chemistry 1 revision cards
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C1 1.1 ATOMS, ELEMENTS & COMPOUNDS
• All substances are made of atoms
• Elements are made of only one type of atom
• Compounds contain more than one type of atom
• Compounds are held together by bonds
• Each element has its own symbol in the periodic table
• Columns are called GROUPS.
• Elements in a group have similar properties
• Rows are called PERIODS
• The red staircase splits metals from non-metals
An atom is made up of a tiny nucleus with electrons around it
C1 1.2 ATOMIC STRUCTURE
• Atoms contain PROTONS, NEUTRONS & ELECTRONS
• Protons and Neutrons are found in the NUCLEUS
• Electrons orbit the nucleus
•ATOMIC NUMBER the number of protons in the nucleus
the periodic table is arranged in this order
•MASS NUMBER the number of protons plus neutrons
Number of neutrons = Mass Number – Atomic Number
Any atom contains equal numbers of protons and electrons
PARTICLE RELATIVE CHARGE
RELATIVE MASS
Proton +1 (positive) 1
Neutron 0 (neutral) 1
Electron -1 (negative) 0
C1 1.3 ELECTRON ARRANGEMENT
• Electrons are arranged around the nucleus in SHELLS (or energy levels)
• The shell closest to the nucleus has the lowest energy
• Electrons occupy the lowest available energy level
• Atoms with the same number of electrons in the outer shell belong to the same GROUP in the periodic table
• Number of outer electrons determine the way an element reacts
• Atoms of the last group (noble gases) have stable arrangements and are unreactive
This is how we draw atoms and their electrons
Low energy shell
High energy shell
Sodium
C1 1.4 FORMING BONDS
• Atoms can react to form compounds in a number of ways:
i) Transferring electrons IONIC BONDING
ii) Sharing electrons COVALENT BONDING
IONIC BONDING
• When a metal and non-metal react• Metals form positive ions• Non-metals from negative ions• Opposite charges attract• A giant lattice is formed
COVALENT BONDING
• When 2 non-metals bond• Outermost electrons are shared• A pair of shared electrons forms a bond
CHEMICAL FORMULAE
• Tells us the ratio of each element in the compound
• In ionic compounds the charges must cancel out:
E.g. MgCl2
We have 2 chloride ions for every magnesium ion
H2 + O2 H2O
Add a 2 to the products side to make the oxygen balance
H2 + O2 2H2O
This has changed the number of hydrogen atoms so we must now adjust the reactant side:
2H2 + O2 2H2O
C1 1.5 CHEMICAL EQUATIONS
• Chemical equations show the reactants (what we start with) and the products (what we end up with)
• We often use symbol equations to make life easier
CaCO3 CaO + CO2
MAKING EQUATIONS BALANCE
Equations MUST balance
We can ONLY add BIG numbers to the front of a substance
We can tell elements within a compound by BIG letters
CaCO3 this is a compound made of 3 elements (calcium, carbon and oxygen)
Ca = 1C = 1O = 3
Ca = 1C = 1O = 3
• This is balanced – same number of each type of atom on both sides of the equation
• We can check this by counting the number of each type on either side
H = 2O = 2
H = 2O = 1
H = 2O = 2
H = 4O = 2
C1 2.1 LIMESTONE & ITS USES
• Limestone is made mainly of Calcium Carbonate
• Calcium carbonate has the chemical formulae CaCO3
• Some types of limestone (e.g. chalk) were formed from the remains of animals and plants that live millions of years ago
USE IN BUILDING
We use limestone in many buildings by cutting it into blocks.
Other ways limestone is used:
Cement = powdered limestone + powdered clay
Concrete = Cement + Sand + Water
HEATING LIMESTONE
Breaking down a chemical by heating is called THERMAL DECOMPOSITION
Calcium Calcium + CarbonCarbonate Oxide Dioxide
CaCO3 CaO + CO2
ROTARY LIME KILN
This is the furnace used to heat lots of calcium carbonate and turn it into calcium oxide
Calcium oxide is used in the building and agricultural industries
C1 2.2 REACTIONS OF CARBONATES
• Buildings made from limestone suffer from damage by acid rain
• This is because carbonates react with acid to form a salt, water and carbon dioxide
Calcium + Hydrochloric Calcium + Water + Carbon
Carbonate Acid Chloride Dioxide
CaCO3 + 2HCl CaCl2 + H2O + CO2
TESTING FOR CO2
• We use limewater to test for CO2
• Limewater turns cloudy
• A precipitate (tiny solid particles) of calcium carbonate forms causing the cloudiness!
