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Chemistry: Acids and Alkalis

Acids and Alkalis

pH scale

0- 14 : Acids ­ 0-6 Neutral ­ 7 Alkalis ­ 8-14

Universal indicator

Red to yellow is acid green is neutral blue to purple is alkali

Acids and alkalis neutralise each other

Acid (pH less than 7) in water creates…

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Making salts

Most chlorides, sulphates and nitrates (salts) are soluble in water ­ notable exceptions are lead chloride, lead
sulphate and silver chloride
Most oxides and hydroxides are insoluble
The method to make a soluble salt depends are whether the base is soluble or not

Making soluble salts from a…

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Chemistry ­

Relative Formula mass

Atomic Mass = A
Ar = the relative atomic mass (usually the same as the atomic mass number)
When an element has more than one isotope then the relative atomic mass number is the weighted average
o Weighted mass means that it is measured by…

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1. Write out a balanced equation
2. Work out the Mr
3. Divide to get one and multiply to get all
a. E.g. What mass of magnesium oxide is produce when 60g of magnesium is burnt in air
b. Step 1: Write a balanced equation = 2Mg + O2 =…

Page 5

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Chemistry ­ Ionic and covalent bonding, polymers and materials

Atoms and Compounds

Atomic number and mass number describe an atom: mass number ­ total of protons & neutrons

Atomic number - number of protons

Compounds are when two are more atoms chemically join together ­ e.g. carbon dioxide ­ they…

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When ionic compounds melt, the ions are free to move and they carry an electric current
However they dissolve easily in the water and they separate
When working out the formula of ionic compounds you need to look at the individual ions:
E.g. Sodium Chloride contains Na+ and Cl- .…

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Covalent substances: Giant Covalent

These are similar to giant ionic structures ­ but no charged ions
All the atoms are bonded to each other by strong covalent bonds
This means they have very high melting and boiling points
They don't conduct electricity ­ except for granite
The main examples are…

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Metallic Structures

Metal Properties are all due to the sea of free electrons

Metals also consist of a giant structure
Metallic bonds involve the all-important `free electrons' which produce all the properties of metals. These
delocalised electrons come from the outer shell of every metal atom in the structure

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o Nanotubes conduct electricity ­ tiny electric circuits for computer chips


Forces between molecules determine the properties of plastics
o Strong covalent bonds hold atoms together in long chains ­ these bonds determine the properties
of plastics
Weak Forces
o Individual tangled chains of polymers held together by weaker…

Page 10

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Use of a gas syringe ­ (see page 108) the faster the volume of gas released and pushes the syringe out the faster
the rate of reaction ­ issue: if the reaction is too explosive and blows the syringe out you can't really measure.


Reaction of hydrochloric acid and…


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