This chemistry video tutorial focuses on pure substances and mixtures. It’s a subtopic of the classification of matter. Pure substances include elements and compounds where as a mixture is a combination of two or more pure substances. A pure element consist of only one type of atom. A molecule consist of multiple atoms and a compound consists of different atoms. Individually, these are all pure substances. Examples of pure substances include hydrogen, water, silver, 24k gold, sugar, and iron metal. Examples of mixtures are salt water, seawater, air, brass – an alloy of copper and zinc, milk, sugar water, sterling silver, soda, wood, wine, soil, and rubbing alcohol. Pure substances have a constant composition where as a mixture can have a variable composition. Mixtures can be separated by a physical process such as evaporation, boiling, decanting, centrifugation, chromatography and filtration. Pure substances that exist as compounds can be broken down into elements using a chemical process such as water converting into hydrogen and oxygen gas by means of electrolysis.
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