03/10/2015 carbon chemistry ocr gateway w richards
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04/19/23
Carbon ChemistryCarbon Chemistry
OCR Gateway
W Richards
Fundamental concepts
Compounds
Compounds are formed when two or more elements are chemically combined. Some examples:
Glucose
Methane
Sodium chloride (salt)
Some simple compounds…
Methane, CH4 Water, H2O
Carbon dioxide, CO2
Ethyne, C2H2Sulphuric
acid, H2SO4
Key
Hydrogen
Oxygen
Carbon
Sulphur
More simple compounds…Water
Carbon dioxide
Carbon monoxide
Sulfur dioxide
Sodium hydrogencarbonate
Sodium carbonate
SO2
H2O
NaHCO3
CO2
Na2CO3
CO
Chemical formulaeThe chemical formulae of a molecule or compound is simply a way of showing the ratio of atoms in it. For example…
Na
Cl = sodium chloride (NaCl)
K I = potassium iodide (KI)
K N
O
O
O
= potassium nitrate (KNO3)
Chemical formulae
Try drawing these:
1) Water H2O
2) Carbon dioxide CO2
3) Calcium sulphate CaSO4
4) Magnesium hydroxide Mg(OH)2
Simple chemical reactions
Mg OH Cl
Mg ClCl
HH OH Cl
Magnesium
+ Copper sulphate
Mg
O
OCu
O
O S Cu Mg
O
O
O
O S
Magnesium
sulphate
Copper +
H2OMgO +
WaterMagnesium oxide
+ Hydrochloric acid
Magnesium chloride
+
2HCl MgCl2 +
MgSO4Mg + CuSO4 Cu +
Naming compoundsRule 1– If two identical elements combine then the
name doesn’t change
This happens with the following elements:
1) H2
2) N2
3) O2
4) F2
5) Cl2
6) Br2
These elements always go around in pairs (diatomic molecules). For example, hydrogen looks like this:
Naming compoundsRule 2 – When two elements join and one is a
halogen, oxygen or sulphur the name ends with ____ide
e.g. Magnesium + oxygen magnesium oxide
1) Sodium + chlorine
2) Magnesium + fluorine
3) Lithium + iodine
4) Chlorine + copper
5) Oxygen + iron
6) KBr
7) LiCl
8) CaO
9) MgS
10)KF
Naming compoundsRule 3 – When three or more elements combine and two of them are hydrogen and oxygen the name ends
with hydroxide
e.g. Sodium + hydrogen + oxygen Sodium hydroxide
1) Potassium + hydrogen + oxygen
2) Lithium + hydrogen + oxygen
3) Calcium + hydrogen + oxygen
4) Mg(OH)2
Naming compoundsRule 4 – When three or more elements combine and one of them is oxygen the ending is _____ate
e.g. Copper + sulphur + oxygenCopper sulphate
1) Calcium + carbon + oxygen
2) Potassium + carbon + oxygen
3) Calcium + sulphur + oxygen
4) Magnesium + chlorine + oxygen
5) Calcium + oxygen + nitrogen
6) AgNO3
7) H2SO4
8) K2CO3
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Balancing equationsBalancing equationsConsider the following reaction:
Na
O
H HH H
Na
OH
Sodium + water sodium hydroxide + hydrogen
+ +
This equation doesn’t balance – there are 2 hydrogen atoms on the left hand side (the “reactants” and 3 on the right hand side (the “products”)
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Balancing equationsBalancing equationsWe need to balance the equation:
Na
O
H H
H H
Na
OH
Sodium + water sodium hydroxide + hydrogen
+ +
Na
O
H HNa
OH
Now the equation is balanced, and we can write it as:
2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)
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Some examplesSome examples
Mg + O2
Zn + HCl
Fe + Cl2
NaOH + HCl
CH4 + O2
Ca + H2O
NaOH + H2SO4
CH3OH + O2
MgO
ZnCl2 + H2
FeCl3
NaCl + H2O
CO2 + H2O
Ca(OH)2 + H2
Na2SO4 + H2O
CO2 + H2O
2
2
2 3
2
2
2
2 3
2
2
2
2
2 4
04/19/23
The structure of the atomThe structure of the atom
ELECTRON – negative,
mass nearly nothingPROTON –
positive, same mass as neutron
(“1”)
NEUTRON – neutral,
same mass as proton
(“1”)
The Ancient Greeks used to believe that everything was made up of very small
particles. I did some experiments in 1808 that proved this and called these particles
ATOMS:
Dalton
04/19/23
Mass and atomic numberMass and atomic number
Particle Relative Mass Relative Charge
Proton 1 +1
Neutron 1 0
Electron Very small -1
MASS NUMBER = number of protons + number of neutrons
SYMBOL
PROTON NUMBER = number of protons (obviously)
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Mass and atomic numberMass and atomic numberHow many protons, neutrons and electrons?
