C7 Reactivity

C7 Reactivity

Reduction and Oxidation

Oxidation Is Loss Reduction Is Gain

Reduction is : 1. Loss of oxygen (covalent bonds)

2. gain of electron (ionic)

The reduced compound is an oxidizing agent

Oxidation is : 1. Gain of oxygen (covalent bonds)

2. loss of electron (ionic)

The oxidized compound is a reducing agent

 

Reactivity with Oxygen

Oxidation reactions – Cu + O2 → CuO, glow + slice flame

Mg + O2 → MgO white flames

Combustion reactions – CnHn + O2 → water + CO2 flames and stuff

 

Reactivity series

K←Na←Li←Ca←Mg←Al←C←Zn←Fe←H←Cu←Ag←Au

Possibly nicer livers can magnetize almonds cars,

zero-fee hype cures silvery golds

 

Metal extraction

Ore is economically viable containing metal rocks. Rock contains metals but not that worthwhile.

1. If metal ore is less reactive than carbon…
   1. Reduce metal with carbon to extract.
2. If it is more reactive
   1. Use electrolysis to split ions.

Alloys are formed to merge several desirable qualities of the different metals. Since lattice structure is disrupted by impurities, boiling point decreases as bonds are weaker.

 

Electrolysis

Electricity pass through electrodes to extract metals. Cations are at cathode and anions go to anode. Electrolyte is the solution that conducts electricity.

Half equations:

Cations: Pb2+ + 2e– → Pb

AnionsL 2Cl– → Cl2 + 2e–

1. 1. Separating seawater: Aqueous sodium hydroxide, hydrogen at cathode and chlorine at anode, sodium hydroxide is leftover – liquid NaCl won’t have leftovers.
   2. Industrial uses include: chlorine for swimming pool disinfectant and cleaning products, sodium hydroxide for stock chemical (strong alkali) and soap, hydrogen for haber process and margarine.
   3. Separating aluminum oxide: Al2O3, aluminum ore called bauxite, can be used to extract aluminum which is lightweight resistant to corrosion and used in airplane and bikes. Cryolite added to lower melting point. Al sinks to the bottom, produces aluminum and oxygen.

 

• molten lead(II) bromide, lead at cathode and bromine at anode

• aqueous copper chloride – copper at cathode and chlorine at anode

• dilute sulfuric acid – hydrogen at cathode and oxygen at anode

• Generally: metals or hydrogen form at cathode and non-metals form at anode.

 

Electrodes can be active or inert. Inert electrodes like graphite are not involved in the reaction and actibe electrodes are involved in reaction. Such as copper plating. Anode will become thinner and cathode thicker, and hence it is used to plate objects and remove impurity, electrolyte usually contains the same ion as anode.

Hoffman Voltameter is used to collect gas from electrolysis, such as water.

 

Blast furnace

Used to extract iron.

1. Add materials: hematite, coke(impure carbon as reducing agent), limestone to remove impurities
2. Make the reducing agent stronger: Carbon must become carbon monoxide
   1. C + O2 → CO2
   2. CO2 + C → CO
3. Reduce the iron:
   1. Fe2O3 + 3CO → 2Fe + 3CO2,
4. Remove impurities
   1. CaCO3 → CaO + CO2
   2. CaO + SiO2 (sand) → CaSiO3 (slag, used in road building, neutralizsation reaction)
5. 1000C and 2000C degrees

 

Rust

Rust is the specific corrosion of iron by oxidation to iron (3) oxide. Salt speeds up rusting and both oxygen and water are needed to produce hydrated iron oxide in a redox reaction.

Surface protection means covering iron to stop water/oxygen from entering, using oil, paint and wax. Specifically, galvanizing means coating with zinc.

Sacrificial protection puts a metal attachment of metals more reactive than iron like zinc and magnesium so water and air reacts with it first.

P6 Electromagnetism and Energy Resources

P6 Electromagnetism and Energy Resources

 

Magnetic effect of current

• Magnetic pattern around straight current carrying wire
• Magnetic pattern around solenoid
• Use right hand rule to figure out (thumb’s up)
• Relay switches use the effect to reduce danger as a circuit can turn on another circuit.
• Increasing current magnitude results in stronger magnetic field proportionally.
• Reversing current direction results in:
  • D.C. North south pole reversed
  • A.C. constantly changing direction of flow.

Motor effect

• A current-carrying wire experiences a force in the presense of a magnetic field.
• A force will be creted and the wire’s movement will confirm the effect.
• Practical applications can be loudspeakers and electric motors.
• Left hand rule for movement, field, current
• Reversing current reverses direction of force.
• Reversing field direction reverses direction of force.
• Force size is the greatest when wire is perpendicular to field.
• No force if wire is parallel to field.

