Electrolysis

Learning Objectives By the end of the lesson I will be able to: 1) Understand the process of electrolysis. 2) Explain how we can use electrolysis to splitting water to produce hydrogen.

Match up the words with their descriptions The substance being broken down Test for Oxygen Positive electrode Test for Hydrogen Makes a ‘popping’ noise when lit Electrolyte Splitting a substance using electricity Anode Relights a glowing splint Cathode Negative electrode Anion Positive ion Cation Negative ion Electrolysis

Electrolysis is splitting up substances using electricity (Lysis is latin for splitting)

What is electrolysis? Electric current is used to breakdown a substance made up of ions An electrolyte is the name for the substance being broken down

Positive Anode Negative Is Cathode Don’t get stressed in the exam: Remember PANIC

Electrolysis Apparatus Electrolyte: this is what will be electrolysed Anode (+ve electrode) Cathode (-ve electrode) power supply

THE ELECTROLYSIS OF WATER The unique way in which the hydrogen atoms are attached to the oxygen atom causes the hydrogen side of the molecule to have a positive charge and the oxygen side to have a negative charge.

The + Hydrogen atoms are attracted to the - charged terminal, and are pulled off the H2O molecule, filling the right tube in this diagram with Hydrogen gas.

The - Oxygen atoms are attracted to the + charged terminal, and are pulled from the H2O molecule, filling the left tube in this diagram with Oxygen gas.

H2O consists of 2 H atoms and 1 O atom so twice as much Hydrogen gas will be produced

Chemical what Happens 2H2O O2+2H2 Anode (positive): Cathode (negative): OVERALL: 2H2O O2+4H++4e- 4H++4e-2H2 2H2O O2+2H2

Electrolysis of Water http://www.youtube.com/watch?v=VnYSw349qvM

True or False Electrolysis is the splitting of a substance using electricity. The anode is negative. Anions are negative Cathode is negative. Cations are negative.

Summary Cathode Negative Anode Positive Positive ions attracted Negative ions attracted REDUCTION happens here ( positive ions gain electrons) OXIDATION happens here (negative ions lose electrons Summary

Uses of Electrolysis

Electro-repairing Electrolysis can be used to repair broken machinery. CRACKED MACHINERY So what happens is they use electrolysis to deposit a metal in this crack, how do they go about doing this?

The whole of the broken object is coated in wax, all except the broken part.

The cracked object is made the cathode Anode The cracked object is made the cathode A pure metal is used as the anode. The cracked object is made the cathode and the pure metal as the anode with a suitable electrolyte in a cell. The metal atoms become oxidised to positive ions (cations), these move through the electrolyte to the cathode. A suitable electrolyte

The cracked object is made the cathode and the pure metal as the anode with a suitable electrolyte in a cell. e- e- e- e- Cathode Anode (Oxidation) (Reduction) The metal atoms on the anode become oxidised to positive ions (cations), (their electrons are stolen) these cations move through the electrolyte to the cathode. As the crack is the only part exposed this is filled with the metal ions which become reduced gaining an electron and so metal atoms are deposited. The metal atoms on the anode become oxidised to positive ions (cations), (their electrons are stolen) these cations move through the electrolyte to the cathode. As the crack is the only part exposed, this is filled with the metal ions which become reduced; gaining an electron and so metal atoms are deposited.

After some time the object is removed from the electrolytic bath, washed and the excess metal is removed by machining the repaired article to its proper size. Good as new!!!!!!!!