Atoms, ions and moleculesAn “atom” is simply one particle on its own in its “normal” state, e.g. a helium atom:
An “ion” is an atom that has lost or gained electrons, e.g. sodium:
A “molecule” is a combination of atoms in a compound:
Na
+
Na
Examples of ionic molecules
Mg
Magnesium chloride:
MgCl2
Cl
Cl
+ Mg
2+
Cl
-
Cl
-
Calcium oxide:
CaO
OCa + Ca
2+
O
2-
04/19/23
Bonding introducedBonding introduced
Hi. My name’s Johnny Chlorine. I’m in Group 7, so I have 7 electrons in my outer
shell
I’d quite like to have a full outer shell. To do this I need to GAIN an electron. Who can
help me?
Cl
Cl
04/19/23
BondingBondingHere comes one of my friends,
Harry Hydrogen
Hey Johnny. I’ve only got one electron but it’s really close to my nucleus so I don’t want to
lose it. Fancy sharing?
Cl
H
Cl
H
Now we’re both really stable. We’ve formed a covalent bond.
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BondingBondingHere comes another friend,
Sophie Sodium
Hey Johnny. I’m in Group 1 so I have one electron in my outer
shell. Unlike Harry, this electron is far away from the nucleus so I’m
quite happy to get rid of it. Do you want it?
Cl
Now we’ve both got full outer shells and we’ve both gained a charge. We’re both called IONS
and we’ve formed an IONIC bond.
Na
Okay
Cl
Na
+-
C1a – Making Crude Oil useful
FuelsA “fuel” is something that can be burned to release heat and light energy. The main examples are:
Coal, oil and gas are called “fossil fuels”. In other words, they were made from fossils.
04/19/23Hydrocarbons and crude Hydrocarbons and crude oiloil
Longer chains
mean…
1. Less ability to
flow
2. Less flammable
3. Less volatile
4. Higher boiling
point
Incre
asin
g le
ng
th
Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples:
Ethane
C C
HH
H
HH
H
Butane
C C
HH H
HH
H C C H
H
HH
04/19/23
Distillation revisionDistillation revision
This apparatus can be used to separate water and ethanol because they have different _____ ______. The ______ will evaporate first, turn back into a _______ in the condenser and collect in the _______. The water remains in the round flask, as long as the _______ does not exceed water’s boiling point. This method can be used to separate crude oil.
Words – temperature, boiling points, ethanol, beaker, liquid
Forces between molecules
Weak force of interaction here
Longer molecules = stronger force of attraction
04/19/23
Fractional distillationFractional distillationCrude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures due to the different intermolecular forces between each molecule:
Fractions with low boiling points condense at the top
Fractions with high boiling points condense at the bottom
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Crude OilCrude Oil
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Using Crude OilUsing Crude Oil
Crude Oil
Benefits Drawbacks
Cheap to extract
Wide range of uses as fuel
Used to make plastics
Getting oil from unstable
countries?Burning
fossil fuels causes
pollution
It takes millions of years to
form
It’s going to run out
04/19/23
CrackingCrackingShorter chain hydrocarbons are in greater demand because they burn easier. They can be made from long chain hydrocarbons by “cracking”:
Butane
Ethane
For example, this bond can be “cracked” to give these:
Ethene
04/19/23CrackingCracking
This is a THERMAL DECOMPOSITION reaction, with clay used as a catalyst
1) Carbon dioxide causes the _________ effect
2) Sulfur dioxide causes _____ _____
3) Plastics are not _____________
Cracking is used to produce plastics such as polymers and polyethanes. The waste products from this reaction include carbon dioxide, sulfur dioxide and water vapour. There are three main environmental problems here:
Long chain hydrocarbon
Heated catalyst
Gaseous hydrocarbon
Liquid hydrocarbon
C1b – Using Carbon Fuels
Choosing a fuel
Does it create pollution?
How much does it cost? Is it easy to use,
store and transport?
Is it toxic?
How much energy does it release?
Which fuel should you use?
Burning Fuels – “Combustion”
Lots of oxygen:
C
H
H
H
HO
O
OO
OH H
OH H
CO
O
Methane Oxygen+ Water+Carbon dioxide
What would a balanced symbol equation for this reaction look like?
