Science
Junior Cert
Chemistry Revision Notes
By Peter Jackson
Junior Cert Science –Chemistry Notes
Peter Jackson
Author
These notes were brought to you by Peter Jackson. Peter is the Head of Science at St Columbas College,
Whitechurch, Co Dublin. Peter has over 30 years teaching experience and has corrected Biology papers for the
Department of Education for over 25 years and also marks appeals for the Department. Peter teaches Science at JC
and Biology and Chemistry at LC. Peter has also recently written a book for Leaving Certificate students 'Essentials
Unfolded - Chemistry ' specifically to help students studying Chemistry at LC. He has also given numerous courses on
Lab Safety and IT in Teaching.
We at mocks.ie are delighted to bring you these excellent notes at an affordable price.
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 2
Junior Cert Science –Chemistry Notes
Contents
CHEMISTRY........................................................................................................................................................................ 4
Elements, Compounds and Mixtures ............................................................................................................................ 4
Mixtures and Compounds ............................................................................................................................................. 7
Acids and Bases ............................................................................................................................................................. 8
Air, Oxygen, Carbon Dioxide and Water ..................................................................................................................... 10
Hardness in Water ...................................................................................................................................................... 13
Water Treatment: ....................................................................................................................................................... 13
Acids and Bases ........................................................................................................................................................... 14
Reactions of Acids and Bases ...................................................................................................................................... 15
Atomic Structure, Reactions and Compounds ............................................................................................................ 16
Basic Atomic Structure ................................................................................................................................................ 16
Isotopes: ...................................................................................................................................................................... 17
Bonding ....................................................................................................................................................................... 17
Ionic Bonds .............................................................................................................................................................. 17
Covalent Bonds ....................................................................................................................................................... 18
Rusting and Corrosion ................................................................................................................................................. 19
Metals ......................................................................................................................................................................... 20
Hydrocarbons .............................................................................................................................................................. 21
Plastics......................................................................................................................................................................... 21
Role of Chemistry ........................................................................................................................................................ 22
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 3
Junior Cert Science –Chemistry Notes
CHEMISTRY
The world is made up of a variety of substances.
Some of these occur naturally in our environment, others are made through the combination of naturally
occurring substances to form new materials.
The study of chemistry can lead us to a better understanding of our material world and the processes by
which materials can change and be changed.
Matter is anything that occupies space and has mass
There are three states of matter
• Solids, Liquids and Gases
Characteristics of the States of Matter
Solid
Fixed Shape
Fixed Volume
Cannot flow
e.g. iron, copper, sulphur
Liquid
Shape of Container
Fixed Volume
Can flow
e.g. water, mercury
Gas
Shape of Container
Shape of Container
Can flow
e.g. hydrogen. oxygen,
methane
Changes of State
Elements, Compounds and Mixtures
Elements: Cannot be broken down into anything simpler using chemical means or
Substance made up of one type of atom
 All the known elements are listed in the Periodic Table Invented by Dmitri Mendeleev
 Vertical columns are called Groups
 Horizontal rows are called Periods
 Metals are to the left of the red line and Non-metals are to the right of the red line
Periodic Table
Solid
Metals
Non-metals
H
1
Li
3
Be
4
Na
11
Mg
12
K
19
Ca
20
Sc
21
Ti
22
V
23
Cr
24
Mn
25
Fe
26
Cu
27
Ni
28
Cu
29
Rb
37
Sr
38
Y
39
Zr
40
Nb
41
Mn
42
Tc
43
Ru
44
Rh
45
Pd
46
Cs
55
Ba
56
La
57-71
Hf
72
Ta
73
W
74
Re
75
Os
76
Ir
77
Fr
87
Ra
88
Ac
89-103
Rf
104
Db
105
Sg
106
Bh
107
Hs
108
Mt
109
Liquid
© Mocks.ie 2011
B
5
C
6
N
7
O
8
F
9
He
2
Ne
10
Al
13
Si
14
P
15
S
16
Cl
17
Ar
18
Zn
30
Ga
31
Ge
32
Se
33
Sc
34
Br
35
Kr
36
Ag
47
Cd
48
In
49
Sn
50
Sb
51
Te
52
I
53
Xe
54
Pt
78
Au
79
Hg
80
Tl
81
Pb
82
Bi
83
Po
84
At
85
Rn
87
Ds
110
Rg
111
Uub
112
Uut
113
Uuq
114
Uup
115
Uuh
116
Uus
117
Uuo
118
Gas
Science – Chemistry Revision Notes Peter Jackson
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Junior Cert Science –Chemistry Notes
Physical Properties of two metals and two Non-metals
Element
Metal or Non-metal
State
Colour
Hydrogen (H)
Non-metal
Gas
Colourless
Carbon (C)
Non-metal
Solid
Black
Copper (Cu)
Metal
Solid
Salmon pink
Mercury (Hg)
Metal
Liquid
Silvery
Compounds: Substance made up of more than one type of atom chemically joined


