[car]

Is it possible to test the rate of reaction by observing changes in colour? If so, how would I do this accurately? A friend told me I might have to do this by observing how long it took for *any* colour change to happen, or by observing how long it took for colour change to stop. Are these ideas plausible? Is judging by colour change too qualitative? Most of my friends are testing with chemicals that create extraneous gas when mixed, which seems easier to quantify. The results I need for my assessment need to be highly quantitative and contained.

If any answers are to be found, I would be greatly appreciative.

[Borek]

If by "observing" we will mean "using spectrophotometer" then yes, you can get highly quantitative results. Observing visually changes in color generally won't work, although may give reasonable results in some particular cases.

[ARGOS++]

Dear car;

Yes - You can! 
There are quite a few methods known, but nearly all use a Spectrophotometer.

The methodology is widely used in “our” plants and for more or less known reactions.
Best preferred are Photo Diode Array Spectrometers (PDA’s/DAD’s).
It’s clear, that the methods “go” from weak to very accurate, with corresponding effort for.
One of the most accurate is MCA, the Multi Component Analysis.

I hope this gives you at least a general idea. - For more, please ask!
Good Luck!
                    ARGOS⁺⁺

[car]

Unfortunately I only have a high school department at my disposal - I doubt a spectrophotometer would be available. It might be possible to borrow one from a local university through my teacher, but that seems a little overkill.

Out of interest, how does a spectrophotometer work? What does it measure? Would I be able to use it to determine changes in a rate of reaction from colour change?

[Borek]

Remember: library first, wiki/google second, ask on forums third!

http://en.wikipedia.org/wiki/Spectrophotometry

http://en.wikipedia.org/wiki/Beer–Lambert_law

Basically: measuring absorbance you can measure concentration.

[ARGOS++]

Dear car;

For “only” teaching and “student learning experiments”, it’s not required to have a PDA/DAD.
There are also sources for cheap mechanical instruments, like second hand shops, and I have even seen some self-made kits.

I think for the “first 200 experiments” not a very high accuracy is required (but of course it’s not for direct kinetic measurements, expect very - very slow once).
In such situation you can start with some simpler experiments, for example: Decolorize a solution by a reaction, or build a color by a coupling reaction, and so on. Most depends on your fantasy!

Later, with some experience you may do reactions where the color changes the “Nuance”, what is a little more complicated, but should be possible with the help of programs like Excel or so.
(Also pH titrations are possible; you may ask Mr Borek.)


For how UV/Vis spectrometers work:
    -  for the Instruments:  "UV-Vis Instruments”
    -  for the theory:         "Beer Lambert Law”

I hope to have been of some help to you.
Good Luck!
                    ARGOS⁺⁺

P.S.:  If you need “a lot” more/specially help you may use pm of the forum