CHEMISTRY UNIT 2 NOTES

Here are my notes for Chemistry Unit 2 - if i need to make any corrections or I'm missing something - please tell me 

But anyways, hope this will help 

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  • Created on: 05-04-13 18:57
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CHEMISTRY UNIT 2 NOTES
Chemistry
Element: A substance made up of one type of atom
Compound: Tow or more different elements chemically bonded together
Mixture: A substance that has two or more different elements which are mixed together
NOT chemically bonded
IONIC BONDING
Ionic Bonding ­ gaining or losing electrons (between metals and non-metals)
Combine by the transfer of electrons
Same electronic structures as noble gases
Positive ions (lose electrons) = CATIONS
Negative ions (gain electrons) = ANIONS
When atoms LOSE/GAIN electrons, they become charged
When atoms LOSE/GAIN electrons, they are called ions
When atoms' outer shell is full it is called a stable octet
LOSE electrons = positive ions (the number of protons is bigger than the number of
electrons)
GAIN electrons = negative ions (the number of protons is less than the number of electrons)
Non-metals usually form negative ions (ANIONS)
Metals usually form positive ions (CATIONS)
The positive and negative ions attract to form an ionic bond, the attraction is called
electrostatic attraction
Hydrogen forms H ions
When calculating formulae NOTE: SO = SULPHATE, S² = SULPHIDE, OH = HYDROXIDE, NH =
AMMONIA ION, NO = NITRATE, CO = CARBONATE, HCO = HYDROGEN CARBONATE,
Fe(ii) = IRON (ii), Fe(iii) = IRON (iii)
PROPERTIES OF IONIC COMPUNDS/ GIANT LATTICE STRUCTURES
High melting/ melting points
Soluble
Crystalline
Hard
COVALENT BONDING

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CHEMISTRY UNIT 2 NOTES
Covalent Bonding ­ sharing electrons (between non-metals)
Electrons are shared in a covalent bond
Compounds produced by covalent bonding form molecules
Molecules are individual particles
Group 7 in the Periodic table (Halogens) are diatomic and come in PAIRS as such as
Hydrogen - H, but Hydrogen IONS can travel on their own as H
Water is an example of covalent bonding between an oxygen atom and 2 hydrogen
atoms
SIMPLE MOLECULES
Simple molecules are individual particles
Simple molecules contain only a…read more

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CHEMISTRY UNIT 2 NOTES
DIAMOND
Diamond is a rare form of carbon ­ each carbon atom is covalently bonded to four other
carbon atoms
This pattern arrangement is repeated millions of times so is a giant lattice
Very hard ­ the hardest substance on earth
Needs a lot of energy to break its covalent bonds because of strong intermolecular forces
high melting & boiling points
Cannot conduct electricity
GRAPHITE (PENCIL LEAD)
Common form of carbon
Each atom covalently bonded to 3 others sea of delocalised…read more

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CHEMISTRY UNIT 2 NOTES
Metals form giant structures most have high boiling and melting points, are hard and
strong
In a metal the atoms are held together by strong bonds in a regular structure
In a metal there are free electrons from the outer shells of the metal atoms which make up a
sea of delocalised electrons
Strong because the regular structure means the layers of atoms can fairly easily slide over
each other without breaking the bonds (though not as easily as graphite)
The…read more

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CHEMISTRY UNIT 2 NOTES
THERMOSETTING POLYMERS
Once moulded, do not soften when heated ­ cannot be reshaped
Polymer chains ­ cross-linkedcannot slide past each other easily
Not broken by heat
Decomposes & chars when heated too far
Cannot be recycled
Much more rigid structure ­ chains are fixed in place by strong permanent covalent bonds
Heat resistance required
POLYMERS
Monomer = one alkene
Polymer = many alkenes joined together
Monomer = double bond
Polymer = single bonds
DRAWING POLYMERS
Same elements in the same places…read more

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CHEMISTRY UNIT 2 NOTES
Elements are made up of one type of atom
Isotopes = Atoms of the same element having the same amount of protons but have
different numbers of neutrons
Isotopes =
o Atoms of the same element
o Different mass no.
o Different neutron no.
The physical properties of isotopes are affected but the chemical properties are affected
slightly
CALCULATIONS
RELATIVE ATOMIC MASS (r.a.m)
The r.a.…read more

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CHEMISTRY UNIT 2 NOTES
(16×2)
= 64 ×100 = 50% of oxygen
EMPIRICAL FORMULA OF A COMPOUND
The Empirical formula gives the simplest ratio of elements present in a substance
This is steps in how to calculate it
o Step 1: Find the masses/percentage of the elements
o Step 2: Find their R.A.M or Ar
o Step 3: Divide masses by R.A.…read more

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CHEMISTRY UNIT 2 NOTES
4Al + 3O2 2Al2O3
CALCULATING THE MASS OF A PRODUCT
When calculating it only calculate the part of the question it wants you to
First calculate the R.F.M of the parts that it wants you to calculate
E.G. What mass of calcium oxide is produced when 10g of calcium burns?
R.F.M of 2Ca = 2 x 40 = 80g
R.F.…read more

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CHEMISTRY UNIT 2 NOTES
GC-MS are instrumental methods
Instrumental methods ­ fast, accurate & sensitive (helps detect very small amounts of a
substance)
GC-MS ­ separating a mixture of compounds
Two phases = mobile phase & stationary phase
Mobile phase = Carrier gas carries sample through the column ­ different compounds
pass through at different speeds become separated
Stationary phase = takes place in the column, involves a liquid covering the surface of a solid
material packed in a long tube, end of column ­…read more

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CHEMISTRY UNIT 2 NOTES
OR
At the start 100% reactant, 0% product
At the end 0% reactant, 100% product
The amount of reactant may be less because some could be lost through a gas
From the x axis draw up o hit the line and go across to get your y axis result
DIFFERENT WAYS OF FOLLOWING THE RATE OF REACTION
Collecting a gas
Weighing the reaction mixture
Observing colour change or precipitate
Precipitate = insoluble solid
COLLISION THEORY & SURFACE AREA
The rate of…read more

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