Elements combine chemically to form compounds
When elements combine they lose their individual properties
o Sodium is a very reactive silvery metal
o Chlorine is a poisonous green-yellow gas
o Sodium chloride (table salt) formed when they react is a white crystalline solid
+
Sodium
=
Chlorine Gas
Table Salt Crystals
Properties of Simple Compounds and their Constituent Elements
Compound
Properties
Elements
Properties
H2O
Colourless liquid
Hydrogen
Colourless gas burns
Water
Does not burn
Oxygen
Colourless gas, supports combustion
CO2
Colourless gas
Carbon
Black solid
Carbon dioxide
Does not burn
Oxygen
Colourless gas, supports combustion
MgO
White powder
Magnesium
Silvery metal, burns
Magnesium oxide
Does not burn
Oxygen
Colourless gas, supports combustion
FeS
Grey solid
Iron
Grey shiny metal, burns if powdered
Iron sulphide
Does not burn
Sulphur
Yellow solid , burns
Mixtures: Substance made up of more than one type of atom NOT chemically joined
e.g. salt and sand, salt and water
Separating Sand and Water by Filtration
Filtration is used to separate an insoluble solid from a liquid
e.g. salt and sand
 Set up the apparatus as in the diagram
 Fold the filter paper twice and place it opened in the filter funnel
 Pour the mixture of sand and water into the filter paper
Result: The sand particles are trapped in the filter paper and
are called the residue. Water passes through and is called
the filtrate
Conclusion: Filtration can be used to separate an insoluble
solid from a liquid
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 5
Junior Cert Science –Chemistry Notes
Separating Salt and Water by Evaporation
Evaporation is used to separate a soluble solid from a liquid
e.g. salt and water
 Set up the apparatus as in the diagram
 Pour the salt water solution into the evaporating basin
 Place the evaporating basin on top of the boiling water bath
Result: The water evaporates leaving the salt behind
Conclusion: Evaporation can be used to separate a soluble solid
from a liquid
Separating Salt and Water by Distillation
Distillation separates a liquid from a soluble solid or another liquid, and collects
the liquid separated
 Set up the apparatus as shown
 Connect the bottom lug to the tap so that water enters the bottom of the
condenser
 The pipe from the top lug should go to the sink
 Heat the flask
 Collect the distillate in a beaker
Result: Water evaporates from the flask and is condensed (turned
back to water) in the Liebig condenser.
Conclusion: distillation can be used to separate and collect a
liquid from a soluble solid
Separating a Mixture of Inks using Paper Chromatography


Place a spot of black ink near the bottom of a strip of chromatography paper
Place the paper in water so that the black ink spot is above the water as
shown in diagram
 Leave for a time and observe the solvent moving up the paper
Result: the different inks are carried up the paper by the solvent at different
rates and so are separated.
Conclusion: Paper chromatography can be used to separate a mixture of inks
Metals

