LESSON 4TOPIC: SEPARATION OF MIXTURES

GRADE: 7

Presented By: Miss Mark

Pitlochry Primary School Educator

KEY CONCEPTS AND MAIN POINTS

• Magnetism as a method of separation•Evaporation as a method of separation.

•Distillation as a method of separation

1. MAGNETISM AS A METHOD Of SEPARATION

We can use magnetism to separate a magnetic substance from a non-magnetic substance.

A magnet can attract iron, cobalt, nickel. This is because iron, cobalt and nickel are magnetic elements.

Examples of using a magnet is real life:

• Magnets are used in recycling to recover magnetic substances from domestic waste.

• When iron is mined, magnets are used to extract the iron.

2. EVAPORARTION AS METHOD OF SEPARATIONCertain solids dissolve in liquid. For example, sugar dissolves in water. In a solution of sugar and water, you cannot distinguish the sugar from the water.A solution is a mixture that consists of a solid dissolved in a liquid.The solid that is dissolved in the liquid is called that SOLUTE.The liquid which the solid is dissolved in is called the SOLVENT.

**Think about why we cannot use filtration to separate a solution.**

However we can use EVAPORATION to recover the solute from the solution. We need to heat the solution. The liquid will boil and escape into the atmosphere. The solute will be left behind.Examples of evaporation in real life:• At a mining site, polluted water is sent to a special dam. The water

evaporates from the dam and the bad chemicals are left behind.

3. DISTILLATION AS A METHOD OF SEPARATIONWhen we evaporate we lose the SOLVENT. We use DISTILLATION to recover both the solute and the solvent of the solution.

What is distillation?Distillation is the process of separating a solution by boiling it, so that the solvent evaporates, and then the vaporised solvent cools and condenses.

What is condensation?Condensation the change of state from a gas to a liquid.

https://www.youtube.com/watch?v=eQlnHr9g6Io

The distillation of salt water

• We boil the water in the flask on the left.

• The water evaporates to the top of the flask. It has nowhere to go but through the tube.

• Once in the tube, it cools down and condenses back to liquid water, and runs into the beaker on the left.

• Once all the water has evaporated (and moved over to the beaker on the right), the salt is left behind in the flask on the left

FRACTIONAL DISTILLATION

• We may also use distillation to separate a solution of TWO liquids. However, the liquids need to have different boiling points.

• For example, take a mixture of ethanol and water. The boiling point of water is 100˚C. The boiling point of ethanol is 78˚C.

• If we heat the solution to 78˚C and keep it there, only the ethanol will evaporate leaving the water behind.

Examples of distillation in real life:• Salt water is turned into fresh water through distillation.• When oil is mined from the ground, it is known as crude oil. Various forms

of fuel such as petrol and diesel, are separated from crude oil by distillation.

KEY TERMS Use the notes above to create definitions for the following terms. Write these down in your classwork books.• Magnetism• Evaporation• Distillation• Fractional distillation• Solute• Solvent• Solution

ACTIVITY 3

Which method would you use to separate the following mixtures into pure substances? Explain why you chose the method. Also use the methods you learnt about in Task 3.

1.Sand in water2.Sugar in water3.Rice and dried beans4.Flour and sugar5.Pieces of iron and wood6.Salad dressing made of oil and vinegar7.Sugar and crushed glass

REMEMBER!!!!

• Please read through and study the notes carefully. Familiarise yourself with all the concepts and then answer the questions in your classwork books. Write the date, topic, question and answer.

• Please also remember to learn the first 20 elements of the periodic table! Learn the atomic number, symbol and the name of the element.

• Here is a link to a fun song to help you remember the order of the elements: https://www.youtube.com/watch?v=rz4Dd1I_fX0

THANK YOU!

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