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Chapter 2: Measurement & Problem Solving
pg. 24-38
LO: I can use unit conversions successfully in mathematic calculations.
Units of Measurement
• Two common systems: English & Metric (International System or SI).
Common Base Units• Meter (m) = length• Kilogram (kg) = mass• Seconds (s) = time
Metric Prefixes
• A numerical prefix that changes a number by powers of 10
ExamplesWhat is the meaning?• Kilometer =• Centimeter =• Decimal =
Scientific NotationPg. 26 of your text!
Unit Conversions
• Converting a given unit into a desired unit
ExamplesHow many feet (ft.) are in 194 centimeters (cm)?
How can we solve this problem?
Unit Conversions
Setting up ratios (comparing one unit to another) in order to convert a given unit into a
desired unit through multiplication.
Solution MapsA great way to
map out a problem so you know what you
need to do!
Solution Maps
Question: How many feet (ft.) are in 194 centimeters (cm)?
• How do we get from centimeters (cm) feet (ft.)?
Example Solution Maps
Question: How many laps should
you run to run 10.0 kilometers
(km)?
Note: Important conversion factors
are on the PDF “End Paper” tab.
Example Solution Maps
Question: How many
centimeters (cm) are in 72 miles?
Note: Important conversion factors
are on the PDF “End Paper” tab.
Unit Conversions
Things to Remember• Always write every number with its associated unit
• Identify your starting point (given unit) and devise a solution map towards what you must find (desired unit)
• Check sig figs last when doing your calculations
• Determine if your answer makes sense
Practice
Ex: How many hours are in 4.5 years?
Practice
Ex: Convert 5.89 x 107 µg to kg
Unit Conversions
What do I do when a unit conversion is raised to a power?• You must also raise the conversion factor to that power.
Unit Conversions
Question: How many cubic feet (ft3) are in 4102 cubic centimeters (cm3)?
Solution Map Solution
Density
What is Density?A ratio of an objects mass to its volume
How is it calculated?Density =_mass_ D = M Volume V
Density is…
…Thus density can be used as a conversion factor!
Density
Ex: Using density as a conversion factor
The density of aluminum is 2.70 g/mL. What is the volume in liters of 256 g of an aluminum sample?
Temperature (Kelvin vs. Celsius)
Kelvin: SI base unit of temperature. 0 K = Absolute zero all particles (atoms) no longer have energy (heat).
Changing between Kelvin & Celsius temperatureKelvin Celsius = Kelvin Temp – 273 = Celsius Temp
Celsius Kelvin = Celsius Temp + 273 = Kelvin Temp
Lesson Summary
• Rate your understanding of the lesson (1-4)
• Think about your learning concerning the following points What types of math computations were discussed in the
chapter and why are they important?
How do solution maps and carrying units help you arrive to a correct answer when doing unit conversions?