Module C5

What Types of Chemicals are there in the earth’s atmosphere?

• The Earth is the

source of all our

materials.

• We can get things

from:

the atmosphere

the lithosphere

the

hydrosphere

Chemicals from the Earth’s spheres

The Earth’s Spheres……..

• We can break down the part of the Earth where we live and move into 4 areas, we call them spheres.

• Lithosphere• Hydrosphere• Atmosphere

Lithosphere• Made up of Crust & part of Mantle• About 80km in depth.• Broken into tectonic plates which are

moving.• Made up:

– Silicates (compounds of Silicon & Oxygen)

– Hydrocarbons (compounds of Hydrogen & Carbon)

– Carbonates (such as chalk, limestone and sea shells)

– Metal ores

Hydrosphere• The hydrosphere contains all the

solid, liquid, and gaseous water of the planet.– 97% of water is salty

• It ranges from 10 to 20 kilometers in thickness.

• Made up of:– Water– Dissolved oxygen– Dissolved nitrogen– Dissolved salts – Sodium Chloride– Calcium Carbonates (sea shells)

Atmosphere• It envelope all air that surrounds

the whole Earth.• It ranges up to 10,000km above

the Crust.• Protects us from UV radiation

from the Sun.• Made up of:

– Nitrogen– Oxygen– Carbon dioxide– Water vapour– Noble gases – Argon.

What molecules are there in the atmosphere?

The atmosphere

OxygenFormula?

Nitrogen.Formula?

Water vapourFormula?

Carbon dioxideFormula?

Inert Gases.Formula?

Pollutants?

What do these substances have in common?

Bpt?State at room temp?

Structure?Type of chemical element?

Bonding?

Covalent Bonds• When Non-metals combine they

share electrons.• i.e. H2• Hydrogen needs 1 electron (it has

one possible bond).• So 2 hydrogen atoms will share

there electrons with each other.• The Molecule is now held

together by electrostatic forces between nuclei & electrons.

• They can’t move any closer because there similar charged nuclei would repel.

Strong & Weak BondingStrong Bonding• The forces inside the molecules holding the atoms

together are many times stronger than the weak interaction between molecules.

• So a very high temperature is needed to break apart an Oxygen molecule (O2).

• The bonds that hold the compounds and molecules in the atmosphere are called Covalent Bonds. In Greek:– “Co” means together– “Valentia” means strong

Strong & Weak BondingWeak Bonding• There is an attractive force between all molecules and

compounds, but this is very weak.• We can think of the molecules moving in the atmosphere very

quickly, so quickly that when they collide this attractive force is still too small to let them join up.

• As we reduce the temperature there is more chance they will join together.

• Watch the animation below, but remember that the boiling point of water is 100oC and Carbon dioxide is -78oC)

• Animation

Attractive forces between molecules are weak.

Small molecules are gases or liquids at room temperature.

A line between element symbols to

show a covalent bond.

H—H

hydrogen, H2

O O

oxygen, O2

N N

nitrogen, N2

O C O

carbon dioxide,

CO2

H

H—C—H

H

methane, CH4

H H      

H—C—C—O—H

H H      

ethanol, C2H5OH

OH H

water, H2O

Chemists have different ways of describing molecules.

molecular formula

2D displayed formulawith lines for covalent bonds

3D ball-and-stick model

3D space-filling model

Is there a correlation between Bpt, Structure and rfm?

Formula Bpt degrees C

Structure rfm

CO2 -78 Molecular 44

CO -191 Molecular 28

O2 -183 Molecular 32

SO2 -10 Molecular 64

C - diamond

Giant 12

• What is the correlation between structure and boiling point?

• Why do molecular substances have a lower boiling point then giant structures?

• What is the correlation between rfm and boiling point for molecular structures?

• Would water fit this pattern? Explain.

• Explain why you think that water shows anomalous ( out of character )behaviour.

Covalent bonding

• Hydrogen H2

Covalent Bonding……………

• Fluorine – F2

• Chlorine – Cl2

Summarising Covalent Bonds.

• Covalent bonds share a pair of electrons that holds two atoms together.

