Unit 1 – Day 2

1. Unit 1 – Day 2 Spectroscopy

2. Qualitative Analysis • Spectroscopy is a type of qualitative analysis. • Qualitative analysis uses chemical and physical properties to identify an unknown substance. • Example: What qualities distinguish different types of berries?

3. Spectroscopy • Spectroscopy is a process where we supply energy to a gas in order to excite its electrons. • When the electrons are excited they jump to higher orbits. • When they fall, they lose energy as light.

4. Spectroscopy • This light can be seen using a spectroscope. • The spectroscope splits coloured light into distinct lines, depending on how much energy it has. • Usually, these lines are blended to form colours. (White is all colours mixed together)

5. Spectroscopy • If an electron falls from a greater distance, it means it has lost more energy. • This means the electron releases higher energy light. • The colour tells us the energy. Violet is high energy, and red is low energy.

6. Spectroscopy as Qualitative Analysis • Each element has a different number of electrons, arranged in a different way. • Because of this, each element produces a different spectrum when excited. • If we want to identify an unknown gas, we can just compare its spectrum to identify it!

7. Identify the Unknown

8. Why lines? • The lines exist because electrons can only exist in specific orbits. • The more possible “jumps” the more lines. • Example: Hydrogen has only one electron, so it can only produce a few lines.

9. Continuous Spectra • Some spectra are continuous, like light from the sun or a fire. This indicates that the light is not produced by electrons, but by heat.