1. Measurements and Conversions.pdf

GENERAL CHEMISTRY CHEM 100 Chapter-1 Measurements and Conversions Prepared by Mrs. Munfis Patel @Mrs. Munfis 1  Learning Objectives At the end of t...

GENERAL CHEMISTRY CHEM 100 Chapter-1 Measurements and Conversions Prepared by Mrs. Munfis Patel @Mrs. Munfis 1  Learning Objectives At the end of the Chapter, students will be able to… *Identify the 7 fundamental units *Rewrite numbers in scientific notation, and vice versa *Convert between various SI units *Convert between non-SI unit *Use density as a conversion factor *Tie in with laboratory course *Use speed as a conversion factor 2 @Mrs. Munfis  Measurement and Units Units of measurement: Quantities with accepted values that can be communicated between people. “10 seconds” “12 centimeters” “47 milliliters” @Mrs. Munfis 3  Numbers Units are an important part of scientific language. Numbers should not be separated from units! Units Cannot be separated! @Mrs. Munfis 4  There are seven fundamental units. Most of the times in labs the unit for mass is used as “gram” which is a common unit; Technically, the corresponding SI units is “kilogram”. @Mrs. Munfis 5  Scientists have to represent very large … and very small Scientific measurements. measurements… notation Hydrothermal worm: 0.0005 meters Earth to the Sun: 149,600,000,000 meters A way to represent numbers of all sizes You will need a calculator today!! @Mrs. Munfis 6  All measurements come with two parts, Measurements numbers and units. There are seven fundamental units in chemistry. Fundamental Numbers units We use scientific notation to write very large and very small numbers. We can also use SI unit prefixes to Scientific SI unit indicate the size of a number. notation prefixes In order to convert between SI unit prefixes, we use ratios (fractions) of Ratios of units. units This technique is called dimensional analysis and it is essential for learning chemistry. Dimensional @Mrs. Munfis analysis 7  103 = 10 x 10 x 10 = 1,000. 102 = 10 x 10 = 100. 101 = 10 = 10. 100 = 1 = 1. 10-1 = = 0.1 10-2 = = 0.01 10-3 = = 0.001 @Mrs. Munfis 8  5.1 x 10 03 = 5100. 5.1 x 102 = 510. 5.1 x 101 = 51. 5.1 x 100 = 5.1 5.1 x 10- = 0.51 1 5.1 x 10- = 0.051 2 5.1 x 10- = 0.0051 3 @Mrs. Munfis 9  Going from Standard to Scientific Notation: 2,500,000. L = 2.5 x 106 L move 6 digits 137,000,000,000 J. = 1.37 x 1011 J move 11 digits 0.000000142 g = 1.42 x 10-7 g move 7 digits (right) 0.000326 cm = 3.26 x 10-4 cm move 4 digits (right) @Mrs. Munfis 10  Going from Scientific to Standard Notation: 1.528 x 105 kg 1.528 00 = 152,800 kg 1.64 x 107 L 1.64 00000 = 16,400,000 L 1.35 x 10-5 m 0000 1.35 = 0.0000135 m 8.28 x 10-3 g 00 8.28 = 0.00828 g @Mrs. Munfis 11  646823208126 Measurement? No. in scientific notation: rounded to three “places”: $21.99 200 g 0.01 g Measurement? Yes. Units: dollars Measurement Measurement ? Yes. ? Yes. in scientific notation: Units: grams Units: grams in scientific in scientific Practice notation: notation: problem Homework assignment: Find the biggest and the smallest numbers in your house. Are they measurements? If so, determine their units. Lastly, convert the number to scientific notation. @Mrs. Munfis 12  160,000,000 bits = 160 megabits 0.0000032 grams = 3.2 x 10-6 grams = 3.2 micrograms @Mrs. Munfis 13  Prefix (symbol) Value giga (G) 109 base unit of length: meter (m) mega (M) 106 1 kilometer (km) = 1000 meter (m) kilo (k) 103 1 centimeter (cm) = 0.01 meter (m) deci (d) 10-1 1 nanometer (nm) = 1×10-9 meter (m) centi (c) 10-2 milli (m) 10-3 base unit of mass: gram (g) micro (µ) 10-6 1 kilogram (kg) = 1000 gram (g) nano (n) 10-9 1 milligram (mg) = 0.001 gram (g) base unit of volume: liter (L) base unit of time: second (s) 1 milliliter (mL) = 0.001 liter (L) 60 seconds (s)= 1 minute (min) 1000 milliliter (mL) = 1 liter (L) 60 minutes (min) = 1 hour (h) 1 mL = 1 cc = 1cm3 @Mrs. Munfis 14  Steps to Problem Solving ❖ Read problem ❖ Identify data ❖ Write down a unit plan from the initial unit to the desired unit ❖ Select conversion factors ❖ Change initial unit to desired unit ❖ Cancel units and check ❖ Do math on calculator ❖ Give an answer using significant figures @Mrs. Munfis 15  Practice 1. A rattlesnake is 2.44 m long. How long is the snake in cm? 1) 2440 cm 2) 244 cm 3) 24.4 cm 2. How many seconds are in 1.4 day? What is wrong with the following setup? 1.4 day x 1 day x 60 min x 60 sec 24 hr 1 hr 1 min 1.4 day x 1 day x 60 min x 60 sec 24 hr 1 hr 1 min Units = day2/hr2 Not the final unit needed @Mrs. Munfis 16  1. How many meters are in a kilometer? 1 km = 1,000 m 2. How many A are in a MA? 1 MA = 1,000,000 A 3. How many mg are in a g? 1 g 1 mg = 1,000 1,000 mg = 1 g @Mrs. Munfis 17  Using Dimensional Analysis to convert metric prefixes A copper pellet has a mass of 231 mg. What is this mass in grams? Dimensional analysis 1000 mg = 1 g starting Conversion ending unit (mg) factor unit (g) Treat units like algebra and you can convert anything. @Mrs. Munfis 18  Note the unit cancellation: How many nanoseconds are in 2 hours? The only unit that doesn’t cancel is nanoseconds Practice this yourself: How many seconds have you been alive? Hint: Use four conversion factors @Mrs. Munfis 19  A hospital administers an IV fluid at a rate of 95.0 cm3 per hour. How many liters of this fluid does the patient receive per day? Volume Time 1 cm3 = 1 mL 24 hr = 1 day 1,000 mL = 1 L 1,000 cm3 = 1 L cm3 x 1L 24 hr L 95.0 x = 2.28 hr 1000 cm3 1 day day cm3 hours to liters to days @Mrs. Munfis 20  You can convert numerators and denominators. Convert one, then convert the other. The speed of light in a vacuum is 3.00 x 108 m/s. What is this speed in miles per hour? 1 mile = 1609.3 meters 1 hour = 3600 seconds 3600 s 1 mi = 6.71 x 108mi/h 3.00 x 108 m/s x x 1609.3 m 1 hr meters seconds to miles to hours @Mrs. Munfis 21  Density is a conversion factor you will use in lab mass density = volume Density converts mass ↔ volume m d= V Aluminum has a density of 2.70 g/mL. What is the mass of a block of aluminum with a volume of 1.32 L? An antifreeze mixture has a density of 1.06 g/mL. If you measure out 600 g of this solution, what volume will it occupy? @Mrs. Munfis 22  A gas fills a volume of 1200. mL and has a mass of 1.60 g. What is the density of the gas? m 1.60 g d= = 1200. mL = 0.00133 g/mL V A cube of pure silver has volume of 8.0 cm3. The density of silver is 10.5 g/cm3. What is the mass of the cube? V = 8.0 cm3 m m d= 10.5 g/cm3 = m = 84 g V 8.0 cm3 @Mrs. Munfis 23  Think-Pair share-Scientific Notation Find the biggest and the smallest numbers in your house or around you. Are they measurements? If so, determine their units. Lastly, convert the number to scientific notation. Kindly do not delete answers by others or the instructions and examples given by me. ------------------------------------------------------------------------------------------ 1 2 $21.99 Measurement? Yes, Unit: dollar in scientific notation 2.199 x 101 3 4 5 6 7 8 9 10