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are shiny (have a lustre) e.g. silver and fresh copper in new coins
can be stretched into wires (ductile) e.g. copper
can be hammered into sheets (malleable) e.g. gold leaf
conduct heat
conduct electricity
are used to make tins, cars, ships, bridges, knives, gold rings and bracelets etc.
Good examples of metallic elements are copper (Cu), zinc (Zn), aluminium (Al), iron (Fe), silver (Ag) and
gold (Au) [Learn these symbols]
Alloys are mixtures of metals (carbon is considered as a metal in this case)
Alloy
Bronze
Brass
Steel
Solder
© Mocks.ie 2011
Constituents
Copper (Cu) and Zinc (Zn)
Copper (Cu) and Tin (Sn)
Iron (Fe) and Carbon (C)
Lead (Pb) and Tin (Sn)
Uses
Ornaments, coins and statues
Door knobs, hinges and musical instruments
Ships, bridges and car bodies
Joining metals in electrical circuits
Science – Chemistry Revision Notes Peter Jackson
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Junior Cert Science –Chemistry Notes
Non-metals
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Are not shiny
Are brittle
Do not conduct heat
Don not conduct electricity (carbon is a notable exception)
Many are gases
You need to know the following non-metals and their symbols:
Carbon (C), Oxygen (O), Sulfur (S), Hydrogen (H) and Nitrogen (N)
Mixtures and Compounds
Compare a Mixture and a Compound made from the same Constituents
 Take some iron filings (14.0g) and powdered sulfur (8g)
 Note their colours (Iron grey and sulfur yellow)
 Mix fully
 Hold a magnet (wrapped in polythene) near the mixture
Result: iron filings stick to the magnet as mixture separates
 Remix the elements and place the mixture in a test tube
 Heat strongly in a Bunsen flame
 Note what happens
 Allow to cool and test once more with a magnet
Result:
 Mixture glows as they react and iron sulphide forms
 Iron sulphide is NOT magnetic
Conclusion:
 The constituents of the mixture retain their original properties
 The compound formed (iron sulphide) does NOT keep the
properties of the original substances
Water and Solutions
Solution: a mixture of a liquid (solvent) and a solid dissolved in it (solute) e.g. water and sugar
Water is a very good solvent
Dilute Solution: contains a small amount of solute (salt) in a lot of solvent (water)
Concentrated Solution: contains a large amount of solute (salt) in a small amount of solvent (water)
Saturated Solution: contains as much solute dissolved in it as is possible at a particular temperature
The Effect of Temperature on Solubility

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
Set up the apparatus as shown
3
Place 10 cm of water in the test tube
Place some copper sulfate (50g) on a filter paper
Weigh it
o
Heat the water bath to 20 C
Add a small amount of copper sulfate to the test tube and stir
Keep adding copper sulfate and stirring till no more dissolves
Calculate the amount of copper sulfate added by the change in weight of the
crystals on the filter paper
o
 Increase the temperature of the water bath to 40 C and repeat
o
 Increase the temperature of the water bath to 60 C and repeat
 Plot a graph of the amount of copper sulfate dissolved against temperature
Result: as the temperature increases the amount of copper sulfate that
dissolves increases
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 7
Junior Cert Science –Chemistry Notes
Conclusion: Solubility increases with temperature
Test for Water


Take some dry cobalt chloride paper (it should be blue)
Put a piece of cobalt chloride paper in (i) a test tube of water and
(ii) a test tube of pure alcohol
Result:
 Water turns the cobalt chloride paper blue
 Alcohol has no effect on the cobalt chloride paper
Conclusion: Cobalt chloride paper can be used as a test for water
Examine the difference between a Dilute, Concentrated and Saturated Solution

Make up three copper sulphate solutions
(i) Dilute
(ii) Concentrated
(iii) Saturated
Compare the solutions

Result
If the solution is coloured the colour gets deeper as the
concentration increases
Note: Copper sulfate solution is clear and blue while water is clear and colourless.
Growing Copper Sulfate Crystals


Dissolve copper sulfate crystals is hot water until you have a saturated solution
Divide the solution equally between two evaporating basins (leave any
undissolved crystals in the container)
 Place one evaporating basin on the bench to cool slowly
 Place the other on ice to cool it quickly
 Compare the two sets of crystals
Result:
o the crystals formed slowly on the bench are large
o the crystals formed quickly on the ice are smaller
Conclusion: The faster crystals are formed the smaller they are
Acids and Bases
An Acid is a substance that turns Blue Litmus Red
A Base is a substance that turns Red Litmus Blue
The pH Scale is a scale from 0 to 14 that tells how strong an acid or a base is

