Catalyst (5 min)

1
Catalyst (5 min)

• Complete the following calculations
• 5.5 4.0 ________
• 7.9 2.7 _______________
• 4.6 7.0 ___________
• 23 273 ________
• X 273 363, X _________
• You will need to bring a calculator tomorrow!

2
Catalyst (5 min)

• Complete the following calculations
• 5.5 4.0 ________
• 7.9 2.7 ________
• 4.6 7.0 ______
• 23 273 ________
• X 273 363, X _________

1.5
5.2
- 2.4
296
90
3
The Metric System

• SI (System International)
• 10/5/10

4
Metric System

• Used by every country in the world, except the
  USA.
• Always used by scientists.
• Also called SI, which is French stands for System
  International.
• Based on the number 10, so its easy!

5
Measuring Length

• Length is the distance between two points.
• Basic unit meter.
• Meter m
• ruler or meter stick

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Measuring Mass

• Mass is the amount of matter (stuff) that makes
  up an object.
• Basic unit gram.(g)
• Tool scales

7
Measuring Volume

• Volume is the amount of space contained in an
  object.
• Base unit Liter (L).
• We measure volume with a graduated cylinder or
  beaker.

8
Measuring Temperature

• Temperature is the measure of the average heat or
  heat energy
• Basic unit degree Celcius (C) or Kelvin (K)
• We use thermometers to measure temperature.
• K C 273

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Lets review our basic units!!!

• Length
• Meter (m)
• Mass
• Gram (g)
• Volume
• Liter (L)
• Temperature
• C or K

• We need more accuracy
• We cant measure everything with just basic units
• We need prefixes!

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Metric Prefixes

• We add prefixes BEFORE basic units to make new
  units that are smaller or bigger
• Common prefixes from large to small
• kilo (k) 1000
• centi (c ) 1/100th
• milli (m) 1/1000th
• Example kilogram (kg) 1000 g
• 100 centimeters (cm) 1 m
• 1000 milliliters (mL) 1 L

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Why is measurement important?

• We make measurements in the lab
• We use measurements to back up our conclusions
• If our measurements are not accurate, our
  conclusions are not supported!

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When is measurement important?

• Why does messing up the dosage of medicine cause
  more problems for children than adults?
• Children have smaller bodies
• A small amount of medicine has a larger affect in
  a child than in an adult
• KEY POINT When measuring, we need to be accurate
  and precise, or end up with some serious
  consequences!

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Accuracy

• Definition how close a measured value is to an
  accepted value
• KEY POINT accurate measurements meaningful

Accurate
Not Accurate
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Precision

• Definition how close a series of measurements
  are to one another
• Key Point more precision more support if
  accurate

Precise
Not Precise
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Accuracy vs. Precision

• Accuracy measurement vs. actual value
• Precision similarity between repeated
  measurements
• YOU CAN BE ACCURATE, PRECISE, BOTH OR NEITHER!

Accurate AND Precise
Accurate
Not Accurate, Not Precise
Precise, not accurate
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Error

• Error is a measurement of accuracy
• Higher error less accurate measurement (BAD!!)
• Equation
• error experimental actual

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Example

• Julio weighed himself at the gym. The scale said
  he weighed 79.3 kg, but he really weighs 81.6 kg.
  What is the error in his measurement?
• error experimental actual
• 79.3 81.6
• -2.3
• 2.3 kg

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Example as a Class!

• Christian measured the length of his Snickers bar
  to be 10 cm long. In reality, the candy bar is
  actually 9.5 cm long. What is the error in his
  measurement??
• Error experimental actual
• 10 cm 9.5 cm
• -0.5 cm
• 0.5 cm!

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BRING A CALCULATOR TOMORROW!
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Classwork Assignment

• Select TWO of the following problems and
  calculate the error in the following measurements
  on a separate sheet of paper. Turn into the
  homework stack when finished. Dont foget units
  in your answers!
• Experimental measurement 4.5 km, Actual
  measurement 3.2 km
• Experimental measurement 12.5 L, Actual
  measurement 11.4 L
• Sandra measured the mass of a ball to be 55.0 g,
  but the ball is really 53.9 g.
• Juan thought the field looked about 122.5 m, but
  it was actually 135.9 m long.
• Maria thought the glass held 344 mL of liquid,
  but it only had 315 mL.