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# Measurement Uncertainty

## Data that is affected by the quality of the measuring tool.

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Going for the Gold

### Measurement Uncertainty

Credit: Michiel Jelijs
Source: http://commons.wikimedia.org/wiki/File:Michael_Phelps_before_the_start_of_the_200m_butterfly_semi-final_-_2009_FINA_World_Championships.jpg

Michael Phelps before the start of the 200M butterfly semi-final at FINA 2009 [Figure1]

In 2008, Michael Phelps won olympic gold in the 100 meter butterfly by just .01 second; just out touching his opponent, Milorad Cavic. Invisible to the naked eye, just one-hundredth of a second determined the difference between gold and silver. Let’s however imagine that the olympic timers were only precise to the nearest second. Who would have won the race then? Would there have been two olympic gold medalists in the 100 fly? A redo? If not for precision, olympic history as we know it could have been different.

Timers in swimming today still only measure to the nearest hundredth of a second. If a tie occurred, how could we determine the winner who won by merely a thousandth of a second? Well, until timers of a higher precision of measurement are used in swimming, there will continue to be a degree of uncertainty in times.

Just as timers in swimming, many instruments in Chemistry and science in general have degrees of uncertainty. For example, let’s say you want to measure the length of a grain of rice, but the only tool you have is a meter stick without any denoted increments of measurement. Simply put, your measurement would not be very precise. We cannot measure to an infinite degree of precision, but we can denote our precision with significant figures in our measurements.

#### Creative Applications

1. Why is it important to have precise measurements in Chemistry?

2. Why might it be difficult to have more precision in measuring instruments?

3. How does precision affect significant figures?

4. Is it as important to have extreme precision in more informal chemical reactions such as cooking or home experiments?

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