AQA GCSE C3 condensed notes

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AQA Chemistry GCSE C3 Condensed Notes
C3 Topic 1: Periodic Table.
Evaluate the work of Newlands and Mendeleev in terms of their contributions to the development of the
modern periodic table.
Explain why scientists regarded a periodic table of the elements first as a curiosity, then as a useful tool and
finally as an important summary of the structure of atoms. Newlands, and then Mendeleev, attempted to
classify the elements by arranging them in order of their atomic weights. The list can be arranged in a table so
that elements with similar properties are in columns, known as groups. The table is called a periodic table
because similar properties occur at regular intervals. The early periodic tables were incomplete and some
elements were placed in inappropriate groups if the strict order of atomic weights was followed. Mendeleev
overcame some of the problems by leaving gaps for elements that he thought had not been discovered.
When electrons, protons and neutrons were discovered early in the 20th century, the periodic table was
arranged in order of atomic (proton) numbers. When this was done, all elements were placed in appropriate
groups. The modern periodic table can be seen as an arrangement of the elements in terms of their electronic
structures. Elements in the same group have the same number of electrons in their highest occupied energy
level (outer shell).
Alkali metals.
The trends in reactivity within groups in the periodic table can be explained because the higher the energy
level:
the more easily electrons are lost
the less easily electrons are gained. The elements in Group 1 of the periodic table (known as the alkali
metals):
are metals with low density (the first three elements in the Group are less dense than water)
react with nonmetals to form ionic compounds in which the metal ion carries a charge of +1. The
compounds are white solids which dissolve in water to form colourless solutions
react with water releasing hydrogen
form hydroxides which dissolve in water to give alkaline solutions.
Transition metals
Compared with the elements in Group 1, transition elements:
have higher melting points (except for mercury) and higher densities
are stronger and harder
are much less reactive and so do not react as vigorously with water or oxygen. Many transition elements
have ions with different charges, form coloured compounds and are useful as catalysts.
Halogens
In Group 7, the further down the group an element is:
the less reactive the element
the higher its melting point and boiling point.
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.

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C3 Topic 2: The Water we Drink.
Drinking Water
Water of the correct quality is essential for life. For humans, drinking water should have sufficiently
low levels of dissolved salts and microbes. Water filters containing carbon, silver and ion exchange
resins can remove some dissolved substances from tap water to improve the taste and quality.
Chlorine may be added to drinking water to reduce microbes and fluoride may be added to improve
dental health. Pure water can be produced by distillation.…read more

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C3 Topic 3: Energy Calculations.
Consider the social, economic and environmental consequences of using fuels. Interpret simple
energy level diagrams in terms of bond breaking and bond formation (including the idea of activation
energy and the effect on this of catalysts).
Evaluate the use of hydrogen to power cars compared to other fuels.
The relative amounts of heat energy released when substances burn can be measured by simple
calorimetry, eg by heating water in a glass or metal container.…read more

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The volumes of acid and alkali solutions that react with each other can be measured by titration using
a suitable indicator.
If the concentration of one of the reactants is known, the results of a titration can be used to find the
concentration of the other reactant.
Candidates should be able to calculate the chemical quantities in titrations involving concentrations (in
moles per dm3 and masses (in grams per dm3). Candidates should be able to carry out titrations using
sulfuric, hydrochloric and nitric acids.…read more

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Ethanol can be oxidised
to ethanoic acid, either by chemical oxidising agents or by microbial action..
Carboxylic acids
Represent the structures of carboxylic acids using the graphical formula and structural formula
(CH3COOH).
Ethanoic acid is the main acid in vinegar.
Ethanoic acid is a member of the carboxylic acids which have the functional group ­COOH.…read more

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