GCES OCR 21st Century Chemistry Chemicals of the natural environment Complete Revision Summary

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GCSE OCR 21st Century Chemistry Chemicals of the natural environment Complete Revision Summary

Chemicals of the natural environment

BONDING Atoms bond to gain full outer shell or noble gas electronic configuration Ionic Bonding

transfer of electron between metals and non metals
between metal and non metals

Covalent Bonding

sharing of electron between non metals
between non metals

Metallic Bonding

Electrostatic force of attraction between fixed positive ions and delocalised electrons.
between Metals

Carbon dioxide (CO2) – Covalent Ammonia (NH3) – Covalent Nitrogen (N2) – Covalent Water (H2O) – Covalent Sodium chloride -Ionic Bonding Calcium fluoride— Ionic Bonding IONIC BONDING: Metals and Non Metals

It is between a metal and a non metal
Metal loses an electron and become positively charged.
Non- Metal gains an electron and becomes negatively charged.
There is a strong electrostatic force of attraction between opposite charged ions resulting in ionic bonding.

Dot and Cross Diagram

Write the symbols
Write electronic configuration
show outer electrons
show transfer
show charges

Example – Aluminium Fluoride Al = 2,8,3 F = 2,7

Example – Magnesium chloride Mg = 2,8,2 Cl = 2,8,7

PROPERTIES OF IONIC COMPOUNDS Ionic Compound Properties

Brittle solids with definite crystal shapes

In Ionic compounds, there is a strong electrostatic force of attraction between the opposite charged ions. This results in the formation of giant ionic lattice.

Good insulators in solid form, but become good conductors in liquid or dissolved form.

In the solid form, the ions are not free to move as they are held together by strong electrostatic force of attraction. In molten or when they are dissolved in water the ions are free to move and conduct electricity.

High melting and boiling point compared to molecular compounds

In Ionic compounds, there is a strong electrostatic force of attraction between the opposite charged ions. This results in the formation of giant ionic lattice. Large amount of energy is required to overcome the strong electrostatic force of attraction. Therefore, ionic compounds have high melting and boiling point. Greater the charge of an ionic lattice, stronger is the electrostatic force of attraction. Greater the melting and bp. For éx – Aluminium chloride > Magnesium chloride > sodium chloride FORMULAE OF IONIC COMPOUNDS

Write the Symbols
Write the charges
(Upto group the charge is same as the group number. After group 4 it is group number -8)
Criss Cross

FORMULAE OF COMPLEX IONS

a) Magnesium Hydroxide	Al2(SO4)3
b) Aluminium Sulphate	Al2(SO4)3
c) Calcium Phosphate	Ca3(PO4)2
d) Magnesium nitrate	Mg(NO3)2
e) Calcium Carbonate	CaCO3
f) Sodium Phosphate	Na3PO4

Positive	Negative
Ammonium = NH4+	Carbonate = CO32-
	Sulphate = SO42-
	Nitrate = NO3–
	Phosphate = PO43-
	Hydroxide = OH–

Chemicals of the natural environ

[download_after_email id=”10047″] COVALENT BONDING

It is between two non metals
It involves the sharing of electrons between two non metals.
More than one electron pair can also be shared resulting in the formation of single double and triple bonds.

Properties of Covalent Compounds

Simple Molecule

Eg – O₂, CH₄
They have weak intermolecular forces in them so have a lower melting and a boiling points
The intermolecular forces increases with increase in size as the surface area between the molecules increases.
Therefore, polymers which have covalent bonding between them have high melting and boiling point due to increase in chain length.

Giant Covalent

Diamond
Graphite
Silicon Dioxide

GIANT COVALENT STRUCTURES

Substances which have huge network of atoms joined together by covalent bonds form giant covalent structures.

DIAMOND	GRAPHITE
It is hard.	It is soft and greasy.
It is an insulator	It is a conductor
It has a high density.	It has a lower density than diamond.
Each carbon atom is covalently bonded to four other carbon atoms giving it a strong rigid structure	Carbon atoms are bonded in the form of layer in the form of hexagons. No covalent bonding between the layers so they can slide past. Each carbon atom is bonded with three other carbon leaving the fourth electron has delocalized
No delocalised electrons present	It has delocalised electrons
Used in cutting or jewellery	It is used in pencil leads.

PROPERTIES OF GRAPHITE

Q1 Why graphite is soft and slippery? Banner 5 In graphite, Carbon atoms are bonded in the form of layers in the form of hexagons. No covalent bonding between the layers so they can slide past each other. The layers have only weak intermolecular forces between them. By applying a little pressure then layers can easily slide past each other making Graphite soft and slippery.