Substances with a pH of 7 are Neutral

Substances with a pH of less than 7 are Acidic

Substances with a pH of more than 7 are Basic
An Indicator is a substance used to show how acidic or basic a substance is
Litmus Indicator is red in acids and blue in bases
Universtal Indicator tells us how acidic or basic a substance is by turning a variety of colours
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 8
Junior Cert Science –Chemistry Notes
Investigate the pH of a Variety of Materials using the pH Scale
 Take a sample of the substance to be tested
 Disolve it in a small amount of water
 Add a few drops of universal indicator and mix
 Note the colour against the supplied chart (see above)
 Record the pH
Results: See table below
Strong Acids
Weak Acids
Neutral
Weak Bases
Strong Bases
Sulfuric Acid
Hydrochloric Acid
Nitric Acid
Vinegar
Lemon Juice
Rainwater
Nettle sting
Pure Water
Alcohol
Sugar solution
Salt Solution
Toothpaste
Baking Soda
Soap
Sodium hydroxide
Potassium hydroxide
Ammonia solution
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 9
Junior Cert Science –Chemistry Notes
Air, Oxygen, Carbon Dioxide and Water
Air, oxygen and carbon dioxide are important chemicals in our everyday lives.
Knowledge of their properties helps us to develop an understanding of the role they play.
Acids and bases are present in many everyday materials, including common household substances, and
salts are produced when acids and bases react.
Air and Oxygen
Air as a mixture of gases because
 the components are not chemically joined
 its composition can vary
 it components can be separated by physical means
Component
Abundance
Nitrogen [N2]
78%
Oxygen [O2]
21%
Carbon Dioxide [CO2]
0.03%
Water Vapour [H2O]
Variable
Other gases [Methane, Noble Gases]
The balance
Show that approximately One Fifth of the Air is Oxygen


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

Note


Set up the apparatus as shown
Heat the copper strongly
Slowly pass the air over the hot copper using the
syringes
Repeat several times
Allow the system to cool
Note the volume of air left in the syringe
3
The change in volume is the volume of oxygen (20 cm )
1
% oxygen = change in volume  100 = 20  100 = 20% ( /5)
A similar result can be achieved by placing a large measuring cylinder over a burning candle floating on water
It is not as accurate because the candle goes out before all the oxygen is used.
Show that there is CO2 and Water Vapour in Air
 Set up the apparatus as shown
 Connect to the suction pump as indicated
 Turn on the suction pump
Result
1. The cobalt chloride paper turns from pink to blue
2. The lime water turns milky
Conclusion
1. Air contains water vapour
2. Air contains carbon dioxide
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 10
Junior Cert Science –Chemistry Notes
Prepare a sample of Oxygen by decomposing H2O2 using MnO2 as a Catalyst

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


Place some Manganese Dioxide (MnO2) into a flask
Slowly drop Hydrogen Peroxide (H2O2) from a dropping funnel
Allow some bubbles of impure gas to escape
Collect the pure oxygen gas over water in a gas jar
Place a gas jar full of water on the beehive shelf as shown
When the gas jar is full lift it slightly and seal it with a lid
Remove the gas jar and replace it with a fresh one
Investigate the ability of Oxygen to Support Combustion in a Wooden Splint and a Candle
 Light a wooden splint (or candle)
 Blow it out so that it splint remains glowing
 Place into a gas jar full of oxygen
Result: the splint (or candle) bursts into flame
Conclusion: oxygen supports combustion.
 This test can be used to identify oxygen
Uses of oxygen
 Respiration in cells to produce energy
 Needed for combustion (burning)
Properties of Oxygen
 Colourless, odourless, tasteless
 Slightly heavier than air
 Neutral to litmus
 Supports combustion
 Reacts with substances forming oxides
Burning Carbon and Magnesium in Oxygen
 Collect some gas jars of Oxygen
 Using a combustion spoon burn some carbon (charcoal) in air
 Quickly plunge it into a gas jar of oxygen
 Then add some damp blue and red litmus paper into the jar
Result:
 The charcoal burns more brightly forming carbon dioxide
 The red litmus is unchanged but the blue litmus turns red
Conclusion: carbon dioxide is an acidic gas
 Repeat using magnesium instead of carbon
Result:
 Magnesium burns with a white flame
 Magnesium burns more brightly forming magnesium oxide
 The red litmus turns blue but the blue litmus is unchanged
Conclusion: magnesium oxide is a basic oxide
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 11
Junior Cert Science –Chemistry Notes
Prepare Carbon Dioxide

