important points - physics. chemistry and mathematics

Quazi Nafiul Islam – www.studenttech.co.cc

Important Points

Chemistry

Unit 1 • Salt preparation:

o For example, the reaction between Copper(II)Carbonate(Cu2SO4) and Sulphuric acid • Observations of alkali metals:

o Lithium Gas given off Fizzing/effervescence Floats on top of the water

o Sodium Gas given off Melts into a ball Floats on water Fizzing/effervescence

o Potassium Gas given off Very fast reaction, in comparison to the other 2 Purple/lilac flame given off Morphs into a ball Floats on top of the water

• When carrying out an enthalpy reaction which involved an exothermic reaction that releases heat, we take a series of temperatures. This is because:

o Any fluctuations in temperature smoothed out o Able to allow for cooling effect

• Poly(propene) does not have a sharp boiling point because poly could mean different chain lengths.

Unit 2 • Indicators

o Litmus Red in Acid Green in neutral Blue in Alkali Range of pH 5 to 8 Link

o Phenolphthalein Pink in Alkali Colourless in acid or near neutral Range of pH 8.3 to 10.0 Link

http://en.wikipedia.org/wiki/Litmus_test_%28chemistry%29

http://en.wikipedia.org/wiki/Phenolphthalein


o Methyl Orange Alkali or neutral is Yellow Acid begins from Orange and works its way up to red Range of pH 3.1-4.4 Link

o Universal Indicator It is a combination of many different reagents, which include Methyl Orange

and Phenolphthalein.

pH Description Colour 0-3 Strong acid Red 3-6 Acid Orange/Yellow 7 Neutral Green

8-11 Base Blue 11-14 Strong Base Purple

o From what we can see Litmus is an indicator for determining whether it is an acid or base

o Phenolphthalein can be used to judge the strength of an alkali o Methyl orange can be used to see the strength of an acid

• Homolytic and Heterolytic bond fission o Homolytic is when a bond is cleaved, and each atom gets an electron o Heterolytic is when a bond is cleaved, and one atom gets on electron and the other

does not get any. • Reactions of Halogenoalkanes

o Substitution Happens when KOH/NaOH is dissolved in H2O Also, dilute KOH and NaOH

o Elimination Happens when KOH/NaOH is dissolved in Alcohol Also concentrated KOH and NaOH

o Reaction with Ammonia This is a special case, because this happens in a sealed tube, as if it were to

happen under reflux, then NH3 would leave the condenser as it simply does not condense.

• Frequently asked bond angles o FBF

120o o NHN

107o o HOH

104.5o • Molecules with H-Bonding

o Molecules with N-H bonds, such as NH3 o Molecules with O-H bonds, such as H2O and C2H5OH

Both happen under reflux.

http://en.wikipedia.org/wiki/Methyl_Orange


83BBut Hydrogen bonding in H2O is stronger than in Ethanol, because the hydrogen bonding is limited by the fact that there is only one hydrogen in each ethanol molecule with sufficient δ+ charge, whereas, in water, there are 2 hydrogen with δ+ charge, thus allowing more bonds to be formed.

o 84BMolecules with H-F, such as HF

190BThe Maxwell-Boltzmann distribution diagram

• 85BIodine and Sodium Thio-sulphate titrations o 86BThe indicator used to find the end point of the titration is Starch.

• 87BBalancing Ionic Equations and Overall Equations o 88BWhen doing this, only certain particles can be added

89BElectrons (e-)

90BWater Molecules (H2O)

91BProtons, or Hydrogen ions (H+)

92BWhen balancing alkaline reactions, OH- ions can be added o 93BYou first have to balance the electrons, by multiplying one side by two different

integers o 94BThen cancel the H+ ions and H2O on both sides o 95BThen the equations should be balanced

• 96BThe boiling point of substances o 97BIt all depends on the intermolecular forces o 98BIn a question, when the only variable is the chain-length, then the longest un-

branched chain will have the highest boiling point. o 99BIf there is a functional group, such as –OH, then this will be the choice, as normally in

organic molecules without special functional groups, there are only London forces. But in alcohols, there are also dipole forces.

500oC

Fewer molecules will have the activation energy, because there is less kinetic energy due to a lower temperature.

At lower oC, the curve will shift to the right.


o 100BA typical example:

191BThe correct answer is D. Because it has –OH and also, the alcohol is primary. In secondary alcohols, the –OH is cluttered by hydrogen atoms, thus the intermolecular bonding is less effect than in D.

8BUnit 3 • 101BEnthalpy Change reactions (EDEXCEL_JUN_09_3B_2)

o 102BIf, in a reaction, a metal is involved, often the mass of the metal is not taken into consideration when measuring the enthalpy change, because the specific heat capacity of the metal is negligible.

o 103BThe reason why the experiment is continuously stirred is to spread out the temperature more uniformly, also to make sure that all the reactants have reacted.

o 104BThe greater the enthalpy change, the greater the difference in reactivity between the reactants(c).

