Catalyst 10/12/10 Knowing what you know about precision, answer the following questions: Of the numbers 1100 cm vs. 1100.0 cm Which is more precise? How precise is each number? Why would you choose one or the other number? Objectives: Identify and convert between units of the SI System. Determine the number of significant figures in numbers.

Agenda 10/12/10 Catalyst (5) Quick Review of Procedures and behavior (10) SI System notes & guided practice (15) Significant figures notes and guided practice (15) Homework: Conversion worksheet & bring calculator tomorrow

New Procedures: Catalysts Catalysts will have a grade for answers and the stamp which will be given for silently working on catalyst 2 minutes after the bell Stampers who stamp students who are not working silently lose their points and will not stamp again You my make up the catalyst question, but not the stamp-except for verified excused absences Excused absences can be verified by having parents sign and put phone number in catalyst for the day

New Procedures: Behavior Every warning/reminder/incidence of inappropriate behavior loses 1 point (up to 5 per day) Every unexcused or unverified absence loses all points Every tardy loses 2 points for the day

SI: Base Units length meter m mass kilogram kg time second s Physical Quantity Unit Name Symbol length meter m mass kilogram kg time second s temperature Kelvin K

SI: Derived Units area square meter m2 volume cubic meter m3 speed Physical Quantity Unit Name Symbol area square meter m2 volume cubic meter m3 speed meter per second m/s weight, force newton N pressure pascal Pa energy, work joule J

Unit Conversions “Staircase” Factor-Label Method Type Visual Mathematical What to do… Move decimal point the same number of places as steps between unit prefixes Multiply measurement by conversion factor, a fraction that relates the original unit and the desired unit When to use… Converting between different prefixes between kilo and milli Converting between SI and non-SI units Converting between different prefixes beyond kilo and milli

1 x 10 = 10 10 X 10 = 100 10 x 100 = 1,000 The Metric System is based on sets of 10. 1 x 10 = 10 10 X 10 = 100 10 x 100 = 1,000

The mnemonic: Memorize this! Kids Have Dropped over Dead Converting Metrics.

“Staircase” Method Draw and label this staircase every time you need to use this method, or until you can do the conversions from memory

You must also know… …how to convert within the Metric System. Here’s a good device: On your paper draw a line and add 7 tick marks:

Next: Above the tick marks write the abbreviations for the King Henry pneumonic: k h d o d c m m l g Write the units in the middle under the “o”.

Let’s add the meter line: k h d o d c m km hm dam m dm cm mm L g

Let’s add the liter line: k h d o d c m km hm dam m dm cm mm kL hL daL L dL cL mL g Deca can also be dk or da

Let’s add the gram line: k h d o d c m km hm dam m dm cm mm kl hl dal l dl cl ml kg hg dag g dg cg mg

How to use this device: Look at the problem. Look at the unit that has a number. On the device put your pencil on that unit. Move to new unit, counting jumps and noticing the direction of the jump. 3. Move decimal in original number the same # of spaces and in the same direction.

Example #1: Look at the problem. 56 cm = _____ mm Look at the unit that has a number. 56 cm On the device put your pencil on that unit. k h d u d c m km hm dam m dm cm mm

Example #1: Move to new unit, counting jumps and noticing the direction of the jump! k h d u d c m km hm dam m dm cm mm One jump to the right!

Example #1: Move decimal in original number the same # of spaces and in the same direction. 56 cm = _____ mm 56.0. One jump to the right! Move decimal one jump to the right. Add a zero as a placeholder.

Example #1: 56 cm = _____ mm 56cm = 560 mm

Example #2: Look at the problem. 7.25 L = ____ kL Look at the unit that has a number. 7.25 L On the device put your pencil on that unit. k h d u d c m kl hl dal L dl cl ml

Example #2: Move to new unit, counting jumps and noticing the direction of the jump! k h d u d c m kl hl dal L dl cl ml Three jumps to the left!

.007.25 Example #2: Move decimal to the left three jumps. (3) Move decimal in original number the same # of spaces and in the same direction. 7.25 L = ____ kL .007.25 Three jumps to the left! Move decimal to the left three jumps. Add two zeros as placeholders.

Example #2: 7.25 L = ____ kL 7.25 L = .00725 kL

Example #3: Try this problem on your own: 45,000 g = ____mg k h d u d c m kg hg dag g dg cg mg

45,000.000. Example #3: Three jumps to the right! k h d u d c m kg hg dag g dg cg mg Three jumps to the right! 45,000.000.

Example #3: 45,000 g = 45,000,000 mg Three jumps to the right!

Example #4: Try this problem on your own: 5 cm = ____ km k h d u d c m km hm dam m dm cm mm

.00005. Example #4: Five jumps to the left! k h d u d c m km hm dam m dm cm mm Five jumps to the left! .00005.

Example #4: 5 cm = .00005 km Five jumps to the left!

Factor-Label Method Multiply original measurement by a conversion factor A fraction that relates the original unit and the desired unit. Conversion factor is always equal to 1. Numerator and denominator should be equal measurements. When a measurement is multiplied by a conversion factor, original units should cancel

Factor-Label Method: Example Convert 6.5 km to m First, we need to find a conversion factor that relates km and m. We should know that 1 km and 1000 m are equivalent (there are 1000 m in 1 km) We start with km, so km needs to cancel when we multiply. So, km needs to be in the denominator

Factor-Label Method: Example Multiply original measurement by conversion factor and cancel units.

Factor-Label Method: Example Convert 3.5 hours to seconds If we don’t know how many seconds are in an hour, we’ll need more than one conversion factor in this problem

Examples #5-9: Solve these problems one by one on your whiteboard using one of the methods described. (5) 35 mm = ____ cm (6) 14,443 L = ____ kL (7) 0.00056 kg = ____ g (8)35.4 L = ____ mL (9)16 mm = ____ km

Counting Significant Figures The Digits Digits That Count Example # Sig Figs Non-zero digits ALL 4.337 4 Leading zeros (zeros at the BEGINNING) NONE 0.00065 2 Captive zeros (zeros BETWEEN digits) 1.000023 7 Trailing zeros (zeros at the END) IF they follow a digit AND there is a decimal point 89.00 but 8900

Calculating With Sig Figs Type of Problem Example MULTIPLICATION OR DIVISION: Find the number that has the fewest sig figs. That's how many sig figs should be in your answer. 3.35 x 4.669 mL = 15.571115 mL rounded to 15.6 mL 3.35 has only 3 Significant figures, So that's how many should be in the answer. Round it off to 15.6 mL

Calculating With Sig Figs ADDITION OR SUBTRACTION: Find the number that has the fewest digits to the right of the decimal point. The answer must contain no more digits to the RIGHT of the decimal point. 64.25 cm + 5.333 cm = 69.583 cm rounded to 69.58 cm 64.25 has only two digits to the right of the decimal. Drop the last digit so the answer is 69.58 cm.

Practice Problems Determine how many significant figures are in each of these numbers and problems 2.03 0.0224 + 1.54 0.00471 - .003 10.00 * 2.0 5000000 / 10.000 1.078509700