Science

Staff

GCSE

Revision

Lower School

Websites

A Level

Staff:

'A' and AS Levels (Physics, Chemistry and Biology)

Course requirements:

These are AQA courses which require the following requirements at G.C.S.E. Either a pass at Grade C and above in the Separate Sciences or Grades A* -B in the Double Award Science together with a pass in Mathematics (Grade B preferred)

Time:

6 periods (5 hours) a week (2 periods practical) in each subject for two years for 'A' Level: for 1 year at AS level.

Practicals:

2 periods a week per subject available

Physics - by exam (possibly by internal assessment)

Chemistry - by internal assessment

Biology - by internal assessment

Throughout the 2 years pupils are encouraged to forge academic and industrial links. In recent years pupils have gained engineering experience on pre-university courses at Loughborough University, insights into the world of medicine on the Medi Link courses and analytical research methods at Shell Thornton. Pupils are also encouraged to attend revision symposia which have the benefit of being run by Chief Examiners of the relevent exam boards.

G.C.S.E. Separate Sciences (Biology, Chemistry & Physics)

These are taught as separate subjects leading to 3 G.C.S.E. grades where pupils who are likely to study the Sciences at 'A' Level have been strongly advised to follow this route. There are 3 periods a week (2hrs.30 mins.) in each subject with the course lasting 2 years. The coursework component accounts for 20% of the final mark with practical assessment done in each subject. Pupils following this route would be in one group who on average number about 18. Results over the last 5 years have been excellent with with a usual pass rate (Grades A*-C) of 100%.

G.C.S.E. Double Award Science

Pupils follow a co-ordinated route and are rewarded with a double G.C.S.E. grade. All the three Sciences are taught with separate exams at the end of the 2 years counting towards a final grade. Coursework demands are less than the Separate Science course but still account for 20% of the final mark. Pupils following this route would be in two ability sets who on average number about 35 for the two sets.

Year 9 (Third Year) Science

Each science is taught as separate subjects (2 periods a week for each subject): Biology, Chemistry and Physics. Here pupils get an excellent grounding for G.C.S.E. both in fundamental principles and in coursework. At the moment the subjects follow in-house schemes of work with the emphasis on learning through experiments leading pupils to an understanding of the world they live in. Pupils are taught in 3 sets according to their ability.

Year 8 (Second Year) Science

Pupils are taught in forms and have 3 periods of general Science a week. Lessons are taught according to the highly regarded Spotlight Science scheme of work and because the topics are arranged in a spiral format, pupils have the opportunity to revisit topics previously covered. This enables pupils to reinforce work covered before taking a particular subject to a higher level. Much effort is made to involve the home, family and the environment around the pupils to make Science more relevant as well as fun.

Year 7 (First Year) Science

Pupils are taught in forms and have 3 periods of general Science a week. Lessons are taught according to the highly regarded Spotlight Science scheme of work and build upon the work covered at Keystage 2. Strong links with the Junior Department ensure a seamless transition into Senior School Science. Much effort is made to involve the home, family and the environment around the pupils to make Science more relevant as well as fun.

GCSE Revision (compiled by the 4th Year)

Themes include:

• Alkali Metals

• Atomic Structure

• Atmosphere

• Enzymes

• Group 7 Elements

• History of the Periodic Table

• Limestone

• Metals and Non-Metals

• Neutralisation

• Rates of Reaction

• Reactivity Series

• Rocks

• Salt Formation

Group 1 - the Alkali metals
There are six metals in this group;

Lithium (Li)

Sodium (Na)

Potassium (K)

Rubidium (Rb)

Caesium (Cs)

Francium (Fr)

v The reactivity increases down the group but the melting and boiling points decrease.

v The alkali metals react with non metals to form ionic compounds, the metal atom loses one electron to form a 1+ ion ( a charged particle. )

Eg; Sodium + Chlorine Sodium chloride.

2Na + Cl2 Ü 2NaCl

v The alkali metals react with water to releasing hydrogen, the hydroxides produced dissolve in water to form alkaline solutions this is why they are called alkali metals.

Eg; Potassium + Water Potassium hydroxide + Hydrogen.

2K + H2O Ü 2KOH + H2

As we go down the group the reactivity increases and so they react more vigorously with water, they may float, melt, or even ignite the hydrogen gas.

