GCE O Level Tuition

Chemistry Reminders

Sat, 29 Oct 2011 12:25:00 +0000

Dear A1 students, do scan through this set of questions. Part 2 incoming. Beep me if you have problem or leave your question in the comment section. Do look through the physics post below too.

Final Reminders Part 1

Kinetic Particle Theory

1 Do you know how to draw the cooling and heating curves?

2 Do you know the state of a substance at a stated temperature, given its MP and BP?

3 Do you know how to describe the 3 states of matter in terms of their arrangement, movement?

4 Do you know that energy is taken in during melting and boiling?

5 Do you know that energy is released during freezing and condensation?

6 Do you know how to explain why temperature remains constant during change of state?

7 Do you know which substances sublime?

8 Do you know how to draw particles in the 3 states?

9 Do you know how to draw particles during change of state?

Measurement, Experimental Techniques and Separation

1 Do you know how to decide which method of separation to use for a particular type of mixture?

2 Do you know why liquids can pass through the filter paper but solids cannot?

3 Do you know why water enters the condenser at the bottom and exit at the top?

4 Do you know why water enters the condenser at the bottom?

5 Do you know the role of fractionating column?

6 Do you know how do decide if a substance is pure?

7 Do you know the principle behind the chromatography separation?

8 Do you know how to calculate RF value for a substance? (PURE chem.)

9 Do you know how to remove carbon dioxide from a sample of gas?

10 Do you know how to remove acidic gases from a sample of gas?

11 Do you know how to remove soluble gases from a sample of gas?

12 Do you know which gases are soluble?

13 Do you know which gases are acidic?

14 Do you know ammonia is the most important alkaline gas?

15 Do you know when to use upward delivery of gas when to use downward delivery of gases?

16 Do you know the estimated Mr of air?

17 Do you know how to decide which gas has a higher rate of diffusion?

18 Do you know the different fractions of air can be separated using fractional distillation of liquid air?

19 Do you know a separating funnel is used to separate immiscible liquids?

20 Do you know pipette has fixed volumes of 10.0, 20.0 and 25.0cm3?

21 Do you know pipette and burette are only 2 equipment that is very accurate?

Element, compounds and mixtures

1 Do you know the difference between compounds and mixtures?

2 Do you know which are the common mixtures?

3 Do you know how to different mixtures, compounds and elements by looking at the particles drawn?

4 Do you know mixtures can be separated using the physical methods of separation?

Atomic Structure

1 Do you know that group number is the same as the number of valence electrons?

2 Do you know the number of electron shells is the same as the period number?

3 Do you know the proton number or the atomic number represents the number of electrons or protons?

4 Do you know mass number or nucleon represents the total number of protons and neutrons?

5 Do you know how to explain why elements like chlorine do not have a whole number for it’s relative atomic mass?

6 Do you know how to explain why noble gases are not reactive?

7 Do you know how to explain why a certain element is a metal?

8 Do you know how to explain why a certain element is a non-metal?

9 Do you know how to define an isotope?

10 Do you know the relative masses of the sub atomic particles?

11 Do you know the relative charges of the sub atomic particles?

12 Do you know where are the sub atomic particles located?

13 Do you know how to calculate the relative atomic mass of various isotopes based on their relative atomic masses? (Pure)

14 Do you know difference in properties of different isotopes?

15 Do you know the similarities in properties of different isotopes?

16 Do you know when an atom loses electron, it becomes positively charged?

17 Do you know when an atom gains electron, it becomes negatively charged?

18 Do you know the motivation behind forming ions is to obtain a stable electronic configuration?

Ionic Bonding and Compounds

1 Do you know they are mainly formed from metal and non-metal chemically bonded to each other?

2 Do you know they are substances with high MP and BP?

3 Do you know they can conduct electricity in molten and liquid state?

4 Do you know they are generally soluble in water?

5 Do you know metals atoms loses electrons and the non-metals atoms gains electrons?

6 Do you know ionic bonds are the electrostatic force of attraction between oppositely charged ions?

7 Do you know during change of state electrostatic force of attraction between oppositely charged ions are broken?

8 Do you know that the electrostatic force of attraction between oppositely charged ions is strong?

9 Do you know giant ionic structure is also known as a lattice structure? (pure)

10 Do you know why MgO has higher melting point than NaCl?

Simple Covalent Bonding and compounds

1 Do you know they are formed mainly from non-metal sharing electrons to form a stable electronic configuration?

2 Do you know they have low MP and BP?

3 Do you know during change of state, simple covalent compounds overcome weak intermolecular forces of attraction between molecules (also known as Van Der Waals forces of attraction)

4 Do you know they are generally insoluble in water?

5 Do you know acids are the only simple covalent molecules that can conduct electricity?

6 Do you know the reason why they can conduct electricity is because acids ionizes to form hydrogen ions in water and hence can conduct electricity?