Q2 Why graphite conduct electricity ? In graphite, Carbon atoms are bonded in the form of layer in the form of hexagons. No covalent bonding between the layers so they can slide past. Each carbon atom is bonded with three other carbon leaving the fourth electron has delocalized. These delocalized electrons are mobiles electrons which can move and conduct electricity.

FULLERENE AND GRAPHENE

Fullerene: Hollow shaped molecule having hexagonal rings like a bucky ball.

Also known as bucky ball or buckminsterfullerene.
Carbon can be in the form of pentagon or hexagon rings
Used as catalyst, drug delivery and treating cancer.
Graphene: Layer of interlocking hexagonal rings like single sheet of graphite.

It is a better conductor than graphite, light and have low density.
Used in making computer chips and flexible electronic displays.

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CARBON NANOTUBES

Cylinderical fullerene with the length greater than the diameter.
High tensile strength – Used in making reinforced composite materials
High electronic conductivity – used in electronic industry

METALLIC BONDING

It is between two metals.
There are fixed positive ions present in the sea of delocalised electrons.
There is strong electrostatic force of attraction between fixed positive ions and delocalized electrons resulting in metallic bonding.

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Properties of Metals

Metals are malleable

Malleable means that the metals can be hammered into any shape.
Metals have layered structure and layers can slide past each other by hammering giving metals different shapes.

Metals are ductile

Ductile means that the metals can be drawn into thin wires.
Metals have layered structure and layers can slide past each other by hammering giving metals a wire shape.

Metallic Bonding

Atoms in a metal are arranged in a regular manner and vibrate about fixed positions.
The outermost electrons move freely, forming a ‘sea of electrons’ enveloping the positive metal ions.

Metals are good conductors of electricity

Metals have delocalised electrons.
They are mobile and conduct electricity.
These mobile electrons or delocalised electrons conduct heat and electricity.

Metals have high melting and boiling points

There is strong electrostatic force of attraction between fixed positive ions and delocalized electrons.
Large amount of energy is required to overcome strong electrostatic force of attraction.

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ALLOYS

Alloys are the mixture of metals with another metal or a non metal which make the metal stronger.
In metals the particles are arrranged in layers. There is a regular arrangement of fixed positive ions which can slide past each by applying pressure.
In alloys there is a mixture of metals with another metal or a non metals. Another metal being different in shape and size distort the regular arrangement of the metal lattice.
As a result the layers of the metal can no longer slide past each other making it strong

Example: Steel is the alloy of iron which is more strong and resistant to corrossion.

NANOPARTICLES

Nanoparticles are the particles that deals with the paricles of size 1 to 100 nm.

KIL- Killing MET – Metal MIL -Milo MIC – Mickey NAN – Nano PIC – Pictures Convert 10 nm to

Metre = 10/10⁹m = 10^-8m
Micrometer = 10/10⁶m = 10^-5m

SURFACE AREA TO VOLUME RATIO

As the size decreases the surface area to volume ratio Increases. Therefore Nano particles being very small in size have large surface area to volume ratio making them very useful in Science and Medicine.

Surface area = 6 x side x side m² = 6 x 1000 x 1000 = 6 10⁶ m² Volume = side x side x side = 10⁹m³ SA: Volume = 6 x 10⁶/10⁹ = 6 x 10³ m

Surface area = 6 x side x side m² = 6 x 1000 x 1000 = 6 10⁴ m² Volume = side x side x side = 10⁶m³ SA: Volume = 6 x 10² m Banner 10

APPLICATIONS OF NANOPARTICLES

MEDICINES

To kill cancer and tuomour cells
For drug delievery

CATALYST

They have large surface area to volume ratio.
Used in small quantities so highly effective

COSMETICS

Used in Sunscreen to block sunlight

HOUSEHOLD

Self cleaning window panes
Nano particles breaks dirty in the presence of sunshine which is washed away by water while raining.

RISKS OF NANOPARTICLES

Due to small size can cause difficulty in breathing
They can accumulate in the envrionment and cause air pollution
Due to their large surface area a small spark can result in violent explosion making them risky to use.
They are toxic and cause breathing and respiratory problems.
Due to their small size they can also cause water pollution and risk the aquation life.

STATES OF MATTER

SOLIDS	LIQUIDS	GASES
Particles are close to each other.	Particles are slightly closer to each other.	Particles are far apart.
Have fixed shape	Do not have fixed shape	Do not have fixed shape
Strong forces between the particles	Weak forces between the particles	Very weak forces between the particles.
Have definite volume	Have fixed volume	Do not have fixed volume
cannot be compressed	Can be compressed	Highly compressible
Cannot flow	Can flow	Can flow

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KEY TERMS !!!!

