Transcript Unit1
Unit 1 Building Blocks
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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
dangerous chemicals.
are attached to
• Hazard symbols are on road tankers to
warn about dangers should the chemicals spill.
• Each hazard which is
corrosive, flammable, harmful irritant toxic, or 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 symbol in the .
elements Periodic Table .
.
• Each element has a name and a • The symbol is usually one capital
letter and one small letter e.g. Ca
• Chemists have arranged elements
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 temperature.
• Mercury
and bromine at room 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 non-
metals.
• Many elements have everyday
uses.
• Aluminium
is used as kitchen foil.
• Carbon
is used in pencil leads.
• Gold, silver
in jewellery.
and platinum are used
• 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
reacting.
occur when two or more substances come together without
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
together.
are formed when elements react
• 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 “ oxygen.
-ate “ contain the two elements named and the element
• 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 more liquid.
by adding
• A
saturated solution which no more substance can be dissolved.
is one in
Substances
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Chemical Reactions
Chemical Reactions
• When a
chemical reaction place one or more new substances are made.
• Burning a match is a chemical
reaction because new substances are made.
takes
• 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 Zymase Protease Papain Makes jeans more faded Changes sugars to alcohol Used in washing powder to remove stains Makes meat tender
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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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 C
3 H hydrogen atoms.
8 means that the molecule of this compound contains 3 carbon atoms and 8
• 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 • Di- • Tri -
means 2 means 3
• Tetra- means 4
• The name can tell
us how many atoms are there.
• Mono- means 1 • Di-
means 2
• Tri -
means 3
• Tetra- means 4
• The name can tell
us how many atoms are there.
• Mono- means 1 • Di-
means 2
• Tri -
means 3
• Tetra- means 4
• The name can tell
us how many atoms are there.
• Mono- means 1 • Di-
means 2
• Tri -
means 3
• Tetra- means 4
• The name can tell
us how many atoms are there.
• Mono- means 1 • Di-
means 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
• nitric acid forms
nitrate salts.
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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