Common Mistakes in Chemistry Part One

Finally, the reason why I started this Blog. Henceforth I will be posting snippets of useful information from the tiny little notebook I carry around that is packed with information. Remember when Mr. Glenn Wong used a lesson to talk about common mistakes made in Chemistry? I copied almost everything down even though none of the mistakes were mine. The same goes with many other subjects, and from time to time I will post information I feel you guys will find useful. Use it well, and get your A's =)

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Chemistry

- "Unsaturated" refers to "An Organic molecule with C=C bonds"
Note: Beware of using the term double C-C bonds because this could mean just mean a C-C bond here and another C-C bond there. The above mentioned definition is the safest.

- SPELL OUT chemicals unless asked for formulas

- When asked for Partial Structures in Organic Chemistry, don't forget to add the brackets and the 'n' symbol.

- There will be NO WRITING OF STATE SYMBOLS BELOW FORMULAS. Instead, write them beside the chemicals otherwise they will be disregarded (according to Mr Wong this is the latest change from MOE or someone higher up so don't complain)

- Ionic and Half Equations REQUIRE state symbols

- The term "precipitate" only refers to reactions between two MIXTURES. Whereas "residue" is used in filtration.

- Mole Calculations require 3 Significant Figures. HOWEVER, during your working, you may come across big values. If they have to be used later, keep them up to about 3 Decimal Places to be safe.

- Final answers during calculations involving Enthalpy Change should be kept exactly. One way to check the answer is that if you know the reaction is Endothermic/Exothermic, you will know the answer should be positive or negative respectively. COMBUSTION is EXOTHERMIC.

That's all for now. If you liked this post, don't bug me when I'm copying stuff down in class, and I'll happily share my notes.

Photos for the Blog Title Picture

See that nice photo of a mountain at the top of the page?

Wouldn't it be great if all of us were at the foot of the mountain?

I think it would. So send me some decent shots of yourself, preferably above the waist WITH CLOTHES ON, and I'll slowly add you guys into the picture, and when it's finished I'll put it up =)

Regarding Names & Authors

In response to the request on the Cbox for all of us to use our real names, YES, please use your real names as well as making sure that if your name is shared by another, include your surname.

On another note, I have sent an email to Jon Poh, to invite him as another Blog author to help post on History and SS. Once I have Joel Khoo's email, the same invitation will be sent. This post is also a call to those of you interested in helping post tips and other things. I already have several positions that I would be glad if some of you could help out with, such as an Activities Planner who can use this Blog to plan class activities, whether they be for leisure or for school-related purposes. Another person could help regularly update the Announcement Board too. I am also ready to give the Cbox account name and password to anyone who is willing to help monitor it to prevent potential spam.

Anyone interested should let me know.

27-28 May SPA Key Sources of Error

NOTE: The key sources of error mentioned below are speculations. Also, do remember that in Physics SPA we are allowed to write as many answers as possible and they will give us marks for one correct answer. For Chemistry SPA, we are allowed ONLY ONE answer. Always remember to write what the errors lead to. It is advisable to rephrase the answers mentioned below to fit the context of the question in the actual exam.

Physics: (topic is Light)

-Involving mirrors
There is glass in between the area where the light ray strikes at the mirror and the silvered surface (where the light ray is reflected), leading to inaccurate angles of reflection recorded.

The mirror is light and is easily shifted by accident, leading to inaccurate drawing of lines for the light rays.

-Involving pins
The pin holes are too big for a pencil to pass through accurately, leading to inaccurate drawing of lines for the light rays.

When pins are required to be placed at the edge of the glass block or mirror, the pins cannot be placed exactly at the edge of the block, leading to inaccurate drawing of lines for the light rays.

- Involving lenses
The exact point where a clear image is formed cannot be defined exactly (for reasons similar to that of comparing colours to the colour comparison chart in Chemistry), leading to...

Chemistry: (topic is Metals)

This topic is somewhat difficult due to the broad scope of possible experiments. I will try my best to cover as many possibilities as possible

- Involving reaction of metals with time as a variable
The stopwatch cannot be started at the exact time when the reaction begins due to human reaction time (remember those experiments involving the small test tubes?), leading to inaccurate timings recorded.

- Involving reactions of metals with heat as a variable
There is heat loss to the environment, leading to inaccurate readings of temperature change in the solution.

It will be great if you guys could inform me of any other possible answers that I have missed out, and I will edit this post accordingly. Good luck, and feel free to ask questions.

The Creation

So begins the blog of ACS(BR)'s 4A3 2008. It is our hope that we can make the best out of this Blog. Let the posting begin!