Questions
Explain why these elements form 1+ ions when they react with non-metals ?

What is the name and symbol for the colourless gas produced when they react with water ?

If universal indicator was in the water what colour would it turn when sodium was added ?

Does potassium or lithium react more violently ?

Atomic Structure

All substances are made up of atoms. If a substance contains only one sort of atom is called an ELEMENT.

An atom consists of:

A small nucleus

Made up of protons and electrons

Surrounded by electrons arranged in shell

furthermore:

The proton is positively charged

The electron is negatively charged

The neutron is neutral (no charge)

Enzymes

An enzyme is a large protein molecule.
Enzymes contain living cells which use chemical reactions to produce new materials.

ie. Fermentation :

Yeast + Glucose ® ethanol + carbon dioxide

This reaction is used to make alcoholic drinks and dairy products

Enzymes help to make yoghurt and cheese from milk.

The enzymes used to make yoghurt come from BACTERIA MILK ! ! !

Bacteria

Lactose ® Lactic acid

(sugar in milk) Enzymes

Enzymes are DENATURED (damaged) by temperatures above 45°C

The optimum temperature for enzymes to work in is 37°C

Limestone

How they form
Limestone is a sedimentary rock that is made from layers of sediments.

The weight presses and cements the particles together as the water gets squeezed out with the salt crystals.

Therefore younger rocks are usually on top.

What they are
Limestone is made from dead shelled creatures with some insoluble calcium salts like calcium carbonate.

They are quite fragile but not as much as the other sedimentary rocks like sandstone.

They often contain fossils that can be used to date the rocks.

What they are used for
Limestone is mainly calcium carbonate and is cheap so it is used in many ways e.g neutralising agent

Acidity in soils can make crops fail to grow properly.

Powdered limestone can be used to correct this although it works slowly.

And it can be washed out by acid rain.

Metal and non-metals

More than three-quarters are metals, leaving one quarter, which are non-metals.

Metals
All are solids at room temperature (Exception: Mercury, which is a liquid at room temp.)

They have high melting points.

They are shiny-especially when freshly cut.

Can be hammered and bent into shape. They are usually strong and tough.

They are good conductors of heat and electricity.

They can form alloys (mixture of metals).

Non-metals
Half of them are gases, though Bromine is a liquid at room temperature.

They have low melting points and boiling points.

They are mostly dull.

They are usually brittle and crumble when they are in a solid form.

They are poor conductors of heat and electricity when they are in a solid or liquid form.

They do not form alloys.

Three good examples are:

COPPER,Cu

Is mixed with tin to form BRONZE, and ZINC to form BRASS.

Is used for pipes, which are used for plumbing.

Is used for electrical wiring.

Is a good electrical conductor.

Can form alloys.

Can be hammered and bent into shape

IRON,Fe

Is used for car engine blocks.

Is mixed with CARBON and small amounts of other metals to form STEEL.

Is used for cast iron saucepans.

Is a good heat conductor.

Can form alloys.

It is strong.

ALUMINIUM,Al

It is used for aircraft bodywork due to its low density.

It is strong and can be bent.

It becomes covered with a layer of aluminium oxide, which means it does not have to be painted,so it can be used for window frames.

Neutralisation

Neutralisation occurs when the right amounts of acid and alkali react together to form a salt and water.

General equation:

ACID + ALKALI à SALT + WATER

For example:

Hydrochloric Acid + Potassium Hydroxide à Potassium Chloride + Water

HCl + KOH à KCl + H2O

An acid (e.g. hydrochloric acid) has a pH of <7.

An alkali (e.g. potassium hydroxide) has a pH of >7.

A neutral substance (e.g. water) has a pH of 7.

We can measure the pH of substances using universal indicator.

Added to a substance, it displays the pH as shown below:

Red = Strong Acid
Orange = Strong-weak Acid
Yellow = Weak Acid
Green = Neutral
Blue = Weak Alkali
Indigo = Weak-strong Alkali
Purple = Strong Alkali

Rates of reaction

Reaction rates are affected by numerous circumstances and can be speeded up and slowed down accordingly.

