SC3 - STATES OF MATTER, SEPARATING AND PURIFYING Flashcards
SOLIDS: arrangement and movement of particles
- ordered, neat rows
- vibrating about a fixed position
LIQUIDS: arrangement and movement of particles
- random arrangement, some particles touch
- particles roll over each other
GASES: arrangement and movement of particles
- random arrangement, spread far apart
- flying around with high energy
state change: gas -> liquid
condensation
state change: liquid -> solid
freezing
state change: solid -> liquid
melting
state change: liquid -> gas
evaporation / boiling
state change: solid -> gas
sublimation
describe state changes on a heating curve
- graph shows temperature + time
- state changes are shown as horizontal lines as during this time, the energy is used to change state and not temperature
mixture definition
mixtures contain substances which are not chemically combined and can be separated
pure material definition
pure materials contain only one substance
impure materials definition
impure materials contain a mixture of substances
melting point of pure substances
sharp melting point
melting point of impure substances
a range of melting points
describe filtration
- filtration can be used to separate an insoluble solid from a liquid or from a solution
- filtration works because the large particles of the residue cannot pass through the small gaps in the filter paper
describe crystallisation
- crystallisation can be used to separate a soluble solid from a solution of that solid
- in crystallisation of a solution the SOLVENT is evaporated from a SOLUTION to leave the SOLUTE
describe chromatography
- used to separate a mixture of substances eg. a mixture of different dyes in an ink
- the mixture separates because some dyes are more attracted to the solvent and some are more attracted to the paper
chromatography: Rf value equation
Rf = distance substance has travelled / distance solvent has travelled
hazard definition
what is dangerous eg. bunsen burner
risk definition
the harm which the hazard could do eg. hair could catch fire
control measure definition
how you could make it safer (minimise the risk) eg. tie your hair back
describe simple distillation
- used to separate a solvent from a solution eg water from a water based ink
- the solution is evaporated and the gas condenses back into a test tube
describe fractional distillation
- used to separate a solvent from a mixture of solvent
- the solution is evaporated and the gas condenses through a condenserback into a test tube
stages of filtration (4)
- course filtration
- sedimentation
- fine filtration
- chlorination
describe stage 1 of water purification - course filtration
the water is filtered to remove twigs etc.
describe stage 2 of water purification - sedimentation
a chemical is added which makes particles sink to the bottom
describe stage 3 of water purification - fine filtration
the water is filtered through sand
describe stage 4 of water purification - chlorination
chlorine is added to kill bacteria
distilled water vs sea water vs mineral water
DISTILLED WATER: pure water and contains NO dissolved salts. used for laboratory tests. uses a lot of energy, too expensive to be used for drinking water
SEA WATER: contains dissolved sodium chloride
MINERAL WATER: contains many dissolved salts