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
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Set up the apparatus as shown
Add dilute hydrochloric acid to the marble chips using the dropping funnel
Collect the CO2 in a gas jar over water
The gas jar is full of CO2 when a lighted splint is extinguished at the top
Put a lid on the gas jar and collect several other jars
To Show that CO2 turns Limewater Milky


Add lime water to a test tube of CO2 and shake it
The lime water turns milky so the gas is CO2
Show that CO2 is Acidic when it Dissolves in Water



Place a piece each of moist red and blue litmus paper in a gas jar and
shake
Result: The red paper remains red but the blue litmus paper turns red
Conclusion: This tells us that CO2 is an acid when it dissolves in water
Show that CO2 is Heavier than Air and Does Not Support Combustion
 Place a burning candle in a beaker
 Pour CO2 into the beaker
Result: The candle goes out
Conclusion:
 Carbon dioxide is heavier than air
 Carbon Dioxide does not support combustion
Uses of Carbon Dioxide
 Fire Extinguishers - because it is heavier than air and does not support combustion
 Fizzy drinks – it gives them the sharp taste and the fizz
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 12
Junior Cert Science –Chemistry Notes
Hardness in Water
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Hard water is water that forms a scum with soap
Soft water is water that forms a lather with soap
Temporary Hardness: hardness that can be removed by boiling
Permanent Hardness: hardness that cannot be removed by boiling.
Hardness is caused by dissolved substances in the water e.g. calcium and magnesium
Hardness can be removed by ion exchange (swopping calcium and magnesium ions for sodium ions)
Test Water for Hardness (Soap Test)
 Dissolve some soap in water
 Place some hard water [bottled water] in a test tube
 Place some soft water [deionised water] in another test tube
 Add soap solution to both
 Stopper the test tubes and shake vigorously
Result: Soft water forms suds [a lather]
Hard water forms a scum [does not lather]
Conclusion: Hard water forms a scum or does not lather with soap.
Soft water forms a lather with soap
Water Treatment: makes water clean and safe to drink

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
Screening: wire mesh removes large pieces of debris from water e.g. nappies, bottles etc.
Flocculation: chemicals [Aluminium sulphate] are added to the water to make small particles clump
together
Sedimentation: Large tanks where water moves very slowly allows these heavy particles to sink to the
bottom of the tanks. Clean water passes on to the next stage of treatment.
Filtration: water is passed through beds of sand which catches particles that are too small to sink
Chlorination: small amounts of chlorine are added to the water to kill any bacteria and make the water
safe to drink.
Fluoridation: small quantities of fluorine are added to the water to prevent tooth decay
Storage: water is stored under cover before distribution to prevent it being contaminated
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 13
Junior Cert Science –Chemistry Notes
Detect the Presence of Dissolved Solids in a Water Sample
 Set up the apparatus as shown
 Place a sample of tap water on the clock glass
 Heat the water on the clock glass so that it evaporates
Result: when the water on the clock glass has evaporated it leaves a white residue
on the clock glass
Conclusion: water contains dissolved solids
Distillation of Sea Water to obtain Pure Water


Place some sea water in the flask
Connect the Liebig condenser as shown with the water supply to the
lower connection and the upper connection to the sink
 Heat the sea water with a bunsen burner
Result: water evaporates and is condensed and pure (distilled) water is
collected in the beaker
Conclusion: Distillation separates pure water from sea water
Electrolysis of Water
 Set up the apparatus as shown
 Fill the voltameter with water plus a little sulfuric acid
 Connect the electrodes to the battery
Result
 A chemical reaction occurs as the current passes through the liquid.
This is electrolysis.
 Hydrogen collects at the cathode. Identified by burning with a slight
pop
 Oxygen collects at the anode. Identified by relighting a glowing
splint
 There is twice as much hydrogen as oxygen
Conclusion: Water is made of two parts hydrogen to one part oxygen. H2O
Acids and Bases
Common Strong Acids and Bases
Strong Acids
Strong Bases
HCl [Hydrochloric acid]
NaOH [Sodium hydroxide]
H2SO4 [Sulfuric acid]
KOH [Potassium Hydroxide]
HNO3 [Nitric acid]
Ca(OH)2 [Calcium hydroxide]
Alkalis are bases that are soluble in water
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 14
Junior Cert Science –Chemistry Notes
Reactions of Acids and Bases
Neutralisation of an Acid with a Base using an Indicator


