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2.1 Scientific Measurement When do we measure?

Measurement takes place during the: “______”Collect & record data phase of the scientific method SI Units

The International System of Units – the set of measuring units that scientists use.

Base Units

 The most basic units of SI measurement are base units. The SI Base units are: . Length: Meter – m . : – kg . Temperature: – . Time: – s . Amount of a Substance: – mol . Electric Current: – A . Luminous Intensity: - cd Derived Units

 Combinations of base units . : Square meter – m2 . : Cubic meter – m3 . : per cubic meter – kg/m3 . Pressure: 's (kg/ms2) – Pa  There are more….. Metric Prefixes

 Kilo  Hecta  Deka  (Meters, liters, or )  Deci  Centi  Milli

 Kangaroos Hopping Down Mountains Drinking Chocolate Milk!!! Drawing the Line!

Prefix Symbol Value kilo k 1,000 103 hecta h 100 102 deka da 10 101 BASE deci d .1 10-1 centi c .01 10-2 milli m .001 10-3

1 Ladder Method 2 KILO 3 1000 HECTO Units 100 DEKA Units 10 Units DECI 0.1 CENTI Unit 0.01 MILLI Meters Unit 0.001 Liters Unit Grams

How do you use the “ladder” method? 4 km = ______m 1st – Determine your starting point. Starting Point Ending Point 2nd – Count the “jumps” to your ending How many jumps does it take? point.

rd 3 – Move the decimal the same number __. __. __. of jumps in the same direction. 4. = 4000 m 1 2 3 Conversion Practice

Try these conversions using the ladder method: 1000 mg = ______1 g 1 L = ______1000 mL

160 cm = ______1600 mm 14 km = ______14000 m

109 g = ______.109 kg 250 m = ______.250 km Practice Problems

 20 km = ______200 hm

 .045 daL = ______450 mL

1 100  1000 mm = ______m = ______cm

Base Units

 Meter measures ______.length

 Grams measure ______.mass

volume  Liters measure ______. Precision vs. Accuracy

 Precision – how exact a measurement is, how repeatable something is.  Accuracy – the closeness of the measurement of the actual value, how close you are to the goal

 Dart Throwing Analogy Accurate or Precise?

Goal: To throw a dart and hit the bulls-eye (red circle)

Neither accurate Precise but not Precise AND nor precise accurate accurate