CIE has changed the following terms:
New term for sulphate is sulfate
thiosulphate is thiosulfate
sulphite is sulfite
sulphur is sulfur
disulphide to disulfide
Tuesday, June 30, 2009
Saturday, June 27, 2009
Xtreme link
Change of Xtremepaper link
http://www.planet-master.com/
Many thanks to you, Leong Seek for your information
http://www.planet-master.com/
Many thanks to you, Leong Seek for your information
Wednesday, June 3, 2009
Important Notice
To all students taking AS and A2 Examinations:
You are reminded again that you are not allowed to discuss anything about the question papers in the forum or blog within 24 hours after your paper. Don't forget some of the candidates in other parts of the world have not sat for the papers due to the different time zones. Failure to observe this rule means you are in trouble. Good luck
You are reminded again that you are not allowed to discuss anything about the question papers in the forum or blog within 24 hours after your paper. Don't forget some of the candidates in other parts of the world have not sat for the papers due to the different time zones. Failure to observe this rule means you are in trouble. Good luck
Sunday, May 31, 2009
Saturday, May 16, 2009
Think before you use
Waste decomposition Rate
Styrofoam is not composed
Plastic bottle takes at least 1 million years
Disposable diaper 500 to 600 years
Aluminium tin 200 to 500 years
Leather shoes 40 to 50 years
Newspaper 1 month
Styrofoam is not composed
Plastic bottle takes at least 1 million years
Disposable diaper 500 to 600 years
Aluminium tin 200 to 500 years
Leather shoes 40 to 50 years
Newspaper 1 month
Source : Star
Tuesday, May 5, 2009
Never judge a book by the cover
I was truly astounded by the talent of Susan Boyle when I watched her singing on the Britain's Got Talent (from Youtube). Her performance received a standing ovation from the live audience and later took the world by storm. The numbers who watched her videos on her audition have climbed to almost 200 millions and the figure is still growing.
What's so special about her? She is a 47 years old lady whose appearance is #@?/... but possess a golden voice. Watch her sing and you would understand what I meant.
http://www.youtube.com/watch?v=9lp0IWv8QZY
What's so special about her? She is a 47 years old lady whose appearance is #@?/... but possess a golden voice. Watch her sing and you would understand what I meant.
http://www.youtube.com/watch?v=9lp0IWv8QZY
Sunday, April 26, 2009
Wednesday, April 15, 2009
AS Practical Guide II
Guide to Potassium manganate(VII) titration
· For KMnO4 titration, no indicator is added because KMnO4 acts as its own indicator and it would change to pale pink colour at the end point.
· KMnO4 titration is used to determine the concentration of Fe2+ (Iron(II) ions) , H2O2 (hydrogen peroxide) and C2O42- (ethanedioate).
· KMnO4 titrations must be carried out in acidified condition because in neutral or alkaline solution, brown solid MnO2 is formed and as a result it would be difficult to detect the end point.
· To acidify, sulphuric acid is used and not other acids such as hydrochloric acid and nitric acid because the chloride ions or nitrate ions would also be oxidised.
· Most KMnO4 titrations should be carried out at room temperature except titration involving C2O42- which is normally carried out at 70 oC. For ethanediote, any temperature lower than 70 oC could cause the precipitation of MnO2.
· Titration using KMnO4 solution should be carried out slowly. A brown precipitate of MnO2 is formed when KMnO4 is dropped from the burette too quickly.
.
Guide to Iodine-thiosulphate titration
· Starch is used as an indicator in this titration
· The starch solution should not be added at the beginning of the titration. The reason is at this stage, there is a high concentration of iodine and iodine would be adsorbed onto the starch molecule.
· The starch solution should be added towards the end of the titration when the reaction mixture turns pale yellow. (Warning: not too pale as you may overshot the endpoint)
· The starch solution will produce a dark blue colour with iodine.
· At the end point ,the solution turns colourless.
· Be careful, the solution may become blue again due to the atmospheric oxidation of iodide (from potassium iodide). You shouldn’t continue titrating again.
· For KMnO4 titration, no indicator is added because KMnO4 acts as its own indicator and it would change to pale pink colour at the end point.