Temperature
Temperature of the reactants has an obvious affect on the rate

If the temperature goes up so does the rate of reaction

If the temperature goes down so does the rate of reaction

Reasoning for this is that at a higher temperature there is more energy available so the particles vibrate faster and there are therefore more collisions. Therefore there is more chance of a successful collision. Also heat is needed to overcome activation energy.

Catalysts
A catalyst is a substance that speeds up the rate of a reaction without being used up in it itself.

They do this by lowering the activation energy for a reaction that will increase the likely hood of a particle having enough energy to react so therefore increasing the rate of reaction.

This have large uses in industry especially cars where platinum and rhodium are used to aid the reaction of dangerous gasses of carbon monoxide and nitrogen monoxide into the harmless gasses of carbon dioxide and nitrogen in a catalytic converter. There are also enzymes that are the same as catalyst's but are living things. Enzymes are used to make alcoholic beverages by speeding up the break down of glucose into ethanol and carbon dioxide. They are also used by speeding up the break down of food quickly into smaller parts

Rocks

There are three types of rocks they are:

1. Metamorphic

Metamorphic rocks are very crystalline and banded

examples are slate and marble

2. Sedimentary

Sedimentary rocks are very grainy and crumbly and may contain fossils

examples are sandstone and limestone

3. Igneous

Igneous rocks are crystalline and very hard

examples are basalt and granite

How they’re formed

Igneous rocks

These form when molten rock cools down to form crystals.

Sedimentary rocks

These form as layers of sediment built up. Under pressure water is forced out and minerals help the sediment stick together to form rocks.

Metamorphic rocks

These are rocks that have been changed by heat and/or pressure

WHEN ROCK COOLS QUICKLY WE GET SMALL CRYSTALS

WHEN ROCK COOLS SLOWLY WE GET LARGE CRYSTALS

Salt Formation

These are the following methods of preparation:

1. an acid + metal = metal salt + hydrogen

eg- hydrochloric acid + iron = iron chloride + hydrogen

2. an acid + a carbonate = metal salt + water + carbon dioxide

eg- sulphuric acid + calcium carbonate = calcium sulphate + water + carbon dioxide

3. an acid + insoluble base = a salt + water

eg- nitric acid + magnesium oxide = magnesium nitrate + water

4. an acid + an alkali* = salt + water

eg- hydrochloric acid + sodium hydroxide = sodium chloride + water

*an alkali is a soluble base

5. Two soluble solutions of salts give an insoluble salt (filter off)

eg- sodium iodide (aq) + lead nitrate (aq) = lead iodide (solid) + sodium nitrate (aq)

6. Direct combination of elements

eg- aluminum + iodine = aluminum iodide

The Atmosphere

The history of the atmosphere
The volcanoes 4 billion years ago released mainly Carbon Dioxide, a small amount of methane and ammonia. There was also water vapour, which condensed to form the oceans.

Over 3 billion years ago the first single-celled plants evolved, this meant the Carbon Dioxide levels were reduced and the Oxygen levels increased as plants give out Oxygen. Carbon Dioxide became locked up in sedimentary rocks and fossil fuels. Some of the Oxygen combined with ammonia to produce Nitrogen. More Nitrogen was produced by the action of denitrifying bacteria on Nitrates from decaying plant material.

Then over 1 billion years ago the first multi-celled plant evolved the Oxygen and Nitrogen levels increased to almost present levels:

21% Oxygen and 78% Nitrogen

Free Oxygen increased and the Ozone layer formed. The Ozone layer filters out harmful U.V. light from the sun; this allowed the evolution of the new land living organisms.

Do you know what percent of carbon dioxide levels are in the atmosphere today?

Acid rain
Sulphur dioxide and nitrogen oxides are produced when fuels are burned in furnaces and engines. These gases then react with water vapour in the atmosphere to produce acids. These acids then fall as acid rain.

The gases themselves can harm plants and animals. Acid rain causes lakes and rivers to become so acidic that plants and animals can not survive. The gases and acid rain causes erosion damage to stone.

