Year 7 And 8 Revision Flashcards
What are the three states of matter?
Solid, liquid, gas
What process causes solids to turn into a liquid?
melting
What process causes a liquid to change into a solid?
Freezing
What process causes a liquid to change into a gas?
Evaporating
What process changes a gas into a liquid?
Condensing
What process changes a solid into a gas?
Subliming
What’s diffusion?
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration through a liquid or gas.
What are examples of diffusion?
- potassium manganate(VII) and water
- ammonia and hydrogen chloride
- bromine gas and air
How is potassium manganate(VII) and water an example of diffusion?
Potassium manganate is bright purple so it’s great for visualising diffusion.
- the random motion of the particles cause it to evenly spread out
- if you add more water it becomes more diluted
How is ammonia and hydrogen chloride an example of diffusion?
A white ring of ammonium chloride will form closer to the hydrochloric acid end of the tube.
-it forms closer to the hydrochloric acid end because the ammonia particles are lighter and smaller
How is bromine gas and air an example of diffusion?
- bromine is a brown strong smelling gas
- fill a glass jar full of bromine gas and another with air separate them with a glass plate
- when you remove the glass plate the bromine gas will slowly diffuse through the air
Define element:
A substance which consists of only one type of atom
Define compound:
A compound is a substance that is made of two or more different elements which are chemically bonded together.
Define mixture:
A mixture is a substance that contains more than one type of atoms but there are no chemical bonds between the different parts of a mixture.
What is filtration?
Using filter paper to separate an insoluble solid from a liquid.
-it can be used in purification as well
What is crystallisation?
How do you crystallise a product?
Crystallisation is used to separate a soluble solid from a solution
- pour the solution into an evaporating basin
- slowly heat the solution and stop heating when crystals start to form
- leave the dish in a warm place for the rest of the solute to evaporate
- finally you’ve got the dry product, you can use a drying agent or a desiccator
Define molecule:
A group of atoms covalently bonded together
What processes do you use to separate rock salt?
rock salt is a mixture of salt and sand
- grinding-grind up the rock salt with a pestle and mortar
- dissolving-dissolve in beaker and stir
- filtering-filter through filter paper in a funnel(removing the sand)
- crystallisation-evaporate in an evaporating dish(forming crystal salt)
How do you do paper chromatography?
How do you make a chromatogram
- draw a lesson near the bottom of a sheet of filter paper
- add dots of different dyes to the line at regular intervals
- put the sheet in a beaker of water
- make sure the dyes aren’t touching the solvent so they aren’t dissolved
- place a lid on the beaker to stop the solvent from evaporating
- the solvent seeps up the paper, carrying the dyes with it
- each dye will move up at different rates
- the end result is a pattern of spots called a chromatogram
How does chromatography separate mixtures?
- chromatography works because different dyes will move up the papers at different rates
- some will stick to the paper whereas others will dissolve more readily in the solvent and travel more quickly
- the distance the dyes travel depends on the solvent and paper you use
How can chromatography identify different dyes?
- you can work out the different dyes that are present in a substance by chromatography
- make a chromatogram for your unknown substance and reference materials(dyes that you think might be in that ink)
- then compare the chromatograms to work out what dyes are in the substance
What’s the use of simple distillation?
Used to separate out solutions
-separate a liquid from a solution
What’s the process of simple distillation?
- the solution is heated, the part of the solution with the lowest boiling point evaporates
- the vapour is then condensed and collected
- the rest of the solution is left behind in the flask
What can you use simple distillation for?
Can use it to get pure water from seawater
- the water evaporates and is condensed and collected
- you’ll eventually just be left with the salt and water separated
What’s a disadvantage of simple distillation?
- you can only use it separate things with very different boiling points
- you can separate out from a mixture with very similar boiling points
What’s fractional distillation used for?
Fractional distillation is used to separate a mixture of liquids
What’s the process of fractional distillation?
Using the example of the fractional distillation of crude oil at a refinery:
- put your mixture in a flask sticking a fractional column on top then heat it
- different liquids have different boiling points so they will evaporate at different times
- the liquid with the lowest boiling point evaporates first, and be the first to reach the top of the column
- liquids with higher boiling points might also start to evaporate but the column is cooler towards the top so they’ll condense and fall back down
- when the first liquid has been collected, you raise the temperature until the next one reaches the top
Describe a test for oxygen:
Oxygen relights a glowing splint
Describe a test for carbon dioxide:
Carbon dioxide turns limewater cloudy
-just bubble the gas through a test tube of lime water and see what happens
Describe a test for hydrogen:
Hydrogen makes a ‘squeaky pop’ with a lighted splint
-the noise comes from the hydrogen burning with the oxygen in the air to form water
Describe a test for water:
Copper sulphate crystals change from being white to being blue