2. Planning how to test fuels
An effective way to convince students that the science that they are studying is relevant to their everyday lives is to perform experiments using substances that are familiar to them. For example, when learning about acids and alkalis, they can test substances at home, such as foods, cleaning materials, toothpaste and soap. They can investigate the properties of metals by using objects from home. For this topic, they can do a proper scientific investigation to compare the amount of heat given out by different fuels (see Resource 5). You should choose fuels that are commonly used for cooking such as wood, kerosene, charcoal and liquid petroleum gas (LPG). In Case study 2, the teacher has very little equipment, but this does not stop her from helping her students to plan an experiment. Activity 2 describes an experiment you can do if you have some equipment such as spirit burners, metal cans, a measuring cylinder or jug and some means of measuring time.
Case study 2: Which is best?
Mrs Atieno of Sengera Girls Secondary School, Kenya, wanted to get her students to plan an experiment to test different fuels and compare the amount of heat given out. However, she did not have enough equipment for everyone to do the experiment. She believes that it is important for her students to learn to think for themselves – she wishes she had had that opportunity when she was at school.
She introduced the experiment by asking them which was better, kerosene or wood? Luci suggested kerosene but Jess said wood, because it is much cheaper. Luci argued that that is not necessarily the case, as you need more wood; kerosene has a hotter flame. They agreed to test their ideas by measuring how long it took for a set quantity of water to boil, using a known amount of fuel. Mrs Atieno divided them into groups and gave each group a set of questions to help them plan the detail of the experiment.
She managed to gather enough equipment for a demonstration. She had a tin lid to put some wood on, some mineral wool, a tin can and some wire to make a handle. She made a tripod out of sticks to hang the tin can from, and she had a stopwatch on her mobile phone.
She chose one group to carry out the demonstration and encouraged the other students to ask them questions. She asked them how they could make sure the heat was not wasted and was delighted when Ella suggested putting a box round the experiment to exclude the draughts.
Activity 2: Comparing different fuels
Remind your students that there are many different fuels and that we use different ones for different jobs, but they all release energy when burnt. In this class practical, students will test different fuels and compare the amount of energy they give out. You should choose fuels that they are familiar with and use at home and suggest that they test the fuels by using them to heat water. Divide your students into groups. Write a set of prompt questions on the board and get them to plan their investigation (Resource 5). When they have a plan, let them prepare the experiment. You will need to do a risk assessment before the lesson. (See C2 Making Science practical, Resource 2 .)
Make sure you don’t tell them what to do – just keep asking questions. The resource also provides an alternative experiment if you do not have the equipment needed to do an investigation.