04/22/23

Carbon ChemistryCarbon Chemistry

W Richards

The Weald School

(OCR Gateway)

04/22/23The 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

04/22/23Mass and atomic numberMass and atomic numberParticle Relative Mass Relative ChargeProton 1 +1

Neutron 1 0Electron 0 -1

MASS NUMBER = number of protons + number of neutrons

SYMBOL

PROTON NUMBER = number of protons (obviously)

04/22/23ElementsElementsIf a solid, liquid or gas is made up of only one type of atom we say it is an element. For example, consider a tripod made up of iron:

These atoms are ALL iron – there’s

nothing else in here

04/22/23CompoundsCompoundsCompounds are different to elements. They contain different atoms. Here are some examples:

Glucose

MethaneSodium

chloride (salt)

04/22/23Some simple Some simple compounds…compounds…

Methane, CH4 Water, H2OCarbon

dioxide, CO2

Ethyne, C2H2 Sulphuric acid, H2SO4

KeyHydrogen

Oxygen

Carbon

Sulphur

04/22/23An Introduction to BondingAn Introduction to BondingHi. 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

04/22/23BondingBondingHere comes one of my friends,

Harry Hydrogen

Hey Johnny. I’ve only got one electron. Fancy sharing?

Cl

H

Cl

H

Now we’re sharing electrons. We’ve formed a covalent

bond.

04/22/23BondingBondingHere 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

I’ve given my electron to Jonny. This is an ionic bond.

Na

Okay

Cl

Na+-

04/22/23Simple chemical reactionsSimple chemical reactionsMg O

H ClMg 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 +

04/22/23Chemical formulaeChemical 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)

04/22/23Chemical formulaeChemical formulaeTry drawing these:

1) Water H2O

2) Carbon dioxide CO2

3) Calcium sulphate CaSO4

4) Magnesium hydroxide Mg(OH)2

04/22/23Naming compoundsNaming 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) Cl26) Br2

These elements always go around in pairs (diatomic molecules). For example, hydrogen looks like this:

04/22/23Naming compoundsNaming 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 + chlorine2) Magnesium + fluorine3) Lithium + iodine4) Chlorine + copper5) Oxygen + iron

6) KBr7) LiCl8) CaO9) MgS10)KF

04/22/23Naming compoundsNaming 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 + oxygen3) Calcium + hydrogen +

oxygen4) Mg(OH)2

04/22/23Naming compoundsNaming 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 + oxygen2) Potassium + carbon + oxygen3) Calcium + sulphur + oxygen4) Magnesium + chlorine +

oxygen5) Calcium + oxygen + nitrogen

6) AgNO3

7) H2SO4

8) K2CO3

04/22/23Balancing equationsBalancing equationsConsider the following reaction:

Na

OH H H 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”)

04/22/23Balancing equationsBalancing equationsWe need to balance the equation:

Na

OH H

H H

Na

OH

Sodium + water sodium hydroxide + hydrogen

+ +

Na

OH H

Na

OH

Now the equation is balanced, and we can write it as:2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)

04/22/23Some examplesSome examples

Mg + O2

Zn + HClFe + Cl2

NaOH + HClCH4 + O2

Ca + H2ONaOH + H2SO4

CH3OH + O2

MgOZnCl2 + H2

FeCl3NaCl + H2OCO2 + H2OCa(OH)2 + H2

Na2SO4 + H2OCO2 + H2O

2 2 2 3

2 2

2 2

3

2

2

2

22 4

04/22/23Periodic Table IntroductionPeriodic Table Introduction

04/22/23

Mendeleev

Periodic tablePeriodic tableThe periodic table arranges all the elements in groups according to their properties.

Horizontal rows are called PERIODS

Vertical columns are called GROUPS

04/22/23

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Fe Ni Cu Zn Br Kr

Ag I Xe

Pt Au Hg

The Periodic TableThe Periodic TableAlkali

metals

Noble gases

HalogensThese elements

are metals

This line divides metals from non-metals These elements

are non-metals

04/22/23The Chemistry of CookingThe 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”

04/22/23The Chemistry of CookingThe Chemistry of CookingNow consider a potato cell:

Cooking a potato causes the cell wall

to break and release starch

grains

04/22/23Baking PowderBaking 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:

04/22/23Artificial AdditivesArtificial 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

04/22/23E numbersE 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:

04/22/23EmulsionsEmulsionsWhat’s an emulsion?

It’s a mixture of oil and water, like in salad dressing…

Paint is an emulsion. Other examples:

Milk Cream Butter

ButterfatWatery liquid

04/22/23Emulsifiers - the detailsEmulsifiers - the details

- ---

+

+

-

-

Emulsifier

Water Oil

04/22/23Active PackagingActive PackagingActive packaging is when a product is packaged with something that improves it, e.g.

Silica gel, to absorb water

A “widget”, to improve appearence and flavour

04/22/23PerfumesPerfumesHere are some facts about perfumes. Why are these things important?

1) Perfumes are non-toxic2) They are non-irritants3) They evaporate easily4) They do not dissolve in water5) They don’t react with water

A typical perfume reaction:

Ethanol + ethanoic acid ethyl ethanoate + water C2H5OH + CH3COOH C2H5OOCCH3 +

H2O

04/22/23Solutions revisionSolutions 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

04/22/23Making a solutionMaking a solutionA solution forms because

there are:1) Weak forces of attraction

between solute molecules2) 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.

04/22/23FuelsFuelsFuels are substances that can be used to release useful amounts of energy when they burn, e.g.

Oil GasWood Coal

These fuels are called “fossil fuels” and are described as being “non-

renewable”.

