What is a pure substance?
A pure substance is a material that consists of only one type of particle and has a fixed composition and definite properties throughout. It cannot be separated into simpler substances by physical methods.
Types of pure substances:
Elements: Iron (Fe), Oxygen (O₂), Gold (Au)
Compounds: Water (H₂O), Carbon dioxide (CO₂), Sodium chloride (NaCl)
Pure substances have uniform composition and characteristic melting and boiling points, which help distinguish them from mixtures.