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.
Monday, March 30, 2009
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
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