Measurement, Units and Uncertainty

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Measurement, Units and Uncertainty
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Topics for Today

• SI units
• Prefixes
• Conversions
• Significant figures
• Density lab

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Mass vs. Weight

• Mass the quantity of matter as compared to a
  standard mass unit. A constant value everywhere.
• Weight the gravitational force on an object.
  Not a constant.

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Making a Measuring Tool

• Demo of the making of a measuring tool.
• Uncertainty in measuring.

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Base SI units

• Length meter (m) (l)
• Mass kilogram (kg) (m)
• Time second (s) (t)
• Temperature Kelvin (K) (T)
• Amount of a substance mole (mol) (n)
• Electric current ampere (A) (I)

See page 34 in the text for a chart.
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Prefixes
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Important Bridgesfor Metric/US Conversions

• Length 1.0 in 2.45 cm
• Mass 1.0 Kg 2.2046 lbs
• Volume 1.0 gal 3.7854 l or use
• 1.0 gal 231 in3

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Significant figures

• Rules for significant figures.
• Why do we need them?
• The rules can be found on page 24 of the text or
  at this location on the web.
• The significant figures in a measurement consists
  of all the digits known with certainty plus one
  final digit, which is somewhat uncertain or
  estimated.

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Rounding Rules
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Density Lab

• Density mass / volume (g/cm3)
• The tools we will use
• Ruler - be sure to read from a graduation mark
  and not the edge of the ruler.
• Balance Do Not put the object on to the bare
  pan!! (Records to a 1/100 of a gram.)
• Graduated cylinder Reading
• Complete three separate readings for each
  measurement. EVERYONE SHOULD DO THIS.

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Lab Instructions

• YOU MUST WARE A LAB APRIN AND GOGGLES WHEN EVER
  YOU ARE IN THE LAB!
• Put stools and chairs under the tables.
• Read the entire lab before you start.
• Be aware of all warnings and cautions.
• If you are not sure about a technique ask for
  help. Doing things the wrong way can lead to
  serious consequences.
• REMEMBER NO FOOD OR DRINKS ALLOWED!

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Lab Write-up

• Lab write-up instructions handout.
• Due next class period.
• I will come around and check each students work
  during class.

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Scientific method

• Observing
• Hypotheses
• Testing
• Theorizing
• Publishing

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Math Skills Assessment

• This not for a grade!!!
• Helps me to know where you are at this point in
  math skills.
• Do the best you can.
• You may use a calculator