04/22/23Crude OilCrude Oil

04/22/23Hydrocarbons and crude Hydrocarbons and crude oiloil

Longer chains

mean…

1. Less ability to flow

2. Less flammable

3. Less volatile

4. Higher boiling point

Increasing length

Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples:

Ethane

C CHH

HHH

H

Butane

C CHH H

HHH C C H

H

HH

04/22/23Fractional distillationFractional distillationCrude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures:

Fractions with low boiling

points condense at

the top

Fractions with high boiling

points condense at the bottom

04/22/23Forces between moleculesForces between molecules

Weak force of interaction here

Longer molecules = stronger force of attraction

04/22/23CrackingCrackingShorter chain hydrocarbons are in greater demand because they burn easier. They can be made from long chain hydrocarbons by “cracking”:

Butane

EthaneFor example, this

bond can be “cracked” to give

these:Ethene

04/22/23CrackingCracking

This is a THERMAL DECOMPOSITION reaction, with clay used as a catalyst

Cracking can be used (as well as fractional distillation) to extract petrol from crude oil.

Long chain hydrocarbo

nHeated catalyst Liquid

hydrocarbon

Gaseous hydrocarbon

04/22/23AlkanesAlkanesAlkanes 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 bonds, for example:

Ethane

Alkanes are fairly unreactive (but they do burn well).

C CHH

HHH

H

Butane

C CHH H

HHH C C H

H

HH

04/22/23General Formulae for General Formulae for AlkanesAlkanesInstead of circles, let’s use letters…

General formula for alkanes = CnH2n+2

Butane (n=4)

H

C CH

HH

H

C CH

HHH H

Methane (n=1)

H

C HH

H

Ethane (n=2)

HH

C CH

HHH

Propane (n=3)

H

C HH

H

C CH

HHH

04/22/23AlkenesAlkenesAlkenes are different to alkanes; they contain DOUBLE COVALENT bonds. For example:

Ethane Ethene

Butane Butene

This double bond means that alkenes have the potential to join with other molecules – this make them REACTIVE.

ALKA

NES ALKENES

04/22/23General Formulae for General Formulae for AlkenesAlkenes

General formula for alkenes = CnH2n

Propene (n=3)

H

C HH

H

C CH

H

Ethene (n=2)

HH

C CH

H

Butene (n=4)

H

C CH

HH

H

C CH

H H

04/22/23Monomers 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

Step 2: Add the molecules together:

This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION

04/22/23Another way of drawing it…Another way of drawing it…Instead of circles, let’s use letters…

Ethene

C CHH

HHC C

HH

HHEthene

H

C CH

HH

H

C CH

HHPoly(e)thene

General formula for addition polymerisation:

C Cn C Cn

e.g. C CnH CH3

HHC C

n

H CH3

HH

04/22/23Some examplesSome examples

C Cn

H H

HH

C Cn

H H

HCl

C CnH H

HH

C CnH H

HCl

C CnH Cl

HBrC C

n

H Cl

HBr

04/22/23Uses of addition polymersUses of addition polymersPoly(ethene) Poly(propene)

Poly(chloroethene), PVC

Poly(styrene)

04/22/23Man made fibresMan made fibres

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”)

04/22/23Structure of PlasticsStructure of Plastics1) Some plastics have ____ intermolecular forces between each molecule – these have __ melting points and can be ________ easily

2) Some plastics have _____ forces between each molecule. These have ____ melting points and are ____.

Words – high, low, strong, weak, stretched, rigid

04/22/23Disposal of plasticsDisposal 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

04/22/23Choosing a fuelChoosing a fuelDoes 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?

04/22/23Burning FuelsBurning FuelsLots of oxygen:

Some oxygen:

Little oxygen:

CH

H

H

HOO

OO

OH H

OH HC

O

O

Methane Oxygen+ Water+Carbon dioxide

Oxygen+

OO

OO

OO

Methane

CH

H

H

H

CH

H

H

H

Carbon monoxid

e

CO

CO

Water+

OH HOH HOH HOH H

CCH

H

H

H

Methane

OO

Oxygen+

OH HOH H

Water+Carbon

04/22/23Endothermic and exothermic Endothermic and exothermic reactionsreactions

If a reaction gives out energy (e.g. it gets hot) it’s an EXOTHERMIC reaction, e.g. burning

If a reaction takes in energy (e.g. it gets cold) it’s an ENDOTHERMIC reaction, e.g. photosynthesis

04/22/23Burning MethaneBurning Methane

CH4 + 2O2 2H2O + CO2

Methane

Carbon dioxide Water

Oxygen

04/22/23Breaking and making bondsBreaking and making bonds

1) To burn methane you have to break all of these bonds:

2) And then you have to make these ones:

Basically, the reaction is EXOTHERMIC if (2) is greater than (1), i.e. More energy is released.

04/22/23Energy from fuelsEnergy from fuelsStep 1: Calculate the energy gained by the water:

Energy gained by water = mass of water x 4.18 J/gC0 x change in temperature

Step 2: Divide this value by the mass of the alcohol used to find out the energy gained by the water per gram of alcohol

Energy gained per gram = (answer to Step 1) / mass of alcohol burned

“specific heat capacity”

04/22/23An example calculationAn example calculationWhile doing this experiment, Gwyn got the following results for methanol:

Step 1: 100g x 4.18 J/gC0 x 35 = 14630 J

Step 2: 14630 / 1.45 = 10090 J/g

Mass of water

Start temp

End temp

Temp diff

Start mass

End mass

Mass diff

100g 16 51 35 159.67 158.22 1.45