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Syllabus/Unit: code: C2 Chemical ResourcesLesson number: 8Lesson Title: Chemicals from the sea - Chemistry of NaCl

Learning Outcomes How I did Targets

Learning Outcome 1:

Describe how sodium chloride is mined.

Grade C

Learning Outcome 2:

Describe the electrolysis of brine and recall the uses of the products formed.

Grade B

Learning Outcome 3:

Explain the electrolysis of brine in terms of loss or gain of electrons.

Grade A/A*

Connector:

What factors can affect the healthy growth of a plant?

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Extended Learning

• Extended Learning task:

• Due date: next lesson

• Criteria for Grade C:

• Criteria for Grade B:

• Criteria for Grade A:

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BIG picture

• What skills will you be developing this lesson?

• HSW- by planning and carrying out an investigation/ Interpreting data/ evaluating an experiment

• Numeracy- by using formulae in calculations• Literacy- by writing explanations using correctly

spelt keywords and good grammar. • Team work- during a practical investigation• Self management- by completing an individual

assignment by …..• Participation- during a practical activity• Reflection- through self and peer assessment of

each outcome

Key Question: How are organisms classified?

•Quick Discussion:•What do you already know?

•How is this lesson relevant to every day life? Identify and maintain global diversity

Where does this lesson fit in to the rest of the topic? Lesson 5

Keywords:• Brine• Solution mining• Subsidence• Bleach

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Put your hand up if there is any key word from the list that you don’t know the meaning of.

New Information for Learning Outcome 1

• The common name for salt is sodium chloride, NaCl.

– Can be used to produce all sorts of material, not just flavour and preserve food.

• But where do we get it from?

1. It can be made from salt water

2. It can also be obtained from salt deposits.

– Underground in Cheshire and elsewhere in UK– Remains of ancient seas that have evaporated

and been covered by rock– Machines cut through salt, forming caverns– Salt mined this way is used for cooking and

salting roads during winter

The chemical name for common table salt is sodium chloride: NaCl

New Information for Learning Outcome 1

• Salt is soluble in water. Concentrated salt solutions are called brine.

• Needed for industry, brine is mined using a method called solution mining:

1. Water pumped from surface into

deposit deep underground

2. NaCl dissolves in the water, brine is made, and the

brine pumped to the surface

3. This is a continuous

process, needing little labour,

keeping costs down

4. Mining salt may cause subsidence-

land slumps downwards due to

mine, causing cracked buildings

and holes in ground.

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Create

Evaluate

Analyse

Apply

Understand

Remember

Understand (D)

What is brine and how and why is it made?

Remember (E)

State two uses of sodium chloride in food

Apply (C)

Suggest why salt for spreading on roads in the winter is mined using cutting machines, rather than by solution mining.

Demonstrate your Learning for Outcome 1

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Learning Outcome 1: Review

Learning Outcome How I did Targets

Learning Outcome 1:

Describe how sodium chloride is mined.

Grade C

Met?

Partly met?

Not met?

How can I improve on Learning Outcome 1?

Go back to your Learning Outcome grid and fill out the ‘How I did’ and the ‘Targets’ column.

New Information for Learning Outcome 2

• New substances can be made from brine by passing electricity through it.

• When you do this, the process is called electrolysis (‘-lysis’ means ‘splitting’):

New Information for Learning Outcome 2

Two electrodes are needed to pass

electricity into the brine

Electrodes are made from inert materials like titanium to prevent reaction with brine

or the products made

Chlorine forms at the positive electrode

(the anode)

Chlorine forms at the positive electrode

(the anode)

Hydrogen forms at the negative electrode

(the cathode)

Hydrogen forms at the negative electrode

(the cathode)

NaOH stays dissolved in solution

NaOH stays dissolved in solution

New Information for Learning Outcome 2

• Brine electrolysis happens in a chlor-alkali plant.

• The European chlor-alkali industry produces 10 millions tonnes of chlorine every year.

• To do this, 36 billion kilowatt hours of electricity is used – enough to supply electricity to 7.5 million homes in the UK!

New Information for Learning Outcome 2

The electrolysis of sodium chloride solution produces three very useful products:

Chlorine used for killing bacteria in water (sterilising it), for making chemicals like HCl, for bleach and making plastics like PVC.

Hydrogen used for making margarine and fertilizers, and for rocket fuel.

Sodium hydroxide used in many chemical reactions, such as making soap, neutralizing acids and making paper. It also reacts with chlorine to make bleach (sodium chlorate):

Sodium hydroxide + chlorine sodium chloride + water + sodium chlorate

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Create

Evaluate

Analyse

Apply

Understand

Remember

Apply (C)

Produce a poster to describe the uses of chlorine, sodium hydroxide, and how both combine to make bleach

Analyse (B)

Produce a poster to describe and explain the process of brine electrolysis, giving the products formed, and explaining their applications.