Incomplete Combustion
Some oxygen:
Little oxygen:
Oxygen+
OO
OO
OO
Methane
C
H
H
H
H
C
H
H
H
H
Carbon monoxid
e
CO
CO
Water+
OH H
OH H
OH H
OH H
CC
H
H
H
H
Methane
OO
Oxygen+
OH H
OH H
Water+Carbon
Incomplete combustion is when a fuel is burned without having a plentiful supply of oxygen, e.g. when the Bunsen’s air hole is closed:
Balanced symbol equations?
Incomplete CombustionAs well as producing carbon monoxide, incomplete combustion can also produce soot:
Little oxygen:
CC
H
H
H
H
Methane
OO
Oxygen+
OH H
OH H
Water+Carbon
“Soot”
C1c – Clean Air
04/19/23
The EarthThe Earth’’s Atmospheres Atmosphere
Carbon dioxide, water vapour
Oxygen Nitrogen Noble gases
For the last 200 million years the atmosphere has remained roughly the same – it contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2
04/19/23The Carbon The Carbon CycleCycle
CO2 in air 1. CO2 is taken
in by plants and algae for photosynthesis and turned into carbohydrates, fats and proteins
2. Plants and algae release CO2 through respiration
3. The carbon taken in by plants is then eaten by animals and the animals that eat them
4. Animals release CO2 through respiration
5. Burning fossil fuels also releases CO2
04/19/23
4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the EarthEvolution of the Earth’’s s AtmosphereAtmosphere
Carbondioxide
Methane Ammonia Oxygen Nitrogen Others
Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2
04/19/23
4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the EarthEvolution of the Earth’’s s AtmosphereAtmosphere
Volcanic activity releases CO2, methane, ammonia and water vapour into the atmosphere. The water vapour condenses to form oceans.
Some of the oxygen is converted into ozone. The ozone layer blocks out harmful ultra-violet rays which allows for the development of new life.
Green plants evolve which take in CO2 and give out oxygen. Carbon from CO2 becomes locked up in sedimentary rocks as carbonates and fossil fuels. Methane and ammonia react with the oxygen and nitrogen is released.
Population and PollutionThe human population is growing exponentially, particularly in countries like China and India:
Population
Time
This has a number of effects on the environment:
Bigger population means…
Resources – more resources
needed, e.g. deforestation
Farming –less land
available for crops
Waste –more waste needs to be disposed of
Pollution –More phosphates,
nitrates, CO2 and SO2
PollutionWhat causes pollution?
Carbon monoxide is a poisonous gas formed by incomplete combustion.
Sulfur dioxide causes acid rain that kills aquatic life and damages buildings and metals. It’s caused when fuels containing sulfur are burned.
Oxides of nitrogen can cause photochemical smog and acid rain, and are formed in internal combustion engines
Reducing Pollution from vehiclesA number of suggestions:
1) Buy a new, smaller, cleaner car
2) Buy a “hybrid” car
3) Convert your car to run on biodiesel
4) Make sure your car has a catalytic converter:
5) Use the train or a bus!
Carbon monoxide + oxygen carbon dioxide
2CO + 2NO N2 + 2CO2
C1d – Making Polymers
04/19/23
Hydrocarbons revisionHydrocarbons revision
Longer chains
mean…
1. Less ability to
flow
2. Less flammable
3. Less volatile
4. Higher boiling
point
Incre
asin
g le
ng
th
Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples:
Ethane
C C
HH
H
HH
H
Butane
C C
HH H
HH
H C C H
H
HH
04/19/23
AlkanesAlkanesAlkanes are SATURATED HYDROCARBONS. What does this mean?
HYDROCARBONS are molecules that are made up of hydrogen and carbon atoms
SATURATED means that all of these atoms are held together by single COVALENT bonds, for example:
Ethane
Alkanes are fairly unreactive (but they do burn well). The general formula for an alkane is CnH2n+2
C C
HH
H
HH
H
Butane
C C
HH H
HH
H C C H
H
HH
04/19/23General Formulae for General Formulae for AlkanesAlkanesInstead of circles, let’s use letters…
General formula for alkanes = CnH2n+2
Butane (n=4)
H
C C
H
HH
H
C C
H
HH
H H
Methane (n=1)
H
C H
H
H
Ethane (n=2)
H
H
C C
H
HH
H
Propane (n=3)
H
C H
H
H
C C
H
HH
H
04/19/23
AlkenesAlkenesAlkenes are different to alkanes; they contain DOUBLE COVALENT bonds (a bond that has two shared electrons). For example:
Ethane Ethene
Butane Butene
This double bond means that alkenes have the potential to join with other molecules – this make them REACTIVE. Alkenes turn bromine water colourless.