• 105BThe way to distinguish halides using sulphuric acid o 106BA chloride, such as Lithium Chloride would give out white/steamy fumes. o 107BA bromide, such as Sodium Bromide would give out brown/orange vapour or liquid. o 108BAn Iodide, such as Potassium Iodide would give a purple vapour / dark solid or liquid

or residue.


3BPhysics

192B

9BUnit 1 • 109BThe point beyond the elastic limit is called the yield point, here there is a large increase in

strain for a small increase in stress, meaning that for a small force there is a large extension.

0BFigure 1: Properties of Materials Stress-Strain graph

• 110BStreamlined flow or laminar flow is flow that has no abrupt change in direction or speed of low, usually this occurs at low speeds. Streamlines do not mix.

• 111BTurbulent flow is flow in which there is abrupt change in speed and direction and thus causes the formation of eddies.

Adobe Acrobat Document

Comment [R1]: In fluid dynamics, an eddy is t swirling of a fluid and the reverse current created when the fluid flows past an obstacle.

http://en.wikipedia.org/wiki/Fluid_dynamics

http://en.wikipedia.org/wiki/Fluid

http://en.wikipedia.org/wiki/Current_%28water%29



112B • 113BThe major difference between ductile and malleable is that the forces of attraction in

malleable materials are weak and thus they can be moulded into shape. But, in ductile materials, the material has empty spaces between the particles in the materials. So ductile materials can be stretched into lines.

• 114BTough materials are those that absorb a lot of energy before breaking. But hard materials cannot, they cannot absorb energy much, but they can withstand large impact forces, i.e. they are hard to scratch or indent.

• 115BA strong material is a material that requires a large stress to break it.

• 116BA hard material is a material with high breaking stress, meaning that a lot of energy is required to break it.

• 117BCompressive strain: 𝐷𝑒𝑐𝑟𝑒𝑎𝑠𝑒 𝑖𝑛 𝐿𝑒𝑛𝑔𝑡ℎ𝑂𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝐿𝑒𝑛𝑔𝑡ℎ

• 118BCompressive Stress: 𝐶𝑜𝑚𝑝𝑟𝑒𝑠𝑠𝑖𝑣𝑒 𝑓𝑜𝑟𝑐𝑒𝐴𝑟𝑒𝑎 𝑜𝑓 𝐶𝑟𝑜𝑠𝑠−𝑆𝑒𝑐𝑡𝑖𝑜𝑛

1BFigure 2: PH01_0906_14-15_Worked

• 119BOften, a data logger is used, because it can accurately record large amounts of data in real time, so it is easier to process, and reduces the chances of human error.

10BUnit 2 • 120BA source of light emits a train of waves lasting 0.04 μs. The light has a wavelength of

600 nm and the speed of light is 3×108 ms-1. How many complete waves are sent out?

A. 121B2.0 × 107

B. 122B4.5 × 107

C. 123B2.0 × 1010

D. 124B4.5 × 1010 o 125BWe need to keep in mind the values of 𝜇 and n, 𝜇=10-6 and n=10-9 o 126BThe total length for the ray of light is 0.04 × 10−6 × 3 × 108 = 12𝑚 o ∴ 𝑒𝑎𝑐ℎ 𝑤𝑎𝑣𝑒 𝑏𝑒𝑖𝑛𝑔 600 × 10−9 ∴ 12 ÷ 600 × 10−9 = 2.0 × 107


o 128BThe single resistor will have 2X the current. o 129BTherefore, as P=I2R, current will be made four times, and therefore quadrupled. o 130BThis is in comparison to one of the two resistors, not both of them. o 131BThus, the first will have 4 times than one at the bottom as 2 is squared.

193BHow much electrical energy is required to move 4.00 mC of charge through a potential difference of 36.0 V?

A. 132B1.11 × 10-4 J B. 133B0.144 J C. 134B144 J D. 135B9000 J

• 136BRemember that 𝑉 = 𝐸𝑛𝑒𝑟𝑔𝑦(𝐽𝑜𝑢𝑙𝑒𝑠,𝐽)𝐶ℎ𝑎𝑟𝑔𝑒(𝐶𝑜𝑢𝑙𝑜𝑚𝑏𝑠,𝐶)

• 137BNTC resistors decrease their resistance as the temperature increases • 138BAs the voltage increases, so does the temperature of the NTC resistor • 139BAs we can see that the curve becomes steeper, so for a larger value of V, there is a greater

increase In I than R, which is the gradient

• 140BThus, the answer is B. Because 𝑹 = 𝑽𝑰

• 141BAnother interesting question is Question 8_SAM_GCE_UNIT2


• 𝜋4

, 𝑖𝑠 18� 𝑡ℎ, 𝑎𝑠 𝑎 𝑐𝑜𝑚𝑝𝑙𝑒𝑡𝑒 𝑤𝑎𝑣𝑒 ℎ𝑎𝑠 𝑎 𝑝ℎ𝑎𝑠𝑒 𝑜𝑓 2𝜋

• 143BSo, 0.5 × 8 = 4, 𝑖𝑠 𝑡ℎ𝑒 𝑤𝑎𝑣𝑒𝑙𝑒𝑛𝑔𝑡ℎ • 144BThis as 𝑣 = 𝑓𝜆, 𝑣 = 10 × 4 = 40 𝑚𝑠−1

• 145BThe rate at which electrons are liberated due to the photoelectric effect, from a metal

surface is depends on the distance between the source of light and the metal surface. Thus, the number of photoelectrons emitted only depends on the intensity, not the frequency.

