C1 Mixtures and Chromatography (page 100) Flashcards
Is there a chemical bond between the different parts of a mixture?
No.
unlike in a compound
Are mixtures easily separated?
yes
(not like compounds)
What are the parts of a mixture?
they can be either elements or compounds.
How can parts of a mixture be seperated out?
by physical methods, such as filtration, crystallisation, simple distillation, fractional distiallation, and chromatography
air is a mixture of gasses, and can be seperated out easily. What is the mixture of air gasses?
mainly nitrogen, oxygen, carbon dioxide and argon.
what is meant by a physical method of separating a mixture?
a physical method is one that doesnt involve a chemical reaction, so it doesnt form any new substances
What is Crude oil a mixture of?
different length hydrocarbon molecules
The properties of a mixture is what?
just a mixture of the properties of the separate parts
the chemical properties of a substance aren’t affected by it being part of a mixture.
eg; a mixture of iron powder and sulfur powder will show the properties of both, iron and sulfur. It will contain grey magnetic bits of iron and bright yelllow bits of sulfur. (iron and sulfur mixed together, but not reacted)
What is Chromatography?
it is a laboratory technique for the separation of a mixture into its components.
What is the process of Chromatography to separate different dyes in an ink?
1) draw a LINE near the bottom of a sheet of FILTER PAPER (use a pencil to do this - pencil marks are insoluble and won’t dissolve in the solvent).
2) Add a SPOT of the ink to the line and place the sheet in a beaker of solvent (eg water)
3) the solvent used depends on what’s being tested. some compounds dissolve well in water, but sometimes other solvents, like ethanol, are needed.
4) Make sure the ink isn’t touching the solvent - you don’t want it to dissolve into it.
5) place a lid on top of the container to stop the solvent evaporating.
6) the solvent seeps up the paper, carrying the ink with it.
7) Each different dye in the ink will move up the paper at a different rate so the dyes will separate out. Each dye will form a spot in a different place - 1 spot per dye in the ink.
8) if any of the dyes in the ink are insoluble (won’t dissolve), in the solvent you’ve used, they’ll stay on the baseline.
9) When the solvent has nearly reached the top of the paper, take the paper out of the beaker and leave it to dry.
10) The end result is a pattern of spots called a chromatogram
What is Chromatography useful for in real life?
It is used to test athletes urine samples for performance enhancing drugs, and also to test unknown substances at crime scenes.
Explain why you shouldn’t use a pen to draw a line on the filter paper for paper chromatography?
The pen ink might dissolve in the solvent and rise up the filter paper.
