⭐️SC1 and SC2 - States And Seperating And Purifying Flashcards
What are the three states of matter?
Solid, liquid and gas
What are the particles of a gas like?
Random, far apart and move quickly in all directions
What are the particles of a liquid like?
Random, close together and move around each other
What are the particles in a solid like?
Regular, close together and vibrate around fixed points
What is sublimation?
Going from solid to gas
What’s deposition?
Going from gas to a solid
What is a physical change?
Reversible change where only
the arrangements and movement and amount of energy stored is changed
How are particles attracted to each other?
By weak forces of attraction
What happens when a substance melts?
Some attractive forces are overcome with the heat energy and so cause it to form a liquid
What must happen for attractive forces to be overcome?
Energy must be transferred from the surroundings to the particle
If a substance is below melting point, the state is…
Solid
If a substance is between the melting point and boiling point the substance is…
Liquid
The substance is above the boiling point the state is…
Gas
Why does the temperature stay constant and when?
When boiling and melting as particles are escaping when boiling or breaking away from their fixed arrangement when melting
The composition of a pure substance…
Can’t change and is the same in all parts of a piece of the substance e.g. pure gold only has gold atoms
Compounds can’t be pure. True or false
False they can be pure
What is a pure substance?
A substance with a fixed composition in all its parts and can’t be separated into other substances using physical methods
What is a mixture?
Elements that aren’t chemically joined together so you can use physical processes to separate them
What’s the melting point?
The temperature at which particles gain enough energy to overcome weak forces of attraction and move further away from each other so the solid becomes a liquid
The difference between the melting point of a pure substance and a mixture?
Pure substance will melt at the same temperature until all the substance has changed so it will have one melting point as it had the same composition in all its parts but a mixture melts over a range of temperatures
What does it look like when a pure substance melts snd is plotted on a graph?
It has curves and stays on one temperature when it melts
Does it look like when an impure substance melts and is plotted on a graph?
The lines are sharp and the melting point is over a range of temperatures
Give examples of filtration in everyday objects
Cars, vacuum cleaners and air conditioners
What’s a solution?
A mixture of solutes (dissolved substances) and the solvent
What’s crystallisation?
Where the solvent is evaporated to leave the solute behind forming crystals whose size depends on if they formed slowly meaning the crystals would be large.
What’s solution mining?
The process that extracts sea salt
What is a saturated solution?
There is the maximum amount of solute that can be dissolved in the solvent at that temperature
Whats the filtrate?
The solvent and solute that have passed through the filter paper
What’s the residue?
The substance left behind in the filter paper
How do you evaporate the filtrate in the lab?
With a Bunsen burner under an evaporating basin which contains the filtrate which is sat on a beaker of boiling water in a tri-stand
What are the risks during crystallisation?
Spitting from the hot crystals and can be reduced via eye protection, removing the Bunsen before the solution is completely dry and using steam to gently heat the evaporating basin
What can chromatography do?
Find out the coloured compounds that make up a mixture
In paper chromatography what is the mobile phase and what’s the stationary phase ?
The mobile phase is the solvent and the stationary phase is the paper
What is the chromatogram?
The paper with the separated components
What is the Rf value?
Distance moved by the coloured spot
————————————————
Distance moved by the solvent
What is significant about Rf value?
It’s always less than 1 and can help identify substances
What can a paper chromatogram do?
Distinguish between pure and impure substances, identify substances by comparing patterns on chromatogram with the patterns of known substances
When is it best to use pure water?
Chemical analysis, car cooling systems and steam irons
What does distillation do?
Separates pure water from its dissolved solids
What happens when mineral water evaporates?
Only water turns to gas and the solid minerals which have much higher boiling points are left behind
Why is the simple method for distillation not very efficient?
As water vapour is lost
How can the simple distillation method be made more efficient?
By adding a condenser which keeps a tube cool so almost all water vapour turns to liquid
What is the use of anti bumping granules?
Make the liquid boil more smoothly and reduce the risk of liquid boiling over due to small bubbles of vapour forming over the granules
What does fractional distillation do?
Can separate two or more liquids as ones with lower boiling points evaporate first.
How is fractional distillation used everyday?
By separating products in crude oil, to make alcoholic drinks like vodka and to separate gases in the air once it’s a liquid at -200 °C
Do you understand distillation process?
If not go to the active learn chemistry text book and read page 11 or look up your tube videos
What’s desalination?
Producing water from the sea
How is desalination carried out?
Sea water is heated so water vapour quickly leaves and is the. Cooked and condensed forming water with no dissolved salts
Why should water for chemical analysis be pure?
So the results won’t be in accurate and no unexpected cloudy precipitates that could hide correct results of the analysis often form using tap water are produced
Where does raw material for producing drinking water come from in the UK?
Aquifers, lakes or rivers
What does freshwater that comes from sources like lakes and rivers contain?
- Leaves/twigs
- small insoluble particles like grit and silt
- soluble particles like salts and pesticides
- bacteria and other harmful microorganisms
What is step one in dealing with impurities in water?
Coarse filtration
What is step two in dealing with impurities in water?
Sedimentation where water goes through sand and gravel to remove small insoluble substances
What is step three in dealing with impurities in water?
Fine filtration
What is step four in dealing with impurities in water?
Chlorination to deal with microorganisms in the water
Why must water be sampled regularly?
To make sure chlorine levels are safe for humans to drink