HEATING CARBONATES
Metal carbonates decompose on heating to form the metal oxide and carbon dioxide
MgCO3 MgO + CO2
C1 2.3 THE LIMESTONE REACTION CYCLE
• Limestone is used widely as a building material
• We can also use it to make other materials for the construction industry
Calcium Carbonate + Heat Calcium Oxide
Calcium Oxide + Water Calcium Hydroxide (Limewater)
Calcium Carbonate
Calcium Oxide
Calcium Hydroxide
Calcium Hydroxide Solution
Step 1: Add Heat
CaCO3 CaO + CO2
Step 2: Add a bit of water
CaO + H2O Ca(OH)2 Step 3: Add more water & filter
Ca(OH0)2 + H2O Ca(OH)2 (aq)
Step 4: Add CO2
Ca(OH)2 + CO2 CaCO3 + H2OLimestone
C1 2.4 CEMENT & CONCRETE
CEMENT
Made by heating limestone with clay in a kiln
MORTAR
Made by mixing cement and sand with water
CONCRETE
Made by mixing crushed rocks or stones (called aggregate), cement and sand with water
C1 2.5 LIMESTONE ISSUES
BENEFITS
• Provide jobs
• Lead to improved roads
• Filled in to make fishing lakes or for planting trees
• Can be used as landfill sites when finished with
DRAWBACKS
• Destroys habitats
• Increased emissions
• Noisy & Dusty
• Dangerous areas for children
• Busier roads
• Ugly looking
C1 3.1 EXTRACTING METALS
• A metal compound within a rock is called an ORE
• The metal is often combined with oxygen
• Ores are mined from the ground and then purified
Whether it’s worth extracting a particular metal depends on:
How easy it is to extract How much metal the ore contains
The reactivity series helps us decide the best way to extract a metal:
Metals below carbon in the series can be reduced by carbon to give the metal element
Metals more reactive than carbon cannot be extracted using carbon. Instead other methods like ELECTROLYSIS must be used
THE REACTIVITY SERIES
C1 3.2 IRON & STEELS
• Iron Ore contains iron combined with oxygen
• We use a blast furnace and carbon to extract it (as it’s less reactive than carbon)
• Carbon REDUCES the iron oxide;
Iron (III) Oxide + Carbon Iron + Carbon Dioxide
• Iron from the blast furnace contains impurities: Makes it hard and brittle Can be run into moulds to form cast iron Used in stoves & man-hole covers
• Removing all the carbon impurities gives
us pure iron Soft and easily shaped Too soft for most uses Need to combine it with other elements
• A metal mixed with other elements is called an ALLOY
E.g. Steel Iron with carbon and/or other elements
There are a number of types of steel alloys:
Carbon steels Low-alloy steels High-alloy steels Stainless steels
C1 3.3 ALUMINIUM & TITANIUM
Aluminium Titanium
Property • Shiny• Light• Low density• Conducts electricity and energy• Malleable – easily shaped• Ductile – drawn into cables and wires
• Strong• Resistant to corrosion• High melting point – so can be used at
high temperatures• Less dense than most metals
Use • Drinks cans• Cooking foil• Saucepans• High-voltage electricity cables• Bicycles• Aeroplanes and space vehicles
• High-performance aircraft• Racing bikes• Jet engines• Parts of nuclear reactors• Replacement hip joints
Extraction Electrolysis
• Aluminium ore is mined and extracted.• Alumminium oxide (the ore) is melted• Electric current passed through at high temperature
Expensive process – need lots of heat and electricity
Displacement & Electrolysis
• Use sodium or potassium to displace titanium from its ore
• Get sodium and magnesium from electrolysis
Expensive – lots of steps involved, & needs lots of heat and electricity
