Topic 2- States Of Matter And Mixtures Flashcards
What are the three states of matter
Solid
Liquid
Gas
What are the Property’s of a solid
- Strong forces between particles that hold them in a fixed position in a lattice arrangement
- Particles don’t move from their positions so all solids keep a definite shape and volume
- The particles don’t have much energy
- Can only vibrate - the hotter a solid is the more they vibrate
What are the Property’s of liquids
- Some forces of attraction between the particles means they’re able to move past each other but they do tend to stick together
- Liquids don’t keep a definite shape but do keep the same volume
- more energy then a solid but less then a gas
- Constantly moving moving with random motion - the hotter it gets the more movement
What are the Property’s of a gas
- No force of attraction between the particles - free to move - move in straight lines and only interact when they collide
- Don’t keep a definite shape or volume and will always fill any container - when particles bounce off of a wall of a container they exert a pressure in the wall
- More energy then a solid and liquid
- Particles move constantly with random motion - the hotter a gas gets the faster it moves - pressure increases
What happens when a solid heats
It can eventually become a liquid
What happens when a liquid freezes
Becomes a solid
What happens when a liquid heats
Eventually Becomes a gas
How does a gas become a liquid
Condensing
What’s harder to reverse physical change or chemical change
Chemical change
What is a pure substance
A substance that is made up of a single element or compound
What’s a mixture
When you have more then one compound present, or different elements that aren’t all part of a single compound
Property’s of pure substances
Specific, sharp , melting and boiling points
Property’s of a mixture
Can melt over a range of temperatures
What’s Simple distillation used for
Separating liquid from a solution e.g. pure water from sea water
What are the Simple distillation (practical) steps using sea water as an example
- Pour your sample of sea water into the distillation flask
- Set up the apparatus. Connect the bottom of the condenser to a cold tap using rubber tubing. Run cold water through the condenser to keep it cool.
- Gradually heat the distillation flask . The part of the solution that has the lowest boiling point - in this case the water.
- The water vapour passes into the condenser where it cools and condenses(turns back into a liquid). It then flows into the beaker where it is collected.
- Eventually you’ll end with just salt in the flask.
What’s the problem with simple distillation
You can only use this to separate things with Very different boiling points because if you have a mixture of two liquids with similar boiling points you can get confused ( this is why fractional distillation exists)
When is fractional distillation needed
When you have a mixture of two liquids that need to be separated e.g. crude oil
How do you test for purity
Using melting points
What are the fractional distillation (practical) steps using. Using crude oil in this case but same rules apply
- Put your mixture in a flask. Attach a fractionating column and a condenser above the flask.
- Gradually heat the flask. The different liquids will have different boiling points - so they will evaporate at different temperatures
- The liquid with the lowest boiling point evaporates first. When the temperature on the thermometer matches the boiling point of this liquid it will reach the top of the column
- Liquids with higher boiling points may start to evaporate. But the column is cooler towards the top, so they will only get part way up before condensing and running back down towards the flask
- When the first liquid has been collected, raise the temperature until the next one reaches the top
What is filtration used for
To separate an insoluble from a liquid
What can filtration be used for
Separation of an insoluble from a liquid. It can also be used for purification
What’s purification
Purification is when solid impurities can be separated out from a reaction using filtration
How does filtration work
Put filter paper into a funnel and pour your mixture into it. The liquid part of the mixture runs through the paper, leaving behind a solid residue
What does crystallisation do
It separates a soluble solid from a solution
How do you crystallise a product
- Pour the solution into an evaporating dish and gently heat the solution. Some of the water will evaporate and the solution will get more concentrated.
- Once some of the water is evaporated, or when you see crystals start to form, remove the dish from the heat and leave the solution to cool.
- The salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solutions.
