CHEMISTRY
FORM 1
Lesson Notes 2013
By OnyangoNgoye
Table of contents
1. Unit 1
Introduction to Chemistry
2. Unit 2
Simple classifications of substances
3. Unit 3
Acids, ashes and indicators
4. Unit 4
Air and combustion
5. Unit 5
Water and hydrogen
UNIT ONE
Introduction to chemistry
Specific objectives.
•Explain what the study of chemistry is.
•Name and state the uses of common apparatus
in the laboratory.
•Describe a Bunsen burner and its flames.
•State laboratory safety rules.
TOPIC SUMMARY
a)Definition of chemistry.
•Chemistry is a branch of science that deals with
structures and composition of substances and the
way they behave under different conditions.
•Chemistry is studied by carrying out experiments
to make some observations and drawing
conclusions from the data collected.
b)Importance of studying chemistry
The study of chemistry enables one to:•Discover new materials and new chemicals
techniques applied in industrial processes.
•Understand and manipulate the environmental a
factors affecting man.
•Have knowledge in extraction of chemicals from
plants and purification of substances.
•It is a career subject.
c)Some chemistry concepts learnt in primary
school level.
Matter
•Matter is anything that has mass and can occupy
space.
•The states of matter are:•Solids
•Liquids
•Gases
Conductors and Non-conductors
•A conductor is a solid substance that allows
electric current to pass through it.
•Conductors are not decomposed by electric
current.
•All metals are conductors. Graphite is also a
conductor.
•Non-conductors are solid substances that do
not allow electric current to pass through them.
All non-metals except graphite are nonconductors
Drugs and drug-abuse
•A drug is any natural or man made substance
which when taken changes in some way the
normal working of a body.
•Drug-abuse is the use of drugs for any other
purpose other than for which it is intended to.
Over-the-counter drugs (OTC drugs)
•These are medicinal drugs that can be bought
from a chemist or a retail shop without doctors
prescription.
•Examples are painkillers and anti acids.
Drugs of Dependency
Drugs of dependency
These are drugs that contain substances that
causes addiction and makes the user
uncomfortable when they have not used them.
How to prevent drug abuse.
•Follow prescription and medicine dosage when
using a medicinal drug.
•Avoid taking any illegal drug.
•Avoid the company of those who abuse drugs.
•Utilize the leisure time properly.
Common Apparatus In A Laboratory.
-A laboratory is a room equipped with chemicals
and apparatus in which chemistry is studied.
-Apparatus are pieces of equipments used to
study chemistry. Apparatus could be made up of
glass, plastic or metal.
-Most apparatus are made up of glass because
glass is transparent and does not react with most
chemicals.
-Apparatus can be classified according to their
uses.
Examples are;
Apparatus for measuring volumes of liquids
Graduated beakers
Measuring cylinder
Conical flask
Volumetric flask
Burette
Apparatus in which substances are heated
Test tubes
Boiling tubes (are larger and wider than
test tubes and gives room for sparting substances)
Deflagrating spoon
Round bottomed flask
Crucible
Apparatus for measuring mass.
• Beam balance
• Electrical balance.
Apparatus for measuring time.
• Stop watch
• Clock
The Bunsen Burner
• Diagram
Functions of the difference parts of a Bunsen burner
• Chimney
-Allows gases to mix.
When gases are ignited they burn
at the end of the chimney
• Collar
Regulates the amount of air
entering into the chimney
• Air hole
-Allows air to enter into the
chimney
• Jet
-Allows laboratory gas into the
chimney.
• Rubber
-Connects the gas inlet to an external
tubing source of laboratory gases.
• Base
-Supports the burner.
Types of flames of Bunsen burner
- The type of flames produced when a Bunsen burner is lit
depends on if the air hole is opened or closed.
-They type of the flame produced when the air hole is
closed is called a luminous flame.
-The type of the flame produced when the air hole is
opened completely is called a non-luminous flame.
Differences between luminous and non-luminous flames.
LUMINOUS
NON-LUMINOUS
Formed when the air hole is closed
Formed when the air hole is opened
Produces a lot of light
Produces a lot
Large and wavy
Small and steady
Produce soot
Does not produce soot
Burns quietly
Burns with a roaring sound
POINTS TO NOTE
-When hot in use a lit Bunsen burner should be turned
into a luminous flame because it is noticeable and does
not ‘strike back’.
-Non-luminous flame is preferred for heating substances
in a laboratory because of its hot and does not produce
soot which make apparatus dirty.
