what is a substance in chemistry? Please give examples also?

Answer 1

"A chemical substance is any material with a definite chemical composition.[1] For example, a sample of water has the same properties and the same ratio of hydrogen to oxygen whether the sample is isolated from a river or made in a laboratory. A pure substance cannot be separated into other substances by any mechanical process.[2] Typical chemical substances found in the home are water, salt (sodium chloride) and sugar (sucrose). Generally, substances exist as solid, liquid, or gas, and may change between these phases of matter with changes in temperature or pressure"