Chemistry SPA Skill 3

The following are some of the things I took note of during Mr Alex Lee's Revision with us on the 1st of July.

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3.1 Planning an Investigation

1. Aim
2. Approach
3. Variables: Varying & Constant

(Mr Lee's advice: do a draft)

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3.2 Planning & Procedure

4. Apparatus & Chemicals
5. Procedure
6. Results
7. Conclusion

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1. Aim
- think of what is the "big picture"
- usually, it can be copied from the worksheet title

2. Approach
- what are you measuring?
- what is the chemical reaction?
- what are the key variables?

"To measure/record the volume of gas collected in a fixed amount of time, when a fixed mass of CaCo3 is allowed to mix with hydrochloric acid of concentrations o.8M (A1), 1.0M (A2) and 1.2 (A3)."

- Start sentence with "measure" or "record"

3. Variables
- List ONE varying and SEVERAL controlled variables
note: be specific (don't use 'amount')
- when using time, mentione time "for what?" (for example, time taken for x reaction to finish)
- when using temperature, use "initial temperature"

tips on choosing a quantity to measure
Speed of Reaction: Measure time take for....
- a solid to completely disappear (easiest)
- a precipitate to form (for slow reactions)
- a fixed volume of gas to be collected

4. Apparatus & Chemicals
- You may specify SPECIFIC ITEMS
- for example, "three micro test tubes, each containing o.30 grams of magnesium powder"
- example 2: "three 2cm magnesium strips, eaqually cut"
this saves you the trouble of making it another step in the procedure =)

5. Procedure
- Don't forget preparation of material
Do NOT write in your procedure
"Identify a key source of error"
"Record your results in a suitable format"

6. Results
- Provide a table to show results
- Fill in values for the independent variable, but NOT results
(Don't forget UNITS)
- Mr Lee: DON'T NEED GRAPH

7. Conclusion
- How your results will provide and answer to your aim
- Use "if" because you do not know the results!

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Mr Lee's Suggested thought process

Read -> Construct Aim -> Visualise Experimental Set Up -> State Variables -> Construct Approach -> Construct Procedure

Voila!

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NOTE:

I did this out of "the kindness of my heart" (sound familiar?)

Please do not use this as an excuse to not pay attention to class and take down your own notes. Each of us hears things differently and tend to take down only things that have significance to ourselves. This means that I may have missed out some points Mr Lee may have mentioned (even my attention span wavers after a while) and you may have jotted down reminders to yourself that are important to yourself but of no significance to me. So, make the best you can out of this, but don't start slacking too much in class =) Good luck for Chemistry SPA Skill 3!

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.