When an acid reacts with a base, a salt and water are formed
This is called neutralisation
Learn all the equations in this chapter carefully - first as word equations and then as chemical equations
Titrate HCl against NaOH, and prepare a sample of the salt NaCl
Titration





3
Put exactly 20 cm of sodium hydroxide solution into a conical flask
Add a few drops of Universal Indicator solution
Slowly add hydrochloric acid from the burette and mix by swirling
When the solution goes green stop adding the acid
Record the amount of acid added
Extracting the salt






3
Take a fresh conical flask and add exactly 20 cm of sodium hydroxide
solution
Add exactly the same volume of acid to it and mix
Place the solution in an evaporating basin
Evaporate the water using a Bunsen burner
Result: sodium chloride salt crystals form in the basin
Conclusion: Neutralising NaOH with HCl forms the salt NaCl and water
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
Page 15
Junior Cert Science –Chemistry Notes
Atomic Structure, Reactions and Compounds
All substances contain atoms.
All atoms contain sub-atomic particles and different atoms contain different numbers of these particles.
The principal sub-atomic particles are protons, neutrons and electrons.
Why and how substances react is related to their atomic structure.
Basic Atomic Structure
Atom: the smallest particle of matter that can exist by itself

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The atom consists of a very small, dense central core called the nucleus
The nucleus consists of protons and neutrons
All atoms have electrons orbiting the nucleus in shells
Lithium Atom
Sub-atomic Particle
Mass
Charge
Location
Proton
1 atomic mass unit
Positive (1+)
In Nucleus
Neutron
1 a.m.u.
No charge (neutral)
In Nucleus
Electron
10.00055 a.m.u.
Negative (1-)
Orbiting the Nucleus
Atomic Number: the number of Protons in a nucleus
Neutral Atom: atoms are neutral because they have the same number of protons and electrons and so their
charges cancel out
Number of Electrons = Atomic Number
Number of Neutrons = Mass Number– Atomic Number
23
Na
11
40
Ca
20
14
N
7
35
Cl
17
© Mocks.ie 2011
Mass Number
Number of Protons plus Neutrons
Symbol
Sodium
Atomic Number
Number of protons (and electrons)
11 P (6 e )
Mass Number
Number of Protons plus Neutrons
20 P and 20 N
Symbol
Calcium
Atomic Number
Number of protons (and electrons)
20 P (20 e )
Mass Number
Number of Protons plus Neutrons
7 P and 7N
Symbol
Nitrogen
Atomic Number
Number of protons (and electrons)
7 P (7 e )
Mass Number
Number of Protons plus Neutrons
7 P and 18 N
Symbol
Chlorine
Atomic Number
Number of protons (and electrons)
Science – Chemistry Revision Notes Peter Jackson
11 P and 12 N
-
-
-
-
17 P (17 e )
Page 16
Junior Cert Science –Chemistry Notes
Electronic Structure


This describes the arrangement of electrons in shells around the nucleus
The electrons are placed in shells starting from the shell nearest the nucleus and moving out to the next shell
once that shell is full
o First Shell can hold up to 2 electrons
o Second Shell can hold up to 8 electrons
o
o
Third shell can hold up to 8 electrons
The remainder go into the fourth shell
Bohr Model of Atom
Bohr Diagram: a diagram showing the arrangement of electrons in an atom
Sodium Na
Bohr Diagram of a Sodium Atom
More Bohr Diagrams
Aluminium
Calcium
Hydrogen
Oxygen
Neon
Isotopes: atoms of an element which have the same number of protons but different numbers of neutrons
Carbon 12
Carbon 14
Noble Gases
 Do not react
 They each have a full outer shell of electrons
 This makes them very stable (unreactive)
Bonding
Molecule: a group of atoms chemically joined or
the smallest particle of a compound that shows the properties of that compound
 When atoms bond they are trying to get a full outer shell
 So that they will be stable like the noble gases
There are two types of bonds used when forming compounds
Ionic Bonds


