Measurement and Chemistry Measurement is central to chemistry
- Slides: 21
Measurement and Chemistry
Measurement is central to chemistry n n Metric system: the set of units used for scientific measurements. SI Units: there are seven base SI units and all other units are derived from these.
Base Units of Measurement (SI UNITS: International System) Measurement Unit Name Mass Length Time Temperature Amount Kilogram Meter Second Kelvin Mole Abbreviation kg m s K mol
Length and Mass n n Note the SI unit for length is the meter (m) whereas the SI unit for mass is the kilogram (kg). 1 kg weighs 2. 2046 lb
Mass and weight Mass is the amount of “stuff” (matter) in a material. To measure use a balance. Weight is the amount of stuff measured by gravity. On earth mass and weight are the same. To measure use a scale.
Derived Units of Measurement Volume n n n The units for volume are given by (units of length)3. SI unit for volume is 1 m 3. We usually use a non-SI unit for volume: liter or milliliter 1 m. L = 1 cm 3. 1 L = 1 dm 3 = 1000 m. L.
Other Units of Measurement (Non-SI Units) Measurement Unit Name Pressure Abbreviation atmosphere millimeters of mercury pascal Temperature Celsius Energy calorie Joule atm mm Hg Pa C cal J
Unit Conversions
A. SI Prefix Conversions 1. Find the difference between the exponents of the two prefixes. 2. Move the decimal that many places. To the left or right?
A. SI Prefix Conversions 532 m NUMBER UNIT 0. 532 km = _______ = NUMBER UNIT
A. SI Prefix Conversions move right move left Prefix mega- Symbol M Factor 106 kilo- k 103 BASE UNIT --- 100 deci- d 10 -1 centi- c 10 -2 milli- m 10 -3 micro- 10 -6 nano- n 10 -9 pico- p 10 -12
A. SI Prefix Conversions 1) 20 cm = 0. 2 _______ m 2) 0. 032 L = _______ m. L 32 3) 45 m = 45, 000 _______ nm 4) 805 dm = _______ km 0. 0805
B. Dimensional Analysis n The “Factor-Label” Method n Units, or “labels” are canceled, or “factored” out
B. Dimensional Analysis n Steps: 1. Identify starting & ending units. 2. Line up conversion factors so units cancel. 3. Multiply all top numbers & divide by each bottom number. 4. Check units & answer.
B. Dimensional Analysis n Lining up conversion factors: 1 in = 2. 54 cm =1 2. 54 cm 1 in = 2. 54 cm 1= 1 in
B. Dimensional Analysis n How many milliliters are in 1. 00 quart of milk? qt m. L 1. 00 qt 1 L 1000 m. L 1. 057 qt 1 L = 946 m. L
B. Dimensional Analysis n You have 1. 5 pounds of gold. Find its volume in cm 3 if the density of gold is 19. 3 g/cm 3. lb cm 3 1. 5 lb 1 kg 1000 g 1 cm 3 2. 2 lb 1 kg = 35 19. 3 g cm 3
B. Dimensional Analysis n How many liters of water would fill a container that measures 75. 0 in 3? in 3 L 75. 0 in 3 (2. 54 cm)3 (1 in)3 1 L = 1. 23 1000 cm 3 L
B. Dimensional Analysis 5) Your European hairdresser wants to cut your hair 8. 0 cm shorter. How many inches will he be cutting off? cm in 8. 0 cm 1 in 2. 54 cm = 3. 2 in
B. Dimensional Analysis 6) Taft football needs 550 cm for a 1 st down. How many yards is this? cm 550 cm yd 1 in 1 ft 1 yd 2. 54 cm 12 in 3 ft = 6. 0 yd
B. Dimensional Analysis 7) A piece of wire is 1. 3 m long. How many 1. 5 -cm pieces can be cut from this wire? cm pieces 1. 3 m 100 cm 1 m 1 piece 1. 5 cm = 86 pieces
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