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Do now

Do now. 1) Round these numbers 19870 to 2 sig figs 0.00598 to 1 SF 2) What would the units be for the following problem 12 g / 3 ml = 4 ??? 3) Put .002104 into scientific notation. Period 4 Test:. This upcoming Wednesday! I am here after school on Tuesday…. Sci. Notation ‘Quiz’.

griffin-townsend
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Do now

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  1. Do now • 1) Round these numbers • 19870 to 2 sig figs • 0.00598 to 1 SF • 2) What would the units be for the following problem • 12 g / 3 ml = 4 ??? • 3) Put .002104 into scientific notation

  2. Period 4 Test: • This upcoming Wednesday! • I am here after school on Tuesday…

  3. Sci. Notation ‘Quiz’

  4. Conversions! • Lets start easy • 2 minutes seconds… • 3 yards  feet • 24 inches  feet • How did you do all these?

  5. Conversion Factors • When converting from one unit to another you use a conversion factor: • 12 in/foot • 24 inches  feet • 24 in / (12 inches/foot)  2 feet • 2 minutes  seconds • 2 minutes x 60 seconds/minute  120 seconds

  6. Its all about units! • You first need to figure out what conversion factor your going to use • Then how you will use it so that your desired units are left and everything else cancels out: • 24 inches  feet • Conversion factor: 12 inches/foot • Multiply or divide?

  7. 12 inches/foot • We want inches to cancel out to get feet… • For that to happen, we need to divide • 24 inches / (12 inches/foot)keep change flip • 24 inches x 1ft/12 inches • 24 ft / 12 • 2 ft

  8. How to Determine if you need to multiply or divide • If the unit you want to cancel out is on the bottom of the CF, multiply • ( a * b/a = b) • If the unit you want to cancel out is on the top, divide • ( a / [a/b] = b)

  9. Converting Prefixes • Often we will have to convert g to mg, or kg, or ml to l and vice versa. • In order to do so we need to look at the values of the prefixes (Ref. Table C)

  10. Conversion • To convert a measurement from one metric unit to another, you must know the difference in magnitude between the two prefixes and use that difference to create a conversion factor which will look like:

  11. How do you figure that out? • You can simply look to Table C of the RT’s to determine magnitude diff. • If there is no prefix then the power of ten is 100

  12. What is the conversion factor for m to km? • No prefix is 100 • k is 103 • Difference is 3 powers of 10 (=1000) • 1000 m/km or 1000 km/m? • The smaller one always gets the number • 1000 m/km

  13. cg  mg • 10-2 and 10-3 • Difference of 1 power of ten (10) • Which is smaller? • 10 mg/cg

  14. mm  km • 10-3 and 103 • Difference of 6 powers of ten (1,000,000) • Which is smaller? • 1,000,000 mm/km

  15. OK, then what? • Going to use the conversion factor (either multiplying or dividing depending on the need) • Example: 2km is how many meters? • Conversion factor: 1000 m/km • Need km to cancel out, and its on the bottom of the CF so we…. • 2 km x 1000 m/km = 2000 m

  16. What if it was the other way? • Converting 2000 m to km • Conversion factor 1000 m/km • Want m to cancel out and is on top of the CF so we… • 2000m / (1000m/km) = 2 km

  17. Convert 20.0 mm to m • mm = 10-3 m = 100 • 3 powers of ten different = 1000 • 1000 mm/m • 20.0 mm / (1000mm/m) = 0.0200 m

  18. How many mm are there in 120 km? • mm= 10-3 km= 103 • Difference of 6 powers of ten • 1000000 mm/km • 120 km x 1000000 mm/km = 120000000 mm • Or 1.2 x 108 mm

  19. Dimensional Analysis simplified 1) Determine the Conversion Factor via looking at table c • Remember; the smaller unit gets the number 2) Determine if you need to multiply or divide • If the unit you want to cancel out is on the bottom of the CF, multiply ( a * b/a = b) • If the unit you want to cancel out is on the top, divide ( a / [a/b] = b) 3) Solve, making sure you have the correct Sig Figs in your final answer

  20. Work on Conversion Homework (p 24-25) • I will be wandering around helping, raise a hand if you have a question/want me to check what you’ve done so far

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