- Filter the crystals out of the solution, and leave them in a warm place to dry. You can dry in a drying oven or a desiccator
What’s a desiccator
A desiccator contains chemicals that remove water from the surroundings
What is chromatography
It’s a method used to separate a mixture of soluble substances and identify them
What are the two stages of Chromatography and explain them
- Mobile phase - where molecules can move . This is always a liquid or gas
- Stationary stage - where molecules can’t move. This can be solid or really thick liquid
How does chromatography work
- The components in the mixture separate out as the mobile phase moves over the stationary stage - they all end up in different places in the stationary stage.
- This happens because each of the chemicals in a mixture will spend different amounts of time dissolved in the mobile phase and stuck to the stationary phase.
- How fast the chemical moves through the stationary phase depends on how it “distributes” itself between the two phases.
What’s the mobile and stationary phase in paper chromatography
The mobile stage is a solvent e.g. water or ethanol
The stationary stage is a piece of filter paper
What are the Paper Chromatography (practical) steps
- Draw a line near the bottom of the paper - this is the baseline. (Use a pencil to do this as pencil marks are insoluble and won’t move with the solvent as ink might.) Put a spot of the mixture to be separated on the line.
- Put some of the solvent into the beaker. Dip the bottom of the paper (not the spot) into the solvent
- Put a watch glass on the top of the beaker to stop any solvent from evaporating away
- The solvent will start to move up the paper. When the chemicals in the mixture dissolve in the solvent, they will move up the paper too.
- You will see the different chemicals in the sample separate out, forming spots at different places on the paper ( if one of your components is insoluble in the mobile phase, it won’t move - it’ll stay as a spot on the baseline)
- Remove the paper from the beaker before the solvent reaches the top. Mark the distance the solvent has moved (the solvent front) in pencil.
What two things depends on the time the molecules spend on each phase
How soluble they are in the solvent and how attracted they are to the stationary phase
What are Rf values in paper chromatography
Is the ratio between the distance travelled by the devolved substance (the solute) and the distance travelled by the solvent
What’s the Formula for Rf values
Rf = distance travelled by solute / distance travelled by solvent
What’s the price of paper you end up with in paper chromatography
Chromatogram
Can you combine separation techniques to analyse mixtures
Yes , simple distillation and paper chromatography is used to analyse the composition of an ink
In paper chromatography if you are using colourless mixtures what do you do to see where the spots are
You have to use a locating agent to show where the spots are
What are the Steps on How do you combine simple distillation and chromatography to analyse the composition of an ink (practical)
- Ink is a mixture of different dyes dissolved in a solvent
- To work out what solvent the ink contains, you use simple distillation. Simple distillation allows you to evaporate ff the solvent and collect it - assuming that’s the solvent has the lowest boiling point of all the substances in the ink, it will evaporate first.
- The thermometer in the distillation is set-up and will read the boiling point of the solvent when it’s evaporating (and therefore when it’s being collected). You can use the boiling point of the solvent to try to determine what it is. For example if the solvent in a certain ink evaporates at 100 degrees, it would be quite likely to be water.
- You can then carry out paper chromatography on a sample of the ink - this will separate out the different dyes in the ink, so that you can see how many there are
- You can compare the Rf values of the different spots on the chromatogram produced with different reference values (or run further chromatography experiments with pure substances) to work out what dyes are in the ink
What is potable water
Water that is fit to drink
Where in the UK do we get out water from
- Surface water: lakes , rivers and reservoirs
- Ground water: from aquifers (rocks that trap water from under the ground)
- Waste water: from water that’s been contaminated by human processes
Where is water purified
In water treatment plants
What are the steps water is treated in water treatment plants
- Filtration - a wire mesh screens out large twigs etc, and then gravel and sand beds filter out any other solids bits.
- Sedimentation - iron sulfate or aluminium sulfate is added to the water, which makes fine particles clump together and settle at the bottom
- Chlorination - chlorine gas is bubbled through to kill harmful bacteria
What’s a way to get potable water
By distilling sea water
What’s the problem with using distillation to make potable water
It’s expensive and takes lots of energy especially if you’re trying to make large amounts
What is deionised water
It’s water that’s had the ions from normal tap water such as calcium, iron and copper ions removed
Why is deionised water used in experiments
As using normal water with ions present can give your experiment false results
