Introduction
If you place a match in water, the flame is extinguished, but when the same match is placed in alcohol it burst into flames. The reason comes from the structure of the molecules and the strength of the attractions that hold the molecules within the liquid phase.
Previously, you learned that some substances are flammable based on their flash point.
In this lesson, we will learn more about flammable liquids, including how they are identified, recovered, and analyzed.
Following successful completion of this lesson, students will be able to...
- Describe methods to identify, collect and analyze ignitable liquids.
- Explain how gas chromatography and mass spectrometry are used to identify ignitable liquids.
Essential Questions
- What type of residue do ignitable liquids leave behind?
- How can residues be recovered and analyzed?
Enduring Understandings
- An exchange of material will occur whenever someone is at a crime scene (Locard's Exchange Principle). Materials left behind (or carried away) from the crime scene as well as markings and impressions from those items can be linked to an individual or item.
- Evidence must be collected in a specific and strategic manner, as well as systematically documented, to ensure that no tampering or contamination occurs.
The above objectives correspond with the Alabama Course of Study: Forensic Science and Crime Scene Investigation standards: 37.