CH1 Chemistry revision fact sheet
ATOMS AND ELEMENTS

Atoms are the building blocks from which everything is made

Atoms have a small nucleus which contains protons and neutrons

Electrons surround the nucleus in shells

Protons have a positive charge

Electrons have a negative charge

Neutrons have no charge and are neutral

The number of protons in an atom is equal to the number of electrons

Elements consist of one type of atom.

Atoms are represented by symbols. Carbon has the symbol C, magnesium has the symbol Mg, sodium has
the symbol Na.

When writing symbols the first letter is a capital, the second letter lower case

The mass number of an element is written above the symbol

The mass number = protons + neutrons

The atomic number of an element is written below the symbol

The atomic number is the number of protons or electrons

Number of neutrons = mass number - atomic number

Elements are arranged in the periodic table

The transition metals are found between groups two and three

Reactive metals are in groups 1 & 2

Metals are found on the left hand side of the periodic table

Non-metals are found on the right hand side of the periodic table

Group 0/8 contains the noble gases. All of these elements are unreactive

Vertical columns are called groups

Elements with similar properties are in the same group
ELECTRON SHELLS

Electrons are arranged in shells

The first shell has to be filled first

The first shell can hold up to two electrons

The second shell can hold up to eight electrons

The third shell can hold up to eight electrons

Elements in group 8 have a full outer shell. This makes them stable which means they don’t react

The electron configuration is a set of number telling you how many electrons are in each shell

Oxygen has an atomic number of 8

It has 2 electrons in the first shell

It has 6 electrons in the second shell

It has an electron configuration of 2.6

It is found in group 6 because it has 6 electrons in the outer shell

The number of electrons in the outer shell tells you which group the element is in
COMPOUNDS AND CHEMICAL REACTIONS

Two or more elements chemically joined together are called a compound

Atoms react to form full outer shells and become stable

There are two types of bonding

Covalent bonding occurs between 2 non metals

The electrons are shared

An example of a covalent compound is hydrogen chloride

Ionic bonding occurs between a metal and a non metal

The metal loses electrons and becomes a positive ion

The non-metal gains electrons and becomes a negative ion

An example of ionic bonding is sodium chloride

The positive and negative ions attract each other and stick together

Chemical equations show reactants  products

The number of atoms at the start of a reaction = the number of atoms at the end of a reaction

magnesium +
oxygen  magnesium oxide
2Mg
+
O2

2MgO
LIMESTONE

The formula of limestone is CaCO3 and the chemical name is calcium carbonate

Limestone undergoes thermal decomposition when heated

The products are calcium oxide and carbon dioxide

Calcium oxide is also known as quicklime and the chemical formula is CaO

Carbon dioxide is tested for using limewater which goes cloudy

Calcium oxide reacts with water to make calcium hydroxide

This is also known as slaked lime and has the chemical formula Ca(OH)2

Slaked lime is an alkali and is used to neutralise acidic soil

Limestone is heated with clay to make cement

Cement is mixed with sand and water to make mortar. This is used for sticking bricks together

Concrete is made by mixing cement, sand and aggregate together

Gravel and water are together known as aggregate

Limestone is obtained by quarrying

Advantages of quarrying
 Supplies materials
 Products for buildings and roads
 Products for neutralisation – of acidic lakes and soil
 Provides jobs

Disadvantages of quarrying
 Ugly
 Noisy
 Produces dust
 Waste
 Destroys habitats
 Pollution
METALS

Ores are rocks that contain metals that can be extracted

Method of extraction depends on place in the reactivity series
Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Copper

Those metals above carbon are extracted by electrolysis

Those metals below carbon are extracted by reduction

Three native metals are silver, gold and platinum. This means they are found naturally

Reduction is the removal of oxygen

The ore is reacted with carbon to produce carbon dioxide

Iron oxide + carbon  iron + carbon dioxide

Electrolysis means splitting by electricity

You need a liquid to conduct electricity

But this means high temperatures and lots of electricity is needed which makes the process expensive