Ions – charged atoms with unequal number of protons and electrons Ionic Bonding — bond formed between a metal and a non metal which involves complete transfer of electrons from metal to a non metal Dot and Cross — diagram that show transfer of electron in an ionic bond or sharing of electrons in a covalent bond. Covalent Bonding— bonding between two non metals which involves sharing of electrons. Metallic Bonding— bonding in metals which involves strong electrostatic forces of attraction between fixed positive ions and delocalised electrons. Intermolecular Forces — The forces between the molecules which determines the melting or a boiling point. Giant Covalent Molecules — Covalently bonded molecules which forms large giant structure Polymers – Molecules which are made up of many repeating units Delocalised electrons — Mobile electrons that are free to move as they are not associated with a bond or an atom. Fullerene— Allotrope of carbon which forms a cage like structure like bucky ball. Graphene— Allotrope of carbon which is equivalent to single layer of graphite Alloys— Mixture of metals with another metal or a non metal. Nanoparticles- particles which are of the size of 1 nm to 100 nm_ Nanoscience—lt is the branch of science that deals with nanoparticles State Of Matter-Different forms that a matter can take They are solids, liquids and gas Solids — States of matter with fixed shape and volume. Liquids— States of matter without fixed shape but fixed volume. Gases— States of matter with fixed shape and volume.

TEST YOURSELF

Q1 Name the type of bonding in the following compounds :

Q2 Draw dot and cross diagram to represent bonding in the following

a) Sodium chloride

b) Water
c) Magnesium

Q3 Differentiate Between Diamond and Graphite

DIAMOND	GRAPHITE
It is hard.	It is soft and greasy.
It is an insulator	It is a conductor
It has a high density.	It has a lower density than diamond.
Each carbon atom is covalently bonded to four other carbon atoms giving it a strong rigid structure	Carbon atoms are bonded in the form of layer in the form of hexagons. No covalent bonding between the layers so they can slide past. Each carbon atom is bonded with three other carbon leaving the fourth electron has delocalized
No delocalised electrons present	It has delocalised electrons
Used in cutting or jewellery	It is used in pencil leads.

Q4 Why Ionic compounds do not conduct electricity in solids ? In solids, the ions are held together by strong electrostatic force of attraction in the giant ionic lattice. In molten state the ions are free to move therefore conduct electricity Q5 Why Alloys are stronger than metals Alloys are the mixture of metals which distors the regular arrangement of metal as a result of which layers are not able to slide past each other making alloys stronger than metals. Q6 Why alumunium has a stronger melting point than sodium Aluminium has a greater charge. Due to greater charge of aluminium there is a stronger electrostatic forces of attraction between fixed positive ions and delocalised elecctrons. As a result aluminium has a greater melting point than sodium. Q7 What are nanoparticles? Write the properties and applications of nanoparticles Nanoparticles are the particles between the size of 1 to 100 nm_ Due to smaller size they have large surface area to volume ratio making them highly useful in medicine, catalysts, cosmetics and electronic industry.

CRUDE OIL

It is a black thick liquid which takes millions of years to form.
It is the mixture of hydrocarbon.
Hydrocarbon are the compounds made up of carbon and hydrogen only.
The components of the crude oil are important and the crude oil is separated by the process of fractional distillation.

HYDROCARBON PROPERTIES

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FRACTIONAL DISTILLATION OF CRUDE OIL

Separating the mixtures on the basis of boiling points.
It is separated in fractionating column with different substances of similar boiling points

LIQUIFIED GAS	FUEL
GASOLINE/PETROL	CAR FUEL
KEROSENE	AIRCRAFT FUEL
DIESEL OIL	FUEL IN DIESEL ENGINES
RESIDUE	MAKING ROADS

L – Look G – Great K – Kid D – Doing R – Roll CRACKING –Thermal decomposition of longer chain hydrocarbon into a shorter chain alkane and alkenes Thermal Cracking Catalytic Cracking It is done at a very high temperature It is done using a catalyst

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WHY CRACKING

Shorter chain alkanes are more in demand as they are more efficient fuel which fractional distillation alone cannot meet.
Alkenes are required for polymerization and synthesize other hydrocarbons which fractional distillation cannot meet.

