Lesson Objectives

• Review how measurements are made in science

• Convert between different units using the Unit Factor Method

​What is a measurement?

• A measurement represents the quantity of an object

  • Written as a number + a unit

    • The unit depends on what is being measured

      • 1 meter

      • 10 kilograms

    • Any value can be a unit, which can lead to confusion

​SI Measurement

• Le Systeme International d'Unites

  • ​A global system of measurement agreed on by scientists that was approved in 1960

  • Has Seven Base Units

  • Also defines a standard way of writing numbers

    • Example: Seventy-five Thousand is written 75 000 and not 75,000

• ​The seven base units in SI Measurement

  • While we use Kelvin temperatures much later, for now we will stick with Celsius beca​use thats what our probes read

  • In chemistry, most of the mass we will work with is in grams

• Converting to units within the SI System is easy, because everything increases or decreases by a factor of ten

  • 100 centimeters in a meter

  • 1000 meters in a kilometer​

​Converting between Units Using the Unit Factor Method

• The Unit Factor Method is a quick way to convert from one unit of measurement to another

  • Depends on the relationship between the two units​

  • You multiply or divide the unit you want to get rid of to cancel it out

  • can be used to go between SI Units as well as the English Standard Units

​Unit Factor Method Example Problem 1

• Convert 3598 grams into pounds.

  • Step one: Identify if there is a direct relationship between grams and pounds

​Unit Factor Method Example Problem 1

• Convert 3598 grams into pounds.

  • Step one: identify if there is a relationship between grams and pounds

    • Yes! 1000 grams = 2.205 lbs

  • We can write this as a ratio in two different ways, and multiply the amount we have by one of these ratios

​Unit Factor Method Example Problem 1

• Convert 3598 grams into pounds.

  • Step one: Identify if there is a relationship between grams and pounds

    • Yes! 1000 grams = 2.205 lbs

  • We can write this as a ratio in two different ways, and multiply the amount we have by one of these ratios

    • We want to cancel out our original unit, so we use the ratio with that unit on the bottom

​Unit Factor Method Example Problem 2

• Convert 50.0 mL to liters

  • Step one: identify if there is a relationship between mL and L

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​Unit Factor Method Example Problem 2

• Convert 50.0 mL to liters

  • Step one: Identify if there is a relationship between mL and L

    • Yes! 1000 ml = 1 L

  • Step 2:Set up your equation so that the ratio will cancel out the unit you are starting with

​Unit Factor Method Example Problem 3

• How many seconds are in 2.0 years?

  • Step one: Identify if there is a direct relationship between seconds and years.

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​Unit Factor Method Example Problem 3

• How many seconds are in 2.0 years?.

  • Step one: identify if there is a direct relationship between seconds and years?

    • no

  • Step 2: Find an indirect relationship

    • We know there are 52 weeks in a year, 7 days in a week, 24 hours in a day, and 3600 seconds in an hour

  • Step three: set up your math by drawing your ratio bars

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