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States of matter
1.1 understand the arrangement, movement and energy of the particles in each of the three states of matter: solid, liquid and gas
1.2 understand how the interconversions of solids, liquids and gases are achieved and recall the names used for these interconversions
Solid > Liquid
This process is called melting: you apply heat.
Liquid > Solid
This is freezing. You remove heat.
Liquid > Gas
Heat is added. The process is evaporation.
Gas > Liquid
Removed heat: condensing.
1.3 explain the changes in arrangement, movement and energy of particles during these interconversions.
SOLID: STATIONARY; NO ENERGY; ALL PARTICLES TOUCHING/COMPACT
LIQUID: MOBILE TO FILL SPACE; SOME ENERGY; ALL PARTICLES TOUCHING/LESS COMPACT
GAS: MOVING FREELY; LOTS OF ENERGY; PARTICLES NOT TOUCHING/LOOSE
1.4 describe and explain experiments to investigate the small size of particles and their movement including:
i. dilution of coloured solutions
ii. diffusion experiments
Dilution: a substance is put in a solvent to reduce its concentration
Diffusion: The movement of particles from an area of high concentration to an area of low concentration
Experiment 1, Diffusion
Hydrochloric acid is placed at one end of a tube, ammonia solution at the other.
Where they meet a ring of ammonium chloride appears.
The diagram shows it is closer to the HCL end.
From this we can tell that ammonia must have travelled faster, as it got further in the time. Lighter particles travel faster- so we can tell that ammonia is a lighter gas.
Experiment 2, Dilution
Put a coloured substance in a solvent (e.g food colouring in water.)
You can see that over time the colour levels out but is weaker than the original colour- this is dilution.
Dilution at different temperatures: more heat; means more energy; means more movement; so the particles can move to different areas more quickly. So applying heat decreases the amount of time taken for the coloured substance to be fully diluted.
1.5 understand the terms atom and molecule
An atom is made up of a nucleus (protons and neutrons) and orbitals with electrons on:
A molecule is two or more atoms bonded together.
1.6 understand the differences between elements, compounds and mixtures
Elements - every atom in an element has the same amount of protons.
Compound - atoms from different elements bonded together
Mixture - different elements not bonded.
1.7 describe experimental techniques for the separation of mixtures, including simple distillation, fractional distillation, filtration, crystallisation and paper chromatography
This consists of a barrier which one component f a mixture can pass through but the other is caught by.
[e.g water goes through filter paper, rocks are caught by it.]
One substance is evaporated off.
[e.g salt water is heated to 100 degrees; water evaporates off (it rises and the goes down into the condenser where it is cooled back into water), the salt is left in the original flask.]
Fractional distillation The mixture is evaporated and rises up the tube.
Different substances have different boiling points and so will condense at different temperatures; as the mixture travels up the tube the temperature decreases, substances begin to condense at different places (due to the change in temperature) and are collected. This separates the mixture into its different parts.
A solution is warmed allowing the solvent to evaporate, the solution is now left to cool and will form crystals.
chromatography paper is placed in a substance, the different components of the substance will travel at different speeds (due to the size of their particles.)
1.8 explain how information from chromatograms can be used to identify the composition of a mixture.
Chromatography: Used to analyse coloured substances
Some coloured substances are better at dissolving in liquid than bonding with paper; so they travel further up the paper
If two substances travel the same distance up the paper, they’re likely to be the same substance (e.g. same colour)
Retardation (retention) Factor Values
The Rf value is calculate by Distance moved by compound divided by Distance moved by solvent.
It’s never more than one. The higher the Rf value, the higher the spot.
The shape on the chromatogram can be compared with that of known substances and where they match they are the same substance.
A visible record (such as a graph) showing the result of separating the components of a mixture by chromatography.
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