ALK
AN
ES
ALK
EN
ES
Testing for alkenesTesting for alkenes04/19/23
Oil Bromine goes colourless
Bromine water This is an
“addition” reaction where the colour change is caused by the formation of a colourless dibromo compound.
04/19/23General Formulae for General Formulae for AlkenesAlkenes
General formula for alkenes = CnH2n
Propene (n=3)
H
C H
H
H
C C
H
H
Ethene (n=2)
H
H
C C
H
H
Butene (n=4)
H
C C
H
HH
H
C C
H
H H
04/19/23
Monomers and PolymersMonomers and PolymersC C
HH
HH
Ethene
Here’s ethene again. Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics…
Step 1: Break the double bond
(this often requires high pressure and a catalyst)Step 2: Add the molecules together:
This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION
04/19/23
Another way of drawing it…Another way of drawing it…Instead of circles, let’s use letters…
Ethene
C C
HH
HH
C C
HH
HH
Ethene
H
C C
H
HH
H
C C
H
HH
Poly(e)thene
General formula for addition polymerisation:
C Cn C C
n
e.g. C Cn
H CH3
HH
C Cn
H CH3
HH
04/19/23
Some examplesSome examples
C Cn
H H
HH
C Cn
H H
HCl
C CnH H
HH
C CnH H
HCl
C CnH H
HCH3
Ethene –
polyethene
Vinylchloride –
Polyvinylchloride (PVC)
Propene –
PolypropeneC Cn
H H
HCH3
C1e – Designer Polymers
04/19/23
Uses of addition polymersUses of addition polymersPoly(ethene) Poly(propene)
Poly(chloroethene), PVC
Poly(styrene)
What properties would these
polymers have?
Structure of Plastics1) Some plastics have ____ intermolecular forces between each molecule – these have __ melting points and can be ______ easily as the molecules _____ over each other.
2) Some plastics have _____ forces between each molecule. These have ____ melting points and are ____.
Words – high, low, strong, weak, stretched, rigid, slide
Outdoor Clothing
I love doing outdoor sports. I’d like to wear clothing that is tough but also lets my sweat
out. What should I wear?
Nylon and Gore-Tex
Nylon – lightweight, tough, waterproof, blocks UV
Gore-tex – nylon coated with PTFE – this means that it can allow perspiration to escape but rain cannot get in (it can “breathe”)
Inner fabric
Gore-tex
Gore-TexGore-tex is a material made from nylon laminated with the polymer PTFE and its invention has been of great use in the world of outdoor sports. Here’s how it works:
Outer fabric
Sweat
Basically, the holes in the material are too small for water drops to pass through but big enough for sweat vapour. On its own, the membrane is too fragile so it is combined with nylon.
Disposal of plastics1) Landfill sites - most plastics do not _________ which means that landfill sites are quickly filled up. Research is being carried out on __________ plastics.
2) Burning – this releases carbon dioxide which causes the ________ effect, as well as other ________ gases.
3) _______ – the best option, but difficult because of the different types of plastic
Words – recycling, greenhouse, decompose, biodegradable,
poisonous
Biodegradable carrier bagsBiodegradable carrier bags04/19/23
This carrier bag has been made with flax fibre from industrial waste.
C1f – Cooking and Food Additives
The Chemistry of CookingThe process of cooking food causes some chemicals to turn into others (i.e. a chemical change) and these are irreversible. For example, consider a protein molecule:
“Denatured”
The Chemistry of CookingNow consider a potato cell:
Cooking a potato causes the cell wall to break, leading to
a softer texture. Starch grains also
swell up and spread out.
Artificial AdditivesWhy do we use additives?
Some examples:
Additive Interesting information
Flavour enhancers Can include traditional ingredients like salt, vinegar etc. Monosodium glutamate is often used in Chinese foods (its found in soy sauce)
Colour enhancers Processing food often results in colour loss so colour enhancers are used. Could be natural like carotenes or artificial like tartrazine
Preservatives Can include vinegar and sugar. Artificial preservatives are used to stop microbes growing and antioxidants stop fats going off
Vitamins and minerals Can be used to replace those lost during cooking
E numbers
E100–E199 (colours)
E200–E299 (preservatives)
E300–E399 (antioxidants, acidity regulators)
E400–E499 (thickeners, stabilizers, emulsifiers)
E500–E599 (acidity regulators, anti-caking agents)
E600–E699 (flavour enhancers)
E900–E999 (miscellaneous)
E1000–E1999 (additional chemicals)
If artificial additives are “approved” they are given an E number:
04/19/23
EmulsionsEmulsionsWhat’s an emulsion?
