Prior Knowledge: Thinking back to the work you did in the previous topic about metals. Write a word equation to show how each of the following metals would be extracted from their ore: Tin oxide Lead oxide Magnesium oxide Zinc oxide Potassium oxide Stretch: Choose two of the above reactions and write balanced symbol equations for these two

Reactivity potential difference spectator ion Chemical cells and batteries Objectives: Grade 4-Describe a simple cell Grade 6-Plan and carry out an investigation of the voltage produced by simple cells using different metals Grade 8-Interpret data on chemical cells in terms of the relative reactivity of different metals Grade 9-Evaluate the use of chemical cells when given information Keywords: Reactivity potential difference spectator ion

Displacement recap: In the previous topic we also used the reactivity of metals to predict displacement reactions, as a more reactive metal displaces a less reactive metal from its compound: Zn(s) + CuSO4(aq)  ZnSO4(aq) + Cu(s) Spectator ions (HT): The sulphate ions do not change in the reaction above. They are spectator ions. They can be left out of the equation and write an ionic equation: Zn(s) + Cu2+(aq)  Zn2+(aq) + Cu(s) You can think of this redox reaction as two half equations. One will represent reduction (gain of electrons): Cu2+(aq) + 2e-  Cu(s) The other will be an oxidation (loss of electrons) reaction: Zn(s)  Zn2+(aq) + 2e-

Cells and batteries: You can use this difference in reactivity to make electrical cells and batteries. If you join two different metals together by a wire and dip them into an electrolyte, such as salt solution, electrons will flow through the wire. In the simple cell shown, zinc atoms donate electrons via the connecting wire to the copper (II) ions; so zinc acts as the negative terminal of the cell. The flow of electrons is an electric current. The current will flow in this circuit until one of the reactants is used up. There is a tendency for any metal atom to give away electrons and form a positive ion. The greater the tendency to for their positive ion, the more reactive the metal is. So the copper (II) ions accept electrons from the zinc atoms and change into copper atoms.

Rechargeable Vs Non-rechargeable: Rechargeable cells and batteries can be recharged because the chemical reactions are reversed when an external electrical current is supplied. In non-rechargeable cells and batteries the chemical reactions stop when one of the reactants has been used up. Alkaline batteries are non-rechargeable.

EXPLAIN Explain how the following cells produce electricity: simple cell non-rechargeable battery rechargeable battery

Progress Check: Why is it not possible to make an electric cell using two electrodes made of zinc metal? An electric cell is made using the metals iron and zinc as the two electrodes, and a salt solution as the electrolyte. Draw a diagram of the electric cell set up with a lamp in the external circuit. Name the metal that is reduced in the cell. Stretch: For the above cell, explain which metal will act as the negative terminal of the cell. Include two half equations in your answer.

Investigation: Aim: To investigate the voltage produced by different metals paired with magnesium ribbon. Equipment: For the investigation you will have the following pieces of equipment available to you: 100mL beaker Salt solution (sodium chloride saturated ) Voltmeter Connecting wires Magnesium ribbon Zinc Iron Copper Tin Method: Write a step by step method as to how you could use the above equipment to investigate the voltage produced by different metals paired with magnesium ribbon. You should include the following in your method: A diagram for the set-up of the equipment How you will ensure it is a fair test (what your control variables are) How you will ensure reliable results for your investigation

Metal to be paired with magnesium Results: Metal to be paired with magnesium Test 1 (V) Test 2 (V) Test 3 (V) Average voltage (V) Zinc Iron Copper Tin Conclusion: Write a conclusion to say what you have found out from your results. Remember to use data from your table to back up what you are saying. Stretch: What is the link between difference in reactivity and voltage produced? Evaluation: How could you extend your investigation to find out if other factors affected the voltage produced?

Reflect: Select two numbers between 1-25, write these in the margin of your book. Now complete the sentence/question from the numbers that you have chosen…