Chemical Reactions – Rusting

Learning Intention: Students will understand that rusting is another type of chemical reaction, in which the products of the reaction are different to the reactants. They will also learn about the process of planning and conducting an experiment, devising an hypothesis and using a control with variables.

Success Criteria: Students will plan and conduct an experiment that tests an hypothesis about rusting.

You will be familiar with ‘rust’ as the orange/brown corrosion that affects some metals. Farmers, engineers, sailors and car-makers are all very aware of the economic impact of rusting. Rusting is a chemical reaction that occurs when metals are exposed to moisture and the air. How Stuff Works has a good article about rust – “How does rust work?”. Read pages 60 and 61 in your text book. Your task is to devise an experiment to investigate rusting. You may like to test the effect of the saltiness of water on the time taken for an iron nail to rust. You may like to test some methods that are used to reduce or prevent rusting. Follow these steps:

  1. Write an hypothesis – a theory about rusting that you want to test. For example, “The greater the concentration of salt, the quicker iron will rust.”
  2. What will be the ‘control’ and the ‘variable’ in your experiment?
  3. Write a list of materials and equipment that you will need to complete the test. Submit your list of requirements to me so we can be sure we have everything you will need.
  4. Formulate a method that describes exactly what you need to do – make sure someone else can use this method to repeat the experiment in exactly the same way you have done.
  5. In your method you need to include how you will record your results – will you measure mass, time, volume, temperature or some other factor/quantity?
  6. Undertake your experiment, recording your results.
  7. Include a discussion of your findings in your report. Were there any sources of error or unexpected results?
  8. Write a conclusion that refers to your original aim/hypothesis. Did you prove or disprove your hypothesis? Do you need to do further experimentation?

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