C1 3.4 EXTRACTING COPPER
COPPER-RICH ORES
These contain lots of copper. There are 2 ways to consider:
1. Smelting
• 80% of copper is produced this way
• Heat copper ore strongly in a furnace with air
Copper + Oxygen Copper + SulphurSulphide Dioxide
• Then use electrolysis to purify the copper
• Expensive as needs lots of heat and electricity
2. Copper Sulphate
• Add sulphuric acid to a copper ore
• Produces copper sulphate
• Extract copper using electrolysis or displacement
LOW GRADE COPPER ORES
These contain smaller amount of copper. There are 2 main ways:
1. Phytomining
• Plants absorb copper ions from low-grade ore
• Plants are burned
• Copper ions dissolved by adding sulphuric acid
• Use displacement or electrolysis to extract pure copper
2. Bioleaching
• Bacteria feed on low-grade ore
• These produce a waste product that contains copper ions
• Use displacement or electrolysis to extract pure copper
C1 3.5 USEFUL METALS
TRANSITION METALS
• Found in the central block of the periodic table
Properties:
• Good conductors of electricity and energy
• Strong
• Malleable – easily bent into shape
Uses:
• Buildings
• Transport (cars, trains etc)
• Heating systems
• Electrical wiring
Example: Copper
1. Water pipes – easily bent into shape, strong, doesn’t react with water
2. Wires – ductile and conduct electricity
COPPER ALLOYS
Bronze – Copper + Tin - Tough - Resistant to corrosion
Brass – Copper + Zinc - Harder but workable
ALUMINIUM ALLOYS
• Alloyed with a wide range of other elements
• All have very different properties
• E.g. in aircraft or armour plating!
GOLD ALLOYS
• Usually add Copper to make jewellery last longer
C1 3.6 METALLIC ISSUES
EXPLOITING ORES
Mining has many environmental consequences:
• Scar the landscape
• Noisy & Dusty
• Destroy animal habitats
• Large heaps of waste rock
• Make groundwater acidic
• Release gases that cause acid rain
RECYCLING METALS
• Recycling aluminium saves 95% of the energy normally used to extract it!
• This saves money!
• Iron and steel are easily recycled. As they are magnetic they are easily separated
• Copper can be recycled too – but it’s trickier as it’s often alloyed with other elements
BUILDING WITH METALS
Benefits
• Steel is strong for girders
• Aluminium is corrosion resistant
• Many are malleable
• Copper is a good conductor and not reactive
Drawbacks
• Iron & steel can rust
• Extraction causes pollution
• Metals are more expensive than other materials like concrete
C1 4.1 FUELS FROM CRUDE OIL
CRUDE OIL
• A mixture of lots of different compounds [A mixture is 2 or more elements or compounds that are not
chemically bonded together]
• We separate it into substances with similar boiling points
• These are called fractions
• This is done in a process called fractional distillation
HYDROCARBONS
Nearly all the compounds in crude oil are hydrocarbons
Most of these are saturated hydrocarbons called alkanes
MethaneCH4
EthaneC2H6
PropaneC3H8
ButaneC4H10
General formula for an alkane is CnH(2n+2)
C1 4.2 FRACTIONAL DISTILLATION
This is the process by which crude oil is separated into fractions
These are compounds with similar sized chains Process relies on the boiling points of these
compoundsThe properties a fraction has depend on the size
of their hydrocarbon chains
SHORT CHAINS ARE: Very flammable Have low boiling points Highly volatile (tend to turn into gases)Have low viscosity (they flow easily)
Long chains have the opposite of these!
