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Contents
Section 1: Principles of Chemistry
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3
b) Atoms
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7
e) Chemical formulae and chemical equations
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8
g) Covalent substances
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13
a) The Periodic Table
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14
c) Group 7 elements — chlorine, bromine and iodine
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16
a) Acids, alkalis and salts
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g
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4 – refer to the
Edexcel IGCSE specification numbers
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Section 1: Principles of Chemistry


a) States of matter





understand the arrangement, movement and energy of the particles in each
of the three states of matter: solid, liquid and gas
understand how the interconversions of solids, liquids and gases are
1
...
3
during these interconversions
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1


When describing states of matter, always consider both the movement of the particles (i
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are they
locked in a lattice or mobile) and also the spacing between particles
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Particles are mobile

Gas
Particles are far apart
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Particles are mobile

Changing state comes as a result of altering the distance between particles – the lower the kinetic
energy, the closer particles are to each other and the higher the density
...

This does not happen at the boiling point
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4





1
...
6
1
...
8

describe and explain experiments to investigate the small size of particles and their
movement including:
i dilution of coloured solutions
ii diffusion experiments
understand the terms atom and molecule
understand the differences between elements, compounds and mixtures
describe experimental techniques for the separation of mixtures, including simple
distillation, fractional distillation, filtration, crystallisation and paper chromatography
explain how information from chromatograms can be used to identify the composition
of a mixture
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g
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Each dilution results in a solution which still retains a lot of the original colour, and it
takes many factors of dilution to see any considerable difference in the intensity of colour
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Brownian motion
means that despite the high velocity of particles, random collisions between them results in a
relatively slow dispersion rate
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Molecule

Two or more atoms chemically bonded to form a discrete entity
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Two or more elements chemically combined in a fixed proportion
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g
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Can be separated by techniques in outlined below
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Simple distillation

Separates soluble solid and solvent

e
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brine, NaCl (aq)



Fractional
distillation


Separates mixtures of miscible liquids

e
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ethanol and water

Separates insoluble solid and liquid


e
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sand and water



Filtration




5






Crystallisation

Separates soluble solid and solvent



e
...
CuSO4 (aq)



Paper
chromatography


Separates miscible liquids or solids

e
...
separating ink dyes













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c) Atomic structure









1
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10
1
...
12
1
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14
1
...



Atoms are made up of protons and neutrons in the nucleus, surrounded by shells of electrons which
orbit around it
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Isotope


The RAM of an element is calculated by considering the abundance of each isotope (i
...
a weighted
average)
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5
100
100

As you move across the Periodic Table, each subsequent element has one extra proton (and
therefore electron)
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Element

Group

Electronic
configuration

No
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4

4

Phosphorus

5

2
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5

5

Calcium

2

2
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8
...
22
liquids, gases and aqueous solutions respectively
1
...
In an
exam, if you include state symbols and they are not required you will not be penalised, so you might
as well include them

For example: CuCO3(s) + H2SO4(aq) → CuSO4(aq) + H2O(l) + CO2(g)


You need to be able to write balance chemical equations for any reaction studied in this
specification
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28 describe the formation of ions by the gain or loss of electrons
1
...
31
the ion is formed
explain, using dot and cross diagrams, the formation of ionic compounds by electron
1
...
33
charged ions
understand that ionic compounds have high melting and boiling points because of
1
...
35
point of an ionic compound
describe an ionic crystal as a giant three-dimensional lattice structure held together
1
...
37 draw a diagram to represent the positions of the ions in a crystal of sodium chloride
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For simple metals (i
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not transition metals), the charge is always positive (from losing
electrons) and is equal to the group number
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Electronic
Element
Ion
configuration
8








Calcium

2
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8
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6

O2-

Fluorine

2
...




It is the resulting strong electrostatic attraction between oppositely charged ions that gives rise to
many of the physical properties of ionic compounds – for example their high melting and boiling
points
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For example, MgO has a higher melting point than NaCl (Mg2+ and O2- vs Na+ and Cl-)
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38
1
...
40







1
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42
1
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44
1
...



Distinct from ionic bonding, covalent bonding involves the sharing of electron pairs between two
atoms – consequently, there are no ions formed
...

At GCSE you should be able to draw dot-and-cross diagrams for only those molecules named in the
specification above
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Covalent bonds are never broken when
a simple covalent molecule is heated to its melting/boiling point
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e
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Uses of giant covalent structures can be related to their properties, for example:
• Graphite has weak forces between layers, so they can slide over each other
...

• Diamond has a rigid 3D network of strong covalent bonds
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Section 2: Chemistry of the Elements


a) The Periodic Table







2
...
2 recall the positions of metals and non-metals in the Periodic Table
explain the classification of elements as metals or non-metals on the basis of their
2
...
4
properties
understand that the noble gases (Group 0) are a family of inert gases and explain their
2
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The position of an element in the periodic table gives an indication of its physical and chemical
properties
...


Elements in Group 0 (or 8), the Noble Gases, have a full outer shell of electrons and are therefore
very unreactive
...

All metal oxides are bases and all non-metal oxides are acidic
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7 describe the relative reactivities of the elements in Group 1
explain the relative reactivities of the elements in Group 1 in terms of distance
2
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2
...

The reason for this is that as the atom gets bigger, the outer electron is held less tightly to the
nucleus and therefore lost more easily (Cs > Rb > K > Na > Li)
...


For example, sodium with water: 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
• Sodium moves randomly on surface of water
• Melts into a sphere
• Effervescence
• Sodium eventually disappears

In the case of potassium, the hydrogen produced might also catch fire and burn with a purple flame
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9 recall the colours and physical states of the elements at room temperature
2
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11 understand the difference between hydrogen chloride gas and hydrochloric acid
explain, in terms of dissociation, why hydrogen chloride is acidic in water but not in
2
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13 describe the relative reactivities of the elements in Group 7
describe experiments to demonstrate that a more reactive halogen will displace a less
2
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Their reactivity trend therefore is reversed – smaller atoms hold on to electrons more easily since
the outer shell is closer to the nucleus
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g
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g
...
It is important to appreciate the differences
between the two in terms of reactivity, colour and bonding
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g
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pale green

V
...


When a halogen reacts with hydrogen it produces the hydrogen halide (HX) – for example, hydrogen
chloride
...


• Hydrogen chloride = HCl (g) – covalent molecule
• Hydrochloric acid = HCl (aq) – dissociated in water
o HCl à H+ + Cl-
• Hydrogen chloride in methylbenzene is not dissociated and hence is not acidic
...


For example:
Cl2(aq) + 2KI(aq) → I2(aq) + 2KCl(aq)

Pale green solution à brown solution





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Section 4: Physical Chemistry


a) Acids, alkalis and salts






4
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2
4
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4


4
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6





4
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8
4
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Acidic compounds dissociate in water to produce a source of H+ ions
...


• HCl (aq) → H+ (aq) + Cl- (aq)
• NaOH (aq) → Na+ (aq) + OH- (aq)


Conveniently, universal indicator can be used to give an approximate pH (measured on a scale of 0 –
14) of an acidic or alkaline solution
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This is most useful when
a sharp change is needed, for example during a titration
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Key to knowing which
reaction to exploit is having an understanding of the solubilities of common salts
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g
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g
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g
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0cm3
pipette
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g
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Add acid to metal hydroxide solution, drop-wise near
endpoint
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g
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Evaporate half water and leave to crystallise
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•
•
•
•
•
•





Add insoluble metal carbonate to acid in excess to ensure
all acid has reacted
...

Evaporate half water and leave to crystallise

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