-The almost colorless region of a non-luminous flame is
cold and consists of unborn gases
Laboratory safety rules
-When observed, safety rules prevent a chemist
from the common laboratory accidents; burns, cuts,
explosives, fire outbreak and eye damage.
The following are the safety rules;
-Enter the laboratory in an orderly manner.
-Never run while in a laboratory.
-Do not taste or eat anything in a laboratory.
-Put off flames not in use.
-Always consult your teacher before trying any new
experiment.
-Label the chemicals you are using to avoid
confusion.
-Put away flammable substances away from flames.
Always use a clean bench when carrying our
experiments.
-Always use a clean spatula to scoop chemicals from
containers.
-Always hold test tubes with a test tube holder when
heating substances.
-When heating substances, never point the open end of
the tube towards yourself or anyone else.
-Experiment in which poisonous gases are produced
should be carried out in a fume chamber or in the
open.
-In case a chemical pours on your skin, rinse it with a
lot of running water.
-
Laboratory Rules Continued.
• Never look directly into flasks where reaction is taking place.
-Never smell gases produced during experiment directly
instead direct the fumes carefully towards you, using your
hand.
-In case of an accident, a student should report the matter to
the person in charge for first aid. Other students should
remain cal, for panicking may worsen the situation.
-Always dispose chemicals already used safely.
-Always clean the bench and apparatus after an experiment.
-Returns the apparatus into their correct place after use.
-Wash your hands with running water before leaving the
laboratory.
Topic Summary
a)Mixtures
• A mixture consists of two or more substances put together and can
be separated by physical means.
• The substance in a mixture are not chemically combined.
• Substances in a mixture retain their physical and their chemical
properties.
b)Types of mixtures
• There are 3 types of mixtures;
• Solid/ solid mixtures e.g. sand and iron filings.
• Liquid/ liquid mixtures e.g. water and ethanol or water and
kerosene.
• Solid/ liquid mixtures e.g. salt and water or sand and water.
c)Separating Mixtures.
To separate an insoluble solid from a liquid e.g.
sand from water.
• There are two techniques:
i)Decantation- the solid particles are allowed to
settle and the liquids is poured off carefully.
• Limitation – some solid particles may drop off
with the liquid that is poured off.
ii)Filtration- the mixture is poured into a filter
funnel fitted with a filter paper.
Application of the separation techniques
• Extraction of salt from seas and salty lakes e.g.
L. Magadi.
• Extraction of sugar from sugarcane.
• Extraction of medicinal substances from plants.
ii)To separate two immiscible liquids e.g. water and
kerosene.
• Liquids are solids to be immiscible if they form
layers when put together
• Separating techniques
• Use of separating funnel
• Use of a teat pipette
• Diagram on use of a separating funnel.
iii)To separate miscible liquids e.g. water and
ethanol.
• Two liquids are said to be miscible if they form a
uniform mixture, when put together.
• Separating technique
• Fractional distillation
• Conditions
• Liquids must have close but different boiling
points.
Application
• To separate components of crude oil at Changamwe Oil
Refinery.
• Large scale isolation of oxygen and nitrogen from air.
• Manufacturing of spirits.
iv)To obtain a solute from a solution e.g. salt from water
• A solute is a solid substance that dissolve in a liquid.
• Solvent is a liquid substance in which a solute dissolves.
• A mixture of a solute and a solvent is called a solution.
• Technique
• Evaporation- the mixture is heated to dryness
Application
v)To obtain both solute and solvent from a
solution e.g. to obtain salt and water from a
salt solution.
• Technique
• Simple distillation
• To obtain pure water from areas where the
available water is salty.
vi)Separating coloured substances e.g.
components of black ink.
• Technique
• Paper chromatography
Points to Note.
• Chromatograms are the rings formed as the coloured
substances separate.
• A suitable solvent (such as propane) is introduced into
the original spot of the dye for the colours to separate.
• A solvent front is the farthest distance moved by a
solvent on a chromatographic paper.
• The ring formed near the solvent front is of the colour
that is more soluble.
• The ring formed near the original spot as of the colour
that is less soluble.
vii)To extract oil from grains e..g elianto pil from maize seeds.
Techniques
• Solvent extraction
Procedure
• Gride the seeds as you add a suitable solvent e.g. propane
• Continue griding until an extract is formed
• Filter the extract and pt the fitrate under the sun for
propane to evaporate.
• Confirm the liquid left as oil using a paper oil makes a paper
to be translucent.
viii)Other separating techniques
• Use of magnet
• Hand picking
• Sublimation
d) Pure substances
• A substance is pure if it does not contain other
substances (impurities) in it.
