(seperation techniques)

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eden !!

Cards (26)

what does it mean if a substance is pure?
a substance is pure if it consists of only one type of compound or element.
what is a substance if more than one substance is present?
mixture
how can you test for purity using melting points?
every pure substance has a specific, sharp melting and boiling point, impure substances will melt over a range of temperatures, because they are effectively mixtures. you can use melting point apparatus
what is the purpose of simple distillation?
used for seperating out a liquid from a solution
what is an example of using simple distillation?
seperating pure water from seawater
what is a disadvantage of simple distillation?
you can only use it to seperate substances with very different boiling points, if you have a mixture of liquids with similar boiling points, you need a different method
how do you use simple distillation to seperate pure water from seawater?
Pour seawater into distillation flask.
Connect the bottom end of the condensor to a cold tap using rubber tubing.
Run cold water through the condesor to keep it cool.
Gradually heat the distillation flask.
The part of the solution that has the lowest boiling point (water) will evaporate.
Water vapour passes into the condensor where it cools and condenses
It then flows into the beaker, where it's collected.
what is the purpose of fractional distillation?
used for seperating a mixture of liquids
what is an example of using fractional distillation?
Separating crude oil into different fractions (such as gasoline, diesel, and kerosene)
what is the purpose of filtration?
used to seperate an insoluble solid from a liquid
how can filtration be used in purification?
solid impurities can be seperated out from a reaction mixture using filtration
what is the method of filtration?
put filter paper into a funnel and pour your mixture into it. The liquid part of the mixture runs through the paper, leaving behind a solid residue.
what is the purpose of crystallisation?
seperates a soluble solid from a solution
how do you crystallise a product?
Heat the solution gently in an evaporating dish.
At the point of crystallisation, remove dish from the heat and leave solution to cool.
The salt forms crystals as it becomes insoluble in the cold, highly concentrated solution.
Filter the crystals out of the solution, and leave them in a warm place to dry.
what are the two phases of chromatograpy?
mobile phase, stationary phase
what is the purpose of chromatography?
used to seperate a mixture of soluble substances and identify them.
what determines how fast a chemical moves through the stationary phase?
how it distributes itself between the two phases
when do the components in the mixture seperate out in chromatography?
as the mobile phase moves over the stationary phase, they all end up in different places in the stationary phase.
why do the components in the mixture seperate out in chromatography?
each of the chemicals in a mixture will spend different amounts of time dissolved in the mobile phase and stuck to the stationary phase
what does the amount of time the molecules spend in each phase depend on?
How soluble they are in the solvent.
How attracted they are to the stationary phase.
how do you calculate the Rf value?
distance moved by substance / distance moved by solvent
what happens to molecules with a higher solubility in a solvent?
they will spend more time in the mobile phase than the stationary phase, so they'll be carried further up the paper.
what are formulations?
mixtures of chemicals that are designed to create useful products.
what are examples of formulations?
fuels
cleaning agents
metal alloys
fertilisers
medicines
how is waste or groundwater treated?
sedimentaation: removing large pieces of insoluble waste.
filtration: removing finer pieces of insoluble.
chlorination: adding chlorine to kill any microorganisms.
how is seawater treated?
distillation: seawater is heated, pure water is evaporated and cooled to condense, leaving behind any salt and other waste.