· KMnO4 titration is used to determine the concentration of Fe2+ (Iron(II) ions) , H2O2 (hydrogen peroxide) and C2O42- (ethanedioate).
· KMnO4 titrations must be carried out in acidified condition because in neutral or alkaline solution, brown solid MnO2 is formed and as a result it would be difficult to detect the end point.
· To acidify, sulphuric acid is used and not other acids such as hydrochloric acid and nitric acid because the chloride ions or nitrate ions would also be oxidised.
· Most KMnO4 titrations should be carried out at room temperature except titration involving C2O42- which is normally carried out at 70 oC. For ethanediote, any temperature lower than 70 oC could cause the precipitation of MnO2.
· Titration using KMnO4 solution should be carried out slowly. A brown precipitate of MnO2 is formed when KMnO4 is dropped from the burette too quickly.
.
Guide to Iodine-thiosulphate titration
· Starch is used as an indicator in this titration
· The starch solution should not be added at the beginning of the titration. The reason is at this stage, there is a high concentration of iodine and iodine would be adsorbed onto the starch molecule.
· The starch solution should be added towards the end of the titration when the reaction mixture turns pale yellow. (Warning: not too pale as you may overshot the endpoint)
· The starch solution will produce a dark blue colour with iodine.
· At the end point ,the solution turns colourless.
· Be careful, the solution may become blue again due to the atmospheric oxidation of iodide (from potassium iodide). You shouldn’t continue titrating again.
Monday, March 30, 2009
Good luck
The AS Mock exam started today. Good luck to those who are taking the exam. I would be extremely busy these coming few weeks. First, I am involved in the time-table committee. I can foresee myself sitting for hours to come out with the new timetables for both the students and the teachers for the next Semester. The only good thing is I can prepare my own timetable to my likes.
Second, 'tons' of students' answer scripts waiting for me. I have five classes under my charge. Not only that, with different styles of handwriting: artistic type, doctor type, miniature type, hilly type (the one with the gradient at 45 degree), my eyesight power will double after that.
Third, need to plan for the coming AS practical exam. (Please don't ask me what will be coming out. Even I am 'tortured' or offered a bribe , I won't reveal a single thing.)
Fourth, need to complete my new book before the deadline.
Fifth...sixth...etc. Who said teaching is easy? Salary is low and plenty of work. The only reward is a good karma or maybe a place in the heaven. That would keep me motivated when I think of that.
Second, 'tons' of students' answer scripts waiting for me. I have five classes under my charge. Not only that, with different styles of handwriting: artistic type, doctor type, miniature type, hilly type (the one with the gradient at 45 degree), my eyesight power will double after that.
Third, need to plan for the coming AS practical exam. (Please don't ask me what will be coming out. Even I am 'tortured' or offered a bribe , I won't reveal a single thing.)
Fourth, need to complete my new book before the deadline.
Fifth...sixth...etc. Who said teaching is easy? Salary is low and plenty of work. The only reward is a good karma or maybe a place in the heaven. That would keep me motivated when I think of that.
Tuesday, March 24, 2009
Tuesday, March 17, 2009
Practical P31/32 (Part 2)
Maximum error
Maximum error is usually marked on the glassware.
Burette
• A pipette has a maximum error of 0.05 cm3 in each measurement.
Calculation of percentage error
Percentage error = (maximum error ÷ quantity measured ) x 100%
Reading burettes
A burette is graduated in divisions every 0.1 cm3.
Using the half-division rule, the estimation is 0.05 cm3.
Burette is recorded to two decimal places with the last figure either ‘0’ or ‘5’.
The maximum error in each measurement = 0.05 cm3.
The overall maximum error in any volume measured always comes from two measurements, so
the overall maximum error = 2 x 0.05 cm3 = 0.1 cm3.
In a titration, a burette will typically deliver about 25 cm3 so the percentage error is small.
Percentage error = (2 × 0.05 ÷25.00) x 100% = 0.4%
The percentage error becomes more significant when burette is used to deliver small volume
For delivery of 2.50 cm3,
Percentage error = (2 × 0.05 ÷ 2.50)× 100% = 4%
Maximum error is usually marked on the glassware.
