1. True or False
20/04/2017
In 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

2. OCR Additional Science
20/04/2017
OCR Additional Science
Chemicals of the Natural Environment

3. The Earth 1) The atmosphere 2) The hydrosphere 3) The biosphere
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1) The atmosphere
2) The hydrosphere
3) The biosphere
4) The lithosphere

4. The Carbon Cycle CO2 in air 20/04/2017 Respiration
CO2 dissolves into the ocean
CO2 in air
Microbes respiring
Photosynthesis
Fossil fuels
Respiration
Carbon is eaten by animals
Death of animals
Death of plants
Cement making
Sediment pressurized

5. The Nitrogen Cycle N2 in air
20/04/2017
4. Denitrifying bacteria convert nitrates and ammonium compounds into atmospheric nitrogen
N2 in air
1. Nitrogen-fixing bacteria convert N2 in the air into nitrates
1. Fertilisers
Denitrifying bacteria
Lightning
Waste and dead animals
5. Nitrifying bacteria convert ammonium compounds into nitrates
6. Nitrates taken in by plants
Nitrates in the soil
3. Decomposers break down waste products and dead animals and plants to form AMMONIUM COMPOUNDS
2. Plants are then eaten by animals – the nitrogen becomes PROTEIN

6. Chemicals in the Air Chemical Structure Diagram Boiling point/OC
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Chemical
Structure
Diagram
Boiling point/OC
Melting point/OC
Oxygen, O2
O=O
-183
-218
Nitrogen, N2
N=N
-196
-210
Carbon dioxide, CO2
O=C=O
-78
No liquid state
Water vapour, H2O
H-O-H
100
Argon. Ar Ar
-186
-189

7. Forces 1) Forces between molecules:
20/04/2017
1) Forces between molecules:
The forces between each molecule are very _____ so the molecules can _____ be pulled apart.
2) Forces within the molecule:
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

8. Chemicals of the hydrosphere - Water
20/04/2017 e-

9. Dissolving a crystal lattice
20/04/2017 + - + - + - + - + -

10. Chemicals of the lithosphere - Silicon Dioxide
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Chemicals of the lithosphere - Silicon Dioxide
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

11. Using Covalent Structures
20/04/2017
Element/ 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

12. Chemicals of the biosphere
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DNA
Glucose

13. Sodium + water sodium hydroxide + hydrogen
Balancing equations
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Consider the following reaction:
Sodium + water sodium hydroxide + hydrogen Na O H O H Na + H +
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”)

14. Balancing equations We need to balance the equation:
20/04/2017
We need to balance the equation:
Sodium + water sodium hydroxide + hydrogen Na O H O H Na O H Na O H + H + Na
Now the equation is balanced, and we can write it as:
2Na(s) + 2H2O(l) NaOH(aq) + H2(g)

15. Some examples 2 2 3 2 3 Mg + O2 Zn + HCl Fe + Cl2 NaOH + HCl CH4 + O2
20/04/2017 2
Mg O2
Zn HCl
Fe Cl2
NaOH HCl
CH O2
Ca H2O
NaOH H2SO4
CH3OH O2
MgO
ZnCl H2
FeCl3
NaCl H2O
CO H2O
Ca(OH) H2
Na2SO H2O 2

16. “Reduce” the oxygen to make iron
Extracting Metals
20/04/2017
Some definitions:
A METAL ORE is a mineral or mixture of minerals from which it is “economically viable” to extract some metal.
Most ores contain METAL OXIDES (e.g. rust = iron oxide).
To “extract” a metal from a metal oxide we need to REDUCE the oxygen. This is called a REDUCTION reaction. To put it simply:
Oxide
Iron
Iron ore
“Reduce” the oxygen to make iron

17. Increasing reactivity
How do we do it?
20/04/2017
Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Copper
Silver
Gold
Platinum
Increasing reactivity
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”
Carbon
Oxide
Iron
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

18. Calculating percentage mass
20/04/2017
Percentage mass (%) =
Mass of element Ar
Relative formula mass Mr
x100%
Calculate the percentage mass of magnesium in magnesium oxide, MgO:
Ar for magnesium = 24 Ar for oxygen = 16
Mr for magnesium oxide = = 40
Therefore percentage mass = 24/40 x 100% = 60%
Calculate the percentage mass of the following:
Hydrogen in hydrochloric acid, HCl
Potassium in potassium chloride, KCl
Calcium in calcium chloride, CaCl2
Oxygen in water, H2O

19. Calculating the mass of metal
20/04/2017
After you’ve calculated the percentage mass you can work out the actual mass of a metal:
Mass of metal = % mass of metal x mass of substance
Calculate the mass of metal in the following:
Potassium in 10g of potassium chloride, KCl
Sodium in 20g of sodium chloride, NaCl
Calcium in 50g of calcium chloride, CaCl2
Magnesium in 100g of magnesium chloride, MgCl2

20. Life Cycle Assessments (LCAs)
20/04/2017
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?

21. Solution containing copper and chloride ions
Electrolysis
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++++
----
Positive electrode
Negative electrode
Cu2+
Cl-
Solution containing copper and chloride ions
Cu2+
Cl-
Cu2+
Cl-

22. Electrolysis
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Electrolysis 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!!!

23. Electrolysis equations
20/04/2017
We need to be able to write “half equations” to show what happens during electrolysis (e.g. for copper chloride):
At the negative electrode the positive ions GAIN electrons to become neutral copper ATOMS. The half equation is:
Cu e Cu 2
At the positive electrode the negative ions LOSE electrons to become neutral chlorine MOLECULES. The half equation is:
Cl e Cl2 2 2

24. Words – melting point, replaced, negative, bauxite, reactive, move
Extracting Aluminium
20/04/2017
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

25. Electrolysis of Aluminium Oxide
20/04/2017
Overall:
Aluminium oxide aluminium + oxygen
2Al2O3(l) Al(l) O2(g)
At the cathode:
At the anode:
Al3+(l) + 3e Al(l)
2O2-(l) - 4e O2(g)

26. Using Iron
20/04/2017
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.

27. Copper, Aluminium and Titanium
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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

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

29. Properties of metals
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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

30. Words – slip, electrons, melting, electricity, strong, ions
A closer look at metals
20/04/2017 +
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 + + + + + + + + + + +