Giant Covalent Molecules (PURE)

1 Do you know that graphite, diamond and sand (silicon dioxide) are giant covalent molecules?

2 Do you know diamond and sand are tetrahedrally bonded, 1 atom bonded to 4 other atoms?

3 Do you know graphite atoms are hexagonally bonded in layers of carbon atoms?

4 Do you know graphite can conduct electricity because each carbon atom is only bonded to 3 other carbon atoms?

5 Do you know graphite can act as a lubricant because the layers of carbon atoms are bonded by weak intermolecular forces of attraction and hence can slide over each other?

6 Do you know diamond is hard because the atoms are arranged in a tetrahedral structure and is very rigd?

Acid, bases and salts

1 Do you know the 4 reactions of acids, namely with metals, metal hydroxides, metal oxides and metal carbonate?

2 Do you know the physical properties of acids?

3 Do you know all acids are good conductors of electricity in the aqueous state?

4 Do you know CaO is added to neutralize acidic soil?

5 Do you know sulfur dioxide and nitrogen dioxide causes acid rain?

6 Do you know you cannot add fertilizer and neutralize acidic soil at the same time?

7 Do you know bases are metal oxides and metal hydroxide?

8 Do you know alkalis are group 1 hydroxides, ammonium hydroxide (also known as aqueous ammonia) and calcium hydroxide (also known as limewater)?

9 Do you know when acid is spilt always use calcium carbonate because it is insoluble?

10 Do you know the middle point of the titration curve is pH of the solution?

11 Do you know sulfuric acid is known as a strong, dibasic acid?

12 Do you know hydrochloride and nitric acid are both strong and monobasic acid?

13 Do you know all other acids are weak?

14 Do you know strong acids undergoes complete ionization of hydrogen ions in water?

15 Do you know weak acids undergoes incomplete ionization of hydrogen ion?

16 Do you know basic oxide dissolves into water to form an alkali?

17 Do you know ammonium salts react with alkali to form salt, ammonia gas and water?

18 Do you know group 1 and ammonium salts are made by titration method?

19 Do you know titration salts require an acid and an alkali?

20 Do you know soluble (non group 1 and ammonium salt) are made by neutralization?

21 Do you know the easiest way to make the neutralization salts is by acid and metal carbonate?

22 Do you know in neutralization method we add excess metal carbonate to react with all the acid?

23 Do you know insoluble salts are made by precipitation?

24 Do you know precipitation salts are easily made by using a nitrate salt and sodium salt?

Periodic Table

1 Do you know down the group, reactivity of group 1 metals increases?

2 Do you know down the group, melting and boiling point of group 1 metal decreases?

3 Do you know down the group, group 1 metals’ density increases?

4 Do you know down the group, reactivity of group 7 elements decreases?

5 Do you know down the group, melting and boiling points of group 7 elements increase?

6 Do you know down the group, the states of group 7 elements are g,g,l,s,s states?

7 Do you know down the group, density of group 7 elements increases?

8 Do you know how to explain reactivity using the concept of atomic radius and screening effect? (more for pure)

9 Do you know group 1 elements are called alkali metals?

10 Do you know group 7 elements are called halogens?

11 Do you know halogens are only coloured when in diatomic form?

12 Do you know the colour of group 7 elements darkens down the group?

13 Do you know across the period, elements changes from a metal to a non-metal?

14 Do you know across the period, elements form basic oxide to amphoteric oxide to acidic oxide?

15 Do you know across the period it changes from metallic element to non-metallic element?

16 Do you know how to explain why noble gases are unreactive?

17 Do you know noble gases are used in cases where an inert environment is needed, for example Ar in the light bulb?

18 Do you know inert means unreactive?

19 Do you know transition metals lies between group 2 and group 3?

20 Do you know transition metals forms coloured compound?

21 Do you know transition metals have high melting boiling point?

22 Do you know transition metals can act as catalyst, eg like nickel in the addition of hydrogen, iron in the making of ammonia.