Crude oil fed in at the bottom
Temperature decreases up the column
Hydrocarbons with smaller chains found nearer the top
C1 4.3 BURNING FUELS
COMPLETE COMBUSTION
Lighter fractions from crude oil make good fuels
They release energy when they are oxidised burnt in oxygen:
propane + oxygen carbon dioxide + water
POLLUTION
Fossil fuels also produce a number of impurities when they are burnt
These have negative effects on the environment
The main pollutants are summarised below
Sulphur Dioxide
• Poisonous gas
• It’s acidic
• Causes acid rain
• Causes engine corrosion
Carbon Monoxide
• Produced when not enough oxygen
• Poisonous gas
• Prevents your blood carrying oxygen around your body
Nitrogen Oxide
• Poisonous
• Trigger asthma attacks
• Can cause acid rain
Particulates
• Tiny solid particles
• Contain carbon and unburnt hydrocarbon
• Carried in the air
• Damage cells in our lungs
• Cause cancer
C1 4.4 CLEANER FUELS
Burning fuels releases pollutants that spread throughout the atmosphere:
CATALYTIC CONVERTERS
• Reduces the carbon monoxide and nitrogen oxide produced
• They are expensive
• They don’t reduce the amount of CO2
GLOBAL DIMMING
• Caused by particulates
• Reflect sunlight back into space
• Not as much light gets through to the Earth
CARBON MONOXIDE Formed by incomplete combustion
GLOBAL WARMING
• Caused by carbon dioxide
• Causing the average global temperature to increase
SULPHUR DIOXIDE
• Caused by impurities in the fuel
• Affect asthma sufferers
• Cause acid rain damages plants & buildings
Carbon + Nitrogen Carbon + NitrogenMonoxide Oxide Dioxide
C1 4.5 ALTERNATIVE FUELS
These are renewable fuels sources of energy that could replace fossil fuels (coal, oil & gas)
BIODIESEL ETHANOL HYDROGEN+ • Less harmful to animals
• Breaks down 5 × quicker• Reduces particulates• Making it produces other useful products
•‘CO2 neutral’ – plants grown to create it absorb the same amount of CO2 generated when it’s burnt
• Easily made by fermenting sugar cane
• Gives off CO2 but the sugar cane it comes from absorbs CO2 when growing
• Very clean – no CO2
• Water is the only product
- • Large areas of farmland required• Less food produced Famine• Destruction of habitats• Freezes at low temps
• Large areas of farmland required• Less food produced as people use it for fuel instead!
• Hydrogen is explosive
• Takes up a large volume storage becomes an issue
C1 5.1 CRACKING HYDROCARBONS
CRACKING Breaking down large hydrocarbon chains into smaller, more useful ones
SATURATED OR UNSATURATED?
We can react products with bromine water to test for saturation:
Positive Test:
Unsaturated + Bromine COLOURLESS hydrocarbon Water
= ALKENES
Negative Test:
Saturated + Bromine NO RECTIONHydrocarbon Water (orange)
= ALKANES
CRACKING PROCESS
1. Heat hydrocarbons to a high temp; then either:
2. Mix them with steam; OR
3. Pass the over a hot catalyst
EXAMPLE OF CRACKING
Cracking is a thermal decomposition reaction:
C10H22 C5H12 + C3H6 + C2H4
ALKENES
• These are unsaturated hydrocarbons• They contain a double bond• Have the general formula CnH2n
Decane Pentane Propene Ethene
800oC
C1 5.2 POLYMERS FROM ALKENES
PLASTICS Are made from lots of monomers joined together to make a polymer
HOW DO MONOMERS JOIN TOGETHER?