Burette
• A pipette has a maximum error of 0.05 cm3 in each measurement.
Calculation of percentage error
Percentage error = (maximum error ÷ quantity measured ) x 100%
Reading burettes
A burette is graduated in divisions every 0.1 cm3.
Using the half-division rule, the estimation is 0.05 cm3.
Burette is recorded to two decimal places with the last figure either ‘0’ or ‘5’.
The maximum error in each measurement = 0.05 cm3.
The overall maximum error in any volume measured always comes from two measurements, so
the overall maximum error = 2 x 0.05 cm3 = 0.1 cm3.
In a titration, a burette will typically deliver about 25 cm3 so the percentage error is small.
Percentage error = (2 × 0.05 ÷25.00) x 100% = 0.4%
The percentage error becomes more significant when burette is used to deliver small volume
For delivery of 2.50 cm3,
Percentage error = (2 × 0.05 ÷ 2.50)× 100% = 4%
Tuesday, March 10, 2009
Practical 31/32 Learn More (Part 1)
1. Titres should be within 0.20 cm3.
2. Candidates were expected to produce a single table.
3. The table should include correct headings and units.
4. Burette readings and the volumes added recorded to the nearest 0.05 cm3.
5. Select appropriate scales when plotting a graph
6. In plotting graph, a line should be best-fit straight line or a smooth curve.
7. A graph should contain at least five ponts.
8. Answer for calculation should be given to at least 3 significant figures
9. Thermometer readings and temperature differences expressed to the nearest 0.5 °C,
10. All weighings and the masses of the solid used should be recorded consistently to 1 decimal place or 2 decimal place depending on the sensitivity of the electronic balance. The balance in our lab can measure up to 2 decimal points.
11. To calculate mcT equation, the m is the mass of solution not the mass of solid.
12. +ve sign or –ve sign should be written on the H value.
13. Common error in thermochemistry experiments:
· heat loss/gain with the surroundings
· acid spray from the vigorous reaction
· the use of a thermometer calibrated by 1 °C
14. Suggested improvement for thermochemistry experiments :
· Suitable additional insulation or use of a lid
· Use of a thermometer with closer graduation or use of a digital thermometer
2. Candidates were expected to produce a single table.
3. The table should include correct headings and units.
4. Burette readings and the volumes added recorded to the nearest 0.05 cm3.
5. Select appropriate scales when plotting a graph
6. In plotting graph, a line should be best-fit straight line or a smooth curve.
7. A graph should contain at least five ponts.
8. Answer for calculation should be given to at least 3 significant figures
9. Thermometer readings and temperature differences expressed to the nearest 0.5 °C,
10. All weighings and the masses of the solid used should be recorded consistently to 1 decimal place or 2 decimal place depending on the sensitivity of the electronic balance. The balance in our lab can measure up to 2 decimal points.
11. To calculate mcT equation, the m is the mass of solution not the mass of solid.
12. +ve sign or –ve sign should be written on the H value.
13. Common error in thermochemistry experiments:
· heat loss/gain with the surroundings
· acid spray from the vigorous reaction
· the use of a thermometer calibrated by 1 °C
14. Suggested improvement for thermochemistry experiments :
· Suitable additional insulation or use of a lid
· Use of a thermometer with closer graduation or use of a digital thermometer
Sunday, March 1, 2009
FRIM Trip
The Science and Maths Society (SMS) organized a trip to FRIM on Sat (28/2/09). I was invited to go along since I am the advisor for the society. This was my second trip to FRIM.
Here we come, leeches and mosquitoes
Assault on the forest
Here we come, leeches and mosquitoes
Assault on the forest
Canopy walk Can’t miss that shot
A view from the canopy
‘Trigonal shape’, that’s what I see. This was related to me by a student from SN9d when she saw this flower.
A view of 'delocalised electrons' in the nature
Safe and sound. Apart from some mosquitos’ bites, no one was victim of the leeches. Maybe our blood is a bit acidic after a strenuous climb or this is not the leech season.
Achieve enlightenment in the forest. I am in the 'nirvana' state. In chemistry, it is equivalent to triple point, a state in which solid , liquid and gas are in equilibrium.
