Catalysts, rates of reaction and what sank the Kursk | 14-16 years

In this activity, students plan an investigation into the effect of catalysts on the rate of a reaction, particularly in the decomposition of hydrogen peroxide. The activity is placed in the context of finding out what sank the Russian nuclear submarine Kursk, and begins with stimulus material in the form of a text document and a teacher demonstration.

After checking and evaluating their experimental plan students carry out practical work, share results and agree on conclusions. Finally, they work in groups to extract information from unfamiliar but contemporary texts.

Learning objectives

Students will be able to:

• Understand that the rate of some reactions can be increased using a catalyst.
• Devise an experimental investigation.

Sequence of activities

Before the lesson

Several days before the first session, give each student a copy of the ’News timeline’ to read, so that they have an answer to the question ‘What sank the Kursk nuclear submarine?’

Introduction

1. At the start of the session, ask what they have found from reading the News timeline. (Many points arise here but they should include that the sinking of the Kursk involved hydrogen peroxide.)
2. Project or display the ‘Seismic data’ table.
3. Arrange students in pairs and issue a mini whiteboard to each. Ask the pairs to write down what information they can deduce from the table. (There were two explosions at roughly the same place in quick succession, the second more powerful than the first.)
4. Demonstrate the decomposition of hydrogen peroxide in a narrow-necked conical or flat-bottomed Pyrex glass boiling tube.
5. Pose questions to highlight that the decomposition:
   • Has been accelerated by the presence of a catalyst.
   • Occurs at a sufficiently high temperature to vaporise the water.
   • Proceeds at a very fast rate, rather like an explosion.
6. Now share the learning objectives with the students.

Planning the experiment

1. Explain that they are to plan an experiment to compare how effective different powders are in catalysing the decomposition of hydrogen peroxide.
2. Take the students through the equipment and materials that are available.
3. Give each student a ’What sank the Kursk? worksheet’ and an ‘Equipment list’.
4. Ask them to draw a diagram of their apparatus for when they begin their experiment.
5. After a suitable time, give out copies of the ’Apparatus diagram’, showing the expected apparatus.
6. Pose questions to make explicit why that apparatus has been chosen.
7. Ask the students to compare their diagram with the one they have been given.
8. Get them to write down an experimental procedure based on the ‘Apparatus diagram’ they have been given (and which someone else could follow).
9. After a suitable time give out copies of the ’Procedure sheet’ detailing the expected procedure.
10. Pose questions to highlight why the procedure has been chosen.
11. Ask students to compare their experimental procedure with that on the ’Procedure sheet’.

Carrying out the experiment

Supervise the students as they carry out the practical, organising them to work in pairs to:

1. Follow the ‘Procedure sheet’ using one of the powders (allocate different powders to different pairs).
2. Record their results in the table provided.

Arrange for the pairs to:

1. Share their results so that they can complete their table.
2. Combine with other pairs to agree what conclusions they can draw from the shared results.

Plenary 1

Bring together students in a plenary:

1. Select individual students to give their conclusions.
2. Encourage other students to add to these.
3. Pose questions to ensure that all students have understood that the decomposition of hydrogen peroxide can be catalysed by some, but not all, solids.

Activity: Peroxide power in torpedoes

Give a copy of ’Peroxide power in torpedoes’ to each student. They are to read the three reports and to answer the questions that follow. Circulate and support the students while they work in groups to:

1. Share their answers.
2. Agree a group answer.
3. Write down what they have learned about extracting information from an unfamiliar piece of text.

Plenary 2

 Bring together students in another plenary. Ask:

1. Individual students to give answers to some of the questions.
2. Other students to add to these answers.
3. About the connection between the teacher demonstration, the student experiments and what happened on the Kursk.

Commentary

The introductory work on the sinking of the Kursk and the teacher demonstration of the decomposition of hydrogen peroxide provides a relevant opportunity for the teacher to share the learning objectives with students.

Students appraise their own experiment plan by comparison with exemplars and this enables them to recognise the standards they are aiming for. When they compare their experimental results with those of others they build their ideas about how some solids can catalyse the decomposition of hydrogen peroxide.

As a further refinement, students extract information from an unfamiliar text and they review their own skills in this area.

Practical notes

Equipment

For the demonstration of the catalytic decomposition of hydrogen peroxide

• 250 cm³ borosilicate conical flask with a narrow neck (30–40 mm), or poly(ethylene terephthalate) (PET) carbonated drinks bottle
• Bung with a hole bored through it
• Filter funnel
• Tissue paper
• Cotton thread

For students’ experimentsto investigate the effect of different powders (catalysts) on the decomposition of hydrogen peroxide

• Eye protection
• Trough
• Burette, 50 cm³, to be inverted
• Conical flask, 250 cm³, with bung fitted
• Small test tube
• Rubber tubing to connect side arm of flask to bottom of upturned bottle
• Boss, clamp and stand
• Stop clock
• Cotton thread
• Funnel
• Measuring cylinder, 100 cm³
• Balance weighing to 0.01 g

For each student

• Mini whiteboard (if available, alternatively use paper and pens)

Chemicals

For the demonstration of the catalytic decomposition of hydrogen peroxide

• 25 cm³ hydrogen peroxide, 100 vol (30%), (HARMFUL, risk of serious damage to eyes)
• c.0.5 g manganese(IV) oxide (HARMFUL by inhalation and ingestion)

For students’ experiments to investigate the effect of different powders (catalysts) on the decomposition of hydrogen peroxide

• Hydrogen peroxide (IRRITANT), about 75 cm³ of 20 volume per test
• Range of powders to test:
  • Zinc oxide
  • Iron(III) oxide
  • Copper(II) oxide (HARMFUL)
  • Manganese(IV) oxide (HARMFUL)
  • Powdered zinc
  • Powdered iron
  • Powdered copper (one powder per pair)

Health, safety and technical notes

• Read our standard health and safety guidance.
• Wear eye protection.
• Use a safety screen for the teacher demonstration.
• It is the responsibility of the teacher to carry out appropriate risk assessments.

Principal hazards

• Hydrogen peroxide.
• Depends on powders selected.

Procedure 

For the demonstration of the catalytic decomposition of hydrogen peroxide

Download teacher and technician notes with details of the procedure as pdf or MS Word, plus view a video with full guidance and to see the full demonstration.

For the students’ experiments to investigate the effect of different powders (catalysts) on the decomposition of hydrogen peroxide

Download the equipment list, diagram of set up and procedure below.