AQA Chemistry- C3 Part 1 Revision

Revision presentation summarising the basic points for AQA GCSE Chemistry.

Preview of AQA Chemistry- C3 Part 1 Revision

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Slide 2

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The Water Cycle & Purifying Water
The Water Cycle:
-Evaporation from rivers, seas etc
-Condensation into clouds
-Precipitation, e.g. rain, back to earth
Water Purifying Process:
1. Filtered through screens to get rid of large solids
2. Ozone added to kill off algae, bacteria and pesticides (excess is
destroyed)
3. Further filtration, through sand and gravel, to get rid of more
solids
4. Passed through activated carbon granules, which have a large
surface areas and are therefore good at getting rid of pesticides
5. Chlorine is used to get rid of remaining bacteria
6. Stored with a little chlorine to ensure it is clean when it reaches
our taps

Slide 3

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Solubility and Saturated Solutions
Solvent= liquid into which the solute dissolves
Solute= material which dissolves
Ionic compounds are usually soluble
Molecular/covalent compounds are usually insoluble
Solubility is given in g/100g of water
To increase solubility in Gases:
-Increase the pressure
-Decrease the temperature
To increase solubility in Solids:
-Increase the temperature
A saturated solution is a solution into which no more solute can be dissolved

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Hard Water
Has dissolved compounds/ions in it
(Mg or Ca)
Reacts with stearate ions in the soap
to form scum:
Calcium ions + stearate ion calcium stearate (insoluble scum)
Hardness is measured as "calcium
carbonate equivalent" in mg/dm^3

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Permanently Hard Water
Contains Calcium Sulfate
Does not soften when boiled

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Temporarily Hard Water
Most contains calcium hydrogen carbonate
(dissolved)
This is formed by the reaction of CO2 in the
atmosphere with water to make acid rain, which then
reacts with CaCO3 on limestone.
When heated, the calcium hydrogen carbonate
decomposes into CO2, H2O and CaCO3 again.
The CaCO3 is the limescale you see on kettles etc
Limescale adds expense as it makes water heated
equipment less efficient
However, hard water has health benefits as it
gives you strong bones and a healthier heart.

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