ALKANES – Saturated Hydrocarbon

Carbon-carbon single bond made up of carbon and hydrogen

General Formulae C_nH_2n+2

Methane – CH₄

Ethane – C₂H₆

Propane – C₃H₈

Butane – C₄H₁₀

Pentane – C₅H₁₂

Homologous Series – Members of the same family have similar functional group similar chemical properties and general formulae but different physical property and each members differs from successive by CH₂.

COMBUSTION

COMPLETE	INCOMPLETE

FUEL IS COMPLETELY BURNED	FUEL IS PARTIALLY BURNED DUE TO LIMITED SUPPLY OF OXYGEN
PRODUCES CARBON DIOXIDE AND WATER	PRODUCES CARBON MONOXIDE AND WATER
IT IS NOT TOXIC	CARBON MONOXIDE IS TOXIC AS IT DECREASES. THE OXYGEN CARRYING CAPACITY OF RED BLOOD CELLS

PRODUCTS OF COMBUSTION Carbon Dioxide Test

Limewater Test Carbon Dioxide will turn limewater milky

Water Test

Banner 4 FUNCTIONAL GROUPS Groups of atoms that give special properties and reactions to the organic molecule

	Functional Groups	Examples	Formation
ALKENES	=	Ethene, propene, butene, pentene	Cracking of crude oil
ALCOHOLS	-OH	methanol, ethanol, propanol, butanol, pentanol	Reaction of alkene with water
CARBOXYLIC ACID		methanoic acid, ethanoic acid, propanoic acid, butanoic acid.	Oxidation of alcohols
ESTERS		methyl ethanoate, ethyl ethanoate	Reaction of alcohols and carboxylic acid

ALKENES

Unsaturated Hydrocarbon

Compounds which have carbon-carbon double bond
Compounds made up of carbon and hydrogen only

GENERAL FORMAULE C_nH_2n

Useful to make polymers, alkanes, alcohols

MANUFACTURE OF ETHANOL

	FERMENTATION	HYDRATION OF ETHENE
REACTION	Glucose Ethanol + carbon dioxide C₆H₁₂O₆2C₂H₅OH + 2CO₂	Ethene + Steam Ethanol
REACTION CONDITIONS	Gentle temperature and pressure. Anaerobic conditions	Nickel catalyst and high temperature and pressure
ADVANTAGES	Uses renewable resources like sugarcane. Less dependent on fossil fuels and due to less energy requirements do not harm the environment.	It is a continuous process. It is rapid more efficient and have 100% atom economy. Produces more pure ethanol
DISADVANTAGES	It is a batch process. The ethanol has to be distilled from time to time as high concentration will kill the yeast. The reaction is slow and produces impure ethanol. Also the atom economy is not 100%	Requires ethene which is dependent on crude oil. Uses non renewable resources.

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REACTIONS OF ALKENES

ALCOHOLS – Have functional Group –OH

General Formulae C_nH2_n+1 OH Formed by replacing hydrogen of alkane with OH group Used as fuel, solvents, spirits

REACTIONS OF ALCOHOLS

COMBUSTION

It can undergo complete or incomplete combustion. Complete combustion produces carbon dioxide and water.
Ethanol + Oxygen = Carbon dioxide + water

C₂H₅OH + O₂CO₂ + H₂O

Incomplete combustion produces carbon dioxide and water.
Ethanol + Oxygen = Carbon monoxide + water

C₂H₅OH + O₂CO + H₂O OXIDATION

Alcohols are oxidised to carboxylic acid in the presence of oxidising agent.
Methanol Methanoic Acid
Ethanol Ethanoic Acid
Oxidising agent used is acidified potassium dichromate solution

METAL Alcohols react with metals to form salt and hydrogen. 2C₂H₅OH + 2Ca2C₂H₅OCa + H₂

CARBOXYLIC ACID

Weak Acids Carboxylic Acids are weak acids as they are partially dissociated in water to release H+ ions. CH₃COOH ⇌CH₃COO^– + H⁺ Metal oxides and Metal hydroxide Carboxylic Acid reacts with metal oxides and metal hydroxide to form salt and water. CH₃COOH + NaOHCH₃COONa + H₂O Metal carbonate Carboxylic Acid reacts with metal carbonate to form salt, water and carbon dioxide. CH₃COOH + Li₂CO₃CH₃COOLi + CO₂ + H₂O

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ESTERS

Fruity smelling compounds
Used in the manufacture of perfumes, foods and cosmetics.

CARBOXYLIC ACID + ALCOHOLS ESTERS + WATER Alkyl alkanoate Methanoic Acid + Methanol Methyl methanoate + Water

ADDITION POLYMERIZATION

The individuals unit that polymerizes to form a polymers is known as a monomers. Eg Ethene
The structure formed by the polymerization of the monomer is a polymers.

