1. Thinking about common fuels
Students often see science as something that they do at school and not necessarily related to their lives. An effective way of demonstrating that this is not the case is to start with the everyday context and use it to draw out the scientific principles. Asking students about things outside school that are important can get them engaged and interested – especially if some controversy is involved. Most real-life situations are actually quite complicated and it is easy to find yourself talking about chemistry, physics or biology, or even wider issues. This will help to keep your students interested in science and help them to see how science can help them to understand the world.
In this unit, we start with aspects of science that are relevant in the home, and move on to consider issues of wider importance to society. In Case study 1, instead of starting with the theory of combustion, the teacher tells her students about something she read in the newspapers. She uses the story to explain the theory of combustion. In Activity 1, you are encouraged to start by asking students how they cook their food at home.
Case study 1: Using a news item to stimulate discussion
Mrs Onyango of Egerton secondary school, Kenya realised that her students had heard of and used different types of fuels at home and in school. She asked the class to name different fuels they knew of and found out that almost every student had used one type of fuel or the other. Mrs. Onyango then gathered her class round the front and told them a story (Resource 2).
Mrs Onyango asked her students some questions: where might the oil have come from? How is oil processed? What might have caused the explosion? What would be formed when it burnt? She explained that aircraft fuel is produced by distilling oil. The oil is imported from the Middle East, processed and then the kerosene is sent by pipeline to Nairobi airport. She explained that kerosene is a ‘hydrocarbon’ and asked her students to write a word equation to explain the combustion reaction. She drew the fire triangle on the board. She extended the discussion to other fires and asked her students about the different ways of putting a fire out. For each suggestion that they made, she related their ideas to the fire triangle. For example, putting water on a fire, removes the heat; putting a blanket over a fire, removes the oxygen.
In about 20 minutes, Mrs Onyango had covered some of the important ideas about fuels and combustion. She noticed that the story really helped to keep her students interested. For homework, she asked them to write a set of safety instructions for people working in a filling station, and to include a reason for each rule
Activity 1: Organising a brainstorm
Gather your class round the front and ask them what fuels they use at home. Write the names on the board. (Resource 3 provides some background information on brainstorming.) The point of this activity is to help your students realise that they already know quite a lot about fuels and combustion. Ask them to tell you any other fuels that they have heard of. Write these on the board as well. Ask them which fuel is the ‘best’. Ask several different students and get them to justify their decision. Resource 4 contains information about common fuels and some questions you might ask to help them decide what makes a good fuel. Divide your class into groups. Write some questions on the board and ask your students to work in groups to answer the questions for each fuel. In some villages, people use charcoal rather than wood. Ask your students why this might be and how charcoal is made. At the end, ask them which fuel is ‘best’ for cooking.
Section 3 : Combustion
2. Planning how to test fuels