Unit 1
Building Blocks
Menu
• To work through a topic click on
the title.
• Substances
• Chemical Reactions
• Bonding
• Acids and Alkalis
• End
Substances
Safety
• Too avoid accidents we must be
careful carrying out experiments.
• Most safety rules are only common
sense.
• Never put chemicals near your
mouth.
• After using chemicals wash your
hands before eating.
• All practical work must be done at
the worktops.
• Do not sit on the worktops.
• Always wear safety goggles.
• If there is any broken glass report
it to your teacher so it can be
cleared up properly.
• Be careful to leave the bunsen
burner with a yellow flame if you
are not using it.
• When heating test tubes make
sure that they are not pointed at
anyone.
Hazards
• There are laws about using chemicals to
help keep safe everyone who works
with chemicals.
• Hazard warning labels are attached to
dangerous chemicals.
• Hazard symbols are on road tankers to
warn about dangers should the
chemicals spill.
• Each hazard which is toxic,
corrosive, flammable, harmful or
irritant is given a simple symbol
which can be easily recognised.
• Here are some of these symbols.
Toxic
Corrosive
Flammable
Harmful
Irritant
Elements
• Everything in the world is made
from about 100 elements.
• Each element has a name and a
symbol.
• The symbol is usually one capital
letter and one small letter e.g. Ca
• Chemists have arranged elements
in the Periodic Table.
The Periodic Table
• The vertical columns are called
groups.
• Elements in the same group of the
Periodic Table show similar
chemical properties.
Elements
• Many elements are solid at room
temperature.
• Mercury and bromine are liquid at
room temperature.
• 11 elements –hydrogen, nitrogen,
oxygen, fluorine, chlorine, helium,
neon, argon, krypton, xenon, radon
- are gases at room temperature.
• Elements can be classified as
metals or non-metals.
• There are more metals than nonmetals.
• Many elements have everyday
uses.
• Aluminium is used as kitchen foil.
• Carbon is used in pencil leads.
• Gold, silver and platinum are used
in jewellery.
• Copper is used in electrical wiring.
• Some elements, including gold,
silver and copper, have been
known for a long time.
• The most recently discovered
elements have been made by
scientists.
Mixtures
• Mixtures occur
when two or more
substances come
together without
reacting.
Air
• Air is a mixture of gases.
• Air is approximately 80% nitrogen
and 20% oxygen.
• The test for oxygen is that it
relights a glowing splint.
• The splint will not relight in air
because there is not enough
oxygen.
Compounds
• Compounds are
formed when
elements react
together.
• Compounds with a name ending in
“ –ide “ contain the two elements
named.
• Copper chloride contains copper
and chlorine.
• Sodium oxide contains sodium and
oxygen.
• Compounds with a name ending in
“ -ite “ or “ -ate “ contain the two
elements named and the element
oxygen.
• Copper carbonate contains copper,
carbon and oxygen.
• Sodium sulphite contains sodium,
sulphur and oxygen.
Solutions
• A solution is formed when a
substance dissolves in a liquid.
• A substance which dissolves in a
liquid is soluble.
• A substance which does not
dissolve in a liquid is insoluble.
• If we only dissolve a small amount
of substance we make a dilute
solution.
• If we dissolve a large amount of
substance we make a concentrated
solution.
• A solution is diluted by adding
more liquid.
• A saturated solution is one in
which no more substance can be
dissolved.
Substances
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Chemical
Reactions
Chemical Reactions
• When a chemical reaction takes
place one or more new substances
are made.
• Burning a match is a chemical
reaction because new substances
are made.
• Melting ice is not a chemical
reaction since ice is solid water.
How do we recognise a
chemical reaction?
• A lot of chemical
reactions occur in
the world around
us.
• When a chemical
reaction takes
place one of the
following may
happen
• a change in
appearance
• a colour change
• a gas produced
• a precipitate
formed.
• an energy change
How do we speed up a
chemical reaction?
• Changes in particle size affects the
speed of reactions, both in the
laboratory and in our everyday life.
• Powders react more quickly than
lumps.
• Mince will cook more quickly than
stew.
• Changes in temperature affect the
speed of reactions, both in the
laboratory and in our everyday life.
• Reactions take place more quickly
at high temperatures.
• An egg will fry more quickly if we
turn up the heat.
• Changes in concentration affect
the speed of reactions, both in the
laboratory and in our everyday life.
• Increasing the concentration of the
chemicals speeds up a reaction.
• Adding more bleach to water
speeds up the whitening of cloth.
Catalysts
• A catalyst is a substance which
speeds up a reaction and is not
used up by the reaction.
• The exhaust system of a car
contains a catalytic converter
(containing platinum) to remove
harmful gases from the exhaust.
Enzymes
• Enzymes are catalysts which affect
living things.
