With a partner, try to complete the following conversions of our wonderful (??) English measurement system: 1760 1 mile = ____________ yards 3 1 yard = ____________ feet 36 1 yard = ____________ inches 12 1 foot = ____________ inches 16 1 pound = ____________ ounces 8 1 cup = ____________ ounces 16 1 cup = ____________ tablespoons 3 1 tablespoon = ____________ teaspoons 32 Water freezes at ____________°F 212 Water boils at ____________°F With a partner, try to complete the following conversions of the metric (SI) system: 1000 1 km= ____________ m 100 1 m= ____________ cm 10 1 cm= ____________ mm 1000 1 kg= ____________ g 1000 1 L= ____________ mL 1 1 mL= ____________ cm3 0 Water freezes at ____________°C 100 Water boils at ____________°C English vs. Metric • Which of the two systems of measurement were the easiest to use? • Why don’t you think that the United States hasn’t switched to the metric system like much of the rest of the world? The Standard Metric Units • The metric system is also referred to as the “International System” of units or SI (Standard International) Units • The standard units of measurement that are used in the metric system are: • • • • For length: meter (m) For mass: kilogram (kg) For time: seconds (s) For temperature: kelvin (K) • Add 273.15 ° to °C to get K Prefix multipliers • The SI system uses prefix multipliers with the standard units of measurement (m,kg,s) • These multipliers change the value of the unit by a power of 10 (Table 2.2, p. 23) – i.e. kilo means 1000 or 103 so 1 kilometer = 1000 meters Prefix multipliers hecto h 100 102 deka da 10 101 Prefix Symbol Multiplier tera T G M K 1,000,000,000,000 1,000,000,000 1,000,000 1,000 Exponential Form 1012 109 106 103 m g s 1 100 d c m n p f 0.1 0.01 0.001 0.000001 0.000000001 0.000000000001 0.0000000000000 01 10-1 10-2 10-3 10-6 10-9 10-12 10-15 giga mega kilo Base: Meters Grams Seconds deci centi milli micro nano pico femto kilo 1000 units 103 hecto 100 units 102 deka 10 units 101 deci .1 units 10-1 centi .01 units 10-2 milli .001 units 10-3 24 grams Convert to kilograms: Move decimal 3 place to the left Or take 24g / 103 = .024 kg Convert to milligrams: Move decimal 3 place to the right Or take 24g x 103 = 24,000 mg Practice • Convert 2,156 g to the following units: – kg – Mg – mg – cg 2.156 kg 0.002156 Mg 2,156,000 mg 215,600 cg Derived Units • Volume: Units of length to the 3rd power become volume (cm3, m3) – length x width x height – water displacement • We will commonly use liters to measure volume • 1 mL = 1 cm3 • 1 L = 1000 mL = 1000 cm3 Derived Units • Density: the amount of “stuff” crammed into something (a ratio of its mass to volume) density = mass volume ***This formula can also help you figure out mass and volume when given the other values Volume/Density Practice • What is the volume of a cube that has a width of 2.5 cm? 15.6 cm3 – How many mL would that be? 15.6 mL • If the cube has a mass of 52.3 g, what is the cube’s density? d=m/v d = 52.3g / 15.6 cm3 = 3.35 g/cm3 • If a copper penny has a density of 8.92 g/mL and a mass of 2.81 g, what is it’s volume? V=m/d V = 2.81g / 8.92 g/mL = 0.315 mL