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