Allow about 10 mins

Students will be very familiar with the idea that fuels are needed in vehicles. In addition, they will know that fuels are “used up” and a car for example would need to be “filled up” at the petrol station using either petrol or diesel.  It is important to remind students that the energy resources such as fuel are being “used up” but the energy stored chemically within the fuel has not disappeared but is now in another store. When a car is accelerating, the energy stored kinetically is increasing. But what about when the car is travelling at a constant speed on the motorway for example? The fuel is certainly still being “used up” in the combustion engine, so the energy in the chemical store of the fuel is decreasing. Where does the energy end up? As the work is done by the resistive forces acting on the car (friction, air resistance), the energy in the thermal stores of the surroundings.

As electric cars become more prevalent on our roads, exam boards are increasingly likely to include questions in exams comparing these cars, powered by electric motors, to traditional cars with combustion engines. Here is part of a typical exam question from AQA (question 6)

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Spend a few minutes considering the answers your students might offer for this question. The first part requires students to extract information from the table – the advantages of a diesel car being the range of the car and the low mass per kilogram of the fuel. The next part requires students to consider the benefits of improving the energy storage capacity of a battery. Once again, the data in the table provides a clue to the answer here – the range of the car would be greater, reducing the number of recharges needed. In addition, the car would be able to reach accelerations greater than the highlighted in the table. 

You can access the mark scheme here (question 6):

There is huge motivation to develop battery technology and improve their energy storage capacity. You could make this relevant to your students by asking them how this might impact their lives. Imagine a time in the future when you only need to charge your phone once a year. Imagine the impact this would have on road transport, aerospace and within our own homes. It would also allow us to transition away from fossil fuels and reach international ambitions of net zero carbon emissions.

Further details on battery storage development can be found from the website of the Faraday Institution including a whole section on their STEM outreach.

https://www.faraday.ac.uk/education-skills/stem-outreach/