 

D.C. motor

• • Converts electrical energy to kinetic energy.
  • There is no current in coil when it’s 90 degree vertical, but it keeps moving due to kinetic energy.
  • A current carrying coil experiences a turning effect in a magnetic field.
  • The right side always causes a downward force.

 

• Commutators also rotate as it reverses current every 180 degree so the movement continues.

• Brushes are made of carbon and they conduct the current to complete the circuit.

• Increase # of turns in coil results in faster movement as there is a stronger magnetic field.

 

• Increase current results in faster movement as there is a stronger interaction with the field.

 

Inducing electromotive force

• Set up magnets and a wire with ammeter, move wire up and down and there will be readings on the ammeter.
• EMF is induced when there is charge in the magnetic field and it’s proportional to charge per second.
• Wire cuts field lines results in small voltage to be induced.
• Moving the wire faster, using stronger magnet, having more coils all increase the EMF.

 

A.C. Generator

• Transforms kinetic energy to electrical energy.
• Slip rings conduct electricity, and the induced current reverses every half turn.

 

Transformers

• • A basic soft iron cored transformer is used to transform voltages.

 

• Step-up transformers increase voltage from primary to secondary.

• Step-down transformers decrease.

 

• Calculation of voltage transformed: Vp/Vs = Np/Ns where N is number of coils.
• Power in equals power out for 100 efficiency: V1I1 = V2I2
• Calculating efficiency: energy input/useful energy output * 100%
• Efficiency is the ratio of the useful work performed by a machine or in a process to the total energy expended or heat taken in
• Uses A.C. due to constant change of voltage.
• A.C. current changes, and magnetic field changes to induce a voltage in secondary coil.
• Electricity is transferred through long distances over wires. When current flows, wire is warm and this wastes energy. (P=I2R)
• When voltage is high, current is kept small, and there is less heat loss.
• Transformers bridge the gaps between electrical cables and home use, reduces danger.

 

Energy

• • Sun is the source of energy for all our energy resources except geothermal and nuclear.
  • Energy is released by nuclear fusion in the sun.

 

• Renewable energy is naturally replenished on a human timescale.

• sunlight, wind, rain, tides, waves, and geothermal heat,

 

• • Non-renewable energy comes from sources that will run out or will not be replenished in our lifetimes.
    • Nuclear, coal, fossil fuels

 

• Electricity can be obtained from…

 

 

Source	Advantages	Disadvantage
Chemical in fuel	readily available relatively cheap Not reliant upon the weather.	highly polluting global warming acid rain. Oil spillages
Water (Waves, tides, dams)	No pollution Costs of running are low Efficient for small islands Good energy storage	High initial cost Unreliable energy output Infrastructure hard to put in
Geothermal	Freely available No environmental impact	Drilling down has high cost
Nuclear fission	Non-renewable Radioactive waste disposal difficult	Creates a lot of energy at once
Heat and light from sun	Reliable source when sun is out Small running costs No pollution	Initial cost very expensive Not very efficient Dependant on sun.

P7 Atomic and Nuclear Physics

Nucleus

Nucleus is composed of protons and neutrons.

Isotopes are multiple forms of the same element containing different numbers of neutrons.

Isotopes can be used to treat cancer, in radiation, etc.

 

Radioactivity

 

• Background radiation is ionizing radiation at an environment that doesn’t come from deliberately introduced radiation materials. Could be naturally occuring radioactive elements, cosmic radiation and fallout. It is always there and measured.

• Radioactive emissions occur randomly over space and time as particles decay.

• Radioactive decay is the process by which an unstable atomic nucleus loses energy and emits radiation to become another element.

• Half-life is the the time taken for the radioactivity of a specified isotope to fall to half its original value. Equation: n*(½)^t

• Detecting radioactivity: Geiger-muller tube and ratemeter counts number of pulses per second. Scaler keeps running total of number of counts

 

 

Alpha, beta, gamma rays

 

	α particles	β particles	Y rays
Charge	+2	-1	Not charged
Mass	4 amu	negligible	none
Nature	Helium nucleus (2 protons, 2 neutrons)	Electron (e-1)	Electromagnetic radiation, short wavelength
Stopping it	A sheet of paper, or 10 cm of air.	Few mm of aluminum	Thick lead or concrete
Range in air	Within centimeters	A meter	High
Ionizing ability	Very strong	Weaker than a, but still ionizing	Weak

 

• Alpha decay equation: AZX → A-4Z-2Y + 42He
• Beta decay equation: AZX → AZ+1Y + 0-1e(β)
• Gamma decay is simply loss of energy.   