Demonstrate your Learning for Outcome 2

Keywords:

Remember (E)

Produce a poster to show the uses of hydrogen

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Learning Outcome 2: Review

Learning Outcome How I did Targets

Learning Outcome 2:

Describe the electrolysis of brine and recall the uses of the products formed.

Grade B

Met?

Partly met?

Not met?

How can I improve on Learning Outcome 2?

Go back to your Learning Outcome grid and fill out the ‘How I did’ and the ‘Targets’ column.

New Information for Learning Outcome 3

Oxidation: is the addition of oxygen to a substance andReduction: is the removal of oxygen from a substance.

lead oxide + carbon leadcarbon monoxide +

oxygen removedreduction

oxygen addedoxidation

Reduction and oxidation always take place together. Why is this type of reaction called a redox reaction?

redox = reduction and oxidation

Which substances are oxidized and reduced in this reaction?

New Information for Learning Outcome 3

Oxidation also means loss of electrons in a reaction, and reduction is a gain of electrons....You can remember this using...............OILRIG!

New Information for Learning Outcome 3

What does OILRIG stand for in terms of redox reactions?

Oxidation

Is

Loss of electrons

Reduction

Is

Gain of electrons

New Information for Learning Outcome 3

heat

In electrolysis, the substance that the current passes through and splits up is called the electrolyte.

Positive ions move to the negative electrode and gain electrons.

This is reduction.

Negative ions move to the positive electrode and lose electrons.

This is oxidation.

The electrolyte contains positive and negative ions.

What happens to these ions during electrolysis?

New Information for Learning Outcome 3

In the electrolysis of NaCl solution, the negative chloride ions (Cl-) are attracted to the positive electrode.

Are the Cl- ions oxidized or reduced?

How many electrons are lost by each Cl- ion?

How many Cl- ions join to make a Cl2 molecule?

What is the half-equation for this redox process?

2Cl- Cl2 + 2e- (oxidation)

oxidized

one

two

Here, the Cl- ions lose electrons to make chlorine atoms, which then form chlorine molecules (Cl2).

New Information for Learning Outcome 3

In the electrolysis of sodium chloride solution, the Na+ ions might be expected to form sodium at the negative electrode.

For all ionic compounds containing a metal that is more reactive than hydrogen, electrolysis of a solution of the compound will produce hydrogen rather than the metal.

At the negative electrode, the H+ ions compete with the Na+ ions. The H+ ions gain electrons; the Na+ ions stay in solution.

Instead, hydrogen gas is produced here.

This is because sodium chloride solution also contains H+ ions from some of the water: H2O (l) H+ (aq) + OH- (aq).

New Information for Learning Outcome 3

In the electrolysis of NaCl solution, the positive hydrogen ions

(H+) are attracted to the negative electrode.

Here, the H+ ions gain electrons to make

hydrogen atoms, which then form hydrogen molecules (H2).

Are the H+ ions oxidized or reduced?

How many electrons are gained by each H+ ion?

How many H+ ions join to make a H2 molecule?

What is the half-equation for this redox process?

2H+ + 2e- H2 (reduction)

reduced

one

two

New Information for Learning Outcome 3

Sodium chloride solution has four types of ions:

What is the overall equation for the electrolysis of a sodium chloride solution?

The Cl- ions form chlorine at the positive electrode and the H+ ions form hydrogen at the negative electrode. So, what’s left?

Na+ and OH- ions are left behind and so a solution of sodium hydroxide (NaOH) is formed.

2NaCl (aq) + 2H2O (l) H2 (g) + Cl2 (g) + 2NaOH (aq)

Na+ and Cl- ions from the sodium chlorideH+ and OH- ions from the water.

New Information for Learning Outcome 3

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Create

Evaluate

Analyse

Apply

Understand

Remember

(A*)

In terms of electrons, using suitable equations, what happens during the electrolysis of brine?

Demonstrate your Learning for Outcome 3

(B)

Give the names of the two gases produced in electrolysis of brine. Give the tests that could be used to identify them.

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Learning Outcome 3: Review

Learning Outcomes How I did Targets

Learning Outcome 3:

Explain the electrolysis of brine in terms of loss or gain of electrons.

Grade A/A*

Met?

Partly met?

Not met?

How can I improve on Learning Outcome 3?

Go back to your Learning Outcome grid and fill out the ‘How I did’ and the ‘Targets’ column.

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Review for Remembering

• Stand up if you have met all three lesson outcomes?

• If not what do you need to do next in order to meet the outcome? Record this in your diary as part of your homework.

• Is there any part of the lesson you think you need to go over again next lesson?

• Tell the person next to you three things you have learnt this lesson.

• How will you remember this for your exam?

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Science Department

Lesson plan

Teacher information

Poster paperGlueColour pensColour pencilsScissorsRulersLaptops if availableReference books if available