Elements, compounds and mixtures

Elements, compounds and mixtures

Separation techniques

Pure substances :

• consists of one type of material

• have fixed melting and boiling points

• melting point is lowered by impurities

• boiling point is raised by impurities

• the purity of substance is determined by the melting and boiling point.

Filtration

filtration is used to separate a liquid from a suspended or settled solid. e.g. soil from water

Evaporation

this technique is used to separate a solid substance that has been dissolved in water

Sublimation

the changing of vapors directly into a solid on cooling.

Crystallization

the process of cooling a hot, concentrated solution of a substance to obtain crystals.

other techniques

• Separating funnel

• Paper chromatography

• Simple distillation

• Fractional distillation

Recap

• How would you separate sand from water ?

• What is the difference between element, a compound and a mixture?

• What technique would you use to separate ethanol and water, vegetable oil and water, and black dye from a fabric?

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