True or FalseTrue or FalseIn a ‘reduction’ reaction Oxygen is added to a metal

In electrolysis a positive ion is attracted to the positive electrode (anode)

Organic chemicals found in the Biosphere are often formed around chains of CARBON atoms

Photosynthesis adds carbon to the atmosphere

Chemicals of the atmosphere have high boiling points and are made up of molecules containing lots of atoms

Giant covalent structures such as Silicon Dioxide have high melting points

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OCR Additional ScienceOCR Additional ScienceChemicals of the Natural Chemicals of the Natural

EnvironmentEnvironment

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The EarthThe Earth

1) The atmosphere

2) The hydrosphere

3) The biosphere

4) The lithosphere

19/04/23The Carbon The Carbon CycleCycle

CO2 in air

Photosynthesis

Respiration

Carbon is eaten by animals

Death of animals

Microbes respiring

Respiration

CO2 dissolves into the ocean

Death of plants

Sediment pressurized

Cement making

Fossil fuels

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The Nitrogen CycleThe Nitrogen Cycle1. Nitrogen-fixing bacteria convert N2 in the air into nitrates

2. Plants are then eaten by animals – the nitrogen becomes PROTEIN

3. Decomposers break down waste products and dead animals and plants to form AMMONIUM COMPOUNDS

4. Denitrifying bacteria convert nitrates and ammonium compounds into atmospheric nitrogen

Nitrates in the soil

Waste and dead animals

6. Nitrates taken in by plants

N2 in air

5. Nitrifying bacteria convert ammonium compounds into nitrates

Lightn

ing

Denitrifyin

g

bacte

ria

1. Fe

rtilisers

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Chemicals in the AirChemicals in the AirChemical Structure Diagram Boiling

point/OCMelting point/OC

Oxygen, O2 O=O -183 -218

Nitrogen, N2 N=N -196 -210

Carbon dioxide, CO2

O=C=O -78No liquid state

Water vapour, H2O

H-O-H 100 0

Argon. Ar Ar -186 -189

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ForcesForces1) Forces between molecules:

2) Forces within the molecule:

The forces between each molecule are very _____ so the molecules can _____ be pulled apart.

Forces within the molecules are very ______ due to the _______ bond so its very difficult to pull apart each molecule

Each line represents an electron being shared between the atoms

19/04/23Chemicals of the hydrosphere - WaterChemicals of the hydrosphere - Water

e-e- e-

e-

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Dissolving a crystal latticeDissolving a crystal lattice

-

-

-

- -

+

+ +

++

19/04/23Chemicals of the Chemicals of the lithosphere - Silicon lithosphere - Silicon

DioxideDioxide

O OO

O

Si

O O

OSi

OO

O

Si

Silicon dioxide forms a giant ______ structure where each atom is covalently bonded, forming a very strong 3-D ______. This causes it to be _____, have high _____ and boiling points and a good electrical ________.

Words – melting, covalent, insulator, hard, structure

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Using Covalent StructuresUsing Covalent StructuresElement/ compound

Property Uses Why?

Carbon – diamond

Very hard Drill tips Extremely strong covalent structure

Silicon dioxide

High melting point (1610OC)

Furnace linings

Very difficult to melt

Silica glass Doesn’t conduct electricity

Electrical insulators

No free electrons to carry charge

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Chemicals of the biosphereChemicals of the biosphere

GlucoseDNA

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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

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Extracting MetalsExtracting Metals

A METAL ORE is a mineral or mixture of minerals from which it is “economically viable” to extract some metal.

To “extract” a metal from a metal oxide we need to REDUCE the oxygen. This is called a REDUCTION reaction. To put it simply:

Most ores contain METAL OXIDES (e.g. rust = iron oxide).

Some definitions:

Iron OxideIron ore

“Reduce” the oxygen to make

iron

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OxideIron

How do we do it?How do we do it?Potassium

Sodium

Calcium

Magnesium

Aluminium

Carbon

Zinc

Iron

Tin

Lead

Copper

Silver

Gold

Platinum

Metals ABOVE CARBON, because of their high reactivity, are extracted by ELECTROLYSIS

Metals BELOW CARBON are extracted by heating them with carbon in a BLAST FURNACE. This is a “displacement reaction”

These LOW REACTIVITY metals won’t need to be extracted because they are SO unreactive you’ll find them on their own, not in a metal oxide

Carbon

19/04/23Calculating percentage Calculating percentage massmass

Calculate the percentage mass of magnesium in magnesium oxide, MgO:

