Jan 20, 2015
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