• The purity of a substance is determined by
melting point or boiling point.
• Impurities rises the boiling point of a substances
and lowers the melting point of a substance.
e) Difference between permanent and non-permanent changes
PERMANENT CHANGE
NON-PERMANENT CHANGE
i) A new substance is formed
i) No new substance is formed
ii) Mass of the substance changes
ii) Mass of the substance
iii) Change is not reversible
iii) Change is reversible
iv) Accomplished by heat changes
iv)Not accompanied by heat
• A pure substance has a definite boiling point
and a melting point.
• Impure substances boil and melt over a range
of values.
• A boiling point is a specific constant
temperature for particular liquid in which a
liquid changes into vapour form.
• A melting point is a specific constant
temperature for particular solid in which a
solid changes into a liquid form.
THE ATOMIC THEORY
• An element is a substance which cannot be split
into any simpler substances by chemical means.
• An atom is the smallest particle of an element
that possibly take part in a chemical reaction.
• A compound is a substances formed when two
or more elements react.
• A molecule is the smallest unit of a compound.
Names of Some Elements &Symbols
ELEMENT
SYMBOL
Carbon
C
Nitrogen
N
Sulphur
S
Hydrogen
H
Oxygen
O
iodine
J
Examples of elements whose symbols are derived from English names and consists of two letters.
ELEMENT
SYMBOL
Calcium
Ca
Chlorine
Cl
Zinc
Zn
Aluminium
Al
Bromine
Br
Magnesium
Mg
Manganese
Mn
helium
He
Argon
Ar
iii)Examples of elements whose symbols are derived from their latin names.
Elements
Latin name
Symbol
Sodium
Natrium
Na
lead
Publum
Pb
copper
cuprum
Cu
Silver
argentum
Ag
Potassium
kallium
K
Iron
Ferrum
Fe
Points to Note
• When a symbol is represented using a single
letter it should be a capital letter.
• When a symbol is represented using two letter
the first should be a capital letter while the
second is a mall letter. The letters should not
be joined.
UNIT THREE
ACIDS, BASES AND INDICATORS
Specific Objectives
• Prepare and use plant extract as acid-base
indicators.
• Use indicators to identify acids and bases.
• State effects of acids on substances.
What is an Acid?
• An acid is a compound containing hydrogen ions
which can be replaced either directly or indirectly
by a metal or an ammonium ion (cationic radical).
There are two types of acids
Organic acid and mineral acids.
Examples
Name of acid
Where found
- Citric acid
-Lemon juice
-tartaric acid
-Baking powder, grapes and tamarids
-carbonic acid
-fizzy drinks
-ethnoic acid
-vinegar
-tannic acid
-tea
Common Mineral Acids
Acid
Chemical formula
- Hydrochloric acid
HCl
-sulphuric acid
H2SO4
-nitric acid
HNO3
-carbonic acid
H2CO3
Properties of Acids
•
•
•
•
•
•
Has a sour taste.
Turns blue litmus paper to red.
Have a pH less than 7.
Reacts with metals to form salt and hydrogen gas.
Reacts with bases to form salt and water only.
Reacts with metal carbonates to form salt, water
and carbon (iv) oxide.
• Reacts with metal hydrogen carbonates to form
salt water and carbon (iv) oxide.
Bases
• Bases are substances which can neutralize
an acid to give salt and water.
• Soluble bases are called alkalis.
Examples of Bases
BASE
CHEMICAL FORMULA
Sodium hydroxide
NaOH
Potassium hydroxide
kOH
Magnesium hydroxide
Mg(OH)2
Calcium hydroxide
Ca(OH)2
Sodium Oxide
Na2O
Potassium Oxide
k2O
Important points to Note
• Metal oxides and metal hydroxides are bases.
• Sodium and potassium oxides and hydroxides
a soluble bases (alkalis)
• Properties of bases
• Turn red litmus papers to blue
• Neutralizes acids to form salt and water only.
• Have pH value of above 7.
Indicators
• An indicator is a substance which changes to a
certain colour in base and into a different
colour in an acid.
• To prepare an acid-base indicator from plant
extract e.g. from flower petals.
Procedure of preparing Indicators from flower Extracts
• Put flower petals into a mortar
• Add a few drops of ethanol (suitable solvent) into
flower petals
• Crush the petals with a pestle as you add ethanol.
• Warm the extract
• Decant/filter the extract into a petri dish for ethanol
to evaporate
• The residue is the acid-base indicators.