23 Do you know group 1 metals have low MP, BP?

24 Do you know group 1 metals are soft?

25 Do you know group 1 metals have low density?

26 Do you know halogens form diatomic molecule?

27 Do you know diatomic means 2 atoms chemically joined together?

Metals

1 Do you know only group 1 and calcium reacts with water to form metal hydroxide and hydrogen gas?

2 Do you know magnesium, zinc and iron reacts with steam to form metal oxide and hydrogen gas?

3 Do you know aluminium is excluded from most reaction because of it’s unreactive aluminium oxide layer which prevents most reaction from happening?

4 Do you know metals higher than hydrogen in the reactivity series reacts with acid to form salt and hydrogen gas?

5 Do you know how to describe displacement reaction observation?

6 Do you know most copper salts are blue?

7 Do you know group 1 carbonates are unable to break down upon strong heating?

8 Do you know the other metal carbonate when heated forms metal oxide and carbon dioxide gas?

9 Do you know green copper (II) carbonate breaks down to produce black copper (II) oxide and carbon dioxide gas?

10 Do you know alloys are stronger than pure metal due to the disruption of regularly arranged atoms in the metal by atoms of different sizes?

11 Do you know brass is zinc and copper?

12 Do you know bronze is tin and copper?

13 Do you know steel iron and carbon??

14 Do you know price of metals are dependent on the metal’s abundance and extraction method?

15 Do you know metals above aluminium is extracted from their ores by electrolysis?

16 Do you know metals below iron, extraction is by reduction using carbon.

17 Do you know the 5 equations of blast furnace?

18 Do you know the chemical name of the molten slag?

19 Do you know why newly extracted iron is too brittle?

20 Do you know why painting, applying oil prevents the rusting process?

21 Do you know how to explain sacrificial protection? (Pure)

22 Do you know zinc is used to prevent ship from rusting and magnesium for underground pipes? (Pure)

Rate of reaction

1 Do you know the 5 factors affecting rate of reaction?

2 Do you know how to explain each factor using collision theory?

3 Do you know how to draw the setup to measure rate of reaction?

4 Do you know how to draw the graphs to indicate rate of reaction?

5 Do you know gradient of the graphs shows you the rate of reaction?

6 Do you know how to explain why reactions are always fast at the beginning and slows down as reaction proceeds?

Physics 2010 Nagging

Sun, 31 Oct 2010 06:28:00 +0000

Dear all, i can't emphasis the importance of this. READ CAREFULLY.

Otherwise do remember the following pointers.

• Everything in 3sf. Don't waste your brain cells struggling the number of sf, just stick to 3. What happens if its exact value. E.g. 1.23N x 3.21m = 3.9483 Nm. So write that down its ok. But after this step, write this again. =3.95 Nm (3 s.f.)

• What to bring for your exams.

o Calculator that works

o Compass and projector (those pesky resultant force questions)

• Speed time graph questions when you are stucked, don’t forget for every section of your speed time graph label AVUTD.

• When does an object experience terminal velocity when it is free falling? Keep points include the weight of the object is the same as the air resistance of the object. When the object moves faster, the air resistance increases. When air resistance is the same as its weight, resultant force acting on the object is zero (this is the main thing i hope you will remember, any resultant force question, you have to phrase it as RF acting on object), therefore acceleration of the object is zero, object moves at constant speed.

• Angles always 1d.p.

• Friction depends on mass of object, surface texture and speed of object. Mass increase, friction increases. Speed increases, friction increases.

• How to calculate friction – a few formulae to calculate them

o Work done against friction = frictional force x distance moved

o Frictional force = mass x deceleration

o Resultant force = applied force - friction

• For pure physics people, becareful of the upthrust question when an object move upwards. When an object moves upwards, resultant force = upthrust – weight.

