His role is to fulfill his responsibilities as a leader.

Organic solvents play an important role in chemical reactions.

It is important to understand the importance of health.

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.