Uncertainty in Measurements

As a recap form the previous lesson "Mixtures" There are many methods to seperate mixtures, depending on the type of mixture.
  - By hand
  - Filtration <------ heterogeneous mixtures only
  - Distillation
  - Crystallization
  - Chromatography

Here is an example of the process filtration ^

Now something new we learned last class was uncertainty in measurements. Here are some few notes:

Accuracy: Degree of closeness of measurements
Precision:  Repeated measurements that show the same results

The image of a dartboard is an excellent example of both Accuracy and Precision.

 Measurements are uncertain for 2 reasons: Measuring instruments are never completely free of flaws & measuring always involves some estimation. We use a plus or minus symbol like this one ----> ±

to show uncertainty of a measurement. 

There is also a metric system called International System of Units, abbreviated SI (after the French System International d'Unites) which had streamlined at an international conference in 1960. The SI is built upon a set of 7 metric units, which are called base units of the SI

But the base SI units are not always convenient to use. There is a convenient way of writing the measurement by using the metric prefix. Metric prefixes are attached to the base unit.

 

 A very important note from the lesson was Percent Error.

 Error as you all may know is an inescapable part of science. One may think that error is a BAD thing in an experiment but it is actually wrong!! In many ways Scientists need error in an experiment in order for the experiment to be succesful. Successful?!? How can this be you may ask well... Error actually helps scientists with experiments because when an experiment ends up not functioning properly, scientists can learn from their mistakes of the FAIL experiment and new measures can be taken up to improve the mistakes.

Here is the equation:

Percent error= measure value-accepted value

                         ------------------------------------     x 100=

                                  accepted value