• There are questions that ask you whether an object will topple off the slope or not. E.g. in the 2009 paper the lorry question. You need to say something like the line of action of its weight is acting within the area of contact, The weight creates a moment that pushes the lorry onto the slope keeping it stable. Otherwise if it topples, say the line of action of its weight is outside the area of contact, therefore the weight creates a moment that topples the lorry.

• For those kind of slope questions, consider lifting an object of mass 10kg up this slope

• If question asks you about work done to lift the object up the answer is simply PE = mgh. In a way 10 x 10 x 3 = 300J. That’s work done to lift it up and i use 3m because the question gives us the mass.

• However if the question asks us for the pulling force to lift the object up the slope? Idea is that you still need 300J to pull it up. Therefore the pulling force is based on 5m length, work done = force x distance. 300 = f x 5 = 60N. So to pull the object

up the slope, a force of 60N is needed to pull the object up the slope over a distance of 5m. Supposed the pulling force is 80N instead of the required 60N. Work done due to the 80N force is 80 x 5 = 400J. You notice that 100J extra is needed instead of the 300J. That extra 100J is work done to overcome friction.

• Convert g/cm3 into kg/m3 simply x1000

• Moment remember to look out for PERPENDICULAR distance to pivot, not perpendicular to your view.

• Nervous, Nervous

• For pure Literature people i pity you, please endure.

• For light questions, if your light ray is moving from dense to less dense medium, never assume refraction occurs. Always check if the angle of incidence in the denser medium is more than critical angle. If it’s more than critical angle, it will undergo total internal reflection.

• Fat lens have short focal length, skinny lens have longer focal length.

• Magnification = image height/object height

• Magnification = image distance from lens / object distance from lens

• Speed of light 3 x 108m/s is defined as speed of light in VACUUM not air.

• CHECK THAT YOUR CALCULATOR IS NOT IN RADIAN MODE!!!!!

• EM waves, you need to memorized position of the waves. Note that high wavelength EM waves like radio,

• Sound moves fastest in solid, slowest in air, since sound energy is transmitted by vibration of particles, the closer they

are together, the faster it is transmitted.

• When doing sound calculations, make sure you account for distance x 2 or time x 2 since it’s echo thing.

• Stupid formulae

o Power = force x velocity

o V = J/C (Victoria jc), EMF = WD (energy)/Charge

• When doing questions on brightness of light bulbs, don’t worry if you have poor imagination, just assigned values to it. EMF let it be 12V, every resistors 2ohms, It should give you nice numbers.

• Calculating how much electricity used, units of electricity = power in kW x Time in hours

• Why must the fuse be in the live wire? When the fuse is in the live wire, it breaks the high potential in the live wire preventing electrical shocks to user. If it is in the neutral wire, although the circuit is broken, the live wire is still at high potential, this causes danger to the user if an electrical fault is present.

• Don’t mixed up fuses and earth wire. Fuses prevent high current from damaging the equipment. When the current is higher than the fuse rating, the fuse will melt and breaks the circuit. For earth wire, it’s a safety feature to protect user in the event that the metal casing is live. If the casing becomes live due to the electrical fault that causes leakages of current to the metal casing. The earth wire will lead the current to the earth thus protecting user from electrical shocks. Hence do not blame SHORT CIRCUIT FOR EVERY OF YOUR PROBLEM, although most of the time sudden increase in current is due to short circuiting.

• Thin wires – Pro- cuts cost since less material is needed.

• Thin wires – Con – thin wire has high resistance, thus producing a lot of thermal energy lost due to heating effect of the wire. This is because power loss due to heating effect of wire can be calculated by P = I2R. Since R is higher for thin wire, the heat loss will also be greater.

• I against V, gradient is 1/R, while V against I, gradient is R.

• Electrical field lines – out of positive charge, going into negative charge ALWAYS

• Magnetic field lines – out of north, going into south

• For Fleming’s Left Hand Rule, make sure you write the following template. The interaction between the magnetic field and the current produces a force. Using FLHR, the force created is ___(in certain direct_____.

• AS OF THIS POINT, Kenneath & Edwin, Melvin, Jet, Grace, that’s it for you. If your name is not these 5, carry on reading.

• Positive static charges NEVER MOVED!!!!! Whenever you talk about induction of static always talk about the charges in your sphere, comb, paper, whatever, before you say electrons are attracted or repelled.