• Covalent bonds are strong. • They also have a definite direction so

that molecules have a specific shape.

Summary1) Our atmosphere is a relatively thin layer of air that

surrounds the Earth 2) Dry air is a mixture of chemicals such as N2, O2, and Ar,

which are elements and CO2, which is a compound3) These chemicals have low boiling points which means they

are gases over the range of temperatures found on the Earth.

4) Harmful gases that are added to the atmosphere by human activity are called pollutants

5) All the chemicals that make up our atmosphere are gases because they are made up of small molecules.

6) Small molecules are made up of atoms of one or more non-metal elements.

7) The atoms in the molecules are held together by strong covalent bonding.

8) The attractive forces between molecules are weak so they have low boiling points and are gases at normal temperatures.

Physical properties of chemicals in the spheres……

• Describe the physical properties of the chemicals found in the:

• Lithosphere.• Atmosphere.• Hydrosphere. Describe solubility, melting points – high or low, and physical

state at room temperature.• Explain why these properties link to the presence of the

chemicals in each sphere.

What Reactions Happen in the Hydrosphere?

Salt harvesters in Thailand raking salt into piles

• A sodium chloride crystal is made up of millions of

Na+ and Cl– ions arranged in a regular pattern.

• The regular pattern is responsible for the cubic

range of all sodium chloride crystals.

Crystals of sodium chloride

Ionic Salt crystals - NaCl

+

• The ions can move independently, so a

solution of NaCl in water conducts electricity.

What happens when water dissolves an ionic salt?

Polar ( Charged) water molecules pull individual ions from the ionic crystal

• A sodium chloride crystal is made up of millions of Na+ and Cl– ions arranged

in a regular pattern called a crystal lattice.

• The lattice is responsible for the cubic shape of all sodium chloride crystals.

Crystals of sodium chloride

• Oppositely charged ions attract each other.

• Each ion will attract oppositely charged

ions from all directions.

• Each of these ions will in turn attract more

ions.

• A giant ionic lattice, made up of millions of

ions, is built up and forms a sodium

chloride crystal.

Physical properties:High Mpt/Bpt...Why?

Electrical Conductivity Solid?Electrical Conductivity in aqueous

solution?

Physical Properties of Sodium Chloride

Are all Ionic Salts Soluble?

What Happens when Lead Nitrate reacts with Potassium Iodide?

Pb( NO3)2 (aq) + K I(aq)

Pb(I)2(ppt) + KNO3(aq)

Soluble

Insoluble - ppt

SolubleSoluble

Precipitates and Predicting if one will form!

Precipitates form when an insoluble salt in formed during a reaction.

Ion Soluble? Insoluble ppts

Nitrate ( NO3) All NoneChloride ( Cl-1) Mostly Ag and Pb ChloridesSulphate ( SO4

-2) Mostly Ba and Pb sulphatesCarbonates ( CO3

-2) Only Na and Potassium Carbonates

Mainly

Predict and Apply!!!!Reactant 1 Reactant 2 Products PPt?

Lead Nitrate Barium Chloride

Sodium Nitrate Barium Chloride

Copper Sulphate Barium Chloride

Copper Sulphate Lead Nitrate

Copper Sulphate Sodium Nitrate

Predict!!!! AnswersReactant 1 Reactant 2 Products PPt?

Lead Nitrate Barium Chloride Yes – Lead Chloride

Sodium Nitrate Barium Chloride No

Copper Sulphate Barium Chloride Yes – Barium Sulphate

Copper Sulphate Lead Nitrate Yes – Lead Sulphate

Copper Sulphate Sodium Nitrate No

Testing for Positive and Negctive Ions in Ionic Salts

Ions such as chlorine, fluorine,

calcium and sulfate are tested for to

check they are within allowed limits.

Metal and non metal ions give characteristic reactions with reagents so

that they can be identified.

Testing for

positive ions

hydroxide ions in sodium hydroxide test solutionOH-(aq)

calcium ions in water sampleCa2+(aq)

Foe example,Calcium ions

have a positive charge. They

form a precipitate when mixed

with sodium hydroxide.