The elements of group 7 (The Halogens)

The 5 elements in this group are non-metals

The Halogens are gases, which have coloured vapours are molecules, made up of pairs of atoms

eg: F2, Cl2, I2

They react with metals to form ionic salts

eg: Calcium + Chlorine à Calcium Chloride

Ca (s) + Cl2 (g) à CaCl2 (s)

A halogen atom gains 1 electron to from a 1- (Halide) ion

The halogen atom has 7 electrons in the outer shell, but the Halide ion has 8 electrons in the outer shell

They become less reactive as you go down the group

They can all form compounds with other non-metallic elements

eg: Chlorine + Hydrogen à Hydrogen Chloride

Cl2 (g) + H2 (g) à 2HCl (aq)

They can all displace less reactive halogens from aqueous solutions of their salts:

Chlorine will displace both Bromine and Iodine (as these are both lower than Chlorine in group 7).

Bromine will displace Iodine but not Chlorine, as Chlorine is higher than Bromine in group 7

eg: Potassium Iodide + Chlorine à Potassium Chloride + Iodine

2KI(aq) + Cl2 (g) à 2KCl (aq) + I2 (aq)

They have higher melting points as you go down the group

A common use of the halogens is in light sensitive paper (photographic film) eg:

Silver Nitrate + Sodium Chloride à Silver Chloride + Sodium Nitrate

AgNO3 (aq) + NaCl à AgCl (s) + NaNO3 (aq)

Silver Halide is used as a coating for photographic paper. For example, Silver Chloride is reduced to silver by light

The History of the Periodic Table

Early Attempts to classify the elements

1820s - Johann Dobereiner
In the 1820s Johann Dobereiner a German chemist tried to make sense of the elements known at the time. He noticed if you took three elements with similar properties there was an interesting pattern. The atomic mass of the middle element was nearly halfway between the masses of the other two. However not many elements fell into this pattern. Most people thought 'triads' were just coincidence.

1864 - John Newlands
John Newlands was an English chemist. He thought if you put the elements in order of atomic mass, then every 8th element was similar. He called this the law of octaves. This only worked for the first 15 known elements. After that his theory broke down. Other scientists suggested putting the elements in alphabetical order.

1869 - Dmitri Mendeleev
Dmitri Mendeleev a Russian chemist finally solved the problem. He put the elements in order of atomic mass like Newland did. Where Mendeleev pattern broke down he would leave gaps for elements not yet discovered. The table he made had similar elements underneath one another. He even changed the order to make sure elements lined up correctly.

This is how the periodic table was formed.

Discovery of Electronic configuration supports the findings of Mendeleev.

The Reactivity Series

The reactivity series is a list of elements, which are put into that order by measuring how efficiently/violently the element reacts with oxygen, water and dilute acid. Group 1 metals (i.e. sodium and potassium) are very reactive, because the formation of the atoms is in the way that they have only one electron in the outer shell causing them to willingly or sometimes even forcibly react, so they appear at the start of the reactivity series. Elements such as Gold or Platinum however are held together in a very tight bond so that they will not react at all. The reactivity series appears as such (least to most reactive):

Platinum à Gold à Silver à Copper à Hydrogen à Lead à Tin à Iron à Zinc à Carbon à Aluminium à Magnesium à Calcium à Sodium à potassium

It goes from Potassium, which will burn fiercely on water, and explode in acid, to Platinum, which will merely sink in acid.

The reactions which these elements are tested on are:

Reaction with air

Metal + Oxygen à Metal oxides

Reaction with Water

Metal + Water à Metal hydroxide (or oxide) + Hydrogen

Reaction with acids

Metal + Acid à Metal salt + Hydrogen

(Hydrogen is tested for by filling and sealing a test tube with the suspect gas, and placing a lighted splint at the opening, unseal it and if there is a 'pop' or a 'squeak' then this gas is Hydrogen)

AS Revision

Themes include:

Catalytic Converters

Extraction of Aluminium

Internal Combustion Engines

Iron and Steel Extraction and Manufacture

Extraction of Titanium

Catalytic Converters
Devises used to remove pollutants from the exhaust gasses of a combustion engine such as:

Carbon monoxide

Nitrogen Monoxide

Un-burnt hydrocarbons

They contain a honeycomb structure coated in a metal such as platinum, palladium and rhodium. These metals act as a catalyst and remove 90% of pollutants using the following reactions.

