What is Chemical substance?​

A chemical substance is any material that has a definite chemical composition. Moreover, a pure substance cannot be separated into other substances by any mechanical process.Chemical elements and compounds are substances, mixtures are not.

Explanation:

hope this helps

he would use the colour black

the cold front replaces the warmer air at the ground level changing the wind to be breezy and denser.there is also an immediate drop in the temperature.