AQA GCSE Chemistry Unit 1

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AQA GCSE Chemistry Unit 1
C 1: Fundamental ideas:
C 1.1. Atoms, elements and compounds:
· All substances are made up of atoms.
· Elements contain only one atom.
· Compounds contain more than one atom.
· An atom has a tiny nucleus in its centre, surrounded by electrons.
C 1.2. Atomic structure:
· Atoms are made up of protons, neutrons and electrons.
· Protons and electrons have equal and opposite electrical charges. Protons are positively charged, and electrons
are negatively charged.
· Neutrons have no electrical charge. They are neutral.
· Atomic number = number of protons (number of electrons.)
· Mass number = number of protons and neutrons.
· Atoms are arranged in the periodic table in order of their atomic number.
C 1.3. The arrangement of electrons in atoms:
· The electrons in an atom are arranges in energy levels or shells.
· Atoms with the same number of electrons in their outermost shell belong in the same group of the periodic
· The arrangement of electrons in the outermost shell of an elements atom determines the way that element
· The atoms of the unreactive noble gases (in group 0) all have very stable arrangements of electrons.
C 1.4. Forming bonds:
· When atoms from different elements react together they make compounds. The formula of a compound shows
the number and type of atoms that have bonded together to make that compound.
· When metals react with non-metals, charged particles called ions are formed.
· Metal atoms form positively charged atoms. Non-metals form negatively charged atoms. These oppositely
charged ions attract each other in ionic bonding.
· Atoms of non-metals bond to each other by sharing electrons. This is called covalent bonding.
C 1.5. Chemical equations:
· As no new atoms are ever created or destroyed in a chemical reaction: total mass of reactants = total mass of
· There is the same number of each type of atom in each side of a balanced symbol equation.
C 2: Rocks and building materials:
C 2.1. Limestone and its uses:

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Limestone is made mainly of calcium carbonate.
· Limestone is widely used in the building industry.
· The calcium carbonate in limestone breaks down when we heat it strongly to make calcium oxide and carbon
dioxide. The reaction is called thermal decomposition.
C 2.2. Reaction of carbonates:
· Carbonates react with dilute acid to form a salt, water and carbon dioxide.
· Limewater turns cloudy in the test for carbon dioxide gas. A precipitate of insoluble calcium carbonate causes
the cloudiness.…read more

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High carbon steels, which are very hard
o Stainless steels, which are resistant to corrosion.
C 3.3. Aluminum and titanium:
· Aluminum and titanium are useful because they are resistant to corrosion.
· Aluminum requires the electrolysis of molten aluminum oxide to extract it as it is too reactive to reduce it using
· Aluminum and titanium are expensive because extracting them from their ores involves many stages and
requires large amounts of energy.
C 3.4.…read more

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When we burn hydrocarbon fuels in the air the carbon and hydrogen in the fuel are completely oxidized. They
produce carbon dioxide and water.
· Sulfur impurities in fuels burn to form sulfur dioxide which can cause acid rain.
· Changing the conditions in which we burn hydrocarbon fuels can change the products made.
· In insufficient oxygen we get poisonous carbon monoxide gas formed. We can also get particulates of carbon
(soot) and unburnt hydrocarbon s especially if the fuel is diesel.…read more

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Smart polymers may have their properties changed by light, temperature or by other changes in their
· We are now recycling more plastics and finding new uses for them.
C 5.4. Plastic waste:
· Non-biodegradable plastics cause unsightly rubbish, can harm wildlife and take up space in landfill sites.
· Biodegradable plastics are decomposed by the action of microorganisms in soil. Making plastics with starch
granules in their structure help the microorganisms break down a plastic.…read more

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Vegetable oils are high in energy and provide nutrients. They are unsaturated and believed to be better for your
health than saturated animal fats and hydrogenated vegetable oils.
· Emulsifiers improve the texture of foods enabling oil and water to mix. This makes fatty food more palatable and
tempting to eat.
C 7: Our changing planet:
C 7.1. Structure of the earth:
· The earth consists of a series of layers.…read more

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