Copper can be purified by electrolysis

It needs to purified for use in electrical wiring

The negative electrode is made of pure copper

The positive electrode is made of impure copper

The liquid used is copper sulphate solution

Positive copper ions are attracted to the negative electrode, which gets bigger
IMPACTS OF EXTRACTING METALS

Metals can be extracted by displacement

This means a more reactive metal will remove a less reactive metal from a compound

Copper sulphate + iron  iron sulphate + copper

There are two new extraction methods for copper

Bioleaching - bacteria separate copper from copper sulphide

A leachate is produced which can be filtered to extract copper

Phytomining – plants are grown in soil containing copper

The copper is absorbed and stored in the leaves

The leaves are then burnt and copper is collected from the ash

Extracting metals is bad for the environment

It creates
 Noise
 Dust
 Damages landscapes and habitats
 Dangerous when mines are abandoned

Reasons for recycling
 Mining is expensive and needs a lot of energy from fossil fuels
 Fossil fuels have to be burnt – which causes pollution so this reduces
 Fossil fuels are running out
 Recycling uses less energy
 Recycling cuts down on landfill sites
PROPERTIES OF METALS

Metals are strong and bendy

Also good conductors of heat and electricity

Found on left hand side of periodic table and in the central block (transition metals)

Copper has properties that make it useful for wiring and plumbing
 Good conductor of heat and electricity
 Can be bent but is still hard
 Doesn’t react with water

Aluminium is low density (light) and resistant to corrosion (doesn’t break down) making it good to use to
make aeroplanes

Titanium is low density and corrosion resistant making it good to use for hip replacements
ALLOYS

An alloy is a mixture of metals

Alloys are harder than pure metals

Iron from the blast furnace contains 96% iron and it is very brittle - useless

Most iron is converted into steel by mixing with carbon

Low carbon steels are easily shaped – useful for car bodies

High carbon steels are hard – useful for bridges

Stainless steels are resistant to corrosion – useful for cutlery

Most everyday metals are alloys

Pure gold, copper and aluminium are too soft and mixed with small amounts of similar metals to make
them harder.
CRUDE OIL

Crude oil is a mixture of hydrocarbons, which only contain hydrogen and carbon

Crude oil can be split into separate groups of hydrocarbons by fractional distillation. Different
hydrocarbons separate at different temperatures and are collected as they condense.

Crude oil is made up of hydrocarbons called alkanes.

Alkanes are made up of carbon atoms surrounded by hydrogen.

Each carbon atoms has 4 other atoms bonded to it.

The general formula for alkanes is CnH2n+2. This means that there are twice as many hydrogen atoms plus
two extra compared to carbons.

The first three alkanes are methane (CH4), ethane (C2H6) and propane (C3H8)

The shorter the hydrocarbon chain
 the less viscous (gloopy) the alkane
 the lower the boiling point
 the more flammable

Crude oil is an important fuel, but it will eventually run out as it is non-renewable.

Burning crude oil releases
 Carbon dioxide
 Water
 Carbon monoxide
 Sulphur dioxide
 Nitrogen oxide

The burning of fuels releases energy

The carbon and hydrogen atoms are oxidised (oxygen is added)

Sulphur dioxide and nitrogen oxide cause acid rain which causes lakes to become acidic and damages
building

Carbon dioxide causes global warming

Solid particles cause global dimming

Sulphur can be removed from the fuels before they are burned

Sulphur dioxide can be removed from waste gases after combustion in power stations

Alternative fuels are being developed such as ethanol, hydrogen gas and biodiesel from plant material

These reduce the amount of pollution produced

Long chain hydrocarbons can be cracked (split up) into more useful products

Cracking is a thermal decomposition reaction – molecules are broken down by heating them

The chain is heated to vaporise it, then the vapour is passed over a catalyst. The long chain is split apart.

