Experiment A-3

Thinking, Observing & Measuring

practicing chemist skills


Doing science requires a collection of processes utilizing our senses and various thinking skills.  These skills are developed and honed by practice.  The following experiments calls attention to several of those skills and provides a little practice.  With a little creativity, a person with intent on developing their skills could create their own tasks.


Describe your clothes

This is NOT an invitation to get undressed!  Scientists, particularly chemists often have to use what they remember, what they already know, in conjunction with their imaginations to investigate further.  This task asks you to practice those skills without first requiring that you learn a lot of chemistry.
  1. Without looking, list each item of clothing you are wearing.
  2. Describe its style, color, and size.
(Use your memory and imagination to gather as much detail as possible.  For example, how long are your shoe laces or your head scarf?)

Measure your ring size

Measuring is a way that humans expand the detail of our ability to observe.  It typically involves comparing with a standard.  Now days this generally involves using one of the units of the System International.  As a general rule, it is considered good practice to measure as accurately (with as much detail) as possible without exaggerating what we can know.  But often we can't directly measure what we want to know, so we have to be creative and figure out a tricky way to make the measurement.
  1. As accurately as you can, measure the circumference of your ring finger.
  2. Estimate the accuracy limits of your measurement and record that with ± nomenclature.
(As an immediate check, presumably you could measure to about ± 0.1 cm.)

Measure your longest hair

Scientists often have to find ways to measure things that they cannot directly see.
  1. Without removing it, find and measure your longest hair.
  2. Estimate the accuracy limits of your measurement.
It is the observation of experienced teachers that occasionally students, for one reason or another, choose to copy the work of others rather than relying on their own skills.  In science, as in much of the rest of the world, copy other's work is considered highly inappropriate. 

Measure a nerve pathway

Often scientists must make estimates based on their best understanding of what they are measuring.  It is wise to try to be aware of any assumptions, to consider the possible consequences to the measurements and to include those in your journal and any report.

Consider a bug is on your little toe.  A nerve signal passes up your leg, into your spine near your tailbone, to your brain for processing.  That results in a nerve signal passing down to a muscle between your fingers which flicks the bug off your toe.

  1. Measure the distance the nerve signal travels from toe, to mid-brain, to muscle.
  2. If a nerve signal travels 120 m/sec, calculate the shortest time the process could take.
  3. Estimate the uncertainty in each part of this measurement and calculation and the overall uncertainty in the elapsed time.

Measure the rate of a chemical reaction

Some chemical reactions (e.g., some in living cells) are extremely fast, while others (e.g., rusting iron) are frustratingly slow.  So lets start with one which has a convenient rate, burning candle wax.
  1. Measure the candle (best way?) before and after burning.
  2. Time the duration of the burn.
  3. Calculate the amount of candle burned per second.
  4. Estimate uncertainty in measurements and calculations.
  5. Consider other ways to measure the process.
  6. Consider how your investigation of this chemistry could be extended.
  7. What new difficulties would occur if you were studying a much faster or slower reaction?  How could you modify your procedure to overcome those difficulties?
(Sometimes chemistry requires creative thinking.  But finding solutions is often enjoyable.)

If you need course credit, use your observations recorded in your journal to construct a formal report.  Be sure to describe the details of the procedures you created to make the measurements.


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created 18 June 2007
revised 18 June 2007
by D Trapp
Mac made