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UNIT II.1 Unit Conversions

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II.1 Unit Conversions You MUST learn and use the unit conversion method (not your own method!) A CONVERSION FACTOR: is a fractional expression relating or connecting two different units.

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II.1 Unit Conversions Example 1: There are 60 seconds in 1 minute. In statement form, 1 min = 60 sec Conversion Factors: The conversion factor relates 2 units (minutes to seconds).

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**II.1 Unit Conversions Example 2: $1.44 per dozen eggs.**

Conversion Factors: Conversion factors do not change the VALUE of something, they just change the UNITS. To change the UNITS, multiply by the CONVERSION FACTOR.

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**II. 1 Unit Conversions THE UNIT CONVERSION METHOD:**

We need 3 important pieces of information: unknown amount and units initial amount and units conversion factor (relating the initial units to units of unknown)

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**II. 1 Unit Conversions Example 3: How many seconds are in 20 minutes? **

Unknown amount: Initial amount: Conversion factor: Solution ** ALWAYS include UNITS in your calculations!

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II.1 Unit Conversions Example 4: If a car can go 90km in 1 h, how far can the car go in 6.5 h? Unknown amount: Initial amount: Conversion factor: Solution

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II.1 Unit Conversions Example 5: If the price of gas is $1.10 per liter (l), how much will it cost to fill a 40 liter tank? Unknown amount: Initial amount: Conversion factor: Solution

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**II.1 Unit Conversions HOW TO PUT EVERYTHING TOGETHER**

The general form of a unit conversion calculation is: (Unknown amount) = ( Initial amount) x (Conversion factor)

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**II.1 Unit Conversions Example 6**

a. If mL of gold has a mass of 3.86 g, what is the mass of 5.00 mL of gold? Unknown amount: Initial amount: Conversion factor: Solution

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II.1 Unit Conversions *Important: Always ask yourself “which way do I have to write the conversion factor so that my units cancel properly?” b. If mL of gold has a mass of 3.86 g, what is the volume occupied by g of gold? Unknown amount: Initial amount: Conversion factor: Solution

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**II.1 Unit Conversions SUMMARY**

Identify unknown amount and its units (put on left side of = sign). Identify the initial amount and its units (put on right side of = sign). 3. Identify conversion factor. (Multiply initial amount by conversion factor in such a way that one of the units cancel. You want to be left with units of unknown amount!) 4. Complete the problem by multiplying and/or dividing amounts of RHS.

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Assignment

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**II.1 Unit Conversions Multiple Unit Conversions **

We can solve problems that require more than one conversion factor. Example: If eggs are $1.44 per dozen, and if there are 12 eggs in a dozen, how many individual eggs can be bought for $4.32? ANALYZE THE PROBLEM: Unknown amount: Initial amount: Conversion factors:

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**II.1 Unit Conversions Solution: we require the connection**

conversion factor 1 gives the connection: conversion factor 2 gives the connection: Combining conversion factors 1 and 2 gives:

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**II.1 Unit Conversions Solve for unknown amount: Unknown amount =**

Initial amount x Conversion factors (1 and 2)

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Assignment

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