Chemistry AQA GCSE (full revision guide)

HideShow resource information
Preview of Chemistry AQA GCSE (full revision guide)

First 318 words of the document:

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 H+ ions
A base (pH greater than 7)
An alkali is a base that can dissolve in water to create OH- ions
Acid + base = salt + water which in ion terms is: H+ + OH- = H2O
Acid + base/ alkali neutralises (to make water
State symbols tell you the physical state of the substance
(s) is a solid
(l) is a liquid
(g) is a gas
(aq) is aqueous ­ means dissolved in water
Acids and metal
Acid + metal = salt + hydrogen
The more reactive the metal the faster the reaction it will and the more explosive
o E.g. sodium very explosive ­ magnesium has a big pop ­ aluminium ­ zinc ­ iron ­ copper (doesn't
react at all with dilute acid so no pop)
o The pop is when you test for hydrogen
Hydrochloric acid would produce chlorides
Sulphuric acid would produce sulphates
Nitric acid produces nitrates
Oxides, Hydroxides, ammonia
Metal oxides and hydroxides are bases
Some dissolve is water and therefore are alkalis
But they still can react with acids even if they don't dissolve in water
Acid + metal oxide = salt + water
Acid + metal hydroxide = salt + water
Ammonia can be neutralised with HNO3 (nitric acid) to make fertiliser
Ammonia + nitric acid = ammonium nitrate
This is different from most other reaction because it only produces a salt
NH3 + HNO3 = NH4NO3
This is really good for plants because it has two forms of nitrogen which plants use to make protein

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

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 metal or insoluble base
You need to pick the right acid ­ pick a metal or insoluble base
You add the metal or insoluble base to the acid
If it a reactive enough metal then…read more

Page 3

Preview of page 3

Here's a taster:

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 how much of the substance there is (so if there is much
more of substance C than there is of C1 then the average would be closer to C)
The relative formula mass is Mr…read more

Page 4

Preview of page 4

Here's a taster:

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 = 2MgO
c. Step 2: 2MgO (Mg = 24 O = 16) 48 + 32 = 80
d. Step 3: Find the ratio of Mg to the total : 48 : 80divide by 48 (1: 1.…read more

Page 5

Preview of page 5

Here's a taster:

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.…read more

Page 6

Preview of page 6

Here's a taster:

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- . The (+1) + (-1) = 0 , the charges are balanced with one of
each ions, so the formula for sodium chloride = NaCl
E.g. Magnesium chloride contains Mg2+ and Cl- .…read more

Page 7

Preview of page 7

Here's a taster:

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 diamond and graphite ­ which are made from carbon atoms and silicon dioxide
Each carbon atom forms four covalent bonds in a very rigid giant covalent structure
This structure makes the diamond the hardest…read more

Page 8

Preview of page 8

Here's a taster:

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.…read more

Page 9

Preview of page 9

Here's a taster:

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 intermolecular forces and are free to
slide over each other
o E.g. Thermo- softening polymer don't have cross linking between chains ­ so the forces are easy to
overcome and so easy to melt.…read more

Page 10

Preview of page 10

Here's a taster:

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 marble chips (see pg. 109) ­ You can use the gas syringe method to measure
the rate of the reaction.…read more


No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all resources »