• Commercial indicators
Commercial indicators
Indicators
Colour in acid
Colour in base
- Litmus paper
- Red
- Blue
-Methyl orange
-Red(pink)
-(yellow
-Phenolphthalein
-colorless
-pink
-screen Methyl orange
-red/pink
-yellow
Important points to Note
• A universal indicator gives a Same of colours depending
on the strength of an acid or a base
• PH 7- neutral solutions
• PH less than 7- bases
• Colour of the universal indicator in a:• Strong acid- red
• Strong base- violet
• Weak acid- yellow
• Weak base- blue
UNIT FOUR
AIR AND COMBUSTION
Specific Objectives
• State the percentage composition of air by volume
• Carry out simple experiments to show that oxygen is the active part of air.
• Determine the percentage of oxygen in air using suitable methods.
• Describe the combustion of specified elements in air and oxygen and name the
•
products.
• Explain how liquefied air can be separated into its components by fractional
•
distillation
• Carry out experiments to investigate the conditions. Necessary for rusting and
•
state the composition of rust.
State methods of preventing rusting
• Prepare oxygen, investigate its properties and state its uses.
• Arrange some elements in order of their reactivity with oxygen using
•
experimental data.
State the uses of reactivity series.
Percentage Composition of Air by Volume
Gas
Percentage composition by volume
- Nitrogen
78%
-oxygen
215
-carbon(iv)oxide
0.03%
-noble gases
0.97%
-water vapour
Variable
-dust particles and other impurities
Variable
Experimental Results
• Mass of crucible + lid =xg
• Mass of crucible + lid + Magnesium ribbon and
before heating = yg
• Mass of magnesium ribbon = X-Y =zg
• Mass of crucible + lid + magnesium after the
experiment =Ag
• Mass of Magnesium Compound after experiment
= A-Y +Bg
• Percentage composition of oxygen
Important points to Note
The mass of crucible contents after experiment
is greater than that of its contents at the
beginning of the experiment because oxygen
is added to magnesium in heating magnesium
ribbon
• Combustion of specifies elements in air and
oxygen
• When a substance burns in air, oxygen is
added (oxidation) and the mass increases.
Examples of Oxides formed under different Conditions.
2C(s) + O2(g)
(limited)
C(s) + O2 (g)
(excess)
4Na(s) + O2(g)
(cold)
2Na(s) +O2(g)
(hot)
4P(s) + 3O2(g)
(limited)
4P(s) + 5O2(g)
(excess)
2CO(g)
(carbon (II) Oxide)
CO(g)
(Carbon (IV) Oxide)
2Na2O(s)
(sodium Oxide)
Na2O(s)
(Sodium Peroxide)
2P2O3
(Phosphorus (III) Oxide)
2P2Os
(Phosphorous (V) Oxide)
Laboratory Preparation of Oxygen
Equation for the reaction
2H2O2 (l)
manganese (IV) OxideO2
(g) + 2H2O(l)
(Catalyst)
Sodium peroxide and water could be
used in place of hydrogen peroxide
and Manganese oxide as in the
equation.
2Na2O2 (s)
O2(g) +
2Na2O (s)
Industrial preparation of oxygen by fractional distillation of liquid air.
Air is a mixture of gases:- Carbon (IV) oxide (CO2), water vapour (H2O),Noble
Gases. Helium and argon, Oxygen (O2) and nitrogen (N2)
The reactivity Series
•
•
•
•
•
•
•
•
•
•
•
•
K
Na
Ca
Mg
Al
Zn
Fe
Pb
Cu
Hg
Ag
Au
Most reactive
Least reactive
Redox
iv)Competition for combined oxygen
Oxidation- addition of oxygen to a substance
Reduction- removal of oxygen from a compound
In a redox reaction, a more reactive metal removes the combined oxygen in a
metal lower than it in a reactivity series.
Example :Reduction reaction
Mg (s) + CuO
MgO + Cu
Oxidation reaction
The substance that undergoes oxidation reaction is called a reducing agent.
The substance that undergoes reduction reaction is called an oxidizing agent.
Chemical &Physical Properties of Oxygen
Physical properties.
• Colourless
• No smell
• Slightly soluble in water
• Slightly denser than air
Chemical properties.
• Reaction with metals to form basic metal oxides.
• Reacts with non-metals to form acidic non-metal
oxides except water and carbon (II) oxide which
are neutral
Uses of Oxygen.
