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CSI 5/11 -  Murder in the Park

  • GCSE
  • Popular Activity
  • Topical

Type: Activity
Learning Strategy: Interactive teaching
Topic: Identifying materials

Fireworks stimulate the senses and fire our imagination. They have done for centuries. Behind the bright colours lies electron hopping. This subatomic dance has matched colours to compounds since the first interstellar gases formed. From ancient China's firecrackers to Las Vegas light displays, the colours tell us which elements are present.

Students do a CSI investigation to find the murderer in the park on Guy Fawkes Night, and they meet a lot of science on the way - from rocket science to electron energy levels. They learn how those colour-giving electrons that make fireworks so much fun, fit into the atoms that make up everything - all year round.

14-16 How Science Works:
1c how explanations of many phenomena can be developed using scientific
theories, models and ideas.

Published: 24th October 2007
Reviews & Comments: 12

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Learning objectives

Students will:
•use flame test data to solve a crime scene investigation.
•model atoms as circular electron energy levels around a central nucleus in order to explain where the coloured light comes from when metal ions are heated.
•describe atoms using this model and relate features of the model to an element’s position in the periodic table.

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GCSE specifications
AQA Additional Module C2: 12.1 How do sub-atomic particles help us to understand the structure of substances?
AQA Chemistry: 13.5 How do we identify and analyse substances?
Edexcel Core Topic 5: Patterns in Properties.
Edexcel Additional Topic 6: In Your Element.
OCR 21st Century Additional Module C4: Chemical Patterns.
OCR Gateway Module C3: The Periodic Table

Running the activity

Page1 sets the scene. A murder was committed during a firework display. Could firework chemicals help solve the crime? What chemicals should forensics look for? Page 2 summarises the science of fireworks and could be used to revisit a number of concepts as appropriate: combustion, what the -ides and -ates mean in compound names, oxidation and reduction.

A class experiment or demonstration could be done at this point to match up colours to the chlorides of metals in groups 1 and 2 (see practical details below). The activity leaves out toxic barium salts, and copper salts, to make modelling electronic configurations easier. If learning about electron configurations isn’t appropriate, students can skip straight to page 4.

Page 3 introduces the standard GCSE electron energy level model. At this point, the electron cards on page 5 could be used to relate features of the model to each element’s position in the periodic table. Students could be asked to arrange the symbol cards in order of atomic number and match two other cards to each symbol. What patterns can they spot? Possible questions to pose are: how can you tell how many electrons each atom has? How do the energy levels fill up? What’s the same about atoms in the same group of the periodic table?

Page 6 has an electron energy level diagram to laminate and keep, and cut out ‘electrons’ to use with it. This could be used to build the electron configurations of other atoms or model the electron transitions that let salts colour flames.

Page 4 returns to the original problem. Students use the flame colours associated with each salt to solve a murder by working out ‘who did it?’ from CCTV images. The evidence points strongly to Sue Little.

Practical details:
Clean Nichrome wire dipped in concentrated hydrochloric acid and a sample of the salt is heated strongly in a bunsen flame on the end of a cleaned nichrome wire. It is best to use chlorides. Note that sodium and potassium chlorides are low hazard but lithium chloride is harmful (Refer to CLEAPSS Hazcard 47B) and calcium chloride and strontium chloride are irritants (refer to CLEAPSS Hazcard 19A). Alternatively, and potentially less messy, use splints soaked in distilled water over night then dipped in solutions of each salt. The expected colours are: lithium - crimson; sodium - yellow; potassium - lilac; calcium - brick red and strontium – red.

It is worth noting that purple fireworks are really made using a mix of strontium (red) and copper (blue) compounds because the lilac colour from potassium is not intense enough. If students can’t see it at all because there is too much sodium around, get them to observe the flame through blue glass.

News links
Very accessible account of how the flame test colours arise.
Detailed account of how firework colours are produced.

Media links

How stuff works
A brief video explanation of the basic chemistry and physics of fireworks.
A 1 minute video – one of the shortest of a number of useful Youtube clips of flame tests and the metals responsible for them.
How to demonstrate the flame test colours using salt solutions in ethanol.
A PowerPoint presentation - filling electron energy levels for atoms and ions up to calcium.
How to use a CD in a home-made spectrometer to view the emission spectra of metal ions – good enough to see some similarity between street lamps and the flame from salt in a gas flame . . . might even spice up a disappointing firework display.

Reviews & Comments

Write your online review to share your feedback and classroom tips with other teachers. How well does it work, how engaging is it, how did you use it, and how could it be improved?

CSI 5/11 -  Murder in the Park review

Apr 26th, 2010

4 Star

very good

Reviewer: Rachel Kershaw

CSI 5/11

Oct 13th, 2009

5 Star

Brilliant! The students really got into the CSI role & the practical investigation - they even produced a role play as a "reconstruction"! Very good for my year 8 group who are not following the WIKID course at the moment, gives them a taste of HSW

Reviewer: Helen Shepherd

CSI 5/11 -  Murder in the Park review

Dec 17th, 2008

5 Star

An excellent resource. I adapted this to use with Year 12s when they were doing about emission spectroscopy. They loved it.

Reviewer: greg turner

Endangered vultures

Jul 18th, 2008

4 Star

This activity worked really well with a Y8 group having just finished Ecological Relationships.
I gave each group a print out of the sheet with the speech bubbles, as well as a BBC News story about the decline of the vultures. Each group made a poster and a presentation to persuade the goverment soemthing needed to be done. It got a class that dont ususally work very well in groups to really improve their teamwork.

Reviewer: Jenny Wells

Colouful chemistry

Jul 4th, 2008

5 Star

Excellent way to introduce the colours of transition metals. Used with year 6 as a simple introduction to the school.

Reviewer: Roger Deadman

CSI 5/11 -  Murder in the Park review

May 16th, 2008

5 Star

Thia acivity is amazing. I used it to help get our students motivated before our state mandated science test. They loved it!

Reviewer: Jamie Spates

CSI 5/11 -  Murder in the Park review

May 14th, 2008

5 Star

Great - the students really got their teeth into it

Reviewer: Steven Diamond


Nov 16th, 2007

5 Star

I haven't used this yet but anything that makes electrons exciting can't be bad!

Reviewer: Ruth Northeast

CSI 5/11 -  Murder in the Park review

Nov 16th, 2007

5 Star

This was a great activity that prompted lots of discussion about flame tests and atomic structure. Students were also engaged in discussing the reliability of forensic data and how this could determine the guilt or innocence of a suspect.

It comfotably occupied 70min lesson for high ability Y10 students.

Reviewer: Prinsep Kate


Nov 5th, 2007

3 Star

Ran the firework bits as part of a Y8 G&T session. They liked the flame tests but the murder mystery bit was easy! Linked it with bicarbonate rockets and hydrogen balloons to show how the rockets lifted off.
Will try it again with Y11 for revision of atomic structure.

Reviewer: simon perry


Nov 5th, 2007

5 Star

Great application of real world science. My kids loved it!
Keep them coming!!!!


Reviewer: Kathy Benash

KS3 Science Club

Nov 1st, 2007

4 Star

Fun Activity, will only ise the chemistry of the fireworks and not all the details of electrons in orbits as it is beyond the ability of the group i am working with but a great way of doing the different flame tests.

Reviewer: Claire Speck


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