S1.1 Flashcards
4 main properties of matter
mass, volume, motion, particles
what can all matter be split up into?
pure or a mixture
what can pure substances be split into?
either elements or compounds
what can a mixture be split into?
heterogenous (non-uniform composition) or homogeneous(uniform composition)
define an atom
smallest particle of an element to show the characteristic properties of that element
define an element
a pure chemical substance composed of atoms with the same number of protons in the atomic nucleus
define a compound
substance made by chemically combining 2 or more elements in a fixed ratio of atoms
define a mixture
components aren’t chemically bonded and not in a fixed ratio so components retain their individual properties
homogeneous
components are in the same state
heterogeneous
components are in different states of matter
what is STP?
273K and 100kPa/1ATM
what is the relative atomic mass?
a weighted average of an element’s isotopes(thats why they’re decimals)
what is filtration used for?
to separate an insoluble solid from a liquid
what can you do if the solid particles are very small for filtration?
process can be done under reduced pressure in a Buchner flask using a vacuum pump
when can evaporation/recrystallisation be used?
if only 1 of the components of the mixture is soluble in a solvent like water/ethanol or in a non-polar solvent like hexane
describe the process of evaporation/recrystallization
1) mixture can be warmed with the solvent to dissolve the soluble component
2) solution is filtered to remove undissolved solid particles and solvent is evaporated to leave solute behind
3) solid can be purified by dissolving in a heated solvent and leaving solution to stand so crystals are formed
4) impurities remain in solution
5) after filtering, crystals can be washed with small amount of cold solvent and dried
what is a separatory funnel used for?
to separate 2 immiscible liquids
how does using a separatory funnel work?
1) mixture is shaken with stopper on and allowed to stand
2) when 2 layers have formed, stopper is removed
3) more dense lower layer run off by opening the tap
what is distillation used for?
to obtain a pure solvent from a mixture(eg seawater)
how does distillation work?
the volatile solvent boils to form a gas which is condensed and collected
what can the distillation apparatus be rearranged for?
for reflux apparatus which is used to allow volatile compounds to react together when heated for a period of time, with no loss of compounds through evaporation or voiling
how to check the m.p. of a substance to see if it is pure or impure?
1) sample placed in a small m.p. tube
2) either use a commercial m.p. apparatus
3)or attach it to a thermometer in an oil bath that is gradually heated
what is paper made of?
mainly cellulose fibres which contains lots of hydroxyl groups making the paper polar and water molecules hydrogen bond to these groups so ‘dry’ paper has 10% water which acts as the stationary phase
how does thin-layer chromatography work?
uses a thin layer of solid egg alumina Al2O3 or silica SiO2 on an inert support like glass; works by adsorption but alumina and silica have a high affinity for water so separation happens by partition with water as the stationary phase
what is one advantage of thin-layer chromatography over paper?
each of the separated components can be recovered pure
when does a solid melt?
when the vibration is sufficient to overcome the forces holding the lattice together
when does a liquid boil?
when the pressure of the vapour is equal to the pressure above the liquid