I am the new spiderman
Friday, February 20, 2009
Mock Exam Paper 1 and Paper 2 2008 (Aug)
Mid-course exam (Trial exam for AS) is coming soon. You can start practising some of the trial exam papers. Answers for the papers will only be published one week later.
Paper 1 2008
Paper 2 2008
Paper 1 2008
Paper 2 2008
Wednesday, February 11, 2009
Acidosis and alkalosis: good to know more
Remember, I mentioned two pH related diseases acidosis and alkalosis in our lesson when I taught buffer solutions and explained why it’s important for our body to maintain a fairly constant pH. Here’s more information about these diseases. This information is just for your general knowledge.
A healthy person has a blood pH close to 7.4.
Acidosis is a state of excess acidity in the blood and occurs when blood pH falls below 7.35 Alkalosis is a state of excess alkalinity when blood pH is over 7.45.
When the blood pH falls below 7.0, it is diagnosed as severe acidosis and in severe alkalosis it may rise above 7.5. Acidosis is more common than alkalosis.
pH in our blood or fluids is controlled by three following mechanisms
1. Blood's protein that's acts as a buffer that limits changes in acidity.
2. Lung, which give off carbon dioxide to prevent accumulation of carbonic acid.
3. Kidneys which manufacture hydrogen carbonate ions and retain acids or bases.
Causes of Acidosis:
1. Kidney failure reduces the efficiency to regulate acidity.
2. Starvation produces excessive acid due to metabolism of large amounts of body fat which produce lactic acid
3. Increased protein intake – eat too much meat
4. Ingestion of large amounts of acidic substances eg pickled fruits
5. Diabetes
Causes of Alkalosis:
1. Severe diarrhea may cause excessive loss of basic fluids
2. Loss of carbonic acid because of fast or rapid breathing.
3. Excessive vomiting causing loss of hydrochloric acid (stomach content)
4. Excessive intake of antacids to relieve acid in the stomach.
A healthy person has a blood pH close to 7.4.
Acidosis is a state of excess acidity in the blood and occurs when blood pH falls below 7.35 Alkalosis is a state of excess alkalinity when blood pH is over 7.45.
When the blood pH falls below 7.0, it is diagnosed as severe acidosis and in severe alkalosis it may rise above 7.5. Acidosis is more common than alkalosis.
pH in our blood or fluids is controlled by three following mechanisms
1. Blood's protein that's acts as a buffer that limits changes in acidity.
2. Lung, which give off carbon dioxide to prevent accumulation of carbonic acid.
3. Kidneys which manufacture hydrogen carbonate ions and retain acids or bases.
Causes of Acidosis:
1. Kidney failure reduces the efficiency to regulate acidity.
2. Starvation produces excessive acid due to metabolism of large amounts of body fat which produce lactic acid
3. Increased protein intake – eat too much meat
4. Ingestion of large amounts of acidic substances eg pickled fruits
5. Diabetes
Causes of Alkalosis:
1. Severe diarrhea may cause excessive loss of basic fluids
2. Loss of carbonic acid because of fast or rapid breathing.
3. Excessive vomiting causing loss of hydrochloric acid (stomach content)
4. Excessive intake of antacids to relieve acid in the stomach.
Friday, February 6, 2009
Chemistry resources
Monday, February 2, 2009
Dare to take this challenge
Take this challenge and download the past year questions for the Chemistry Olympiad UK. Give yourself a Chemistry test. Reminder: Look at the answers only after you have tried the questions.
Chemistry Olympiad 2008 Examination
Answer
Chemistry Olympiad 2008 Examination
Answer
Important AS Definitions Part II
Activation energy is the minimum energy required by colliding particles to start off a reaction.
A catalyst is a substance which changes the rate of a chemical reaction without itself undergoing any chemical change at the end of the reaction.
Homogenous catalyst is a catalyst in which the physical state is in the same phase as the reactants.
Heterogenous catalyst is a catalyst in which the physical state is in the different phase as the reactants.
Increase the concentration of reactants will increase the rate since there will be more molecules per unit volume resulting in an increase in the collision frequency between the reactants. This leads to higher number of effective collisions.