 

Electric and Magnetic Field effects

Positive attracts negative beta particles and negative attracts positive alpha particles, while gamma rays pass uneffected. The same goes on in magnetic fields.

 

Beta deflects more than alpha because it has a larger mass.

 

Safety

• • Hazards of ionizing radiation:
    • Damagement of living cells causing cancer
    • Affecting DNA and causing mutation

 

• Minimizing hazards:

 

• • Handling: Using tongs used to pick up sources
  • Protective clothing worn by those who work with radioactivity
  • Storage: Sources are kept in lead-lined containers
  • Usage: Sources are never pointed at people
  • Exposure times are limited

 

P7 Equations

• Alpha decay equation: AZX → A-4Z-2Y + 42He
• Beta decay equation: AZX → AZ+1Y + 0-1e(β)
• Half life equation: n*(½)^t

Language Exam Techniques

Supposedly, these are the skills you need to function in an English speaking country, and here are the skills you need to prove that you have these skills.

Paper 2 – Reading (Three Questions)

NOTE ON READING

The most important overall thing that you should pay attention to across this paper is to write what you are thinking down. Write down everything that crosses your mind. When you are secretly commenting on how things lack common sense in the paper, or when you think a character is stupid, or when you believe it to be bad writing, write it down. I have been victim to implicitly thinking implicitly on this paper without showing it for too long, and this is exactly what they are looking for.

NOTE ON WRITING

This paper also grades you for the quality of your writing. For this, read more libros. If you have no time, read Pale Fire by Nabokov and copy his style in which you use advanced words and syntax to intimidate the examiner. Either that, or you can quote authors exhaustively, or pay tribute. Maybe that’ll help.

Question 1

1. Read the question before the excerpt. Extract CARPF – Content, Audience, Register, Purpose, Form from the question.
2. Read the excerpt with the question in mind.
3. On either the first or second reading, highlight the points you want to make from the passage.
4. Check that they are separate points. (However, GCSE has this weird logic about separate points, so good luck.)
5. Upon writing, infuse yourself into a mood in which you are the greatest, most expressive and fluent prosier of the century. Use complex words and sentence structures to integrate ideas but also make ideas very, very, very clear.
6. One paragraph per bullet point, five points per bullet point. Include introduction and sign-offs as necessary.

Question 2

This question is especially painful because they are asking you to analyze bad writing. However, there are tricks to it.

1. Pick the most out-of-place words. They are imagery. If an air-conditioner is being described and the word ‘bird song’ pops up, analyze that.
2. Write it as you would a regular unseen.
3. Make sure to include an ‘overall’ thesis at the top of each paragraph.
4. Never include more than four words.

Question 3

1. Again, read the question before the excerpt.
2. As you read and highlight fifteen points, make sure nothing repeats off of each other.
3. Organize. Organize points into umbrella ideas and use them to write your summary.
4. Summarize away, using your own words and concise sentencing.

Paper 3 – Writing (Directed, Creative)

Question 1 Directed Writing

Do this question as you would do question 1 of Paper 2. However, this is supposedly easier to do because you can include your own points. You are mainly graded on making explicit and implicit points.

1. Read the question before the excerpt. Extract CARPF – Content, Audience, Register, Purpose, Form from the question.
2. Read the excerpt with the question in mind.
3. On either the first or second reading, highlight the points you want to make from the passage.
4. Think about the points you can derive from the passage.
5. Use bullet points. There should be an equal spread between bullet points.

You should use 10 minutes to plan and 50 minutes for actual writing.

Question 2 Creative Writing

You could also do argumentative or something else, but my school only taught descriptive writing. It is the easiest out of everything and it’s the easiest to make interesting for the eyesore examiner.

Choose a question quickly and copy your favorite author. Copy copy copy away, the words they use, the sentence structures they like, the paragraphing, the style. Show your individuality and flair that you shamelessly stole from a group of literary giants. Show it.

If English is not your native language, translate proverbs, idioms and sayings in your native language to English as they’ll likely provide good and unique imagery that will certainly impress a (likely British) examiner.

Make sure to describe and not narrate, show not tell, use the five senses, extend your imagery, use motifs and metaphors if possible, but mostly, copy your favourite author.

It’s also important to make your writing cogent and cohesive. This means to have a clear structure, such as zooming in and panning out. Make sure that the progression is logical.