Download Barnard Castle School Chemistry Department

Barnard Castle School Chemistry Department
for the Summer Exam 2014
Topic 8.1: Atoms, Elements and the Periodic Table (textbook p45-47)
You should know that:
o An element is a substance which cannot be broken down into simpler substances by
chemical means.
o Each element is represented by a different chemical symbol. You should know the
symbols of the first 20 elements, as well as any others you have used in this topic.
The Periodic Table is a way of listing elements which makes their study more logical and
therefore easier. It is arranged in Groups (columns) of elements with similar chemical
properties. A row on the Periodic Table is called a Period. The metallic elements are on the left
hand side of the Periodic Table and the non-metals are on the right. All the different types of
atoms are listed on the Periodic Table in order of increasing atomic number. An element is a
substance made up of only one type of atom.
Chemical Formulae
1. Use valencies to work out chemical formulae of compounds using hooks or arms or charges.
To include chlorides, fluorides, bromides, oxides, sulfides, hydroxides (including using
brackets).
2. Understand how to name compounds from their formulae. To include oxides, sulfides,
hydroxides, carbonates, sulphates.
3. Construct word equations to describe chemical reactions.
Topic 8.2: Reactions of Metals and their Compounds (textbook chapter 5)
Physical Properties of Metals (text book p130-136)
More than three quarters of the elements are metals which:
o are solids at room temperature (except mercury)
o mostly have a high melting point
o are shiny when freshly cut
o form alloys, which are mixtures of metals
o are mostly tough, strong and can be easily hammered or bent into shape (malleable)
o are good conductors of both heat and electricity when solid or liquid
You should be able to give some common uses of copper, iron and aluminium that depend on
these properties.
Less than a quarter of the elements are non-metals which:
o mostly have low melting points and boiling points (half are gases and one, bromine, is a
liquid at room temperature)
o are mostly dull in appearance
o are mostly brittle and crumbly when solid
o are mostly poor conductors of heat and electricity when solid or liquid
Diamond and graphite, two types (allotropes) of carbon, are exceptions to the general rules.
You should be able to set up a simple electrical circuit to test for conductivity.
The reactivity series of metals (textbook p137-143)
You should know that some metals are more reactive than others.
By observing whether or not various metals react:
o with air to produce metal oxides
o with water (cold, hot or as steam) to produce metal hydroxides (or oxides) and hydrogen
o with dilute acids to produce metal salts and hydrogen
and by observing how vigorous these reactions are, a reactivity series can be produced. This
lists metals in order of their reactivity, the most reactive metal being placed at the top of
the list and the least reactive at the bottom.
Group 1 metals are particularly reactive (p178).
Test for hydrogen: hold a lit splint to a test tube of the gas. If it is hydrogen, the gas will
burn with a squeaky ‘pop’ or a squeaky explosion.
A more reactive metal can displace a less reactive metal from its compounds.
You should be able to place other metals correctly in the reactivity series on the basis of your
knowledge and/or information you are given about the reactions of these other metals.
Oxidation (textbook p150-160; p162)
Some chemical reactions are not useful.
Reactions with oxygen (oxidation reactions) produce compounds called oxides.
metal + oxygen  metal oxide
The reaction of copper with oxygen from the air, using gas syringe apparatus, can show that air
is 20% oxygen. Metal oxides are basic: they react with acids and have a pH greater than 7
when dissolved in water. Not all metal oxides are soluble, but all will react with acids.
Non-metal oxides are acidic: they react with bases and have a pH less than 7 when dissolved
in water.
Iron is a very useful metal but it corrodes (rusts) when exposed to air and water. Rusting is
the corrosion of iron and steel. Rusting is very costly as the metal is destroyed. Rusting is an
oxidation process. Rusting of iron needs the presence of both water and oxygen. Rusting is
faster if salt or an acid is dissolved in the water.
The rusting of iron can be prevented by placing a physical barrier around the metal. This
prevents air and water from coming into contact with the iron or steel. Barriers used in rust
prevention include painting, greasing and coating in plastic.
Rusting can also be prevented by sacrificial protection, where a more reactive metal is
attached to the iron and corrodes instead of the iron (e.g. magnesium plates on the hulls of
ships). Another method to protect iron and steel is to coat it with zinc. This is called
galvanising.
Topic 8.3: Reactions of Non-Metals and their Compounds (textbook p108-112)
Air
Air is a mixture of gases that make up our lower atmosphere. Air is 78% nitrogen and 21%
oxygen, with small amounts of argon, carbon dioxide, water and other gases. The gases in air
can be separated by fractional distillation of liquid air.
Reaction of elements with oxygen is called oxidation. Combustion reactions involve reaction with
oxygen, and give out heat energy. They require a fuel, oxygen and heat. Respiration also
requires oxygen. A test for oxygen is that it relights a glowing splint. The copper syringe
experiment can be used to demonstrate that there is 20% oxygen in air. Oxygen can be
prepared by the decomposition of hydrogen peroxide solution using a manganese oxide catalyst.
Nitrogen and argon are both unreactive and are used to prevent other things reacting with
oxygen or water in the air.
Carbon Dioxide
Carbon dioxide is required by plants for photosynthesis. A test for carbon dioxide is that it
turns limewater cloudy. A use for carbon dioxide is in the fizzy drinks industry (where carbon
dioxide is forced into the drink under pressure, resulting in the ‘fizz’). Carbon dioxide can be
prepared by the reaction of a metal carbonate (e.g. calcium carbonate) with an acid (e.g.
hydrochloric acid).
Burning non-metals in air
Burning non-metals in air forms non-metal oxides. Examples are carbon dioxide, sulphur dioxide
and nitrogen dioxide. Sulphur burns with a blue flame to give sulphur dioxide.
Non-metal oxides are acidic. If sulphur dioxide and nitrogen oxides are released into the
atmosphere, they can dissolve into rainwater droplets and cause acid rain. This can damage
limestone buildings and kills fish and other aquatic life. All rainwater is slightly acidic as it
usually contains some carbon dioxide dissolved into it from the air.
8.4 Formation of salts (textbook p78-88)
Salts form when an acid reacts with a metal or metal compound. We expect you to be able to
describe how certain salts can be made in the lab. First you should check on your knowledge of
acids and pH.
Acids, Bases (or Alkalis) and Neutralisation
Acids and alkalis are types of solutions. They are found all around us, both in the laboratory and
in our homes.
An acid tastes sour and an alkali feels soapy to the 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 is 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, the formation of slag in the Blast
Furnace and treating acidic soil are examples of neutralisation reactions.
Reactions of Acids (this is how we get salts)
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. Metal oxides (e.g. copper oxide), metal hydroxides (e.g.
sodium hydroxide) and metal carbonates (e.g. copper carbonate) are all examples of bases.
You should be able to cope with word and chemical equations for:
acid + base
 salt + water
acid + alkali
 salt + water
acid + metal oxide
 salt + water
acid + 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
 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 produces 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. Be careful: only use this method
for safe metals (i.e. not Na, K, Li) and not unreactive metals (Cu, Ag won’t react).
acid
+
metal

