Chemistry – Sept 2, 2016  P3 Challenge –  1. How many sig figs do each of these contain?  A) 1.2 x 10 8 B) 4700 C)  2. Perform the following operations and round to the proper number of sigfigs.  A) m x 23.5 m  B) m – 23.5 m  Get out Metric Conversions Homework for check

Objectives and Agenda  Objectives  To perform unit conversions using the factor label method (dimensional analysis)  Agenda  The Factor Label Method  One step conversions  Multi-step conversions  Metric – English conversions  Ratio conversions  Square conversions

Metric WS Ans  1. a) 1.20 cm  b) L  C) kg  D) m 2  E) 970 m  F) 1,580,000  G)  H) 6200 μs  2. a) 5.48 x nm  B) 13 L  C) 3.17 x m 2  D) 1.92 x 10 6 mm 2  E) 7.79 μm  3. a) 6.51 m  B) 7,835 g

Metric WS Ans  4. a) 2.77 m  B) 620 m  C) 3,857,000 mg  D) 3.40 x 10 2 L or 340. g  E)2.3 x L or L  F) x 10 4 km or 12,750 km  G) mL  H) 3.4 x 10 2 ms or 340 ms  I) 3 x 10 2 Mm or 300 Mm  J) 3.6 μL  K) kg  L) 8.06 x mm  M) m 2

Today’s Assignment  What’s Due? (Pending assignments to complete.)  Complete the Factor Label Conversions Worksheet  What’s Next? (How to prepare for the next day)  Read the Lab Report Format posted online

Unit Conversions (Factor-Label method) 1. Write the measured value with its unit. (Given) 2. Draw the multiplication symbol and a division line. 3. Copy the unit to the bottom of the conversion factor to cancel. “Times sign, draw a line, copy the unit” 4. Write the target unit on the top of the conversion factor. 5. Find an equivalence using these two units and complete the conversion factor. 6. Multiply and cancel units. (Multiply by tops, divide by bottoms) 7. Report value with the target unit. (Use correct sigfigs)

Unit Conversions (Factor-Label method)  “Times sign, draw the line, copy the unit.”  Variations on the theme  Multistep conversions  Metric to English conversions  Squared unit conversions  Ratio unit conversions

Multistep conversions  “Times sign, draw the line, copy the unit.”  If you do not know of the equivalence between the measured unit, and the target unit, consider a third unit that has an equivalence with both.  Ex: convert 4.75 miles to inches (remember sigfgs) mile footinch 4.75 miles miles1 = inches foot1 feet inches = inches = 3.01 x 10 5 inches

Metric to English conversions  You need to know at least one conversion between English and metric for each type of quantity.  Length: 1 inch = 2.54 cm (this is one to memorize)  Mass: 1.0 pound = 454 g  Volume: 1 quart = L  Ex: Convert 25.0 miles to km.

Squared unit conversions  If a unit is raised to a power, often 2 or 3, to perform a conversion, you must raise the entire conversion factor to that power.  Convert 22 cm 2 to in 2 22 cm 2 cm in = 3.4 in 2 2

Ratio unit conversions  Many derived units involve ratios of units. Mi/h, km/hr, m/s 2 …  If a unit on the bottom needs to be converted, “copy the unit” to the top.  Ex: Convert 25 m/s to km/h meter km min m1000 = 90. km/hr min1 km s 60 1 s hr s1 25 m hr1 min 60

Exit Slip - Homework  (Use the factor label method to convert 25 km/h to m/s. )(No time due to shorted Friday special event schedule.)  What’s Due? (Pending assignments to complete.)  Complete the Factor Label Conversions Worksheet  Justify answers on the Metric Conversion Worksheet as needed.  What’s Next? (How to prepare for the next day)  Read the Lab Report Format posted online