•
•
•
•
•
Enzymes are used to make:
Yoghurt
Cheese
Medicines
Beer
Uses of Enzymes
Enzyme
Use
Cellulose
Makes jeans more
faded
Changes sugars to
alcohol
Used in washing
powder to remove
stains
Makes meat tender
Zymase
Protease
Papain
Word Equations
• In a chemical reaction the
substances which react together
are called the reactants.
• The substances which are
produced are called the products.
• In a chemical equation we show
the reactants and products,
separated by an arrow, which
means “change into”.
• Reactants Products
• In a word equation we use the
names of the reactants and
products.
hydrogen + oxygen  water
Chemical Reactions
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Reactions
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Bonding
Atoms
• Every element is made up of very
small particles called atoms.
• Atoms of different elements are
different.
• Each element in the Periodic Table
has a number called the atomic
number.
The Periodic Table
Molecules
• Some substances are made up of
molecules.
• Molecules are made up of two or
more atoms held together by
strong bonds.
• Bonds between molecules are
weak.
Ions
• Some substances are made up of
ions.
• Ions can be positively or negatively
charged.
• Ionic compounds are made up of
oppositely charged ions.
• Bonds between ions are strong.
Formulae
• A chemical formula uses chemical
symbols to show the number and
type of atom present.
• For example C3H8 means that the
molecule of this compound
contains 3 carbon atoms and 8
hydrogen atoms.
• We can write
formulae by
counting the
atoms in a model
or picture.
• We can write
formulae by
counting the
atoms in a model
or picture.
• We can write
formulae by
counting the
atoms in a model
or picture.
• We can write
formulae by
counting the
atoms in a model
or picture.
• We can write
formulae by
counting the
atoms in a model
or picture.
• We can write formulae by counting the atoms
in a model or picture.
• We can write formulae by counting the atoms
in a model or picture.
• The name can tell us how many
atoms are there.
• Mono- means 1
• Dimeans 2
• Tri means 3
• Tetra- means 4
• The name can tell
us how many
atoms are there.
• Mono- means 1
• Dimeans 2
• Tri means 3
• Tetra- means 4
• The name can tell
us how many
atoms are there.
• Mono- means 1
• Dimeans 2
• Tri means 3
• Tetra- means 4
• The name can tell
us how many
atoms are there.
• Mono- means 1
• Dimeans 2
• Tri means 3
• Tetra- means 4
• The name can tell
us how many
atoms are there.
• Mono- means 1
• Dimeans 2
• Tri means 3
• Tetra- means 4
Bonding
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Acids and Alkalis
The pH scale
• The pH scale ranges from below O
to above 14.
• Acids have a pH of less than 7
• Pure water and neutral solutions
have a pH equal to 7
• Alkalis have a pH of more than 7.
• To find the pH of solutions we can
use:
• Universal indicator
• pH paper
• A pH meter
Acids and pH
• The lower the pH of an acid, the
greater the acidity
• Diluting acids makes them less
acid and so makes the pH lower.
Alkalis and pH
• The higher the pH of an alkali, the
greater the alkalinity.
• Diluting alkalis makes them less
alkaline, and so increases their pH.
Acids
• Acids are often used in the home,
in industry and the laboratory.
• The common laboratory acids are
hydrochloric acid, sulphuric acid
and nitric acid.
• Some household acids are vinegar,
lemonade, soda water and Coke.
Alkalis
• Alkalis are often used in the home,
in industry and the laboratory.
• The common laboratory alkalis are
sodium hydroxide, lime water and
ammonia solution.
• Some household alkalis are baking
soda, oven cleaner, dishwashing
powder, bleach and soaps.
Neutralisation
• Neutralisation takes place when
acid and alkali are mixed.
• When alkalis and acids react they
form salt and water
• Acid + Alkali  Salt + Water
• The salt contains the metal from
the neutraliser.
• When carbonates and acids react
they form salt, water and carbon
dioxide.
• Acid + Carbonate  Salt + Water + Carbon dioxide
• The salt contains the metal from
the neutraliser.
• Neutralisation increases the pH of
the acid up towards 7.
• Neutralisation decreases the pH of
the alkali down towards 7.
• Everyday examples of
neutralisation include reducing soil
acidity, reducing acidity in lakes
and treatment of indigestion.
Salts
• In neutralisations
• hydrochloric acid forms chloride
salts
• sulphuric acid forms sulphate salts
• nitric acid forms nitrate salts.
Acid Rain
• Carbon reacts with oxygen to
produce carbon dioxide.
• Sulphur reacts with oxygen to
produce sulphur dioxide.
• Nitrogen reacts with oxygen to
produce nitrogen dioxide.
• All of these oxides dissolve in
water to form acid solutions.
• Sulphur dioxide, produced by the
burning of fossil fuels dissolves in
water in the atmosphere to
produce acid rain.
• Nitrogen dioxide, produced by the
sparking of air in car engines
dissolves in water in the
atmosphere to produce acid rain.
• Acid rain damages
• Buildings made from carbonate
rock
• Structures made of iron or steel
• Soil
• Plant and animal life.
Acids and Alkalis
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Alkalis.
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The End
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