AQA Chemistry Specification

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Chemistry Specification
C1
C1.1. The Fundamental Ideas in Chemistry
Atoms and elements are the building blocks of chemistry. Atoms contain protons, neutrons and
electrons. When elements react
they produce compounds .
C1.1.1. Atoms
All substances are made of atoms . A substance that is made of only one sort of atom is called an
element . There are about 100 different elements . Elements are shown in the periodic table . The
groups contain elements with similar properties .
Atoms of each element are represented by a chemical symbol , eg O represents an atom of
oxygen, and Na represents an atom of sodium.
Atoms have a small central nucleus , which is made up of protons and neutrons and around which
there are electrons.
The relative electrical charges are as shown:
Proton: +1
Neutron: 0
Electron: ­1
In an atom, the number of electrons is equal to the number of protons in the nucleus. Atoms
have no overall electrical charge .
All atoms of a particular element have the same number of protons . Atoms of different elements
have different numbers of protons .
The number of protons in an atom of an element is its atomic number . The sum of the protons
and neutrons in an atom is its mass number .
Electrons occupy particular energy levels . Each electron in an atom is at a particular energy level
(in a particular shell). The electrons in an atom occupy the lowest available energy levels
(innermost available shells).
C1.1.2. The Periodic Table
Elements in the same group in the periodic table have the same number of electrons in their
highestenergy level
(outer electrons) and this gives them similar chemical properties .
The elements in Group 0 of the periodic table are called the noble gases. They are unreactive
because their atoms have stable arrangements of electrons .
C1.1.3. Chemical Reactions
When elements react , their atoms join with other atoms to form compounds . This involves giving,
taking or sharing electrons to form ions or molecules .Compounds formed from metals and
non-metals consist of ions. Compounds formed from non-metals consist of molecules . In
molecules the atoms are held together by covalent bonds.
Chemical reactions can be represented by word equations or by symbol equations.

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No atoms are lost or made during a chemical reaction so the mass of the products equals the
mass of the reactants.
C1.2. Limestone and Building Materials
Rocks provide essential building materials. Limestoneis a naturally occurring resourcethat
provides a starting point for the manufacture of cement and concrete .
C1.2.1. Calcium Carbonate
Limestone , mainly composed of the compound calcium carbonate (CaCO3 ), is quarried and can
be used as a building material.…read more

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New ways of extracting copper from low-grade ores are being researched to limit the
environmental impact
of traditional mining. Copper can be extracted by phytomining , or by
bioleaching .
Phytomining is when some plants absorb copper compounds through their roots. They
concentrate these compounds as a result of this. The plants can be burned to produce an ash that
contains the copper compounds .
Bioleaching is when some bacteria absorb copper compounds .…read more

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A mixture consists of two or more elements or compounds not chemically combined together .
The chemical properties of each substance in the mixture are unchanged . It is possible to
separate the substances in a mixture by physical methods including distillation .
Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms
only (hydrocarbons) . Most of these are saturated hydrocarbons called alkanes , which have the
general formula CnH2n+2.
C1.4.2.…read more

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The products of cracking include alkanes and unsaturated hydrocarbons
called alkenes. Alkenes
have the general formula CnH2n.
Unsaturated hydrocarbon molecules can be represented in the following forms:
C3H6
H H H
I I I
H ­­ C ­­ C == C
I I
H H
Alkenes react with bromine water , turning it from orangeto colourless.
Some of the products of cracking are useful as fuels.
C1.5.2. Polymers
Alkenes can be used to make polymers such as poly(ethene) and poly(propene).…read more

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Vegetable oils are important foods and fuels as they provide a lot of energy . They also provide us
with nutrients .
Vegetable oils have higher boiling points than water and so can be used to cook foods at higher
temperatures than by boiling. This produces quicker cooking and different flavours but increases
the energy that the food releases when it is eaten .
C1.6.2. Emulsions
Oils do not dissolve in water. They can be used to produce emulsions .…read more

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Small proportions
of various other gases, including carbon dioxide ,water vapour and noble
gases .
During the first billion years of the Earth's existence there was intense volcanic activity . This
activity released the gases that formed the early atmosphere and water vapour that condensed
to form the oceans .
There are several theories about how the atmosphere was formed .…read more

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C2.1.1. Structure and Bonding
Compounds are substances in which atoms of two or more elements are chemically combined .
Chemical bonding involves either transferring or sharing electrons in the highest occupied energy
levels (shells) of atoms in order to achieve the electronic structure of a noble gas (full outer
shells).
When atoms form chemical bonds by transferring electrons , they form ions . Atoms that lose
electrons become positively charged ions . Atoms that gain electrons become negatively charged
ions.…read more

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Substances that consist of simple moleculesdo not conduct electricitybecause the moleculesdo
not have an overall electric charge.
C2.2.2. Ionic Compounds
Ionic compounds have regular structures (giant ionic lattices) in which there are strong
electrostatic forces in all directions between oppositely charged ions . These compounds have
high melting points and high boiling point s because of the large amounts of energy needed to
break the many strong bonds.…read more

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When heated, the atoms in thermosoftening polymers vibrate more, so they move away from
each other, making the intermolecular forces are weaker. The polymer can stretch and become
elastic.
C2.2.6. Nanoscience
Nanoscience refers to structures that are 1­100 nm in size, of the order of a few hundred atoms .…read more

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