Polymers are materials made by linking up smaller repeating chemical units. Some bend and stretch – rubber and polyester. Some hard and tough – epoxies and glass.

ADDITION POLYMERS

a) Formed by addition reaction.
b) Require only one monomer generally an alkene
c) Nothing is lost in the reaction.

eg Polyethene, polypropene

CONDENSATION POLYMERS

a) Requires two monomers
b) Requires two functional group
c) Formed by condensation reaction.
d) A small molecule of water is
e) Example: Nylon a polyester

NATURAL POLYMERS

a) They are found naturally
b) All the complex biomolecules are polymers

Monomer	Polymer
Glucose	Starch
Proteins	Amino Acid
Nucleotide	DNA

DNA

a) DNA is polynucleotide
b) Nucleotide = Phosphate + Sugar + Nitrogenous Bases
c) There are four bases present in the DNA

Adenine
Thymine
Guanine
Cytosine

KEY TERMS

Hydrocarbon – Hydrocarbon are the compounds made up of carbon and hydrogen only. Crude Oil – It is a black thick liquid which takes millions of years to form. It is the mixture of hydrocarbon. Fractional Distillation – Separating the mixtures on the basis of boiling points. Alkanes – Saturated Hydrocarbon. Carbon-carbon single bond. Made up of carbon and hydrogen only Saturated hydrocarbon – Saturated Hydrocarbons have only carbon-carbon single bonds. Unsaturated hydrocarbon – Unsaturated Hydrocarbons have carbon-carbon double bonds and triple bonds. General Formula – It applies to families of compounds; provides a way to predict the molecular formula of the molecule, based on the number of carbon atoms it contains. Viscosity – movement of flow. A fluid with low viscosity flows easily Flammable – Flammable materials are combustible materials that can easily ignite at room temperature Complete Combustion – Fuel is completely burned. Produces Carbon dioxide and water. Incomplete Combustion – Fuel is partially burned due to limited supply of oxygen. Produces Carbon Monoxide and Water. Cracking – Thermal decomposition of longer chain hydrocarbon into a shorter chain alkane and alkenes Alkenes – Unsaturated Hydrocarbon. Compounds which have carbon-carbon double bond. Compounds made up of carbon and hydrogen only Functional Group – Groups of atoms that give special properties and reactions to the organic molecule Homologous Series – Members of the same family have similar functional group similar chemical properties and general formulae but different physical property and each members differs from successive by CH₂ Alcohols – Have functional Group –OH. The General Formulae of Alcohols is CnH_2n+1 OH. Used as fuel, solvents, spirits Carboxylic Acid – Carboxylic Acids are weak acids as they are partially dissociated in water to release H+ ions. Esters – Fruity smelling compounds. Used in the manufacture of perfumes, foods and cosmetics. Fermentation – Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. Weak Acid – Weak acids are only partially ionized in their solutions. Monomers – The individuals unit that polymerizes to form a polymers is known as a monomers. Eg Ethene Polymers – The structure formed by the polymerization of the monomer is a polymers. Polymers are materials made by linking up smaller repeating chemical units. Some bend and stretch – rubber and polyester. Some hard and tough – epoxies and glass. Addition Polymerization – It is the process of repeated addition of monomers with double or triple bonds to form polymers. There is no loss of an atom or a molecule. Ex – PVC, polyethene, Teflon. Condensation Polymerization – It is a process that involves repeated condensation reactions between two different monomers. There is a loss of a molecule of water, ammonia etc as a by-product. Ex – Nylon, bakelite, silicon. Monosaccharide – Simplest carbohydrates (single units). They cannot be hydrolyzed into smaller units. Ex – Glucose, fructose. Polysaccharide – Formed of numerous monosaccharide units. Ex – starch, cellulose Starch – It is the reserve food material of plant cells. It consists of two components- amylose and amylopectin, both glucose polymers. Cellulose – Main structural polysaccharide of plants. It is a long, unbranched chain of about 6,000 glucose units with molecular weight between 0.5 to 2.5 million. Proteins – The proteins are linear unbranched polymers of Amino acids. The proteins are composed of carbon, hydrogen, oxygen, nitrogen, and Sulphur. DNA – It is a long, double chain of deoxyribonucleotide units. DNA is the genetic material and forms molecular basis of heredity in all organisms. Banner 12 Disclaimer: I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it. References: BBC Bitesize Wikipedia Wikimedia Commons Image Source: Wikipedia Wikimedia Commons Flickr Pixabay