It’s a mixture of oil and water, like in salad dressing…
Paint is an emulsion. Other examples:
Milk Cream Butter
Butterfat
Watery liquid
04/19/23
Why use emulsions?Why use emulsions?Emulsions can have varying textures and this makes them useful. Some examples:
Different thicknesses
of cream
Paint and mayonnaise
04/19/23
EmulsifiersEmulsifiersAn emulsifier is an additive that will stop oil and water from seperating, like in mayonnaise.How they work:
Water Oil
I’m an emulsifier – I’ll sort this out with my hydrophobic end and my hydrophilic end!
I don’t want to mix with you!
The water and oil drops become “coated” and insulated from one another, which prevents them from seperating.
04/19/23
Uses of emulsifiers in foodUses of emulsifiers in food
Emulsifiers are used:
1) In bread, to stop large _____ developing when it bakes
2) In low fat spreads, to allow the oil and water to be _____
3) In ice cream and spray cream, to ______ the foam
4) In sponge cakes, to make tiny pockets of ____
5) In chocolate, to stop melted chocolate forming _______
Words – crystals, air, holes, mixed, stabilise
Baking PowderBaking powder is used to make bread rise:
Sodium hydrogen carbonate sodium carbonate + water + carbon dioxide
NaHCO3(s) Na2CO3(s) + H20(g) + CO2(g)2
Gas
Limewater turns milky/cloudy
LimewaterTesting for carbon dioxide:
C1g – Smells
PerfumesPerfumes are synthetically made from chemicals called “esters”. Here are some facts about perfumes. Why are these things important?
1) Perfumes are non-toxic
2) They are non-irritants
3) They evaporate easily
4) They do not dissolve in water
5) They don’t react with water
A typical perfume reaction:
Ethanol + ethanoic acid ethyl ethanoate + water
C2H5OH + CH3COOH C2H5OOCCH3 + H2O
Solutions revision
If a substance CAN be dissolved it is called __________
If a substance CANNOT be dissolved it is called _________
Words – soluble, solute, solvent, solution, insoluble
Solubility words
Solute
Solution
Solvent
Soluble
Insoluble
Saturate
d
Solubilit
y
Something that CAN dissolve is described as
being…
How much of something that can be dissolved is
called…
Something that CANNOT be dissolved is
described as being…
A solution that CAN’T dissolve anything else is…
The solid that will be dissolved is the…
The mixture of solute and solvent is called the…
The liquid that the solute will be dissolved into is
the…
Making a solutionA solution forms because
there are:
1) Weak forces of attraction between solute molecules
2) Strong forces of attraction between solute and solvent molecule
For example, nail varnish remover works because the nail varnish remover molecules are attracted to the nail varnish molecules with a stronger attraction than water molecules are. Esters can be used as solvents.
CosmeticsI think that the testing of cosmetics
should be allowed.
No way! I totally disagree.
The testing of cosmetics on animals is currently banned in the EU. Who do you agree with and why?
C1h – Paints and Pigments
PaintPaint is an example of a “colloid” – a mixture of one or more substances in a liquid but which are not dissolved. The molecules have a large surface area:volume ratio and, as such, they have a large surface tension and are difficult to separate.
“Ingredients” in paint
Function
Solvent Gives the paint its colour
Pigment Sticks the pigment to the surface
Binding medium Thins the paint, making it easier to spread
Water based vs Oil based“Water-based paints”
“Oil-based paints”
In water-based paints the paint dries when the _______ evaporates, causing them to dry in around one ______. In oil-based paints the solvent has to ________ and then the oil is _______ by oxygen in the air, which takes longer and paint brushes have to be cleaned with ____ ___ rather than water.
Words – white spirit, evaporate, water, hour, oxidised
Thermochromic PaintThermochromic paint is paint that changes colour when heated. Some uses:
Acrylic paints can be added to thermochromic paint to give it an even wider range of colours.
Here’s a strange use of this paint:
Phosphorescent PaintPhosphorescent paint is paint that contains pigments that can glow in the dark. They do this by “storing” energy and then release it over time:
The original “glow-in-the-dark” paint contained radioactive materials so this paint is much safer!
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