This chemical reaction is very dangerous.

It's difficult to understand his explanation.

Thermochemistry is a part of chemistry that deals with the reactions of heat and matter.

Calculating enthalpy is important for understanding the heat effects of chemical reactions.

It's difficult to understand his explanation.

Health is very important.

His opinion is very important.

This chemical reaction is very dangerous.

This chemical reacts when heat is added.

He is majoring in chemistry at university.