c2.1 Flashcards
(24 cards)
element
a substance containing only one type of atom
compound
a substance containing two or more different types of atoms chemically bonded
conservation of mass
no atoms are lost or made during a chemical reaction
mixture
different substances or elements that are not chemically bond, eg- solutions
solution
when one substance dissolves into another
solute
substance that dissolves
solvent
substance it dissolves in
filtration
removes large insoluble substance (in solid state) from a liquid - sand from water
requires:
- funnel
- filter paper
- conical flask
- residue
- filtrate
sand and water
grains of sand too big to pass through filter paper - stays in filter paper and builds up as residue
water molecules small enough to pass through filter paper - filtrate
crystallisation
leaves behind crystals of solute if heated gentle
requires:
- bunsen burner
- water
- evaporating basin
heat solution gently (solvent evaporates) until becomes saturated solution (no more solute can be dissolved at that temp)
crystals will start forming, let solution cool slowly
as solution cools, solubility of solute decreases - more crystals formed
filtration can be used to remove remaining solution + dry drying them/patting them with filter paper
distillation
separates solvent from solution
relies on solvent having lower boiling point
requires:
- condenser
- flask
- bunsen burner
solution heated, solvent evaporates first, escapes in gas state and goes through condenser, condenser cools it back to a liquid, poured into new flask. Solvent and solute separated
good for purifying
fractional distillation
separates two or more substances from a mixture in liquid state
relies on each substance having different boiling point
requires:
- fractionating column
- flasks
- condenser
substance with lowing boiling point vaporizes first, going through the fractionating column (hotter at bottom cooler at top)
vapours then condense at different levels depending on boiling points
separate into different flasks
chromatography
stationary + mobile phases
paper chromatography
separates coloured substances
stationary - paper
mobile - solvent
starting line drawn in pencil (so doesnt smudge) just above water
thin layer chromatography
stationary - thin layer of silica or alumina powder
put solvent in chromatography tank to a depth of 1cm
add small amount of sample to base line, taking care not to damage powder on plate
let solvent travel through powder and take plate out before it reaches the top
analyse pattern of coloured spots (chromatogram)
component travels further up = stronger bonds with mobile phase
component doesnt travel as far = stronger bonds with stationary phase
starting line drawn in pencil (so doesnt smudge) just above water
gas chromatography
stationary = silica or alumina powder packed into metal column
mobile = unreactive carrier gas such as nitrogen
sample turned into gas state when inserted into column
carrier gas pushes sample through column
different components take different times to travel through column depending on how strong the bonds made with the stationary phase are
detector sends signal to computer as each sample leaves the column
chromatogram produced
rf value
distance travelled by substance/ distance travelled by solvent
pure substance
high melting point
specific melting point
impure substance
lower melting point
range of melting points
test if substance is pure using chromatography
can use paper and tlc and gas
tlc better because
- quicker
- more sensitive so smaller sample can be used
- larger range of stationary phases and solvents to choose from
insoluble and soluble substances
dissolving followed by filtration
a solute dissolved in a solvent (a solution)
crystallisation to obtain solute
simple distillation to obtain solvent
two or more substances in a liquid
fractional distillation
coloured soluble substances
paper chromatography or tlc chromatography