salt
+
hydrogen
Examine the pictures of how the salts are made depending on the type of reactants (i.e.
filtering off excess solid metal oxide; using pH paper to check for neutrality when using alkalis;
crystallisation of soluble salts and washing and filtering insoluble salts (199-201); or you may
have a booklet on Salts from your teacher.
Topic 8.5: Environmental Chemistry (textbook p113-129)
Coal, crude oil and natural gas are fossil fuels. The burning of fossil fuels produces pollutants
such as carbon dioxide, carbon monoxide, soot, sulphur dioxide and nitrogen oxides. The amount
of carbon dioxide in the atmosphere is increasing and is thought to be causing global warming.
Sulphur dioxide and nitrogen oxides cause acid rain. Fossil fuels are non-renewable because
they cannot be replaced once they have been used. Sugar (used to make alcohol) and wood are
renewable fuels because more can be grown to replace that which is used.
Topic 8.6: Earth Science (textbook p99-107)
Types of Rocks
Rocks are made up of minerals. A mineral is a chemical element or compound that was formed
naturally within the Earth. There are three main types of rocks:



Igneous rocks are made when magma cools down and crystallises. The more slowly it
crystallises, the larger the mineral crystals. Igneous rocks formed underground are
known as intrusive igneous rocks. Extrusive igneous rocks are formed on the surface,
where cooling is faster, so they have smaller crystals. Igneous rocks are hard and have
randomly arranged, interlocking crystals.
Sedimentary rocks are formed from the hardening of sediment over time. They are
often softer than igneous rocks and are made up of separate grains.
Metamorphic rocks are formed by the action of heat and/or increased pressure on other
rocks. They are mostly hard and consist of crystals, but the crystals may be arranged in
layers (unlike igneous rocks).
Weathering
All rocks are eventually weathered which means they are broken down into smaller pieces.
Physical weathering is where forces cause rocks to break up (by the freeze-thaw of water, or
by the expansion and contraction of rocks in sunlight – exfoliation or onion-skin weathering).
Chemical weathering is where rock reacts with substances such as water or substances
dissolved in water e.g. limestone damaged by acid rain. Biological weathering is where plants and
animals cause the rocks to break up. Erosion is where broken up pieces of rock are moved by
natural forces e.g. the wind or the sea. Erosion is the reason that pebbles in the sea are
smooth.
Rocks are recycled naturally by the Earth and are changed from one type to another over
millions of years. This process is known as the rock cycle.
Exam duration: 1 hour