Download Barnard Castle School Chemistry Department

Barnard Castle School Chemistry Department
for the Summer Exam 2014
You will need to go back over everything we covered in the Christmas exam AND thoroughly
learn all the new topics covered since January. A summary of ALL topics is given below but you
should use your Activity Books, extra sheets and work in your exercise book too.
Topic 7.1: Introduction (textbook p2-13)
You should know:
o how to keep notes neatly in your ring binder
o how you are expected to behave in the laboratory
o the laboratory safety rules
o how to write up an experiment
What is Chemistry?
You should know that:
o Chemistry is the study of SUBSTANCES/MATERIALS. Substances can be changed into
new substances by CHEMICAL REACTIONS. The CHEMICAL INDUSTRY makes useful
materials on a large scale, often using RAW MATERIALS straight from the Earth.
Chemistry is involved in every aspect of everyday life.
o examples of RAW MATERIALS include coal, crude oil, natural gas, air, water, metal ores
such as haematite, bauxite and galena, minerals such as rock salt, limestone and sulphur.
o examples of MAN-MADE MATERIALS include plastics, many metals e.g. iron, aluminium
and lead, cement, paints and medicines.
Bunsen Burner
You should know:
o the name of all the parts of a Bunsen burner
o how to light and operate the burner
o the appearance of the roaring and luminous flame
o which flame to use for which purpose
o the blue cone consists of unburnt gas and is cool
Apparatus
You should be able to recognise and draw diagrams of the simple chemical apparatus you have
used. Diagrams should be drawn in pencil, using a ruler for straight lines, and should be labelled
in ink.
Hazard Symbols
You should be able to recognise and explain the meanings of the following hazard symbols. You
should be able to state one example of each type of hazardous substance.


OXIDISING substances provide oxygen which allows other materials to burn more
fiercely e.g. potassium chlorate, potassium manganate(VII).
HIGHLY FLAMMABLE substances easily catch fire e.g. ethanol, hydrogen.