2CO + 2NO 2CO2 + N2

C8H18 + 25NO 8CO2 + 12 N2 + 9H2O

Exhaust gases in

CO, NO, C8H18

Catalytic Converter

Gases out

CO2, N2, H2O

Extraction of aluminium
Dissolved in molten cryolite (Na3AlF6), aluminium oxide (bauxite, Al2O3), usually melting at over 2000oC, is dissolved, and the melting point is reduced to 970oC. In a large cell, two carbon electrodes (positive and negative) ensure the following reactions:

Al3+ + 3e- Al (at the negative electrode [cathode])

2O2- O2 + 4e- (at the positive electrode [anode])

At such high temperatures, some of the O2 molecules react with the carbon anode to form carbon monoxide and carbon dioxide:

2C + O2 2CO

C + O2 CO2

In the reaction, large amounts of electricity (this is needed to melt the cryolite and decompose the bauxite) are used. The reaction is a continuous one, but of course more bauxite must be added, and the anode must be replaced intermittently as it is converted to carbon dioxide and monoxide. There is also a possible environmental problem with the removal of cryolite with fluoride pollution

Internal combustion engines

C8H18 + 81/2 O2 8CO + 9H2O

Carbon monoxide is formed by the incomplete combustion of petrol in a car engine.

Oxides of nitrogen are formed when the air/petrol mixture is sparked and explodes.

A temperature of 2500oC can be reached when burning petrol vapour. This provides sufficient activation energy for nitrogen to react with oxygen to form nitrogen monoxide.

N2 + O2 2NO

On cooling NO reacts with more oxygen to form NO2, which with water form Nitric acid, which can lead to acid rain.

2NO + O2 2NO2

4NO2 + 2H2O + O2 4HNO3

Nitrogen dioxide also reacts with oxygen or hydrocarbons in the presence of sunlight to form an irritating photochemical smog.

Iron and steel manufacture
Iron is a very versatile metal that can be used in many ways in industry and construction. The process used to extract the iron from its ore is that of reduction; as iron is normally found combined with oxygen. The process occurs in a blast furnace at temperatures of over 2000 0C, including oxygen, coke, and limestone. This is a continuous process in which iron (III) oxide, coke and limestone are fed into the top of the blast furnace and hot air is blown in through the bottom.

Initially, coke reacts with the hot air in a strongly exothermic reaction:

C(s) + 02 (g) 2CO(g)

This reaction produces the heat needed for the reduction of the iron (111) oxide. The carbon dioxide formed reacts at high temperature with unreacted coke to form carbon monoxide:

CO2 (g) + C (s) 2CO(g)

The carbon monoxide reduces most of the iron (III) oxide at around 1200oC.

Extraction of metals: Titanium
Properties of Titanium

low density

high strength

high resistance to corrosion

Titanium Ore: Rutile- Titanium (IV) Oxide (TiO2)

Method of Extraction: Extracted form its chloride by reduction with an active metal

Reaction 1

TiO2 + 2C + 2Cl2 TiCl4 + 2CO

Conditions

900oC

Titanium (IV) Chloride is a colourless liquid. It is purified from other chlorides by fractional distillation in an argon atmosphere.

In the UK it is then reduced by sodium in the following exothermic reaction:

Reaction 2

TiCl4 + 4Na Ti + 4NaCl

Conditions

Initially 550oC but rising to 1000oC

Inert argon atmosphere

The Sodium Chloride by-product is washed out leaving titanium as a granular powder.

This is an expensive process because:

It is a batch process

Chlorine and sodium have to be produced first

High temperatures are involved in both stages of production

TiCl4 reacts violently even with water so care must be taken when handling it

An argon atmosphere has to be maintained to prevent oxidation

Titanium is a metal with very desirable properties and a high abundance but its use is limited by the high cost of production.

Useful and Interesting Websites

Bitesize Revision
BBC Education Bitesize revision guides for Key Stage 2, 3 and GCSE Exams in a wide range of subjects.

BBC
Designed to help ease the move from GCSE to AS level. Currently there is help for English, Maths and Biology, but the Study Skills section will be useful for all subjects.

International Space Station
Spotting the International Space Station. The International Space Station has now been orbiting the Earth over 15 times a day for more than three years, yet how many of us have actually seen it? Spotting the ISS is not as difficult as it might seem – if you know where to look. This site gives all the information needed.

Chemistry Society
Lots of useful chemistry links.

Missions to Mars
Find out about the successful missions that actually made it to Mars.

A Level Revision and General Chemistry
This site gives many links to general chemistry sites including A level revision.

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