This substance undergoes a chemical change when heat is applied.

In this experiment, you can observe a chemical reaction.

This chemical reaction is very dangerous.

He is thinking about the lower verse of the Tanka.

It's high temperature today, it's hard to go out.

He pointed at the location on the map.

This is a kind of flower.

His attitude suddenly changed.

We cannot live without oxygen.

Chemotransmitters play an important role in the transmission of information between nerve cells.