TOXIC substances can cause death by poisoning. They can act when swallowed or
breathed in or absorbed through the skin e.g. sodium cyanide, bromine.
HARMFUL substances are similar to toxic substances but are less dangerous e.g. copper
sulphate.
CORROSIVE substances attack and destroy living tissues, including eyes and skin e.g.
concentrated sulphuric acid; sodium hydroxide.
IRRITANT: these substances are not corrosive but can cause reddening or blistering of
the skin e.g. calcium chloride, dilute sulphuric acid.
Topic 7.2: Physical and Chemical Changes (textbook p14-29)
A CHEMICAL CHANGE, or a CHEMICAL REACTION, involves the formation of one or more new
substances. Evidence for a chemical reaction may be a PRECIPITATE forming (a solid formed
from mixing solutions) or EFFERVESCENCE (which is the fizzing that occurs when a reaction
produces a gas). There may also be a colour change observed. Most chemical reactions involve an
energy change. EXOTHERMIC reactions give out heat. ENDOTHERMIC reactions take in heat.
Most chemical changes are DIFFICULT TO REVERSE.
A PHYSICAL CHANGE is usually easy to reverse. A physical change may involve MIXING
substances together e.g. DISSOLVING. A physical change may involve a CHANGE OF STATE.
There are three STATES OF MATTER: SOLIDS, LIQUIDS and GASES. All matter is made up
of tiny PARTICLES. There are spaces between the particles.
o The particles of a solid are CLOSELY PACKED and they VIBRATE ABOUT A FIXED
POSITION.
o The particles of a liquid are CLOSE TOGETHER but they can MOVE AROUND EACH
OTHER.
o There are LARGE SPACES between the particles of a gas, and the particles MOVE IN
ALL DIRECTIONS.
The main CHANGES OF STATE are MELTING, FREEZING, BOILING, EVAPORATION or
CONDENSATION.
o The MELTING POINT and BOILING POINT of a pure substance are the fixed
temperatures at which those changes occur.
o The state of a substance depends on the temperature.
o Increasing the energy of a substance e.g. by heating gives the particles more energy. As
they have more energy, they move faster and the temperature of the substance
increases.
Changes of state can be explained by changes in the movement of the particles.
o The melting point and freezing point of a pure substance is the fixed temperature at
which melting or freezing occur.
o The boiling point of a liquid is the fixed temperature at which the liquid rapidly changes
into a gas.
o Sublimation is changing from a solid straight to a gas (or gas to a solid).
Gases are easily compressed as their particles are furthest apart. Solids and liquids are not
easily compressed.
Topic 7.3: Elements, Mixtures and Compounds (textbook p42-70)
An element is a substance that contains only one type of atom. An element cannot be broken
down into anything simpler in the laboratory. Elements are listed on the Periodic Table and all
are given a chemical symbol. Elements are either metals (which are usually shiny when polished,
strong and conductors of heat and electricity) or non-metals (which are generally dull, brittle
and do not conduct electricity or heat). The particles that make up an element can be either
atoms or molecules.
A compound is a substance that contains more than one kind of atom chemically joined
together. There are only about 100 known elements, but millions of known compounds. A
compound contains a fixed number of atoms of each kind, and has a formula to show how many
of each atom is used.
Be familiar with the names and symbols of the 1st 20 elements in the Periodic Table (ie. H, He,
B, Be …….to Ca).
Compounds have very different properties to the elements from which they are formed. It is
often difficult to break compounds up into their elements (because the atoms are chemically
joined together). Some compounds can be broken down into their elements by a decomposition
reaction, which usually requires energy.
Define a mixture as two or more substances mixed together, but not chemically joined. An
example of a mixture is air, which contains elements such as oxygen and nitrogen and
compounds such as carbon dioxide. Mixtures can contain any amount of the substances in it. The
substances in a mixture behave the same way as they would on their own. It is easier to
separate the substances in a mixture because the separate substances are not chemically
joined together.
You must be able to define these terms that are to do with substances that are dissolved.
A solution is a type of a mixture, usually formed by dissolving a solid into a liquid (often water).
A solute dissolves in a solvent to form a solution. A solution is a mixture of a solute and a
solvent, and is clear in appearance.
An example of a common solution is sea water. The solute is salt (sodium chloride) and the
solvent is water.
A substance is soluble in a solvent if it dissolves in it, but insoluble if it does not dissolve.
A saturated solution is one in which no more solute can dissolve at that temperature. As the
temperature of a solvent increases, more solid can dissolve.
As the temperature of a solvent increases, less gas can dissolve.
Dissolving can be speeded up by heating, stirring or crushing the solid. There are many
different solvents (although water is the most common one used in the laboratory). Different
substances are soluble in different solvents.
Mixtures can be separated using a variety of methods:
 To separate an insoluble solid from a liquid use decanting (pouring off the liquid) or
filtration. If filtration is used, the residue (solid) remains in the filter paper, and the
filtrate is the liquid that passes through the filter paper into the flask.
 To obtain a soluble solid (solute) from a solution use evaporation and/or crystallisation.
 To obtain a solvent from a solute in a solution use distillation.
 To separate miscible liquids (liquids that mix together), use fractional distillation. The
liquid with the lowest boiling point will be collected first.
 To separate immiscible liquids, use a separating funnel. The least dense liquid (which
makes up the top layer) will stay in the funnel and the most dense liquid (bottom layer)
can be run into a flask.
 To separate soluble substances, chromatography can be used. This is particularly useful
for coloured dyes e.g. inks and food dyes.
 To separate small particles from a suspension e.g. to remove fine particles of mud and
dirt from cloudy pond water, or to separate red blood cells from blood plasma in a blood
sample, use a centrifuge.
Topic 7.4: Acids and Bases (textbook p78-94)
Acids, Bases (or Alkalis) and Neutralisation
Acids and alkalis are types of solution. They are found all around us, both in the laboratory and
in our homes.
An acid tastes sour and an alkali feels soapy to touch (but neither of these are sensible tests
for acids and alkalis in a laboratory). A more sensible test is to use an indicator. Indicators are
substances which change colour in acids and alkalis. Examples are universal indicator, methyl
orange and phenolphthalein.
Universal indicator (UI) has a range of colours depending on the pH of the solution. The pH
scale measures acid and alkaline properties: below 7 is acidic, 7 in neutral (neither acidic nor
alkaline) and above 7 is alkaline. UI gives a range of colours showing pH 1 (red) to 14 (purple),
whilst 7 is green. Remember the colour depends on the indicator used!
When acids and alkalis are added together they react and ‘cancel out’. This is called
neutralisation. Treating indigestion, bee stings, wasp stings, cleaning teeth and treating acidic
soil are examples of neutralisation reactions.
Reactions of Acids
A base is a substance that reacts with an acid to produce a salt and water. An alkali is a base
that can dissolve in water.
This is a neutralisation reaction
Bases are the opposite of acids and are sometimes called antacids or neutralisers. Metal oxides
(e.g. copper oxide), metal hydroxides (e.g. sodium hydroxide) and metal carbonates (e.g. copper
carbonate) are all examples of bases.
Word
acid
acid
acid
acid
equations:
+ base  salt + water
+ alkali  salt + water
+ metal oxide  salt + water
+ metal carbonate  salt + water
+
carbon dioxide
Carbon dioxide can be identified by bubbling the gas through limewater. If carbon dioxide is
present, the limewater will turn cloudy.
The name of a salt is determined by the acid and base used. Hydrochloric acid produces
chlorides, sulphuric acid produces sulphates and nitric acid produces nitrates. Examples are:
hydrochloric acid + sodium hydroxide  sodium chloride + water
sulphuric acid + copper oxide  copper sulphate + water
Metals and Acids can also react
Some metals also react with acids to produce salts. Reaction with metals produce hydrogen gas
as another product. This can be identified by holding a lit splint to a tube of the gas. A ‘squeaky
pop’ or ‘squeaky explosion’ indicates that hydrogen is present.
acid
+
metal

salt
+
hydrogen
Acid rain is rainwater that has a pH significantly less than 7. Rainwater can become slightly
acidic by dissolving carbon dioxide gas from the air. Some polluting gases dissolve in rainwater
to make it more acidic.
Exam duration: 1 hour