Topic 3 - States Of Matter & Methods Of Separating And Purifying Substances Flashcards
filtration
process used to separate a soluble substance from an insoluble substance
crystallisation
when solutes are separated from a solution by evaporating the solvents to leave the solutes behind
rf value
distance moved by the spot / distance moved by the solvent
distillation
to purify a liquid by doing evaporation followed by condensation
what are the 3 states of matter
liquid, solid, gas
particle model
a diagram that explains state changes in a substance in terms of the arrangement, movement and energy stored in its particles
what is the movement like in a gas
fast in all directions
what is the movement like in a liquid
move around each other
what is the movement like in a solid
vibrate in a fixed position
what’s the arrangement of particles in a gas
random and far apart
what’s the arrangement of particles in a liquid
random and close together
what’s the arrangement of particles in a solid
regular and compact
what is a state change
a physical change of matter
what happens to the particles in a state change
the particles do not change, only their arrangement, movement and amount of stored energy
how are particles attracted to another
by weak forces of attraction
how do you change from a solid to a liquid
melting
how do you change from a liquid to a gas
evaporation and boiling
how do you change from a gas to a liquid
condensing
how do you change from a liquid to a solid
freezing
how do you change straight from a gas to a solid without passing the liquid stage
deposition
how do you change straight from a solid to a gas without passing the liquid stage
sublimation
what needs to happen for these weak forces of attraction to be overcome (solid -> liquid)
energy must be transferred from the surroundings to the particles
what needs to happen for these weak forces of attraction to form (liquid -> solid)
energy must be transferred from the particles to the surroundings
how can you predict the state of a substance
if you know its temperature, melting point and boiling point
what state is the substance of its below the melting point
a solid
what is the state of a substance if it’s above melting point but below boiling point
a liquid
what state is the substance if it’s above boiling point
a gas
pure substance
an element or compound made up of one type of particle
tell me about the composition of a pure substance
- cannot be changed
- is the same in all parts of the substance
- only contains one substance
what does a mixture contain
elements and/or compounds that are not chemically joined together (doesn’t have a fixed position)
physical property
how a substance responds to forces and energy (something you can see)
solute
a substance that has dissolved in a liquid to make a solution
solvent
the liquid in which a solute dissolves to make solution
what sized crystals will be made of it forms slowly
bigger crystals
what sized crystals will be made of it forms quickly
smaller crystals
how to filter solution in the laboratory
- a filter funnel is lined with filter paper that has holes in in
- the solvent and solutes pass through the fine holes to form the filtrate
- bits of insoluable substances cannot fit through the holes and so leave a residue
how to crystallise a filtrate
- a Bunsen burner is placed under boiling water
- the filtrate is placed on top of the boiling water
- this evaporates the filtrate carefully
- leaves behind crystals which can be scraped from the container
what’s a hazard in crystallisation and how do we reduce it?
the hazard is crystals spitting out
- reduce this by wearing eye protection, removing the Bunsen burner before the solution is completely dry and/or using steam to heat the evaporating basin gently
paper chromatography
simply technique that finds out which compounds the mixture contains
- a solvent moved along a strip of paper and it carries substances in the mixture at different speeds so they are separated
why do you need a condenser in a distillation apparatus
contains cold water that keeps the tube cool so that almost all of the vapour condenses and turns into a liquid
what is fractional distillation used for
to separate mixtures of liquids
what is simple distillation used for
to separate a solvent from a solution
in distillation, why is there bung at the top of the flask
so that no gas can escape
how does fractional distillation work?
- a fractionating column is fixed above the distillation flask (contains little glass rods)
- the hot vapour rises at the column
- Hot vaporises at the column heating up - thus creates temperature gradient (hotter at the bottom, cooler at the top)
- the fraction with the lowest boiling point (the same as or lower than the temperature) will reach the top of the column and the vapour will pass to the condenser
- if the boiling point is higher than the temperature, then it will condense when it hits the cool glass and drips back down into the flask
- if you keep heating, fractions with higher boiling points with them rise up the column and can be collected later
how does simple distillation work
- the solution is heated until it reaches its boiling point and the solvent evaporates
- the solvent is then condensed, and it turns back into a liquid and its collected as a pure liquid
solution
formed when a substance has dissolved in a liquid
filtrate
a solution passing through a filter
residue
material remaining in the filter after mixture has passed through it
sedimentation stage in producing safe water
small particles are allowed to settle to the bottom
filtration stage in producing safe water
particles are removed by passing the water through sand and gravel beds
chlorination stage in producing safe water
chlorine is added to the water to kill bacteria and other microorganisms
what stages are used to produce safe drinking water
1) sedimentation
2) filtration
3) chlorination
reason for chlorination
to kill bacteria
reason for filteration
to get rid of insoluble substances
how do you know when a food colouring has the greatest number of coloured substances
it will have greatest number of spots
mobile phase in chromatography
where molecules can move
stationary phase in chromatography
where the molecules can’t move
from solid to liquid to a gas what’s happening to the energy transfers
Energy is transferred from the surroundings to the particles
For a gas to a liquid to a solid what’s happening with the energy transfers?
Energy is being transferred from the particles to the surroundings
what state is the substance in if it’s below the melting point?
solid
What state is substance in between the melting point and the boiling point?
Liquid
What state is the substance in if it’s above boiling point?
Gas
What is the mobile phase in paper chromatography
The solvent
What is the stationary phase in paper chromatography
Solvent and substances move
What is the chromatogram in paper chromatography?
The paper with the separate components on it
if a substance is pure what does this look like on paper chromatography
there’s only one spot on a chromatogram
Why do some spots travel higher than other spots in paper chromatography?
Because more soluble compounds are carried up the paper faster than less soluble ones
Why do ants keep bumping granules improve the safety of the method?
Because they make the liquid boil more smoothly - small bubbles of vapour form on the corners of the granules and reduce the risk of the liquid boiling over
Why is distilled water more suitable than tapwater for doing a chemical analysis?
- Tapwater contains small amounts of dissolved salts which may react to form unexpected cloudy precipitates which may hide the correct result of the analysis
- Also the machines used for an analysis made a test results again leading to an incorrect conclusion
what is chemical analysis?
Process of identifying and quantifying the components of a sample to understand its nature and composition
