culture and society.

This reaction occurs through a chemical process.

He is an excellent chemist who made many discoveries.

He is an expert in petrochemistry.

It's difficult to decipher this chemical equation.

Understanding chemical equations is difficult.

He is an expert in chemical analysis.

We are growing vegetables without using chemical fertilizers.

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