One type of atom loses electrons to get a full outer shell and becomes positively charged
The other type of atom gains electrons to get full outer shell and becomes negatively charged
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
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Junior Cert Science –Chemistry Notes

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These two opposite charges attract each other and form an ionic bond
Ion: is an atom (or group of atoms) with a charge
Examples of Ionic Bonds
Magnesium Oxide - MgO
Sodium Chloride - NaCl
Covalent Bonds

Atoms share electrons in pairs, one electron from each atom, to get a full outer shell
Examples of Covalent Bonds
Note
The inner electron shells have been left out to make
things clearer. You do not have to draw them
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
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Junior Cert Science –Chemistry Notes
Properties of Ionic and Covalent Substances
Covalent Compounds
Ionic Compounds
Made of molecules
Made of oppositely charged ions
Usually Liquids or solids
Usually crystalline solids
Low melting and boiling points
High melting and boiling points
Usually insoluble in water
Usually soluble in water
Do not conduct electricity
Conduct electricity when molten or dissolved in water
Investigate the Ability of Ionic and Covalent Substances to Conduct Electricity
 Set up the apparatus as shown
 Pour in a covalent compound (e.g. pure water)
 Close the switch and record what happens
Result: the bulb does not light
 Empty the apparatus and replace with an ionic compound (e.g. salt
solution)
 Close the switch and record what happens
Result: the bulb lights
 Empty the apparatus and repeat with a number of ionic and covalent
compounds
Conclusion: ionic substances conduct electricity when in solution and
covalent substances do not.
Rusting and Corrosion




Rusting as a chemical process in which iron becomes a new
compound: iron oxide
Rust flakes off exposing more iron
Rusting needs water and oxygen
The presence of salt makes rusting worse
Flaking Rust
Demonstrate that Oxygen and Water are Necessary for Rusting



Set up the apparatus as shown
Tube A has both oxygen and water
Tube B has no water as calcium chloride absorbs any water
present
 Tube C has no oxygen as boiling removes the oxygen and the
oil stops any getting back into the water
Result: nail in test tube A rusts. B and C don’t rust
Conclusion: oxygen and water are both needed for rusting
Preventing Rusting




Rusting is prevented by keeping either water or oxygen or both away from the iron
Paint: keeps out air and water
Oil: keeps out air and water
Galvanising: i.e. covering with a layer of zinc, keeps out air and water
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
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Junior Cert Science –Chemistry Notes
Metals
Alkali Metals
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
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

Group I of the Periodic Table
They have similar properties because they all have one electron in
their outer shell
They are soft and can be cut with a knife
When fresh they have a metallic lustre (sheen)
They react rapidly with air and quickly tarnish (turn dull) each forming its
oxide e.g. sodium + oxygen = sodium oxide
They react rapidly with water forming hydrogen and a hydroxide
o Lithium + water  lithium hydroxide and hydrogen (fast)
o Sodium + water  sodium hydroxide and hydrogen (very fast)
o Potassium + water  Potassium hydroxide and hydrogen
(extremely fast, often catches fire and may explode)
Stored under oil to prevent reaction with air and water
As you go down the group they become more reactive
Potassium and water reacting
Alkaline Earth Metals


The elements of Group II are the alkaline earth metals
They are less reactive than the alkali metals
The Reaction between Zinc and HCl, and a Test for Hydrogen



Place some dilute hydrochloric acid in a test tube
Add a little zinc
Place your thumb lightly over the mouth of the test
tube and wait a couple of minutes
Result: the test tube fills with hydrogen gas
Test: place a lighted taper to the mouth of the test tube.
Result: the gas burns with a squeaky pop
Conclusion: the gas is hydrogen
Zn +
2HCl

