Separating mixtures Flashcards
A student is given a mixture of salt and sand
Describe a method that can be used to separate the mixture to obtain dry sand and salt crystals
[6 marks]
1) Pour the mixture into a beaker
2) Pour 20cm3 of distilled water into the beaker and stir using a stirring rod
3) Then filter the mixture uisng a funnel and filter paper
4) The residue will be sand, ry the sand residue in a warm over to obtain dry sand
5) Pour the rest of the solution into an evaporating basin.
6) Prepare a water bath by heating a beaker of water over a bunsen burner and place the evaporating basin onto the water bath to allow the water from the filtrate to evaporate
7) Then leave the solution in a cool area to cool and form crystals
8) Then remove the crystals and pat them dry using filter paper
In distillation, three liquids are separated
Suggest why after a few minutes, one of the liquids is already being collected in the beaker
[1 mark]
It has the lowest boiling point
Alcohols are flammable
Suggest how a mixture of alcohols should be safeley heated to separate them
[1 mark]
Heat the mixture using a water bath
Why are alloys hard?
The different atoms are different sizes
This makes the layers distorted and
So the layers cannot easily slide over eachother
What is a mixture of metals called?
An alloy
In crystalisation suggest one way to ensure that all of the salt is fully dissolved in the water
Stir the solution
or heat the solution
Suggest a saftey precaution that students should take when doing practicals
Wear safety goggles
Why should the start line in chromatography not be drawn in ink?
The ink line will dissolve in the solvent
Why should the start line not be below the surface of the solvent
Because the inks drops will be dissolved in the solvent and wash off of the paper
How can you tell that two inks are the same from the results of a chromatography?
The inks will have the same Rf values
Give two advantages of gas chromatography compared with paper chromatography
More accurate
More sensetive