Ar for magnesium = 24 Ar for oxygen = 16

Mr for magnesium oxide = 24 + 16 = 40

Therefore percentage mass = 24/40 x 100% = 60%

Percentage mass (%) =

Mass of element Ar

Relative formula mass Mr

x100%

Calculate the percentage mass of the following:

1) Hydrogen in hydrochloric acid, HCl

2) Potassium in potassium chloride, KCl

3) Calcium in calcium chloride, CaCl2

4) Oxygen in water, H2O

19/04/23Calculating the mass of Calculating the mass of metalmetal

After you’ve calculated the percentage mass you can work out the actual mass of a metal:

Calculate the mass of metal in the following:

1) Potassium in 10g of potassium chloride, KCl

2) Sodium in 20g of sodium chloride, NaCl

3) Calcium in 50g of calcium chloride, CaCl2

4) Magnesium in 100g of magnesium chloride, MgCl2

Mass of metal = % mass of metal x mass of substance

19/04/23Life Cycle Assessments Life Cycle Assessments (LCAs)(LCAs)

Step 1: Manufacture

What resources are needed? What effect will this have on the environment?

Step 2: Use

How much energy will be needed? What is the effect on the environment?

Step 3: Disposal

How is the product disposed of? What is the effect on the environment?

19/04/23ElectrolysisElectrolysis

++++

----

Positive electrode

Cu2+

Cu2+

Cu2+

Negative electrode

Cl-

Cl-

Cl-

Solution containing copper and

chloride ions

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ElectrolysisElectrolysisElectrolysis is used to separate a metal from its compound.

= chloride ion

= copper ion

When we electrolysed copper chloride the _____ chloride ions moved to

the ______ electrode and the ______ copper ions moved to the ______

electrode – OPPOSITES ATTRACT!!!

19/04/23Electrolysis equationsElectrolysis equationsWe need to be able to write “half equations” to show what happens during electrolysis (e.g. for copper chloride):

2 2

2

At the negative electrode the positive ions GAIN electrons to

become neutral copper ATOMS. The half equation is:

Cu2+ + e- Cu

At the positive electrode the negative ions LOSE electrons to

become neutral chlorine MOLECULES. The half equation is:

Cl- - e- Cl2

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Extracting AluminiumExtracting Aluminium

Aluminium has to be extracted from its ore (called ________) by electrolysis. This is because aluminium is very ___________. The ore is mixed with cryolite to lower its ________ ________. The ore is then melted so that the ions can ______. The positively charged aluminium ions gather at the ___________ electrode. Oxygen forms at the positive electrode and causes it to wear away, which means that they have to be __________ frequently.

Words – melting point, replaced, negative, bauxite, reactive, move

19/04/23Electrolysis of Aluminium Electrolysis of Aluminium OxideOxide

Overall:

At the cathode: At the anode:

Al3+(l) + 3e- Al(l) 2O2-

(l) - 4e- O2(g)

Aluminium oxide aluminium + oxygen

2Al2O3(l) 4Al(l) + 3O2(g)

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Using IronUsing Iron

Iron produced by the blast furnace (“cast iron”) contains about 96% iron and 4% impurities. These impurities make it very brittle and easy to break.

Ironbridge, Shropshire – made out of cast iron and safe for horses and carts but not modern vehicles.

19/04/23Copper, Aluminium and Copper, Aluminium and TitaniumTitanium

Metal Uses and why

Extraction method

Problems

Copper Electrical wires – good conductor

Electrolysis Limited supply

Aluminium and titanium

Planes – light and corrosion

resistant

Complicated and

expensive

Expensive and difficult to extract

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MetalsMetals

Metal atoms are very closely packed together in a regular arrangement. The atoms are held together by metallic bonds.

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Properties of metalsProperties of metals

Metals have very high melting points (which means that they are usually _____) whereas non-metals will melt at lower ___________

All metals conduct heat and __________ very well, whereas non-metals don’t (usually)

Metals are strong and ______ but bendable. Non-metals are usually _____ or they will snap.

Metals will _____ when freshly cut or scratched, whereas non-metals are usually dull.

Metals have higher _______ than non-metals (i.e. they weigh more)

Metals can be used to make ______ (a mixture of different metals)

Words - alloys, electricity, solids, weak, densities, temperatures, tough, shine

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A closer look at metalsA closer look at metals

+ + + + +

+ + + + ++ + + + ++ + + + ++ + + + +

+ + + + +

+ + + + +

+ + + + ++ + + + +

Metals are defined as elements that readily lose ______ to form positive ____. The ions are closely packed (hence the metal is ______) and they have strong bonds holding them together (hence the high _______ points). The presence of free electrons means that metals can conduct ______. Metals can bend because the layers can “____” over each other:

Words – slip, electrons, melting, electricity, strong, ions