states of matter Flashcards
paper 1
negatives of the particle model
- inaccurate
- particles are not solid, inelastic or spheres
- they are either atoms, ions or molecules
- does not include how strong the forces between them are
what is a liquid and a solid that does not dissolve (insoluble)
mixture
what is a liquid and soluble solid
solution
what is filtration
separating insoluble solids with liquids in mixtures
example of how to filter
using filter paper in a filter tunnel
what are the 2 ways of separating a solution
evaporation or crystallisation
benefits and negatives of evaporation
its quick and easy but some solids decompose when heated, called thermal decomposition
what is crystallisation
the solution is placed in an evaporating dish and heated, like evaporation, but we use a water bath instead of a bunsen burner. when crystals begin to form, we stop heating and let it cool then filter out the crystals and dry them
why do we use crystallisation instead of evaporation
to stop thermal decomposition
what is simple distillation
separating a liquid from a solution
what equipment is needed for simple distillation
- a flask containing the solution
- a bung at the top of the flask with a thermometer through it
- a condenser consisting of a main pipe and a water jacket
- a beaker at the end of the condenser
- some form of heater, e.g bunsen burner
how do we perform simple distillation
- heat up mixture so the desired liquid evaporates
- the pressure forces the gas down the condenser
- the cold water in the water jackets cools the gas so it condenses to liquid
- condensed liquid runs down the pipe and is collected in the beaker
why do we use fractional distillation
if the boiling points in the solution are similar, more than 1 will evaporate in simple distillation so we use fractional
what is the difference of equipment in fractional distillation
rather than evaporating straight into the condenser, the gas has to pass through a fractionating column
what are the 2 key features of a fractionating column
- its full of little glass rods with a high surface area
- since the column is so tall, its cooler at the top than it is at the bottom, meaning the substances with higher boiling points will cool before reaching the condenser
what is chromatography
general technique to separate substances in a mixture so we can identify them
how do we perform paper chromatography
- take filter paper and use a pencil to draw a line near the bottom of the sheet called a baseline
- add your substance of ink to the pencil line
- get a beaker and fill a shallow amount of your solvent
- place the paper into the solvent, careful not to submerge the baseline
- wait for the solvent to move up the paper
- the different dyes in the ink will move up with it at different rates, separating out
- insoluble solvents stay at the baseline
- take the paper out and leave to dry, then observe the different colours called a chromatogram
what two phases can we use to describe why the solutes move at different rates
the mobile and stationary phase
what is the mobile phase
the substance the molecules can move in (liquid or gas) or solvent used
what is the stationary phase
a substance the molecules cannot move in ( a solid or really thick liquid) e.g paper
what determines how fast the substances move
how long they spend in the 2 phases
e.g. the ones at the top of the paper spent more time in the mobile phase and at the bottom, more time in the stationary phase
what else determines how far substances move up the paper
how long we perform the experiment
what do we measure instead of the distance travelled
the ratio or Rf value
how do we calculate the Rf value
distance travelled by substance/ distance travelled by solvent
