At the end of the lesson, students are able to:

I.State the characteristics of pure substances

II.Describe the different methods of purification of substance

III.Relate the characteristics of substances to the method of purification used

IV.Explain with examples the method of purification used to produce substances used in daily life

Pure substance do not contain any impurities

Pure substances always have specific melting point and boiling point

Pure water boils at 100 0 c and ice melts at 0 0 c

Any impurities added to pure substance will increase the boiling point or lower the boiling point of that substance

Water added with salt will boil at a temperature higher than 1000 c

Purification is the process of separating substances in a mixture to obtain pure substance

There are two types of purification technique that are commonly used; which are distillation and crystalisation

Way to obtain pure liquid from a solution which contain impurities

Distillation involves the process of heating liquid until it become vapour (gas). This vapour then condensed to become pure liquid

Distillation of sea water:

Dram and labeled the diagram above

Purification method carried out to obtain pure crystals from a saturated solution of the substance

Example: Purification of salt from saturated solution

CRYSTALISATION OF SALT

DISTILLATIONA) Breaking crude petroleumB) Production of pure oxygenC) Production of pure waterD) Obtaining pure ethanol

CRYSTALLISATION

Production of salt from sea water

Preparation of white sugar crystal from sugarcane juice