DA SUPER NERDS -o.o-

updates class links crap homework birthday memories

Helloooooooooooo

WHO ARE YOU?

Anyway welcome to 3/5'09's class blog (:
We are

DA SUPER NERDS

yaw.

hello everyone.

im back from church. :)

uh here's what the chem teacher wanted to say...

Annoucements:

1. Class test on SEPARATION TECHNIQUES next Tuesday 14th April, CME Period slot. (30mins)

2. CTSS mid year that was supposedly due during wed's remedial slot, will now be brought forward to TUESDAY's CME slot to go through.

3. Practical worksheets on chromatography & crystallisation DUE MONDAY MORNING. (in Mrs Yeo's pigeon hole)
(the lab is ALWAYS open. if not, go to the 3rd floor to look for the lab tech to get him/her to open for you)

4. I handed out 4 sets of extra worksheets to Joshua. If u want them, specifically which ones, SOMEONE please take the initiative to compile a list, and i'll print the final numbers for those people who wants. Maybe almas you can take charge.

5. Attached you'll find the answers to worksheet 1 on purity, and worksheet 3 on chromatography, so you can mark them yourselves. You were supposed to have done them!
worksheet 2 on distalliation has already been done in class..

6. I pinned topic 6 notes (on separation techniques) on the class notice board (if anyone noticed), because there were some blanks that we didnt have time to fill. so do go fill them up.

7. when you study the topic on separation techniques, in addition to knowing the methods (such as filtration, crystillation etc), you are also expected to know the uses of basic laboratory apparatus, and is expected to be able to come up with designs to carry out an experiment, given a scenario.

here are the answers

Worksheet 1: Need for Purity & Separation Techniques

1a solid

1b water. Boiling point of water is lower at 100ºC

1c The boiling point of Panium will increase, at the same time causing panium to boil over a range of temperatures.

1d The melting point of Panium will decrease, at the same time causing panium to melt over a range of temperatures.

A	Sublimation
B	Evaporation
C	Condensation
D	Melting
E	Boiling
F	freezing
G	boiling

Chalk

Pure water

Air

sugar

A	Fractional distillation
B	Sublimation
C	Separating funnel
D	Fractional distillation
E	Chromatography
F	Crystallisation
G	Sublimation or filtration
H	Crystallization

Worksheet 3: Chromatography

1e(i) Method A is known as descending chromatography. It is faster as the solvent now not only moves down by capillary action, but also by the force of gravity.

1e(ii) It is to make sure that the atmosphere in the beaker is saturated with solvent vapour. By saturating the atmosphere, it prevents the solvent from evaporating as it rises up the filter paper.

1e(iv) advantage: better separation of spots

Disadvantage: inconvenient experimental set-up.

2a(i) B

2a(ii) C

2a(iii) D

2a(iv) C

2b ethanol

2c 0.675

3a To prevent the sample mixture from being dissolved in the solvent even before chromatography takes place.

3b ink contains dyes that can also be soluble in the solvent, hence interfering and contaminating the dyes in the samples, leading to inaccurate results.

3c To ensure maximum separation of the spots for clearer analysis.

also, the following things will be tested for next week E math.

1. Arithmetic- maths in practical situations (refer to notes)

2. Graph notes. - speed-time, distance-time,Exercise 7

3. Matrices- Addition and Multiplication

4. Linear Inequalities.

VERY IMPORTANT STUFF! please uh, tell everyone to visit class blog

thank you.

-joshua

On Friday, April 10, 2009 at 1:59 PM

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