Alternative fuels and low-carbon technology in cars | 16-18 years

In this session, students begin by observing the electrolysis of water and exploring the use of hydrogen fuel cells to power cars. They then engage in a role play that imagines they are taking part in a government meeting to decide which of three types of car – petrol, hydrogen or petrol–battery hybrid – should be recommended for purchase as the main type of car in the UK.

Learning objectives

Students will:

• Recognise that hydrogen and a petrol–battery hybrid can be used to power cars.
• Understand why low-carbon technology (LCT) vehicles are essential to help reduce emissions and conserve fossil fuel supply.
• Be able to describe how science is vital to helping governments make sound decisions.

Sequence of activities

Introduction

1. Introduce the activity by asking students what other means than fossil fuel combustion may generate energy for driving cars. The list may include wind, wave and solar power to charge batteries for electric cars.
2. Introduce the formation of water in the reaction between hydrogen and oxygen as a suitable reaction that can be used in hydrogen fuel cells.

Demonstration: how much energy comes from making water?

1. Give each student the worksheet ‘How much energy comes from making water?’.
2. Demonstrate the electrolysis of water.
3. Circulate and support as students complete the questions on their sheet.

Plenary 1

1. In a plenary, review the responses to the questions.
2. Use further questions to widen the discussion, such as:
   • How could this reaction be turned into a useful source of energy for cars?
   • Where could we get hydrogen and oxygen from?
   • How would emissions be affected if cars ran on hydrogen?
   • Would using hydrogen-powered cars have a positive or negative impact on the greenhouse effect?
   • What would be the implications of having hydrogen fuel stations?
   • What are the potential dangers of hydrogen and petrol. Which is safer?
   • To what extent are we just ‘used to’ using petrol? Can we adapt to other fuels?

Role play: which car?

1. Introduce the role play that assesses whether hydrogen-powered cars are a realistic alternative for the future.
2. Give each student a copy of ‘Collision course – which car?’ and organise them into eight groups, assigning a role to each group.
3. Support the groups as they:
   • Carry out the background research to prepare their roles.
   • Prepare their presentations or questions for the ‘meeting’ according to their roles.
   • Prepare written reports according to their roles.
   • Hold the ‘meeting’, allowing the Minister (or Ministerial team) to come to their conclusion.

Plenary 2

In a plenary:

1. Debrief the students by stating explicitly that they are no longer in role.
2. Review the learning from the exercise, revisiting the questions above.

Feedback

Take in the written reports from the role play and use them as a basis for written feedback on learning. Check that students apply what they know about fuels to the situation facing our way of life.

Commentary

Written and verbal questions are used to stimulate reflection on the topic.

The role play involves students in peer assessment through taking different responsibilities. The quality of their input will be seen to directly affect the outcome of the ‘meeting’. During the plenary, students can think again about what they have learned.

The written feedback gives the teacher the opportunity to respond to individuals.

Demonstration notes

Apparatus

• Eye protection
• Conical flask, 500 cm³, with a sidearm and rubber tubing attached
• Bung to fit flask with two holes to take the electrodes
• Power pack
• Two leads with clips
• Two pieces of 18 SWG solder wire electrodes, about 15 cm long, coiled
• Shallow dish
• Plastic pipette to fit the rubber tubing
• Adhesive tape
• Safety screen
• Splint, matches
• Metre rule

Chemicals

• Soap solution (MINIMAL HAZARD), about 50 cm³
• Sulfuric acid 2 mol dm^-3 (CORROSIVE), 300 cm³

Procedure

1. Put the soap solution in the dish to two-thirds full.
2. Fit the solder wires through the rubber bung so the ends protrude by about 2 cm. Tape these in place if necessary.
3. Attach the plastic pipette to the rubber tubing and the other end of the tubing to the sidearm of the flask.
4. Put the sulfuric acid in the flask to about two-thirds full.
5. Fit the bung to the flask. Make sure the coiled leads sit in the sulfuric acid.
6. Connect the leads between the power pack and electrodes.
7. Turn on the power supply to 3‑5 V.
8. Allow the electrolysis to proceed for several minutes to ensure the rubber tubing and flask are empty of air. Check for bubbles in the flask.
9. Place the tip of the pipette in the soap solution.
10. Bubbles will form on the surface of the soap solution. These can be lighted with a splint. To do this, remove the pipette, move the dish away from the flask then scoop the bubbles up using the metre rule. Light the splint and then the bubbles at arm’s length.
11. A large bubble can be made and floated off. To do this, keep the pipette in one place while a large bubble grows on the end. Lift the pipette in the air and allow the bubble to float off. Light the bubble with the splint at arm’s length.

Health, safety and technical notes

• Read our standard health and safety guidance.
• Wear eye protection.

Role play notes

• Ensure that the room for the meeting is appropriate – a fixed laboratory setting will make the meeting difficult to run. Choose a location with moveable furniture and arrange this appropriately.
• Restrict presentation times so that everyone has a fair chance: 5–10 minutes for each should be ample.
• Ensure the Minister keeps time fairly.
• Ensure the Minister provides a running order in advance so that everyone knows when to make their presentations.
• Ensure that time for questions from the journalists is allowed before the decision is made.
• Consider inviting an outside guest to hear the meeting – this can provide an extra ‘buzz’ to help enhance performance.

Answers

How much energy comes from making water?

1. Heat is produced.
2. Making bonds between hydrogen and oxygen.
3. It is produced as a vapour.
4. The equation is 2 H₂ + O₂ → 2H₂O.
5. 4 –O‑H bonds are formed.
6. 4 x 463 = 1852, hence -1852 kJ mol^-1.
7. 1 x O=O, 2 x H-H 498 + (2x 432) = +1362 kJ mol^-1.
8. 1 x O=O, 2 x H-H 498 + (2x 432) = +1362 kJ mol^-1.
9. Enthalpy change = bonds broken – bonds formed, so 1362 – 1852 = - 245 kJ mol^-1.
10. To make the car move.
11. Out through the exhaust pipe.
12. Advantages include: low pollution, energetically favourable, clean. Disadvantages include: refuelling system is not in place yet, hydrogen storage is more difficult, probably less power per mole compared with petrol.