His role is to fulfill his responsibilities as a leader.

Gender roles are an important element in defining individual behavior in society.

It is important to understand the importance of health.

The use of chemical weapons is prohibited by international law.

Analytical chemistry is a science that reveals the composition and structure of substances.

I am majoring in physical chemistry at university.

This chemical reaction is very dangerous.

I am majoring in inorganic chemistry at university.

My major is chemical engineering.

I am majoring in biochemistry at university.