• What are the possible reasons why a transformer is not ideal? Standard answers will be heating effect of wires, eddy current produced on the soft iron core,

• Why transformer needs an a/c source? Remember its that changes in magnetic flux needed for a continued induction of EMF. Full story in template.

The Confusion of Vectors and Scalars

Tue, 01 Jun 2010 03:46:00 +0000

One of the more commonly asked question is the classification of vector and scalar quantities.

Basically we know that vector quantities has both magnitude (value like 2m/s, 400m etc) and direction (which means there is a possible of positive or negative figures like -5.2m/s).

Fortunately, an easy rule can help us to remember them.

Most of us can remember the 3 usual suspects

DISPLACEMENT, VELOCITY AND ACCELERATION.

The last member of this select group is FORCE.

Basically anything that has the unit of NEWTON, we can safely classify it under vector quatity. For example, friction, weight, pulling force, pushing force, contact force etc. The list can go on and on. You get the drift.

Which brings us to scalar, quatities which has magnitude and no direction. Since we are able to classify vectors, simply label the other components as scalar. Its that ez!

Json

www.oleveltuition.com

Acid Reactions

Sat, 01 May 2010 00:25:00 +0000

Dear all doing acids for this exam,

for reactions of acids, refer to this link.

http://olevelchemistry.blogspot.com/2009/08/acid-reactions-part-1.html

for oxide types

http://olevelchemistry.blogspot.com/2009/08/types-of-oxide.html

for salt making

http://olevelchemistry.blogspot.com/2009/08/salt-making-selection-of-method.html

Will be adding a more keep in view

Regards

Json

MCQs Answer for 21st Discussion

Wed, 14 Apr 2010 13:23:00 +0000

Chemistry

1-10

B C A A B D D B C D

11-20

A D C B C B B B D A

21-30

C D D C A A B D C B

31-40

D A C D D B D C B C

Physics

1-10

B C C B A D D B D A

11-20

A A D D A B C D B D

21-30

B D B D B D B A C A

31-40

C D C B A A B C D C

To er is human, if you suspect any wrong answers, dont struggle gimme a text i will check. Enjoy and remember 3 ilttle pigs.

A piece of history for all of you, why Raffles named our beloved Island City, Singapore ............ possibly.

Topics for Chemistry and Physics MCQ Test

Sat, 20 Feb 2010 08:46:00 +0000

Chemistry MCQ Topics, 10 Questions

1)Gas collection, Volume Measurement, Apparatus

2)Seperation Techniques, Kinetic Particle Theory

3)Atomic Structure, Bonding

4)Periodic Table

5)Metals

6)Mole Calculations

7)Acid Bases Salts

8)Rate of Reactions

9)Redox

10)Heat Changes

Physics MCQ Topics, 10 Questions

1)Kinetics

2)Dynamics

3)Moments

4)Pressure

5)Power, Energy

6)Heat Transfer

7)Heat Calculations, Thermometry

8,9)Electricity Calculations

10)Static Electricity

If the topics are not being taught yet, do worry just do whatever you can. Enjoy and have fun.

HCl, is it an ionic or covalent molecule?

Thu, 21 Jan 2010 12:28:00 +0000

From Nicole today, she asked if HCl should be considered an ionic or covalent substance, should it possess ionic or covalent properties.

The answer is very simple, HCl is a simple covalent molecule. It is bonded covalently so it has the standard properties of simple covalent molecules.

This link http://www.gcsescience.com/Hydrogen-Chloride-Molecule.gif shows you the dot and cross structure of HCl. Furthermore, its made up of 2 non-metal atoms. All these evidences points to simple covalent properties.

However, HCl being an acid, will ionize in water producing hydrogen and chloride ions. Hence despite being a covalent molecule, it is able to conduct electricity in the aqueous state. Hence acids hold the distinction of having and being covalent properties in nature but still conduct electricity.

Information correct as of O levels, A level chemistry has a different story all together :)

Wanton Recipe Part 2

Fri, 31 Jul 2009 05:40:00 +0000

Wanton Recipe Part 1

Fri, 24 Jul 2009 05:44:00 +0000

There has been a lot of queries about how to prepare the tasty! wanton i made for my tuition students. So this is the recipe revealed!!