I didn't have a clue what the instructor was talking about, but on the test questions he gave only the exact information needed, and if I set up everything so the units cancelled, I always got the right answer.
While I'm not advocating being ignorant of chemistry, I think you get my point: This is a powerful technique. Cancelling units also known as "unit analysis" or "dimensional analysis" is based on the principal that multiplying something by " 1 " doesn't change the value, and that any value divided by the same value equals " 1 ". Page 1 Page 2. All right reserved.
Web Design by. Skip to main content. Cancelling or Converting Units Process Examples. Purplemath To convert between units, you're usually given one measure and asked to convert to another measure. In these simple scenarios, all you have to do to convert is remember a fairly simple rule: going to smaller units means going to bigger numbers, so multiply going to bigger units means going to smaller numbers, so divide.
Content Continues Below. Then: Answer: 12 quarts. Answer: 4. Looking in the back of my textbook which is frequently a handy resource, along with the endpages of many dictionaries , I find the following conversion factors among the many listed: 60 seconds : 1 minute 60 minutes : 1 hour 1 mile : feet 1 foot : 12 inches 2.
Share This Page. Terms of Use Privacy Contact. Say we buy some tangerines: I buy 6 and you buy 2. What have we bought together? Not merely 8, but 8 tangerines. Tangerines are our units. Units indicate what the numeral 8 represents. Here's a more complicated example. Since the two quotients are equal to 1, multiplying or dividing by the quotients is the same as multiplying or dividing by 1. It does not change the equation, only the relative numerical values within the various units.
You can also use these quotients to convert from inches to feet or from feet to inches. For example, how many inches are in 5 feet? If there is confusion regarding which quotient to use in the conversion, just make sure the units cancel out correctly. In the first equation, the unit feet is in both the numerator and denominator of the expression, so they cancel. The units behave just like numbers in products and quotients—they can be multiplied and divided.
Then use this number in the equation to get 1. The equation is set up correctly because all the units cancel out to give moles. Privacy Policy.
Skip to main content. Introduction to Chemistry. Search for:. Dimensional Analysis Converting from One Unit to Another Converting units using dimensional analysis makes working with large and small measurements more convenient.
Learning Objectives Describe the purpose of unit analysis. Key Takeaways Key Points Dimensional analysis is the process of converting between units. The International System of Units SI specifies a set of seven base units from which all other units of measurement are formed.
Derived units are based on those seven base units. Dimensional analysis involves using conversion factors, which are ratios of related physical quantities expressed in the desired units.
Key Terms dimensional analysis : A method of converting from one unit to another. It is also sometimes called unit conversion. Example 1 For example, say you were trying to convert 3.
Step F is the unit cancellation step. The gram unit from the top or numerator of the fraction is canceled from the bottom or denominator leaving only the kilogram unit. Dividing by yields the final answer in step G. The final answer is: There are 1. Be sure to watch for exact numbers and significant figures. Rounding errors or other inaccuracies can make the difference between a right or wrong answer! Finally, check your conversion to make sure it makes sense. You know a gram is a smaller unit than a kilogram, so if you do the conversion between them the wrong way, you'll wind up with a ludicrous value.
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