Topic 2 Methods Of Seperating And Purifying Substances Flashcards Preview

Chemistry > Topic 2 Methods Of Seperating And Purifying Substances > Flashcards

Flashcards in Topic 2 Methods Of Seperating And Purifying Substances Deck (20):

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



The liquid in a locution



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