The amount of precipitate

indicates the amount of

calcium in the water sample. calcium hydroxide precipitateCa(OH)2(s)

Positive Ions Test Reaction with NaOH

Name of Ion Observed colour : Product?

Iron(II), Fe2+ green precipitate

Iron(III), Fe3+ red-brown precipitate

Copper(II),Cu2+ light blue precipitate

Calcium, Ca2+ white precipitate

Zinc , Zn2+ white precipitate dissolves in excess sodium hydroxide solution

These positive metal ions form insoluble metal hydroxides with a characteristic colour

Testing for

negative ions

barium ions in barium chloride test solutionBa2+(aq)

sulfate ions in water sampleSO4

2-(aq)

For example, sulphate ions

have a negative charge. They

form a precipitate when mixed

with barium chloride.

The amount of precipitate

indicates the amount of

Sulphate in the water sample. barium sulfate precipitateBaSO4(s)

Negative Non Metal Ion TestsName of Ion and formulae Observed colour : Product?

Negative ion solution Result of test for ion

chloride, Clwhite precipitate with silver nitrate

bromide, Br

cream precipitate with silver nitrate

iodide, Iyellow precipitate with silver nitrate

sulfate, SO42

white precipitate with barium Sulphate

carbonate, CO32 Bubbles of CO2 gas;

limewater turns cloudy with HCl and limewater

These negative non metal ions form insoluble solids when reacted with another chemical reagent such as silver nitrate

What types of chemicals make up the Earth’s

Lithosphere?

Giant Covalent Structures…….

• Diamond – C.

• Graphite – C.

• Quartz – SiO2

Structure of diamond and Graphite.

Explain why diamond has a high melting point

Explain why diamond does not conduct electricity

Explain why diamond does not dissolve in water

Explain why diamond is one of the hardest known materials.

Why do you think Graphite is a softer material than both SiO2 and diamond?

How many bonds does each Carbon atom make in Diamond? ……. In Graphite?

Why does Graphite conduct electricity?

In terms of structure what does SiO2resemble………. How does this explain its properties?

Bonding in SiO2 ……………………

• How many bonds does each silicon atom make ?

• How many bonds does each Oxygen atom make?

• What group is Silicon in? Use this information to explain why Si makes four bonds.

• Why does Oxygen only make 2 bonds?

Si

Silicon dioxide (SiO2) – explaining the observations……………..

• Why does SiO2 have a high mpt?

• Why Is SiO2 crystalline?

• Why is SiO2 a non conductor of electricity?

• Why is SiO2 a hard substance?

• Why is SiO2 not soluble in water?

How can we extract Useful Metals From

Minerals?

Iron

GoldAluminium

CopperSilver

Examples of common andimportant metals.

What is an ore?

• An ore is a volume of rock containing components or minerals in a mode of occurrence that renders it valuable for mining.

• The impurities are removed so that the real metal can be seen or used.

• Examples of metal ores are Haematite and Bauxite

Extraction processes

The ReactivitySeries

potassium

sodiumcalciummagnesium

aluminium

zinciron

copper

gold

(carbon)

Incr

easi

ng r

eact

ivity

Metals above carbon must be extracted using electrolysis.

Metals below carboncan be extracted from the ore by reduction using carbon, coke, or charcoal.

Gold and silver often do not need to be extracted. They occur native.

The reactivity of a metal determines the method of extraction.

lead

silver

Apply.• The metal ores that can react with the carbon are: Copper Oxide Iron Oxide Zinc Oxide

• This is because Carbon is more reactive than these metals therefore can REDUCE the metal oxide

Explain the terms OXIDATION and REDUCTION.

Oxidation and Reduction reactions – how do they work?

• CuO + C

• FeO + C

The Electrolysis of Molten Lead Bromide

• Electrolysis is the decomposition of an ELECTROLYTE with an electric current.

• N:\C5 EAM\IC5_9.swf ( use this file to explain the process of electrolysis)

• Metals form at the Negative electrode

• Non Metals form at the positive electrode

• Reaction at the negative electrode:

• Pb+2

• Reaction at the positive electrode:

• 2Br-1

+

Lead Bromide

PbBr2

Heat

Electrolysis of Lead Bromide.

