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What is a pure substance?

A pure substance is a substance that cannot be separated by physical means. eg. filtration, evaporation, distillation or chromatography.

Examples of pure substances include water, gold, glucose, carbon dioxide, oxygen and hydrogen.

A pure substance is made up of one type of particle. The particle that makes up water is H2O. The particle that makes up carbon dioxide is CO2.

Each pure substance has its own set of unique set chemical and physical properties which helps identifies it. 

Water has a melting point of 0°C and a boling point of 100°C. It is also colorless and odorless. Gold however, is yellow in color, solid at room temperature and pressure and is is good conductor of electricity.

Pure substances can be divided into two groups, elements and compounds.

Elements are made up the same types of atoms. The known elements are listed in the Periodic table. Examples of elements include hydrogen, helium, nitrogen, oxygen, iron and gold.

Compounds are composed of one or more different types of atoms that joined togther by chemical bonds. Examples of compounds include water, glucose, methanol, DNA and carbon dioxide.