• Complete the word search of the keywords of today’s lesson.

• Complete it quietly and on your own.

Learning Outcomes

ALL – State what electrolysis is MOST – Predict the products of electrolysis

SOME – Describe how electrolysis works in terms of ions, electrodes and charges

• http://www.youtube.com/watch?v=i9xS9t-KMpc

Electrolysis is splitting up Electrolysis is splitting up substances using substances using

electricity electricity (Lysis is latin for splitting)

What is electrolysis?What is electrolysis?• Electric currentElectric current is used to

breakdown a substance made up of ions ions

• An electrolyte electrolyte is the name for the substance being broken substance being broken down down

• Electrolysis requires a liquid to conduct the electricity, called the electrolyte.

• Electrolytes contain free ions — they’re usually the molten or dissolved ionic substance.

• In either case it’s the free ions which conduct the electricity and allow the whole thing to work.

Electrolytes

• Electrolysis is based on an electrical circuit that includes an electrolyte and two electrodes.

• In electrolysis, the electrodes are placed into the electrolyte and ions move from one electrode to the other — this allows the conduction of electricity through the circuit.

How electrolysis works…

• Electrons are taken away from ions at the positive electrode

• Electrons are given to other ions at the negative electrode.

• As ions gain or lose electrons they become atoms or molecules and are released.

• These atoms or molecules are the products of electrolysis.

Gaining/Losing Electrons

• Lead bromide (PbBr2) is an ionic compound, so when it is molten it will conduct electricity.

• Electrolysis of lead bromide breaks it down into lead (Pb) and bromine (Br2).

• So, the electrolyte is lead bromide and the products of electrolysis are lead and bromine.

• Here’s how it works...

Example – Lead Bromide

Molten lead bromide contains positively charged lead ions and negatively charged bromide ions.•The positive ions are attracted towards the negative electrode. Here, each lead ion gains two electrons and becomes a lead atom.•The negative ions are attracted towards the positive electrode. Here, bromide ions lose one electron each and form bromine molecules (Br2).

Electrolysis set up

Cathode (-ve

electrode)

Anode (+ve

electrode)

Electrolyte: this is what will be electrolysed

d.c. power supply

Don’t PANIC - Positive Anode, Negative Is Cathode.

Demo of how to do the experiment

If you understand, hold up the green card.

If your unsure, hold up the red card.

Electrolysis Practical

• Carry out the practical in pairs. • Follow the instructions.• Whilst you are waiting, you can complete the

diagram of electrolysis

Complete the worksheet on your own

You have 4 minutes

Now pass to the person your sitting next to, they will mark it for.

Set your partner a target

Electrolysis doesn’t involve

electricityFalse

The anode is the positive electrode

True

The cathode attracts positive ionsTrue

We used carbon electrodes in today’s practical

False

The anode attracts

positive ionsFalse

Electric currentElectric current is used to breakdown a substance made up of ions ions

True

An electrolyte electrolyte is the name for the substance being made substance being made up. up.

False