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?
Popsome filter paper into a funnel and pouryour 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 aevapourating 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 formcrystals 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
A disadvantage of using evapouration
Some solids decompose when heated