• Double bond between carbons ‘opens up’• Replaced by single bonds as thousands of monomers join up• It is called POLYMERISATION
MONOMERS POLYMER
EthenePoly(ethene)
nSimplified way of writing it:
‘n’ represent a large repeating number
C1 5.3 NEW & USEFUL POLYMERS
DESIGNER POLYMER Polymer made to do a specific job
Examples of uses for them:
• Dental fillings
• Linings for false teeth
• Packaging material
• Implants that release drugs slowly
Light-Sensitive Plasters
• Top layer of plaster peeled back
• Lower layer now exposed to light
• Adhesive loses stickiness• Peels easily off the skin
SMART POLYMERS Have their properties changed by light, temperature or other changes in their surroundings
Hydrogels
• Have cross-linking chains• Makes a matrix that
traps water• Act as wound dressings• Let body heal in moist,
sterile conditions• Good for burns
Shape memory polymers
• Wound is stitched loosely• Temperature of the body
makes the thread tighten• Closes the wound up with
the right amount of force
C1 5.4 PLASTIC WASTE
NON-BIODEGRADABLE
• Don’t break down
• Litter the streets and shores
• Harm wildlife
RECYCLING
• Sort plastics into different types
• Melted down and made into new products
• Saves energy and resources…BUT
• Hard to transport and
• Need to be sorted into specific types
DISADVANTAGES OF BIODEGRADABLE PLASTICS
• Farmers sell crops like corn to make plastics
• Demand for food goes up
• Food prices go up less can afford it STARVATION
• Animal habitats destroyed to make new farmland
• Unsightly
• Last 100’s of years
• Fill up landfill sites
BIODEGRADABLE PLASTICS
• Plastics that break down easily
• Granules of cornstarch are built into the plastic
• Microorganisms in soil feed on cornstarch
• This breaks the plastic down
C1 5.5 ETHANOL
There are 2 main ways to make ethanol
2) ETHENE
Hydration reaction water is added
Ethene + Steam Ethanol
C2H4 + H2O C2H5OH
+ Continuous process – lots made!+ Produces no waste products
- Requires lots of heat and energy- Relies on a non-renewable resource
1) FERMENTATION
Sugar from plants is broken down by enzymes in yeast
Sugar + Yeast Ethanol + Carbon Dioxide
80% of ethanol is made this way
+ Uses renewable resources
-Takes longer to produce- CO2 is given off
A molecule of ethanol
HH-C-C-OH
H
H
H
USES FOR ETHANOL
• Alcohol
• Perfume
• Rocket Fuel
• Solvents
• Antiseptic wipes
C1 6.1 EXTRACTING VEGETABLE OIL
There are 2 ways to extract vegetable oils from plants:
2) DISTILLATION
1. Plants are put into water and boiled2. Oil and water evaporate together3. Oil is collected by condensing (cooling
the gas vapours)
Lavender oil is one oil extracted this way
1) PRESSING
1. Farmers collect seeds from plants2. Seeds are crushed and pressed3. This extracts oil from them4. Impurities are removed5. Oil is processed to make it into a
useful product
FOOD AND FUEL
Vegetable oils are important foods:
• Provide important nutrients (e.g. vitamin E)
• Contain lots of energy so can also be used as fuels
• Unsaturated oils contain double bonds (C=C) they decolourise Bromine water
Food Energy(kJ)
Veg Oil 3900
Sugar 1700
Meat 1100
Table for info only – don’t memorise it!
C1 6.2 COOKING WITH VEGETABLE OILS
COOKING IN OIL
• Food cooks quicker• Outside becomes crispier• Inside becomes softer• Food absorbs some of the oil• Higher energy content• Too much is unhealthy
HARDENING VEGETABLE OILS
• Reacting vegetable oils with HYDROGEN hardens them increases melting points
• Makes them solid at room temperature makes them into spreads!
• Double bonds converted to single bondsC=C C-C
• Now called a HYDROGENATED OIL
• Reaction occurs at 60oC with a nickel catalyst
+
60oC + Nickel catalyst
Double bonds converted to single bonds
Margarine
C1 6.3 EVERYDAY EMULSIONS
Oils do not dissolve in water
Emulsion Where oil and water are dispersed (spread out) in each other
These often have special properties
EMULSION EXAMPLES
1. Mayonnaise2. Milk3. Ice cream4. Cosmetics – face cream, lipstick etc5. Paint
EMULSIFIERS
• Stop water and oil separating out into layers
• Emulsifiers have 2 parts that make them work:
1.Hydrophobic tail – is attracted to oil
2.Hydrophilic head – is attracted to water. It has a negative charge
Oil droplet
Emulsifier molecule
Water
-
C1 6.4 FOOD ISSUES
E NUMBER
Additives approved for use in Europe
EMULSIFIERS
• Improve texture and taste of foods containing fats and oils
• Makes them more palatable (tasty) and tempting to eat!
