C12 - experiential techniques & chemical analysis (Physical, chemical and separation techniques) Flashcards
define physical change
involves a change in substance’s form
define chemical change
involves making a new substance and change in energy
what measures time and units
-stop watch
-seconds
what measures temperature and units
-thermometer
-degrees Celsius
what measures mass and units
-mass balance
-grams
what measures volume in liquid and units-1
-burette
-cm^3
what measures volume in liquid and units- 2
-volumetric pipette
-cm^3
what measures volume in liquid and gas and units
-measuring cylinder
-cm^3
what measures volume in gas and units
-GAS syringe
-cm^3
define pure
a substance that contains a single element or compound, not mixed with any other substances
define impure
a substance that contains more than 1 element or compound, mixed with other substances
define solvent
substance that dissolves a solute
define solute
a substance that is dissolves in a solvent
define solution
mixture that is made up of 1 or more substances
define mixture
contains 2 or more substances not chemically combined
define votality
how easily a substance evaporates (changes from liquid to gas)
define solubility
how easily a substance dissolves
is a solution a new product
no
define saturated solution
solution containing maximum concentration of a solute dissolved in a solvent at a given temp.
(no more solute can dissolve in it)
opposite of saturated
diluted
define residue
a substance that remains after distillation, evaporation or filtration
define crystallisation
when a liquids that contains soluble solute is evaporated to leave the soluble solute behind
define filtrate
solution at pass through a filter paper
explain diluted, concentrated, saturated
diluted:
-little solute
concentrated:
-moderate solute
saturated:
-max solute
what must the solute be for filtration and why
insoluble so it’s too big to pass through the holes in the filter paper
names 6 separation techniques
-simple distillation
-fractional distillation
-filtration
-evaporation
-crystallisation
-chromatography
define evaporation
turning the liquid into gas to be lost from the substance using heat
define filtration
passing solution over a filter paper and collecting the filtrate
define immiscible and miscible
-immiscible- liquids that don’t mix
-miscible- liquids that mix
how to get
-insoluble solute from mixture of soluble and insoluble solute/ solution with insoluble solute
filtration
how to get solute (soluble or insoluble) from solution
evaporation
how to separate 2 immiscible liquids
separating funnel
how to
-at least 2 miscible liquids
-solutions with liquids that have close boiling points to each other
-fractional distillation
how to get solvent from soluble solute
-simple distillation
how to separate 2 or more soluble solutes
-paper chromatography
why does filtrations work to separate insoluble solute from solute
insoluble solute cannot pass through filter paper and is left as an residue. soluble solutes can pass through the paper
why does evaporation work to get a solute from a solution
the solvent must have a lower boiling point than the solute
why does a separating funnel work to separate 2 immiscible liquids
-there is a difference in density
why does fractional distillation work to separate 2 miscible liquids
there is a difference in boiling points between the liquids
why does simple distillation work to separate solvent from solute
there is a difference in boiling points between solvent and solute
define chromatography
method of separating mixtures of soluble substances
define stationary phase
the paper in paper chromatography
define a chromatogram
result of separating the components of a mixture by chromatography
define the mobile phase
solvent in paper chromatography
define Rf value
retention factor
formula for Rf value
distance of travelled by solvent (solvent front)
(in decimal)
define solvent front
-furthest point the solvent travels
-for calculating Rf value
define baseline
line that is drawn in an insoluble substance and where the inks are placed
meaning of composition
what it’s made up of
the more it’s attracted to stationary phase, the ?
closer it is to baseline
the more soluble, the ?
further it travels up the paper
how much must the solvent be
below the baseline but touches the paper
what is the baseline drawn in and why
-pencil
-it is insoluble so it doesn’t travel up the paper
where do you measure how far the solute travelled
the middle of the spot
what happens if the solvent is above the baseline
solutes will just dissolve in liquid and not move up
where is the water put from in the condenser of distillation
the lower part down the condenser
3 ways purity of a substance can be assessed
-melting point
-boiling point
-chromatography
what does impurities do
-lower melting point
-increase boiling point
(melts over a greater range)
what is the difference between melting and boiling points of pure and impure substances
pure- has a sharp melting/ boiling point
impure- melts/ boils over a range
how many spots will a pure and impure substance have on chromatography
pure- 1
impure- more than 1
describe how to obtain a pure dry sample of a substance from a chromatogram
-isolate substance
-dissolve in solvent
-evaporate solvent
note: learn how to draw apparatuses
do permanent markers work for chromatography
no, it’s insoluble
-substance melts at 96 but melts completely at 113.
-date book says melting point of substance is 116.
-explain is substance is impure or not
-impure
-melts over a range
-melting point is different to data book value.
describe how to get a pure dry sample of a compound from a chromatogram
-isolate the substance
-dissolve the compound in a solvent
-evaporate the solvent
explain if a substance is impure or pure
-range it melts over
-different from data book value
2 processes to obtain pure sodium chloride from mixture with insoluble sulfer and sodium chloride in water
filtration and crystaillisation
2 processes to separate water from insoluble chalk and soluble salt
filtration and crystalisation
apparatus to measure volume of gas
gas syringe
-colorings S,T and U are -soluble
-use chromatography in candy to find them
measurements?
-height of each spot and height of solvent front
-compare Rf values of colourings and candy
-colorings S,T and U are -soluble
-use chromatography in candy to find them
method?
-crush candy and dissolve in solvent
-pencil line on paper
-add each colours and sweet solution to paper
-remove paper before solvent reaches the top
-mark solvent line and find Rf value
-colorings S,T and U are -soluble
-use chromatography in candy to find them
use of results?
-if candy spots are same height up paper as S, T, S, then substances are in the candy
-if same ratio of spot distance to solvent front distance (Rf value), substance is in candy