chemical analysis Flashcards
pure substances
a single element or compound not mixed with any other substance
pure substances
diamond, pure water and gold
mixtures
crude oil, air and sea water
melting point
when a solid changes into a liquid
boiling point
temperature at which a liquid changes into a gas
formulation
mixture that has been designed as a useful product
formed by mixing together several different substances in carefully measured quantities to ensure product has required properties
alloy
mixture of two or more elements where at least one is a metal resulting mixture has metallic properties
formulation made my mixing measured quantities to ensure the alloy has specific properties required for its use
medicine
tablets are formulations of the active drug along with ingredients such as corn starch to bind the tablet together and a lubricant to make it easier to swallow
fertilisers
contains mixtures of nitrogen, phosphorus and potassium compounds. Different formulations are suitable for different plants
mixture
two or more substances mixed together
solute
the substance which dissolve in the solvent
solvent
the liquid in which the solute dissolves
solution
a solute dissolved in a solvent
soluble substances
one which will dissolve in a solvent
filtration
used to separate an insoluble solid from a liquid
filtrate
the liquid which passes through the filter during filtration
residue
the solid that remains on the filter paper after filtration
evaporation
change of state from liquid to gas
to remove soluble substance from a solution( remove salt from salt water)
saturated solution
one in which no more solid can dissolve at that particular temperature
crystallisation
involves heating the solution to boil off some solvent, creating a saturated solution
this saturated solution is the cooled.
The dissolved solid becomes less soluble and cannot remain dissolved. it crystallises out of solution. The crystals may then be separated from saturated solution by filtrate
simple distillation
used to separate a solvent from a solution
condensation
the change of state from gas to liquid when cooled
anti bumping granules
added to promote smooth boiling
distillate
the liquid that is cooled from vapour and is collected during distillation
fractional distillation
used to separate miscible liquids which have different boiling points
immiscible liquids
liquids that do not mix well together by from two distinct layers e.g. oil and water
miscible liquids
liquids that mix together like ethanol and water
how fractional distillation works
mixture of miscible liquids is heated
liquid boil one by one as temperature rises
each vapour rises up and condenses in the fractionating column, falling back down to the mixture in the flask
only the vapour from the liquid with the lowest boiling point passes into the condenser, condenses into a liquid , and is collected as a fraction
how does fractional distillation provide better separation
the evaporated liquids below their melting points do not reach condenser- they condense on the glass beads in the fractioning column and return to the flask
chromatography
used to separate mixtures of soluble substances in a solution, e.g. inks and dyes
chromatography method
using a pencil, draw a base line on chromatography paper, around 1 to 2cm from the bottom
use pencil as it will not dissolve in solvent and interfere with results
using a capillary place a spot of substance to be analysed on base line.
. when dry add another spot on top to make it concentrated
place paper in beaker with solvent at bottom
the pencil line and spots must be above level of solvent so that the spots do not dissolve into the solvent in the beaker
solvent travels up paper by
when solvent has reached the top, take paper out of solvent and mark level solvent has reached, known as solvent front
leave paper to dry
mixtures should have separated into different components, seen as spots on the paper
mobile phase
stationary phase
water
paper
relative attraction
substances with a stronger attraction to the solvent and are more soluble in it, move quickly and travel a long way up the paper
substances with a stronger attraction to the paper move slowly and only travel a short distance up the paper
Rf values
Rf= distance moved by substance
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distance moved by solvent
