Scientific Measurement

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Scientific Measurement

• Questions to Ponder
• Why is measurement important?
• What are the different types of measurement?
• What is the history of measurement?
• What do you know already?
• What do you think we will focus on when studying
  measurement?

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Types of Measurements
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Types of Measurements
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Types of Measurements
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Types of Measurement
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Types of Measurements

• Qualitative Measurements
• Descriptive, nonnumerical form
• Quantitative Measurements
• Definite form, numbers and units

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Practice Qualitative or Quantitative?

• Basketball is brown
• Diameter of basketball is 31 cm
• Air pressure in the basketball is 12 psi.
• Surface of basketball has indented seams.

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Accuracy vs. Precision

• Accuracy how close to actual or true value
• Precision how close measurements are to one
  another

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Percent Error, Experimental Error

• Accepted value correct value established by
  references
• Experimental Value measured in lab
• Error accepted experimental
• Percent Error error/accepted x 100
• Percent Error vs. Percent Yield

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Practice Calculating Percent error

• Estimated volume 150 mL, Accepted volume 158
  mL
• Calc Percent error
• Practice Precision or Accuracy?
• Multiple measurements
• Correct
• Repeatable
• Reproducible
• Single Measurement
• True value

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Using Scientific Notation

• Useful for large and small numbers
• 2 numbers Coefficient 10 raised to power
• Addition and Subtraction
• Exponents must be same to add coefficients
• Multiplication
• Multiply coefficients and add the exponents
• Division
• Divide coefficients and subtract exponents
• EE button on calculator

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Practice Change to/from Scientific Notation

• 91.4m
• 0.00000154 m
• 6378000 m
• 8.2 x 10-3 m
• 1.469 E 5 m

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Significant Figures

• Important when making measurements in experiments
• All digits known with certainty plus one
  estimated or uncertain digit
• Calculated answers depend on number of sigfigs.

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Examples What is the Rule?

• 1) 24.7m (3)
• 2) 7003 m (4)
• 3) 0.0071 m (2)
• 4) 25.0 (3)
• 5) 27,210 m (4)
• 6) 18 students in classroom (infinite)

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Rules Explained

• 1) Nonzero digits are always significant (24.7m)
• 2) Zeroes in between are significant (7003m)
• 3) Left zeroes are not significant (0.0071 m)
• 4) Right zeroes are significant (25.0 m)
• 5) Right zeroes left of understood decimal are
  not sig.(27,210m)
• 6) Unlimited sigfigs
• Counting, exact quantities (60min1hr)

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More Rules

• Rounding answers cannot be more precise than
  least precise measurement from which it was
  calculated
• Add/Subtract round to least significant place
• Mult/Divide round to same as least number of
  sigfigs

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SI units and Prefixes - MEMORIZE

• International System of Units (SI)
• SI Base Units (table 3.1)
• Length, Mass, Temp, Time, Amount
• SI Unit Prefixes
• Table 3.2 G,M,k,d,c,m,µ,n,p
• Derived Units
• Density, volume

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List of Unit Prefixes

• Powers of ten Java
• http//micro.magnet.fsu.edu/primer/java/scienceopt
  icsu/powersof10/
• List of 20
• http//physics.nist.gov/cuu/Units/prefixes.html
• Common ones
• http//lamar.colostate.edu/hillger/common.htm
• Prefixes revisited
• http//www.wordwizz.com/pages/10exp0.htm

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Length

• Basic SI unit meter
• Common millimeters, centimeters, kilometers
• Running races 5K, 10K
• Table 3.3 perspective on length

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Volume

• Derived unit cubic _____meters
• CCs cubic centimeters
• 1 CC 1ml
• 1 cubic decimeter 1L
• Volumetric flasks, graduated cylinders
• Table 3.4 perspective on volumes

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Mass vs. Weight

• Mass amount of matter (1 kg)
• Weight force on mass by gravity (Physics)
• Table 3.5 perspective on mass

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Temperature

• Temperature
• Determines direction of heat transfer
• Thermal expansion
• Generally expand as temp increases, contracts as
  temp decreases
• Celsius history
• Kelvin -273.15 C 0 K
• Accounts for absolute zero (-273.15C)
• Practice Temperature Conversions
• 170 Celsius to Kelvin
• 87 K to Celsius

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Energy

• Capacity to do work or to produce heat
• SI Unit Joules (J)
• Calories vs. Joules
• 1 J 0.2390 cal or 1 cal 4.184 J

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Density

• Density Mass/Volume
• Characteristic of substance (type of property?)
• Water displacement technique
• Temperature increases, Density decreases (V
  increases)
• Densities of Common substances (table 3.6)

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Practice using Density Formula

• Volume 245 cm3 and mass of 612 g. Is it
  aluminum? (dAl 2.7 g/cm3)
• density of gold 19.3 g/cm3. What is volume of
  5-g sample?
• Plastic ball with volume of 19.7 cm3 has a mass
  of 15.8 g. Sink or float in gasoline (0.67g/cm3)?

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Dimensional Analysis Converting Units

• Purpose express a quantity in a different way,
  not changing its value.
• Process
• Write starting quantity
• Write conversion factors (ratio of equivalent
  measurements)
• Numerator What are you trying to convert into?
• Denominator What are you converting from?
• Which one is bigger? 1
• How many does it equal?
• 1 m 100 cm
• 1000 m 1 km

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Practice Converting Units

• 0.044 km to meters
• 860 mg to grams
• 6.7 s to milliseconds

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Multistep Problems

• Use more than one conversion factor
• Practice
• 261 nm to millimeters
• 642 cg to kilograms
• Complex Units
• Examples Areas, Volumes, Speeds
• Practice
• 1000 sq. ft. to sq. meters
• 55 mph to m/s
• 1.54 kg/L to grams per cubic centimeter

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END
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Specific Gravity

• Comparison of density of substance with density
  of reference, usually at same temp.
• Specific Gravity density of substance/density
  of water
• The specific gravity of urine is the measurement
  of density of these minerals and toxins in the
  urine in relation to the density of the water
  basically, specific gravity is measuring the
  concentration of solutes in the solution.

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Exit Slips - Feedback

• On a separate sheet of paper labeled Exit Slip,
  please include the following
• 1 thing you learned today
• 1 thing that still confuses you
• Any other comments about the pace, methods, labs,
  etc.
• Thank you!