Zinc + Hydrochloric
acid
ZnCl2 + H2
Zinc
Hydrogen
chloride
Relative reactivities of Ca, Mg, Zn, and Cu based on their reactions with water and acid
Reaction with Water
 Place a sample of each metal Ca, Mg, Zn, and Cu in a test tube
 Add water to each test tube
 Note what happens
Result: Calcium reacts and produces hydrogen gas
Conclusion: Calcium is the most reactive of the four metals
Reaction with Dilute Hydrochloric Acid
 Place a sample of each metal Ca, Mg, Zn, and Cu in a test tube
 Add dilute hydrochloric acid to each test tube
 Note what happens
Result: Calcium reacts and produces lots of hydrogen gas bubbles
 Magnesium produces bubbles but not as many as calcium
 Zinc produces bubbles but not as many as zinc
 Copper produces no bubbles
Conclusion: In order of decreasing activity Ca, Mg, Zn and Cu
(Equations not required)
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
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Junior Cert Science –Chemistry Notes
Hydrocarbons
Hydrocarbons are compounds that are made of carbon and hydrogen only

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Fossil fuels are our main sources of hydrocarbons
Made from the fossilised remains of plants and animals millions of years ago
o Coal
o Crude oil
o Natural gas which is mainly methane
o Peat (much more recent 5 – 10,000 years ago)
Not made any more as conditions have changed
Limited supply (non-renewable) so they will run out sometime
Need to be conserved
They are used as fuels and to make plastics
Many contain traces of sulphur
Oil Well - Gusher
Combustion of Fossil Fuels




We burn huge amounts of fossil fuels petrol, diesel, kerosene (jet fuel)
Hydrocarbon + Oxygen  CO2 + H2O + heat when burned
CO2 is a greenhouse gas and contributes to global warming
CO2 dissolves in rain to form carbonic acid. This is not acid rain (normal rain is slightly acidic)
Acid Rain
Cause
 The sulphur impurities in fossil fuels produce SO2 when they burn
 SO2 dissolves in rain to form sulphuric acid and this is acid rain
Effects
 Kills plants,
 Kills fish and other aquatic life
 Reacts with limestone dissolving it quickly and leading to corrosion of buildings
 Reacts with iron in cars and buildings causing corrosion
 Reduces the fertility of agricultural land
Corroded Statue
Remedies
 Use low sulfur fuels e.g. natural gas
 Acidified lakes can be improved by adding lime (a base) which neutralises the acid
Dying Trees
Plastics


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Substances that are made from chemicals obtained from crude oil
Good heat insulators
Good electrical insulators
Waterproof
Strong and flexible
Long lasting
Resistant to chemical attack
Everyday Applications of Plastics
Plastic
Use
Properties on which use depends
Polythene
‘Plastic’ bags, squeezy bottles, lunchboxes
Flexible, strong, resistant to chemicals
Rigid PVC
Window and door frames, gutters, floor tiles
Weather resistant, long lasting
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
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Junior Cert Science –Chemistry Notes
Flexible PVC
Electric wire insulation, hosepipes
Electrical insulator, flexible, long lasting
Polystyrene
Yoghurt pots, food containers
Strong (but brittle), waterproof
Expanded
Polystyrene
Shock proof packaging of delicate objects,
drink cups, insulation in cavity walls
Very good heat insulator, good shock
absorber
Nylon
Tights, shirts, carpets, combs
Can be spun into fibres, dirt resistant
Perspex
Windows, light covers in cars
Tough, rigid, transparent, light
Plastics and Pollution




Substances which are not broken down by bacteria, fungi and other
living organisms are said to be non-biodegradable
They can last for thousands of years and can thus cause pollution
e.g. plastic bags look terrible in hedges, can choke and kill animals, etc
Recycling reduces pollution
Tax on plastic bags has greatly reduced pollution
Role of Chemistry
Chemistry affects most areas of our daily lives

Pharmacy
o Making perfumes and soap
o Making medicines

Fuels
o To keep us warm
o Drive our vehicles

Food
o
o
Making packaging e.g. crisp packets
Modifying food e.g. turning vegetable oils into margarine

Agriculture
o Making fertilisers
o Making cleaning chemicals

Building Industry
o Making cement and concrete
o Making PVC windows, doors and gutters

Household Appliances
o Making plastics for kitchen utensils
o Television cases
© Mocks.ie 2011
Science – Chemistry Revision Notes Peter Jackson
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