![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/1/18/Kochendes_wasser02.jpg/640px-Kochendes_wasser02.jpg&w=640&q=50)
Chemical substance
matter of constant composition best characterized by the entities (molecules, formula units, atoms) it is composed of and characterized by physical properties like density / From Wikipedia, the free encyclopedia
A chemical substance is any material with a known chemical composition.[1] For example, water has the same properties and the same ratio of hydrogen to oxygen whether it came from a river or was made in a laboratory. Typical chemical substances found in the home include water, salt (sodium chloride) and bleach. Generally, substances exist as a solid, a liquid, or a gas, and may change between these phases of matter when there are changes in temperature or pressure.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/1/18/Kochendes_wasser02.jpg/640px-Kochendes_wasser02.jpg)