• 146BUV light only transfers energy to the metal surface, not electrons, so on a positively charged metal surface, on an electroscope, it would have no effect.

•

• 147BThe difference between sound waves and radio waves:

Radio Waves Sound waves 1. 148BTransverse 2. 149BTravels through Vacuum 3. 150BMuch faster than sound 4. 151BInfinite range of frequencies

1. 152BLongitudinal 2. 153BTravels through medium 3. 154BMuch slower than radio 4. 155BFrequencies between 20Hz-20KHz


• 156BThe higher the frequency, the lower the wavelength, because all electromagnetic waves have a speed of 3 × 108.

• 157BAs 𝑣 = 𝑓𝜆, i.e. 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 = 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 × 𝑊𝑎𝑣𝑒 − 𝑙𝑒𝑛𝑔𝑡ℎ

This question is taken from Edexcel June 2009 Physics paper2. Section A question 2.


11BUnit 3

This Value is the mode, and the other value, thus has a chance of being an error.

The equipment used is not has errors. The piece of equipment most probably used is a micrometer which has a percentage error. The actual reading is too far away from the ones obtained, so not C. D is also not the answer because the actual reading is to one decimal place as well. It is not A, because the students recordings are very close to each other, and therefore we may presume that he/she has made very few mistakes. Thus leaving B, as the most logical conclusion.


4BBusiness Studies

12BTechnique • 158BWhenever reading through a case study, try to understand the motives of the business, and

evaluate the position from their point of view. • 159BWhen answering a context in Edexcel, these are the guidelines that you have to follow:

o 160BKnowledge, most of the time, this is a definition o 161BApplication o 162BAnalysis, this is where you analyse the data o 163BFor higher marked questions, there will be an evaluation.

• 164BThis is an example of the shorter questions: • 165BExamine one way in which Innocent Drinks achieved a competitive advantage.SAM 9(b) [6] • 166BCompetitive advantage is any feature of a business that allows it to compete effectively. In

this case, the endorsement by Coffee Republic, by stocking their goods. As Coffee Republic is an established brand, having many stores, this would mean that more people will have a chance to try out the product, so it would raise consumer awareness. Furthermore, as a brand has endorsed ID, that in itself is an as now a brand image is attached to their name.

16BAnswering MCQs in both Unit 1 and Unit 2 194BFrom Edexcel Business Studies June 2009 Unit 2

195B6. Chocolate maker Green & Black’s objective is to increase profit.

196B(a)Which one of the following is most likely to be the best tactic? [1]

197B(b)Explain why your answer is correct? [3]

• 167BThe first mark would be a mark for knowledge, so the definition of either tactic or profit would be acceptable, as they are key terms in the question. So, thus would be the knowledge mark

• 168BThe second mark would be an explanation as to why you chose D, thus showing your understanding, a third mark could also be scored out of this

• 169BHowever, easier way of getting a mark is to explain why the other options are wrong, so for example why would ceasing advertising be the wrong thing to do.

• 170BBut, there is a fundamental mark for why you chose your option. The other two marks are optional marks, they can be gained from further explaining your choice or the application of your knowledge

Comment [R2]: Knowledge. Here we have defined what Competitive advantage means.

Comment [R3]: Application of your knowledge

Comment [R4]: Analysis1, the advantages of having Coffee Republic help you out.

Comment [R5]: Analysis2

Comment [R6]: Key term

Comment [R7]: Key term


Unit 1

• Competitive advantage: Any feature of the business that enables it to compete effectively. It may be based on price, quality, service, reputation for innovation of the product.

• Also, in Dave Hall defined as an advantage which allows the business to perform better than its rivals.

• The difference between Unique Selling Point and Competitive advantage is that a unique selling point may provide a competitive advantage, meaning that it is a feature that may give the business a competitive advantage. So, it is a PART of competitive advantage. Or, a feature of the business that may provide a competitive advantage.

• Usually the term USP is referred to niche markets and Competitive advantage to mass markets.



S1 Coding

• Mean

o Affected by all, to calculate the actual mean, just equate it back through the coding • Standard Deviation

o Just affected by division and multiplication o Just multiply it by the factor you divided by, and vice versa

• Product moment correlation o Not affected

• 𝐲 = 𝐚 + 𝐛𝐱 o This is affected by all, just equate a and b back through the equation

• Variance o Affected by what you have multiplied it by, and nothing else. o If Var(a+bx) o Then the answer would be b

M1 Vectors

• When something is due south or due north of a point.

• Whenever calculating the acceleration in Chapter 3 question, always calculate them for the entire body at all times.

C3 Trigonometric Identities

important points - physics. chemistry and mathematics

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