SI Measurements Numbers are tools, not rules. G. O. Ashley

Why is the SI System Common? 1.The SI system uses a decimal system as its base. 2.The SI system has seven standard or base units and all other units are combinations of these seven. The U.S. is one of the few countries that has not switched over completely. However, when it comes to science we do use the metric system !

SI System Prefixes

What are the SI Prefixes? DO NOT COPY THIS CHART PrefixMultipleScientific NotationAbbreviation mega-1,000,000 (Million)10 6 M kilo-1,000 (Thousand)10 3 k hecto-100 (Hundred)10 2 h deka-10 (Ten)10 1 da deci-0.1 (Tenth)10 -1 d centi-.01 (Hundredth)10 -2 c milli (Thousandth)10 -3 m micro (Millionth)10 -6 μ nano (Billionth)10 -9 n

What are the SI prefixes?

I Do (Don’t write, just watch): 492 km = __________________________ cm Which one is larger? 8.20 g or 45.8 cg?

We Do: 1.2 mg = _______________ g Circle the one that is correct: 7.52 L = mL or 3.4 cm = 34 mm You Do: 5.12 m = ______________ dkm Circle the one that is correct: 59.0 mg = g or 0.82 kg = g

What is the difference between precision and accuracy? Precision – how well repeated measurements of a value agree with one another (Precision is a measure of exactness) Accuracy – is determined by the agreement between the measured quantity and the correct value. (Accuracy is a measure of rightness)

Precise or Accurate?

Which group(s) made precise measurements? Which group(s) made accurate measurements? (accepted value is 4.01 mL) Group123 Trial mL4.01 mL25.02 mL Trial mL4.02 mL25.01 mL Trial mL4.00 mL25.03 mL

Practice Measuring With Precision Length: ______________