Designing and Recording Laboratory Experiments
Designing and Recording Laboratory Experiments
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Laboratory experiments allow scientists to test hypotheses, observe
scientific phenomena, and discover relationships. Most experiments
consist of the following steps:
- Forming a hypothesis that predicts what will occur, or
that describes why or how something occurs.
- Designing an experiment to test the hypothesis
- Performing the experiment
- Recording the data and observations
- Summarizing the results and communicating them to other
Obviously, the better an experiment is designed, the easier it is to
perform the experiment, obtain data, and draw conclusions. Most
successful experiments are the result of careful planning, attention to
detail, multiple attempts, and learning from past mistakes. The more
careful you are about designing and performing your experiments, the
more sense your results will make, and the easier it will be to describe
your experiment in a report.
Chemistry experiments generally involve the use of specific laboratory
techniques applied in a manner that enables the researcher to collect
data. Researchers therefore need to understand and be comfortable with
techniques before using them in an experiment.
The Goal or Objective
This should be obvious, but you should have a goal or objective in mind
before you plan your experiment. Every step of the experiment should
take you closer to achieving the goal.
As you are designing your experiment, you may think of extra steps or
measurements you can perform along the way that will give you additional
useful data, even if those data don't meet the primary goal of the
experiment. When this happens, you have two options:
- Add secondary goals to the experiment. If you do this, you will
need to re-visit your experimental plan to make sure all of the
necessary elements are there to meet your secondary goals, as well
as the primary goal.
- Use the secondary goals to design future experiments. If the
secondary goals end up making the experiment too large or complex,
or make it more difficult to obtain the data you need, it's a sign
that you need to turn these secondary goals into a separate
The Experimental Plan
Before you perform an experiment, you need to have an experimental plan.
Your plan is an overview or "scheme" for the experiment-usually in
the form of an outline or flow chart that describes what you intend to
do. It serves the same purpose as an outline serves for writing-it
keeps you organized and oriented toward your goal.
Your plan also serves as a checklist for the main parts of your
experiment. It helps to keep you on task and helps you remember where
you are in the process. The better you can understand and keep track of
the flow of your experiment, the less likely you will be to lose your
place and miss an important detail or data point.
Performing the Experiment
The carpenter's adage, "Measure twice; cut once." applies to lab
experiments. Because you will be performing your own experiment (and
not somebody else's from their detailed write-up), you will not have a
step-by-step procedure to make sure you haven't forgotten anything.
Before you perform each step, double-check:
When you believe you have finished performing your entire experiment, go
back and re-read your objective and plan before you clean up, to make
sure you haven't left anything out.
- Have I finished recording the previous step and the necessary
data and observations?
- Am I following my plan?
- Was there anything I need(ed) to do before this step?
- What data or observations will I need to record during this step?
- What will I be doing after this step? Should I do anything
special in this step to set myself up for the next step?
- Am I ready to record the procedure and data?
Recording the Procedure
By the time you have finished your experiment, you should have a
detailed record of everything you did. As you perform each step, be
sure that you have recorded all of details you think may be relevant
before going on to the next step. (In a closely-timed experiment, you
may want to write out the steps for the timed part before performing
them, and then make any corrections as you go.)
Read over your procedure while it is still fresh in your mind (between
the time you finish your experiment and the end of the day) so that you
can add any missing details before you forget them.
The success of your experiment relies on the data and observations that
you record. Record every detail that you think might possibly be
significant in your notebook. After you finish your experiment, glance
over your data tables to make sure you haven't missed any data points.
After your experiment is complete and you have finished filling in the
details of your procedure and data points, you are ready to begin
analyzing your data. In general, your analysis will be whatever you
need to do to use your data to answer your objective. If the experiment
involved measurements, the data analysis will usually involve
calculations and error analysis.
Your analysis should consider any possible sources of error (especially
any errors that you believe actually occurred), considerations to keep
in mind the next time you perform a similar experiment, and suggestions
for future related experiments.
Pavia, Donald L., Gary M. Lampman, George S. Kriz, and Randall G. Engel.
Introduction to Organic Laboratory Techniques, A Microscale
Approach. (Philadelphia: Saunders College Publishing, 1990).
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On 29 Oct 2010, 22:45.