Dimensional Analysis/Conversio
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Warm-up (9/24/15)
• Please put stow your bags and your electronic devices.
• Quietly read the directions and begin working on the warm-up problems you picked up on your way in.
How many seconds are in a year?
• Think about the question above. (1 minute)
• Brainstorm how you might solve this problem if all you have is a piece of paper, a pencil, and a calculator. Write down any ideas on the back of your warm-up.
• Talk to your partner and discuss your ideas. Try to solve the problem using the ideas you discussed (2-3 minutes)
• We will come back to this problem again at the end of this presentation.
What is Dimensional Analysis?
• The process used to convert a value from one unit/sets of units to another.
x x =
What is the point of learning dimensional analysis?
• Dimensional analysis is something that we do everyday, many times on a small scale without even realizing it.
• You want to buy a candy bar that is $1.25 but you only have quarters. How many quarters will you need to buy the candy bar?
• We will be doing a lot of dimensional analysis later on in the school year when we begin learning about stoichiometry. It is best to start slow and get a good understanding of the concepts now to make it easier for you later.
How to Solve a Dimensional Analysis Problem
• When reading a problem, you have to identify three things:1. What units am I starting with?2. What units do I need to end with?3. What conversion factors do I have to use to get from my starting point to my ending point?
• Conversion Factor = Fractions where the numerator and denominator are a given quantity expressed in different units. • 2.54 centimeters (cm) = 1 inch (in.)
• Can be written as =
Lets Try a Problem!
• If Tim is 6.00 feet tall, how tall is he in centimeters?
• What units am I starting with?• feet
• What units do I need to end with?• Centimeters
• What conversion factors will I use?
and
If Tim is 6.00 feet tall, how tall is he in centimeters?
• 6.00 feet x x = ?
• 6.00 feet x x = 183 centimeters
• Tim is 183 centimeters tall.
Let’s try one more…
• One gallon of milk is equal to how many milliliters of milk?
• What units am I starting with?• gallons
• What units do I need to end with?• milliliters
• What conversion factors will I use?
and and
One gallon of milk is equal to how many milliliters of milk?
• 1 gallon x x x = ?
• 1 gallon x x x = 3780mL (or 3.78x 103mL)
• One gallon of milk is 3.78x103mL
Lets go back to how many seconds are in a year.
• Now that we have tried some practice problems, look back at the initial problem.
• Reflect, was your method correct? If not, what do you need to change?
• Discuss with your partner the changes you would make if any, and solve the problem.
• Volunteer to come do the problem on the board?
After your notes, write 2-3 conversion factors of your own.
• Write 2 or 3 conversion factors that you can come up with that are not on your conversion sheet or something we already talked about today
• Be creative, there are so many options!
Lab Work Expectations
• Work quietly with your group (voices should be heard by group members, but not across the room)
• Work at the lab station you are assigned until directed to move to the next station. You will have 6 minutes at each lab station.
• Allow an opportunity for every group member to participate
• Stay on task (you should be working on/discussing the assignment at hand)
• Raise your hand if you have a question and wait patiently until I can get to your station
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