Paper 2 (8) Flashcards
Chemical analysis (also known as analytical chemistry) is about:
The instruments and methods we use to separate, identify, and quantify different substances.
In chemistry, a pure substance is a:
Single element or compound that hasn’t been mixed with any other substances
Give an example of a pure substance:
Distilled water
True or false? Pure substances always melt and boil at specific temperatures.
True
Pure water boils at 100°C, and freezes at 0°C.
A student is given an unknown, transparent, colourless liquid.
What 2 tests could be done to see if the liquid is pure water?
Boil it, and see if the boiling point is 100°C
Freeze it, and see if the freezing point is 0°C
A student tests the melting point of a sample of salol. The sample starts melting at 36°C, but it doesn’t melt completely until the temperature is 48°C. Is the sample chemically pure, or impure?
Chemically impure.
Pure substances melt at a specific temperature. As this substance melted over a range of temperatures, it must be impure.
Formulations are ________ that have been prepared using a specific ________.
mixtures
formulas
Formulations are made from ______ amounts of different _________, and each component has a particular _________.
precise
components
function
Give 2 that would require a formulation.
Medicines
Paints
Cleaning agents
Which techniques can be used to separate substances? Give 3
Filtration
Chromatography
Crystallisation
Distillation
If we test a substance for purity by measuring its boiling point, is that a physical test or a chemical test?
Physical
Chromatography is a chemical analysis technique used to ________ substances in a _______.
separate
mixture
What is paper chromatography used for?
To separate a mixtures of soluble substances in liquids
What is the name given for the pencil line in chromatography?
The baseline
Why should we use pencil for the baseline rather than pen?
Pen ink would dissolve in the solvent and move up the paper
