2.5 What is this thing called Stoichiometry?

Learning Intentions (L.I)

At the end of this video, you should be able to:

  • describe how centrifugation works and state the physical property of the mixture it relies on.
  • list several applications of centrifugation to separate mixtures.
  • define key subject specific terminology (SST terms): insoluble solid, soluble solid, solution, precipitate, supernatant liquid, miscible and immiscible liquids and decantation.
  • describe the technique of decantation and describe why it might be used inthe lab with examples.

Success Criteria (S.C)

You should be able to do the following to illustrate how you know the L.I:

1) Correctly identify and name the physical property of the mixture that the separation technique relies on for effective separation.

2) Explain how the technique of centrifugation works. What force causes the materials in the mixture to move downwards and


3) Use several examples of where centrifugation is used and be able to recall those when asked.

4) Define, explain with or without a diagram the SST above.

5) Describe correctly the technique of decantation.


In this section we dive into the first two separation techniques:

  • Centrifugation and
  • Decantation

These two techniques are common the lab and in industry to quickly separate mixtures. For decantation, you may have done this to separate insoluble solids from a liquid after it has been settled OR in separating two liquids that are immiscible.

The video looks are these processes and gives you real life examples of these techniques which are based on the physical properties of size, density and solubility.

Resources & Ideas

  • Complete quiz to check your understanding
  • Make some flash cards (remember to make them based on questions, diagrams etc). Watch the making Flash card video in the study techniques course if needed or the YouTube video below.
  • Highlight your notes using the Traffic Light technique. This technique allows you to identify quickly what is OK, what needs further attention.