Planning A:
Background Info - General info about enzymes & how they work. Briefly describe reaction equation for breakdown of peroxide by catalase. May include an explanation of how the selected variable affects the reaction rate of catalase. May include a chart predicting what will happen to the enzyme as the variable is manipulated.
Question & Hypothesis - Lists a plausible hypothesis, and explains what will happen (may have been done with background info which is ok!)
Variables - Lists the Independent (experimental) Variable, Dependent Variable, measured variable/s (time and foam height or foam volume), positive control, negative controls, and variables to attempt to keep constant.
Materials - Complete listing. Many left out either the ruler or timer.
Procedure - Organized, but not overly long. Shows cleanliness, what tests are positive & negative controls, how to specifically measure time, height or volume, how to prepare each solution or temperature...........
Number of tests / Number of trials - Indicates at least 3 trials and as many tests (the different concentrations and different temps) as possible.
Table of Raw Data - Table manipulated into a finished clear form (not your actual lab sheet with chicken scratches & love-life remarks), Specific title (typically the Effects of IV on DV of Catalase, etc), all column labels and units. May include manipulated data and a brief description of what the data table shows.
Raw data processed correctly. Averages calculated (at a minimum), but also slope of line, range of data amongst trials, +/- correlation, standard deviation.....etc. One example of each type of calculation shown.
Manipulated data displayed in titled table, and titled graph (showing averaged results only!) A brief explanation of what the table or graph show is often quite helpful.
a) Convert drops to % concentration.
b) Graph mean trial data.
c) Consider use of best fit curve.
Conclusion -
Lists general trends, and specific averaged data coordinates to compare to the restated hypothesis. Many did not state reaction rate as height (or volume) per time!
Notes data that agrees with or disagrees with hypothesis.
Attempts to explain data.
Potential Problems with Data / Experiment -
This was not an accurate way to collect this data. Always question your technique / procedure / measuring abilities!
a) Major difficulties in reading height/ volume / time (When does reaction start? When is it done?) That affects both height and time.
b) Since the foam produced is often small, small mistakes in measurement create large variation in data/trial. Especially mistakes in time as it is the denominator!
c) Accuracy of measuring devices - rulers are accurate down to about 0.1-0.2 mm, watches to ? depending on device, which introduces error. This error is greater for small measurements than for larger ones!
d) For many, you could have mentioned the variation in data for your 3 trials to show this! (some showed graphs of this but did not mention it.)
e) For some the number of trials was insufficient, or the number of different tests of your variable was insufficient. If you have time in lab, always test as many situations of your variable as possible!
f) How dropper was held. Size of drops. Small changes in drop size can affect output of foam greatly, thus changing results.
g) Drops on test tube walls.
h) Components mixed wrong. Soap (high pH) may denature catalase if mixed prior to adding to peroxide!
i) Even with soap in mixture, some oxygen escapes, so readings not totally accurate.
j) Cleanliness of test tubes, beakers & droppers.
k) Not drying test tubes & droppers adds a component of error (extra water introduces error due to volume changes- This is reduced when using large volumes of reactants!)
l) Using peroxide or catalase from different sources - may have been mixed differently.
*m) Not using labeled glassware - Some mix water and peroxide up, which reduces or increases reaction accordingly!
n) Human error - Not having the same people repeatedly do the same procedural operation!
Proposes Specific Methods to improve data collection, & / or refines Procedure to Reflect Problems listed above.
You might think that with all these sources of error and imprecision experimental results are worthless.
This is not true, it is understood that experimental results are only estimates.
What is expected of a scientist is that they:
i. make the best effort to avoid errors in their design of investigations and the use of instruments.
ii. are aware of the source of errors and to appreciate their magnitude.[The Open Door Web Site (Error Analysis In Biology)