The purpose of this experiment is to discover the behavior of the oscillating reaction as a function of light absorption. Are the periods faster or slower compared with the 20C reaction? What are they? Are these periods regular or not? As before the behavior of the system may be discovered by observing one particular color change and timing it. It is, again, a purpose to obtain quantitative measures of periods at a different temperature by having several observers make measurements and then finding an average.
If there are several groups of observers then we may determine a group average of the period as well as an overall grand aveage. The spread of these measurements lets us know something about their validity. This also teaches us something about measurement and statistics.
Prepare the B-Z solutions. Obtain a light source that delivers 7000 A light and a filter that passes 7000 A light. A phocell that detects this wave length is placed on the other side of the reaction vessel. The output of the photocell is measured with a high impedance voltmeter (or a galvanometer).
First set (and measure) the temperature of the reaction mixtures to temperature, 15C or 59F, or a suitable temperature as determined by past experiments.
Mix the three solutions in a large beaker placed on a magnetic stirrer and at the time when complete mixing has occurred start timing the color change. As the reaction proceeds the meter readings are taken as a function of elapsed time. Record these times and enter them in a lab notebook, or a computer spread sheet.
Each group should have collected three sets of data for a number of time periods during the extent of the oscillating reaction. Each observer should average their total set of times and each group should make an average of each time period. An average and a standard deviation should be recorded. The easiest way to do this is to use a spread sheet on a computer.
For a more sophisticated discussion of data analysis go to statistics