Increase in the temperature will increase the rate since at higher temperature the particles gain more kinetic energy resulting an increase in collision frequency at higher temperature. In addition, more molecules have kinetic energy greater than or equal to the activation energy. Consequently, the number of effective collisions increases.
A catalyst operates by providing an alternative route of lower activation energy for the reaction.
Geometric isomers are compounds with different spatial arrangement due to the restriction in the rotation about the double bond in an alkene. In geometric isomers, two different groups at each end of the double bond can either be on the same side (cis) or on opposite sides (trans)
Optical isomers are mirror images that have the same geometric and structural formula, but cannot be superimposed onto one another.
Cracking is a process to break long alkane into a shorter alkane and an alkene. Hydrogen may also be produced. Thermal cracking requires temperature between 400°C to 900°C and high pressure whereas catalytic cracking requires a zeolite catalyst and a temperature of about 450°C. The purpose of cracking is to form extra gasoline and to produce alkenes with higher commercial value
Homolytic fission is the breaking a covalent bond in which one electron goes to each atom to form free radicals.
Heterolytic fission is the breaking a covalent bond in which one atom takes both electrons forming negative and positive ions.
A free radical is a highly reactive atom or molecule with an unpaired electron.
An electrophile is an electron-deficient species that can form a new covalent bond by accepting an electron pair provided by the carbon compound. Example : positive ion such as hydrogen ion or nitronium ion and a polar molecule with a d+ charge
A nucleophile is an electron-rich species with a lone pair of electrons that can form a new covalent bond by donating a pair of electrons to the electron deficient carbon atom. Example : negative ions with at least a lone pair.
A catalyst is a substance which changes the rate of a chemical reaction without itself undergoing any chemical change at the end of the reaction.
Homogenous catalyst is a catalyst in which the physical state is in the same phase as the reactants.
Heterogenous catalyst is a catalyst in which the physical state is in the different phase as the reactants.
Increase the concentration of reactants will increase the rate since there will be more molecules per unit volume resulting in an increase in the collision frequency between the reactants. This leads to higher number of effective collisions.
Increase in the temperature will increase the rate since at higher temperature the particles gain more kinetic energy resulting an increase in collision frequency at higher temperature. In addition, more molecules have kinetic energy greater than or equal to the activation energy. Consequently, the number of effective collisions increases.
A catalyst operates by providing an alternative route of lower activation energy for the reaction.
Geometric isomers are compounds with different spatial arrangement due to the restriction in the rotation about the double bond in an alkene. In geometric isomers, two different groups at each end of the double bond can either be on the same side (cis) or on opposite sides (trans)
Optical isomers are mirror images that have the same geometric and structural formula, but cannot be superimposed onto one another.
Cracking is a process to break long alkane into a shorter alkane and an alkene. Hydrogen may also be produced. Thermal cracking requires temperature between 400°C to 900°C and high pressure whereas catalytic cracking requires a zeolite catalyst and a temperature of about 450°C. The purpose of cracking is to form extra gasoline and to produce alkenes with higher commercial value
Homolytic fission is the breaking a covalent bond in which one electron goes to each atom to form free radicals.
Heterolytic fission is the breaking a covalent bond in which one atom takes both electrons forming negative and positive ions.
A free radical is a highly reactive atom or molecule with an unpaired electron.
An electrophile is an electron-deficient species that can form a new covalent bond by accepting an electron pair provided by the carbon compound. Example : positive ion such as hydrogen ion or nitronium ion and a polar molecule with a d+ charge
A nucleophile is an electron-rich species with a lone pair of electrons that can form a new covalent bond by donating a pair of electrons to the electron deficient carbon atom. Example : negative ions with at least a lone pair.
Monday, January 26, 2009
Red, red....almost everyone is red
Class SN9p.. must act cute, you know
SN9deg..........wonder who's the 'old' student on the right hand corner in the first row?
Even the lecturers are not spared from red
SN9deg classes... even Indian students joined in the fun
SN 9pq .........very sporting ....is it the hand sign for the bull horn? Year of the OX, ma.
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