Seperation techniques Flashcards
What does pure mean?
How can we check?
A substance is pure if it is completely made up of a single element or compound
Every pure substance has a specific, sharp melting and boiling point. For example pure ice melts at 0c and pure water boils at 100c
Such as H20 or Al
How will impure substances like a mixture melt?
Over a range of temperatures
What is the difference between a pure substance and a mixture
A mixture two or more substances not chemically joined to gather but a pure sunstance only contains a single element or compoud
What is distilation?
Distilation is used to seperate mixtures that contain liquids
What is simple distilation?
Simple distilation is used for seperating out a liquid from a solution
Breifly explain simple distilation
As water starts to boil the lowest boiling point of the solution (could be water) starts to evapourate
The water vapour passes into the condenser (water jacket of cold water) where it cools and condenses
Then flows into the beaker where its collected
Eventually, you’ll end up with just the salt left in the flask.
What is fractional distilation?
It is used to seperate a mixture of liquids
What is the use of the fractionating colum?
Full of little glass roods which increase the surface area
Cooler at the top than the bottom
Therefor if the other substances of the mixture have a high boiling point they would also evaporate but those glass rods which are much cooler than their boiling point, they’d condense back into liquid form and into the flask
Is it easier or harder to seperate two liquids which have very similar boiling points
It is much harder so we might need to carry out several rounds of fractional distilation
Can seperation techniques seperate compounds
no
What is filtration?
Filtration is used to seperate a insoluble solid from a liquid
How does filtration work?
Pop some filter paper into a funnel and pour your mixture into it.
The liquid part of the mixture runs through the paper, leaving behind the solid residue
What is crystalisation
Crystalisation is used to seperate a soluble solid from a liquid
How does crystalisation work?
Pour the solution into a evapourating dish and gently heat the solution
Some of the water will evaporate and the solution will get concentrated
Once some of the water has evaporated or once you start to see crystals remove the dish from the heat and leave solution to cool
The salt should start to form crystals as it becomes insoluble in the cold highly concentrated solution
Filter the crystals out of the solutions and leave then to dry in a warm place such as a drying oven
What is evapouration?
Place our solution in a evapourating dish and place a on a tri pod.
Slowly heat it with a bunsen burner
This will cause the solvent to start to evapourate and the remaining solution to become more concentrated
After a whilr crystals will start to form because its so concentrated
Eventually all the solvent will disapear
A disadvantage of using evapouration
Some solids decompose when heated
Difference between crystalisation and evapouration
Crystalisation is slightly slower
Why do we draw our origin line in pencil ?
In chromotography
Because the pen ink could dissolve in the solvent and move up the paper
moving faster
What is the moblie phrase?
In chromotograpy
Substance that the molecules can move in
Liquid or gas
In paper chromotography it will be our solvent used
What is the satationary phrase?
In chromotograpy
A substance or material that a molecule can’t move in
Solid or thick liquid
In paper chromotograpy it’s the paper
moving slower
What will happen to a pure substance in chromotograpy
A pure substance won’t seperate our at all just a single spot
We’ll get specific Rf value
What is paper chromotography?
Paper chromotography allows us to seperate substances based on their solubilities
What will happen to a substance more soluble in the mobile phrase?
A substance which is more soluble in the mobile phase will spend more time in the mobile phase. This means it will move faster, and travel a further distance up the paper.
Which is the stationary phase in paper chromatography
the paper
A substance which is less soluble in the mobile phase will spend more time in the stationary phase, so move slower, and not travel very far up the paper.
Surface water
Lake, river
Easy to acess
Replaced frequently
Can dry up
Ground water
Aquifers
Permeable rock trap water
What does formulation mean?
Formulations are mixtures that have been prepared using a specific formula
Formulations are made from precise amounts of different components, and each component has a particular function
(paints and medicine)
What is a solvent?
A liquid in which substances can dissolve
How does sewage treatment work?
Screening - The sewage is passed through gratings and meshes to remove anything large.
Sedimentation - The sewage is left to sit in a settlement tank, so that the heavier particles settle at the bottom as sludge, while the lighter particles settle at the top as effluent.
Aerobic digestion - Air is pumped through the effluent to supply the bacteria with oxygen
Anaerobic digestion - The sludge is sealed in a container to prevent the entry of air, which ensures anaerobic respiration.
