Topic 2 Methods Of Seperating And Purifying Substances Flashcards
What is the difference between a pure substance and a mixture?
A pure substance consists of either 1 single element or 1 types of molecule
A mixture has multiple different elements and/or molecule, and all are not chemically bonded
Melting points of mixtures
Have multiple melting points due to the different substances melt at different temperatures
At pure substance’s melting point
The atoms vibrate more as they gain more energy and move apart slightly
Filtration can separate what mixtures
Mixtures with solids and liquids, e.g. sand in water
Crystallisation can separate what substances?
(Evaporation)separates liquids and solid which have been dissolved into the water, e.g. salt or sugar dissolved in water
How are substances separated by filtration?
There are small holes in filter paper, which allows the liquids through, but not the larger
Solvent
The liquid in a locution
Solute
The solid dissolved in a solution
How does crystallisation work?
As the solvent is evaporated, the solution becomes more concentrated until the saturated solution starts to deposit the solute and slowly more solute is attached to the crystals and they grow larger
What mixtures can be separated by chromatography?
Pigments in solutions such as ink can be separated by chromatography
What do pure substances look like on chromatography paper?
Pure substances have 1 dot with 1 pigment
What do mixtures look like on chromatography
Mixtures contain multiple different pigments which appear as different dots on the paper
How are substances separated in chromatography?
Different substances are separated because they have different amounts of solubility, which allows them to move further up the sheet with the water
How to calculate Rf value?
Distance travelled by solute/distance traveled by water
What is simple distillation?
Simple distillation is used to separate a single solvent from a solute in a solution, such as taking the water from saline water
What is fractional distillation?
Fractional distillation is used to separate multiple liquids from a mixture to separate crude oil
How does fractional distillation work?
Fractional distillation works because all of the liquids have different boiling points and so in the fractioning columns there are sections at different temperatures where the different substances will condense and be seperated
Why must water used in chemical analysis not contain dissolved salts
The salts could react with other chemicals being used an change the reaction
How can fresh water be produced from sea water?
Sea water can be distilled to get fresh water and salt
What are the steps needed to make fresh water suitable for drinking(3 main steps)
Reservoir, so the large bits can settle or float to the top, the water is extracted toward the bottom but up a bit so logs float to the top and larger silt sinks to the bottom
Filtration through sand then gravel, to remove smaller particles
Chlorination, to remove bacteria
