Separation techniques Flashcards
What are the differences between elements, compounds and mixtures?
Element: A pure substance consisting of one type of atom only ( Oxygen, Hydrogen)
Compound: A substance made of 2 or more elements chemically joined together. (Water, CO2)
Mixture: 2 or more substances mixed together but NOT chemically joined together. (Tea and milk)
Describe what happens to sugar when you add it to a cup of hot tea.
The sugar dissolves in the hot tea. The solid sugar particles break apart from each other and become weakly bondedto the liquid particles in the tea
What is a solute?
A solute is a substance that can be dissolved. An example would be sugar or salt.
What is a solvent?
It is a substance which has the ability to dissolve another substance. An example of a solvent is water or nail polish remover (Acetone).
How could you separate salt from sea water?
Sea water can be filtered and then evaporated.
Filtration gets rid of any solid particles from the solution.
Evaporation will cause the water to leave the salt solution and salt will be left behind.
Describe what chromatography is.
It is the separation of 2 or more solids in a solution.
Heavier solids will travel less distance and will stay near the bottom of the chromatogram.
A pencil line is used to show where the original sample was placed.
Draw the following particle models:
- Salt dissolved in water
- Sugar mixed in sand
- 2 elements mixed together
Look on sheet
Explain how distillation can separate ethanol (alcohol) from water.
Ethanol is a liquid. When it is in a solution with water it can be hard to separate.
By distilling it, Water and ethanol have different boiling points, we can extract ethanol from the solution.
Heating the solution up, ethanol will boil first and condenses as it passes through the condenser.
What is a saturated solution?
A solution which cannot dissolve any more solute.
What is a Liebig condenser? How does it work?
It is a condenser which has cold water flowing around an inner tube where steam passes through. The steam cools down, condenses and collects at the end of the condenser.
What is filtration?
When you use filter paper to separate solids from a mixture in a liquid.
Draw a sketch graph of what you would expect a pure substance to produce when heated.
This chromatogram is from Suspect A and a sample from the crime scene. What can you conclude? Explain your answer.
Look at diagram on revision sheet
Look at revision mat for answer
Suspect A did not commit the crime because the sample taken from him/her does not match the sample from the crime scene as not all of the marks on the chromatogram line up at the same points. Only the red is a common solute.