Most of the products of cracking are alkanes and alkenes

Alkenes have a carbon – carbon double bond. They are unsaturated

The general formula is CnH2n. There are twice as many hydrogen atoms as carbon atoms

The first 2 alkenes are ethene (C2H4) and propene (C3H6)

Alkenes contain a double C=C bond – they are unsaturated

Unsaturated alkenes react with orange bromine water and turn it colourless
POLYMERS

Alkenes can be used to make polymers

Polymerisation is the process by which lots of small alkenes (monomers) are joined together to make
large long chain molecules called polymers

Lots of ethene molecules can be joined together to make poly(ethene)

Different polymers have different physical properties that are affected by temperature and pressure

Polythene is used to make plastic bags

Polymers are cheap but don’t biodegrade. It is difficult to get rid of them

Plastic bags are being made from polymers and cornstarch so they break down more easily

Ethene can be reacted with steam to produce ethanol.

A catalyst is used to speed up the reaction

Ethanol can also be produced by fermentation with yeast.
Sugar  carbon dioxide and ethanol
PLANT OILS

We can extract oils from plants. These oils can be used for food or fuel

The plant material is crushed and pressed to remove the oil. Distillation refines the oil and removes
water, solvents and impurities

Vegetable oils are used in food and provide a lot of energy

Vegetable oils have higher boiling points than water so can be used to cook at higher temperatures

This produces quicker cooking and different flavours, but increases the energy released when eaten

Emulsions can be made from oil and water.

Emulsions are made from lots of droplets of one liquid suspended in another liquid

The more oil you have the thicker the emulsion

Emulsions provide better texture, coating ability and appearance

Salad dressing, ice cream, cosmetics and paints are examples of emulsions

Emulsifiers have hydrophilic (water seeking) and hydrophobic (water avoiding)properties.

Vegetable oils that are unsaturated contain double carbon= carbon bonds

These are detected by bromine water

Unsaturated oils can be hydrogenated – hardened by reacting them with hydrogen in the presence of
a nickel catalyst at about 60oC.

Hydrogenated oils have a higher melting point so they are more solid at room temperature, which
makes them more useful as spreads and for cake baking
THE EARTH

The Earth consists of a crust, mantle, outer and inner core

The crust is the very thin outer layer.

The mantle has all the properties of a solid but it can flow. Within the mantle radioactive decay takes
place producing a lot of heat, which causes the mantle to flow in convection currents.

The core of the Earth is made of nickel and iron.

The Earth’s surface is made up of tectonic plates, which drift because of convection currents in the
mantle.

The movement of the plates can be sudden and disastrous

Earthquakes are caused by the plates moving very quickly

Volcanoes form at the boundaries between 2 tectonic plates

Wegener proposed a theory of continental drift to explain how the plates moved

Originally the land was joined in a big mass called Pangaea

The convection currents formed in the mantle caused the plates to slowly move apart

Initially people didn’t believe his theory and thought mountains were formed from the shrinking of the
Earth as it cooled

Wegener proved his theory by
 Matching shape of continents – South America and Africa
 Matching rock samples – found on different continents
 Similar fossils found on different continents
THE EARTH’S ATMOSPHERE

The atmosphere has evolved and changed over time

Currently the atmosphere is roughly 78% nitrogen, 21% oxygen and 1% other gases

During the first billion years on Earth there was intense volcanic activity

This released gases that formed the early atmosphere and water vapour

The water vapour cooled and condensed to form the oceans

There are several theories as to how the atmosphere was formed.

One suggests that the atmosphere was mainly carbon dioxide and little oxygen. There would have been a
little water vapour and some methane and ammonia

The green plants evolved and began to produce oxygen by photosynthesis

This was the oxygen that is now in the atmosphere.

Most of the carbon dioxide in the air became locked up in sedimentary rocks and fossil fuels

The oceans also absorb carbon dioxide, but increased amounts of carbon dioxide impact on marine life.

Carbon dioxide is now released by the burning of fossil fuels.

It is a greenhouse gas and contributes to climate change