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:
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.”
What will be the ‘control’ and the ‘variable’ in your experiment?
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.
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.
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?
Undertake your experiment, recording your results.
Include a discussion of your findings in your report. Were there any sources of error or unexpected results?
Write a conclusion that refers to your original aim/hypothesis. Did you prove or disprove your hypothesis? Do you need to do further experimentation?
Learning Intention: Students will understand the meaning of exothermic and endothermic reactions.
Success Criteria: Students will be able to identify exothermic and endothermic reactions and give examples of each. They will be able to explain why these processes to considered to be exothermic or endothermic.
Endothermic reactions absorb energy, causing a decrease in temperature (eg. photosynthesis, melting and evaporation all require energy to be added to the system). Exothermic reactions release energy, causing an increase in temperature (Combustion, freezing, and condensation release energy from the system).
Mr Kent’s Chemistry page has some excellent examples of exothermic and endothermic processes and chemical reactions. We will be conducting four experiments in class and measuring the temperature change to determine which are endothermic and which are exothermic reactions. Leave comment below about what you found from your experiments. Can you think of any examples of exothermic and endothermic processes from home?
Thanks to Duncan Patti for producing the slideshow above, which is a good summary of what you should know about chemical reactions from Year 7 and 8 science and an introduction to Year 9 Chemistry. You need to know the difference between a physical change and a chemical reaction (what evidence is there for a chemical reaction?). You also need to know the four ways in which you can increase the rate of a reaction. It is also very helpful if you can remember the chemical formula for the first twenty elements, as well as some other common ones (iron, copper, silver and lead).
Welcome back to school for another fabulous year of science and learning! Please bookmark this site for future reference as this will be the starting point for all our science studies during the year. Our first unit of work will build on your knowledge of matter, atoms and molecules, elements and compounds and chemical reactions.
(1) Students will understand that all matter is made of atoms which are composed of protons, neutrons and electrons; natural radioactivity arises from the decay of nuclei in atoms.
(2) They will know that chemical reactions involve rearranging atoms to form new substances; during a chemical reaction, mass is not created or destroyed.
(3) Students will understand chemical reactions, including combustion and the reactions of acids, are important in both non-living and living systems and involve energy transfer.
This a rusty tractor engine, captured at Jurien Bay, WA.
Over the next few weeks we will be doing many different experiments, including turning grass into paper. After you have finished this unit of work, you should be able to answer the following questions:
What are the two main differences between physical change and chemical reactions?
What are four signs that new products are formed during a chemical reaction?
Name four ways you can increase the rate of a reaction.
Freezing, melting, evaporation and condensation are all physical changes of state in which molecules of a substance gain or lose kinetic energy. Many common changes that occur around us are actually chemical reactions – when iron rusts, apples go brown, silver tarnishes or copper develops a green tinge, oxidation is occurring. Combustion (burning) is also a form of oxidation. In a chemical reaction new products are formed and this may result in a colour change, a precipitate being formed, the release of gases or energy in the form of light or sound. The following resources may help you to learn about chemical reactions: