This chemical reaction is very dangerous.

He is an expert in chemistry.

This lemon is sour.

Please add a little vinegar to this salad.

The basicity of this compound is very high.

There is a class observation at my son's school tomorrow.

The use of mobile phones is prohibited during class.

She overreacted to his words.

Nuclear reactions are used for mass production of energy.

His single word triggered a chain reaction, and everything changed.