Cells & Batteries (AQA GCSE Chemistry)

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Simple Cells

  • A simple cell is a source of electrical energy
  • The simplest design consists of two electrodes made from metals of different reactivity immersed in an electrolyte and connected to an external voltmeter by wire, creating a complete circuit
  • A common example is zinc and copper
  • Zinc is the more reactive metal and forms ions more easily, readily releasing electrons
  • The electrons give the more reactive electrode a negative charge and sets up a charge difference between the electrodes
  • The electrons then flow around the circuit to the copper electrode which is now the more positive electrode
  • The difference in the ability of the electrodes to release electrons causes a voltage to be produced
  • The greater the difference in the metals reactivity then the greater the voltage produced
  • The electrolyte used also affects the voltage as different ions react with the electrodes in different ways

How Reactivity Affects Voltage in Cells 1, downloadable IGCSE & GCSE Chemistry revision notes

 

How Reactivity Affects Voltage in Cells 2, downloadable IGCSE & GCSE Chemistry revision notes

Simple cell made with Cu and Mg. These metals are further apart on the reactivity series than Cu and Zn and produce a greater voltage

Exam Tip

Use the reactivity series of metals to compare different cells and deduce the relative voltages.

Batteries

  • Electrochemical cells include the familiar batteries used in everyday appliances and cars
  • Batteries work by connecting two or more cells in series, which combine to give a larger overall voltage
  • Over time the electrodes degrade as the reactions that occur there are irreversible
  • Cells produce a voltage only until one of the reactants is used up and when this occurs the battery dies or goes flat
  • The products formed cannot be reverted back into reactants as the reaction is irreversible and the battery must be replaced
  • This happens in non-rechargeable batteries such as alkaline batteries
  • In rechargeable batteries the reactions are reversed by connecting the cells to an external electrical supply
  • This reverses the chemical reactions taking place allowing the cycle to be repeated

Exam Tip

You should be able to describe the differences between rechargeable and non-rechargeable batteries.

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Stewart

Author: Stewart

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.