A crime occurred at an art gallery where a valuable painting was targeted but not stolen. Forensic scientists Billie and Dragon are investigating and finding fingerprints on the painting's frame. They learned that iodine vapor can reveal hidden fingerprints because iodine particles adhere to the oil residues left by fingerprints. Understanding particles and their behavior in different states of matter is important to forensic science investigations.

2. Activity 1: What was the crime? 4 Hello, and welcome to your forensic science work placement. I’m Dr Sherl, your mentor. You must be Billie, right? Yes, that’s me. I can’t wait to get started! I’ve seen lots of forensics on TV, but this is the real thing… I’ve paired you up with Dragon, our other trainee. Do you know what forensic scientists do? Engage Elicit Explore Explain Elaborate Extend Evaluate

3. 5 Activity 1: What was the crime? Absolutely right Billie! I hope you’re ready to start, because I’ve just received news of a major crime. A crime always leaves traces . Don’t forensic scientists use special techniques and try to find evidence to pin the suspect to the crime scene? Engage Elicit Explore Explain Elaborate Extend Evaluate

4. 6 Activity 1: What was the crime? Engage Elicit Explore Explain Elaborate Extend Evaluate It happened at an art gallery and it reminds me of a film. Watch this clip – it might give you some ideas.

5. 7 Activity 1: What was the crime? Police are reporting a strange break-in at a local art gallery. A rare and priceless painting seems to have been the target but the criminals may have escaped empty-handed; reports say the painting is still hanging in the gallery. A local police officer has told us that the case is being investigated by forensic scientists who are looking for clues to investigate. Engage Elicit Explore Explain Elaborate Extend Evaluate It happened at an art gallery… the newspapers are starting to report the story.

6. 8 Activity 1: What was the crime? There’s not much evidence so far – just a statement from the duty guard. You might find the crime scene drawing useful, too. Engage Elicit Explore Explain Elaborate Extend Evaluate One of the rooms with a priceless 17th-century painting looks like it’s been broken into. Here, take a look.

7. 9 Activity 1: What was the crime? SS1 Engage Elicit Explore Explain Elaborate Extend Evaluate

8. 10 Activity 1: What was the crime? SS2 This page may have been changed from the original Engage Elicit Explore Explain Elaborate Extend Evaluate

9. 11 Activity 1: What was the crime? So Billie, how can we find out what happened ? Engage Elicit Explore Explain Elaborate Extend Evaluate

10. Activity 1: What was the crime? 12 Engage Elicit Explore Explain Elaborate Extend Evaluate Yes – but it might have been tampered with. Maybe we should check if it has been touched. How can we do this? We have to figure out what the crime was. It must be something to do with the painting – but it looks fine!

11. Activity 1: What was the crime? 13 Engage Elicit Explore Explain Elaborate Extend Evaluate Just look for fingerprints, Billie. It’s easy – his fingerprints will be all over the frame! OK. But how can we find them?

12. Activity 1: What was the crime? 14 Engage Elicit Explore Explain Elaborate Extend Evaluate Whenever you touch a surface, you leave traces of oil from the ridges on your fingertips. These hidden fingerprints show up if you brush charcoal dust onto the prints. The charcoal sticks to the oil.

14. Engage Elicit Explore Explain Elaborate Extend Evaluate Activity 1: What was the crime? 16 This page may have been changed from the original Dr Sherl has lent me her book. It shows us how to use iodine to show up hidden fingerprints on the frame. This technique looks great – I’ll try it.

15. Activity 1: What was the crime? 17 Engage Elicit Explore Explain Elaborate Extend Evaluate Particles? What are they? And why do they matter to forensic scientists? Hmm. How does iodine show up the fingerprints? I think maybe iodine moves to the fingerprint, but how? It doesn’t look like it’s moved…and the lump of iodine doesn't get any smaller. Better ask Dr Sherl… OK Billie, I’ll give you a clue. It’s all to do with particles.

16. Activity 1: What was the crime? 18 Engage Elicit Explore Explain Elaborate Extend Evaluate If you take a solid and cut it in half again and again, you will eventually get a bit that is just too small to cut up. What would this piece look like if we could zoom in on it?

17. Activity 1: What was the crime? 19 Engage Elicit Explore Explain Elaborate Extend Evaluate Substances can exist in three forms: solid, liquid and gas. These are the states of matter. In each state, the particles are arranged differently , and move differently .

18. Activity 1: What was the crime? 20 Engage Elicit Explore Explain Elaborate Extend Evaluate If we transfer energy to or from the substance, its state changes.

19. Activity 1: What was the crime? 21 Engage Elicit Explore Explain Elaborate Extend Evaluate When iodine warms up, it doesn’t melt like most solids. It turns into a gas. This change is sublimation .

20. Activity 1: What was the crime? 22 Engage Elicit Explore Explain Elaborate Extend Evaluate I tried the iodine out and it worked! It showed up a couple of thumbprints on the front, and lots of fingerprints on the back. So we’ve got our man… Unknown prints Gallery owner’s prints Well, we’ve got some more evidence, but we still can’t be sure what happened …or who did it. And Dr Sherl keeps going on about how particles are so important to forensic scientists…What does she mean?

21. Activity 1: What was the crime? 23 Engage Elicit Explore Explain Elaborate Extend Evaluate SS3 Have a think about it, Billie. Without particles, you and Dragon would never have found the fingerprints. Explain why . Now can you explain why particles are so important to forensic scientists?

22. Picture Slide Credit Picture credits Activity from the Forensics unit © Association for Science Education and Centre for Science Education 2010. Teachers and others who download this material may use it freely within their institution. For any other usage consult the upd8 team, upd8@ase.org.uk ASE and upd8 are not responsible for any revision that may be made to the material after it has been downloaded.