TOOLS

• Exact Numbers are not measured they are counted.
• UNCERTAINTIES

  • DIGITAL INSTRUMENTS: have the uncertainty of the smallest unit
  • ANALOGUE INSTRUMENTS: have their uncertainty listed on the instrument (by manufacturer) OR can be calculated
• To calculate the uncertainty of an instrument, you must HALF the smallest unit/graduation
• Accuracy is how similar the results are to the true value.
• Precision is how similar the results are to each other.
• More precision = more decimal places in results = less uncertainty = closer values (to each other)
• Random errors can affect the results in either direction.
• Random errors include...

  • confounding variables
  • unpredictable changes in the environment
  • all uncertainties
• Examples of random errors include...

  • room temperature
  • insufficient data (not enough trials)
• Systematic errors are consistent in one direction. They are usually caused by the instrument/procedure of/in the experiment
• Random errors cannot be fixed, but can be reduced, by repetition.
• Systematic errors affect accuracy of results.
• Systematic errors can be fixed by changing the procedure or changing apparatus.
• '5 beakers' has how many significant figures?

  Infinite, because it is an exact number.
• 27.00°C has how many sig figs?

  4 sig figs.
• 300cm has how many sig figs?

  Unspecified because there are zeros following the number '3' without a decimal. This answer should have been written in scientific notation (3.00x10^2).
• '0.01°C' has how many sig figs?

  1 sig fig. The zeros preceeding/leading the number '1' do not count, regardless of there being a decimal, they are 'placeholders'.
• 0.0400g has how many sig figs?

  3 sig figs. The zeros leading the '4' are INsignificant. although the zeros after are significant.
• 501 g has how many sig figs?

  3 sig figs. The zero in between IS SIGNIFICANT as it is surrounded by "actual" numbers.