• Mountaineering
• In hospitals to people with breathing problems
• In steel making
• Purification of metals such as iron from the ore
• Rocket fuel
• Oxy-hydrogen flame sued in wedding
Rusting (hydrated iron (III) oxide)
• Rust is reddish brown in colour
Conditions necessary for Rusting
• Moisture (water)
• Oxygen (air)
Methods of preventing rust
• Paintings, greasing and oiling
• Coating with other metals
• Plastic coating
• Alloying
• Silica gel
• Sacrificial protection
Uses of Reactivity Series
• Enables one to select suitable metals to be
used as electrodes in cells
• Used in sacrificial protection to prevent iron
from rust.
UNIT FIVE
WATER AND HYDROGEN
Specific Objectives
-State the sources of water
-Describe an experiment to show that water is a product of burning
organic matter.
-Describe an experiment to show that water contains hydrogen.
-State the products of reaction of cold water and steam with different
metals.
-List the order of reactivity of metals as obtained from metal-water
reaction.
-Prepare hydrogen, investigate its properties and state its uses.
-Define oxidation as oxygen gain and reduction as removal, of oxygen.
-Explain metal oxide reactions with hydrogen in terms of reduction and
oxidation.
Sources of Water
Lakes, rivers, seas, oceans etc.
Water as a product of burning organic matter.
Products of burning Candle Wax
• Points to note;• Candle wax is a hydrocarbon (organic compound) consisting of hydrogen
and carbon atoms only.
• When burned in air, the hydrogen atoms reacts with oxygen to form
water which carbon atoms reacts with oxygen to form carbon atoms
reacts with oxygen to form water which carbon atoms reacts with
oxygen to form carbon iv oxide.
• The vapour of water are condensed and collected as the colourless liquid
in the set-up
• Presence of carbon (IV) oxide are confirmed by use of calcium hydroxide
solutions in which a white precipitate is formed.
• ii) confirmatory test of water
• Has no effect on litmus paper
• Boils at 100 c at sea level
• Change white anhydrous copper (II) sulphate to blue
• Changes blue anhydrous cobalt chloride to pink
To Show that water Contains Hydrogen
• Hydrogen is burnt in air. A colourless
liquid (water) which boils at 100 c at sea
level and turns white anhydrous copper
(II) sulphate blue is formed.
• Equation for the reaction
• 2H (g) + O2 (g) 2H2O (g)
Reaction of Sodium with Water.
• Equation
Mg (s) + 2H2O(l)
Mg(OH)2 (aq) +H2 (g)
Zinc, iron and copper.
• Do not react with cold water
• Reaction of metals with steam
Reduction of Steam
Magnesium
Reaction is fast
Equation
Mg (s) + H2O(g)
Zinc and iron
React slowly
Equation
Zn(s) + H2O (g)
3Fe (s) + 4H2O (g)
MgO(s) +H2 (g)
ZnO(s) + H2 (g)
Fe2O4(s) + H2 (g)
Reactivity Series
Copper Does not react with steam.
Order of reactivity series based on metal water reaction.
K
most reactive
Na
Ca
Mg
Al
Zn
Fe
Pb
Cu
Least reactive
Important point to Note
• Aluminum is more reactive than zinc and iron
but does not react with steam because when
exposed in air a layer of aluminum oxide
which is insoluble in water is formed
preventing the aluminum underneath from
reacting with steam.
• Aluminium is therefore used in making
saucepans, Electric cables etc.
Laboratory Preparation of Hydrogen
A displacement reaction. Hydrogen is displaced from HCl by Zinc to form Zinc Chloride.
Equation of Reaction: Zn(s) + 2 HCl (aq)
ZnCl2 (aq) + H2 (g)
Physical properties of hydrogen gas
• Colourless
• No smell
• Insoluble in water
• Less dense than air
• No effect on litmus paper
Test for hydrogen gas
• A burning splint burns with pop sound in
hydrogen gas.
Uses of Hydrogen
•
•
•
•
•
•
Manufacture of margarine
Rocket fuel
Manufacture of ammonia in the haber process
Manufacture of HCl
Welding (oxy-hydrogen flame)
Weather stations balloons.
Reaction of Metal Oxides with Hydrogen
Metal oxide reaction with oxygen
Reducing Properties of Hydrogen
• Oxides of metals reduced by hydrogen are
those oxides of less reactive metals: copper,
zinc and lead.
• Equations
CuO(s) + H2 (g)
Cu(s) + H2O(l)
ZnO (s) + H2(g)
Zn(s) + H2O (l)
PbO(s) + H2 (g)
Pb(s) + H2O(l)