methods of purifying substances

LEARNINGOUTCOMES

CONTENTS ACTIVITIES

At the end of lesson, students should be able to:

state the characteristics of pure substances

describe the different methods of purification of substancesrelate the characteristics of substances to the methods of purification usedexplain with examples the methods of purification used to produce

substances used in daily life

Characteristic of pure substances

Methods of purification

Pure substance

Selecting methods of Purification

Pure substance

• Example:– Distilled water contains only

molecules of water– Pure oxygen gas contains

only molecules of oxygenH H

OO H

• Pure substance is a substance that is made up of only one substance.

Do not mix with other substances and does not contain any impurities (bendasing).

Characteristic of pure substances

Has fixed melting and boiling point.Examples: melting and boiling point for pure water is 0 oC and 100 oC.The presence of impurities will affect the melting and boiling point that is reduce melting points of ice but increase the boiling point of water.

Methods of purification

Purification is a process of separating substances in a mixture to obtain a pure substanceThere are too many ways or methods of purification and it is depends on the physical properties of substances that mixed. Two common methods for purification are:

Distillation (Penyulingan)Crystallization (Penghabluran)

Distillation is a way of obtaining pure solvent from a solution.

Crystalisation is a way to separate insoluble (tidak larut) solid from soluble (larut) solid by using filtration.

– example: mixture of sand and salt

1. The mixtures of substances that have different boiling point are filled into round bottom flask.

2. The mixture is heated then the gas produce is flow through Liebig condenser.

3. Liebig condenser is used to cool and condensed the gas into liquid.

4. The pure substance that has a lower boiling point comes out first from Liebig condenser. While the substance with higher boiling point still remain in the flask.

5. The beaker used to collect pure substance is take out and the heating is stopped.

Purification by Distillation

Page 96_text book

Thermometer

Round botto

m flask

Liebig condenser

Bunsen burner

Purification by Crystallization

Water

Mixture of sand and salt

MixtureResidue (sand)

Salt solution

Salt solutionSalt

1 Add water to mixture

2 Filter the mixture

3 Heat and filtrate until it is

saturated4 Leave to cool

Selecting methods of Purification

Refer page 97 in text book

The End