CSI Lesson 4

We did a flame test!

1. How and what is a flame test used for in "crime scene investigations/forensic science"?
2. If there are more than one trace metal present, is it the flame test still suitable technique to identify the trace metals?
3. Is flame test sufficient to identify the trace metal(s) present?
4. What is "Mass Spectrometer"?

Answer Q1: It is used to separate and identify the componential elements in a sample from a crime scene. Different metals change the colour of the flame when they are heated. Flame tests are based on the physical and chemical principle that atoms return to their normal energy state by giving off excess energy in the form of light when heated by a flame. Each element has its own characteristic light frequency. In this way, flame tests help to identify essential elements present at a crime scene and hence, narrow down the search for the perpetrator.

Answer Q2: No. More than one trace metal would result in a flame comprising of a mixture of colours, making it difficult to identify the various trace metals involved.

Answer Q3: No. The test cannot differentiate between all elements as some produce the same flame colour while others do not change the flame colour. Also, impurities or contaminants can affect the test results. For example, Sodium is present in most compounds and could influence the colour of the flame.

Answer Q4: It is an instrument that can measure the masses and relative concentrations of atoms and molecules by making use of the basic magnetic force on a moving, charged particle.