FOOD ADDITIVES
Substance added to food to:
• Preserve it• Improve its taste• Improve its texture• Improve its appearance
VEG OILS
Unsaturated Fats:
• Source of nutrients like vitamin E• Keep arteries clear• Reduce heart disease• Lower cholesterol levels
ANIMAL FATS
Saturated Fats:
• Are not good for us• Increase risk of heart disease• Increase cholesterol
E.g. chocolate!
C1 7.1 STRUCTURE OF THE EARTH
Atmosphere:
Most lies within 10km of the surface
Rest is within 100km but it’s hard to judge!
Crust:
Solid
6km beneath oceans
35km beneath land
Core:
Made of nickel and iron
Outer core is liquid
Inner core is solid
Radius is 3500km
Mantle
Behaves like a solid
Can flow very slowly
Is about 3000km deep!
C1 7.2 THE RESTLESS EARTH
MOVING CONTINENTS
The Earth’s crust and upper mantle are cracked into a number of pieces TECTONIC PLATES
These are constantly moving - just very slowly
Motion is caused by CONVECTION CURRENTS in the mantle, due to radioactive decay
PANGAEA
If you look at the continents they roughly fit together
Scientists think they were once one large land mass called pangaea, which then broke off into smaller chunks
PLATE BOUNDARIES
Earthquakes and volcanoes happen when tectonic plates meet
These are very difficult to predict
C1 7.3 THE EARTH’S ATMOSPHERE IN THE PAST
PHASE 1:PHASE 1:Volcanoes = Steam & CO2
• Volcanoes kept erupting Volcanoes kept erupting giving out giving out Steam and and CO2
• The early atmosphere was The early atmosphere was nearly all COnearly all CO22
• The The earth cooledearth cooled and and water vapour water vapour condensedcondensed to form the to form the oceansoceans
Like this for a billion years!
PHASE 2:PHASE 2:Green Plants, Bacteria
& Algae = Oxygen• Green plants, bacteria Green plants, bacteria
and algae ran riot in the and algae ran riot in the oceans!oceans!
• Green plants steadily steadily converted CO2 into O2 by the process of by the process of photosynthesis
• Nitrogen released by released by denitrifying bacteria
• Plants colonise the land. Oxygen levels steadily increase
PHASE 3:PHASE 3:Ozone Layer = Animals
& Us• The The build up of Obuild up of O22
killed off early killed off early organisms - allowingorganisms - allowing evolution of complex evolution of complex organismsorganisms
• The The O2 created the created the Ozone layer (O3) which which blocks harmful blocks harmful UV rays from the sunfrom the sun
• Virtually no COVirtually no CO22 leftleft
C1 7.4 LIFE ON EARTH
No one can be sure how life on Earth first started. There are many different theories:
MILLER-UREY EXPERIMENT
• Compounds for life on Earth came from reactions involving hydrocarbons (e.g. methane) and ammonia
• The energy for this could have been provided by lightning
OTHER THEORIES
1. Molecules for life (amino acids) came on meteorites from out of space
2. Actual living organisms themselves arrived on meteorites
3. Biological molecules were released from deep ocean vents
The experiment completed by Miller and Urey
C1 7.5 GASES IN THE ATMOSPHERE
THE ATMOSPHERE TODAY:
The main gases in the atmosphere today are:
1. Nitrogen 78%2. Oxygen 21%3. Argon 0.9%4. Carbon Dioxide 0.04%
CARBON DIOXIDE:
• Taken in by plants during photosynthesis
• When plants and animals die carbon is transferred to rocks
• Some forms fossil fuels which are released into the atmosphere when burnt
The main gases in air can be separated out by fractional distillation.
These gases are useful in industry
C1 7.6 CARBON DIOXIDE IN THE ATMOSPHERE
The stages in the cycle are shown below: Carbon moves into and out of the atmosphere due to
• Plants – photosynthesis & decay
• Animals – respiration & decay
• Oceans – store CO2
• Rocks – store CO2 and release it when burnt
CO2 LEVELS
Have increased in the atmosphere recently largely due to the amount of fossil fuels we now burn
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