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.

Health is very important.

His opinion is very important.

It's difficult to understand his explanation.

The effect of this medicine appears immediately.

He is majoring in chemistry at university.

He missed school because he had a fever.