Reaction at the anode and cathode

The reactions are as follows:at the anode:• 2Br –

(l) → Br2(g) + 2e– Oxidation

at the cathode:• Pb2+

(l) + 2e– → Pb(l) Reduction

Extraction of Al from it’s ore by Electrolysis

• http://www.rsc.org/learn-chemistry/resource/res00001027/industrial-process-videos?cmpid=CMP00001681

• ( 7 minute video of the extraction )

A bauxite / cryolite mixture is melted in a steel container containing a carbon lining.

Graphite (carbon) anodes

Tanklinedwith

carboncathode

Molten electrolytebauxite + cryolite

Steelcase

Graphite anodes are inserted into the molten electrolyte ready for electrolysis.

Electrolytic extraction

Aluminium formationOxygen formation

Anode (+ electrode)2O2-

(l) O2 (g) + 4e-

Cathode (- electrode)Al3+(l) + 3e- Al(l)

Carbon dioxide formation at anode

• Carbon dioxide is formed at the anode rapidly .

• Explain why this is an added cost to the Al extraction industry.

• Write a chemical equation for this reaction.

• Why is there formation of carbon dioxide at the anode, explain in terms of ions, electrons and charge

.

Extraction of aluminium using electrolysis – half reactions

Anode (+ve electrode)2O2-

(l) O2 (g) + 4e-

Cathode (-ve electrode)Al3+ (l) + 3e- Al (l)

Overall2Al2O3 (l) 4Al (l) + 3O2 (g)

The anode reacts to form carbon dioxide

C + O2 CO2

Why are metals so Important?

• Uses related to strength, malleability, high melting point and electrical conductivity

Metals are bonded so that the positive nuclei are surrounded by a sea of electrons that are free to move –

this explain conductivity. Malleability the atoms have the ability to slip over the top of

one another High melting point – strong forces of attraction between the

electrons and the +ve nuclei

How much metal can be extracted form it’s ore?

Quantitative Chemistry………

• What does ram stand for?• Relative atomic mass• What does rfm stand for?• Relative formula mass.• Calculate the rfm of H2SO4. (H=1,S=32,O=16)• 98g.• Calculate the rfm of Al2(SO4)3(Al=27,S=32,O=16)• 342g

Calculating the % of an element in a compound.

• Calculate the % of Nitrogen in NH4NO3.N=14; H=1;O=16)

• 35%• Calculate the % the metal in each of these

compounds.• Copper chloride• Sodium Oxide• Iron (III) Oxide.

How much metal using %s

• Calculate the mass of Copper that would be extracted from 75kg of the ore – Copper oxide.

• Stage 1 – Calculate the % of copper in the compound.

• Stage 2 – Using this % calculate the mass of Cu in 75kg.

Your turn…………………..

• The formula of red lead oxide is Pb3O4. Work out:

• The rfm of the red lead oxide• The % of lead in red lead oxide• The mass of Pb that would be extracted from

150kg of the ore.

Question 2

• Work out the % of copper in these minerals:• Cuprite Cu2O

• Chalcopyrite CuFeS2

• Malachite Cu2CO3(OH)2

• Calculate the mass of Cu that would be extracted from 3000kg of each mineral.

Using balanced Equations……..

• Calculate the mass of MgO that forms when 10.5g of Mg is burned in excess air?

• Write the equation for the reaction.• Identify chemicals in question.• Convert formulae to grammes using RFMs.• Calculate for 1g.• Calculate for quantity in question.

Questions……………………

• What mass of copper oxide would form from the thermal decomposition of 1 tonne of copper carbonate?

Questions……………………

• What mass of copper would form from the reaction of carbon with 0.75 tonnes of copper oxide?

Identify from the list those you can do and explain how they are done….

• I can calculate rfms…….• I can calculate %s of element in a compound…..• I can calculate the mass of a metal that would be formed from

a kg quantity of ore…………• I can balance and use chemical equations to calculate reacting

masses using gramme quantities………• I can balance and use chemical equations to calculate reacting

masses using gramme quantities using Kg quantities…..• I can balance and use chemical equations to calculate reacting

masses using metric tonne quantities………