Transcript Slide 1
Measurement and Units • Seven Fundamental SI Units of Measurement. Physical Quantity Mass Length Temperature Amount of substance Time Electric current Luminous intensity Name of Unit kilogram meter kelvin mole second ampere candela Abbreviation kg m K mol s A cd 1 Measurement and Units 2 Measurement and Units • Some Prefixes for Multiples of SI Units. Factor 1,000,000,000 = 109 1,000,000 = 106 1,000 = 103 100 = 102 10 = 101 0.1 = 10-1 0.01 = 10-2 0.001 = 10-3 0.000,001 = 10-6 0.000,000,001 = 10-9 0.000,000,000,001 = 10-12 Prefix giga mega kilo hecto deka deci centi milli micro nano pico Symbol G M k h da d c m µ n p 3 Measurement and Units 4 Measurement and Units • Some Derived Quantities. Quantity Definition Derived Unit (Name) Area Volume Density Speed Acceleration Force Pressure Energy Length times length Area times length Mass per unit volume Distance per unit time Change in speed per unit time Mass times acceleration Force per unit area Force times distance m2 m3 kg/m3 m/s m/s2 (kg·m)/s2 (newton, N) kg/(m·s2) (pascal, Pa) (kg·m2)/s2 (joule, J) 5 Measurement and Units • Density relates the mass of an object to its volume. • Density decreases as a substance is heated because the substance’s volume increases. • Knowing the density of a substance allows measurements in volume to be recorded in mass. 6 Measurement and Units 7 Measurement and Units • Densities of Some Common Materials. Substance Ice (0.0°C) Water (4.0°C) Density (g/cm3) 0.917 1.0000 Substance Human Fat Cork Density (g/cm3) 0.94 0.22–0.26 Gold Helium (25.0°C) Air (25.0°C) 19.31 0.000164 0.001185 Table Sugar Balsa Wood Earth 1.59 0.12 5.54 8 Measurement and Units • What is the density of glass (in grams per cubic centimeter) if a sample weighing 26.43 g has a volume of 12.40 cm3? • Chloroform, a substance once used as an anesthetic, has a density of 1.483 g/mL at 20°C. How many mL would you use if you needed 9.37 g? 9 Measurement and Units 10 Measurement and Units • Temperature Conversions: • The Kelvin and Celsius degree are essentially the same because both are one hundredth of the interval between freezing and boiling points of water. 11 Measurement and Units • Temperature Conversions: • Celsius (°C) — Kelvin temperature conversion: Kelvin (K) = °C + 273.15 • Fahrenheit (°F) — Celsius temperature conversions: 5 C (F 32) 9 9 F C 32 5 12 Measurement and Units • Carry out the indicated temperature conversions: (a) –78°C = ? K (b) 158°C = ? °F (c) 375 K = ? °C (d) 98.6°F = ? °C (e) 98.6°F = ? K 13 English System of Units Volume: Gallon (gal) = 4 quarts (qt) = 8 pints (pt) = 128 fluid ounces (fl oz) Length: Mile (mi) = 1760 yards (yd) = 5280 feet (ft) = 63360 inches (in) Mass: 1 ton = 2000 pounds (lb) = 32000 ounces (oz) 14 Measurement and Units • Dimensional-Analysis method uses a conversion factor to express the relationship between units. Original Quantity ´ ConversionFactor = Equivalent Quantity Example: Express 2.50 kg in lb. ConversionFactor: 1.00 kg = 2.205 lb arranged as 2.205 lb 1.00 kg \ 2.50 kg ´ 2.205 lb = 6.00 lb (correct to 3 significant figures) 1.00 kg 15 Common Conversion Factors 2.54 cm = 1 in 454 g = 1 lb 0.946 L = 1 qt 1 mL = 1 cm3 = 1 g water 16 Ball Park Conversion Factors 1 m ~ 1 yd 1 L ~ 1 qt 1 kg ~ 2 lb 17 Conversion Factors 18 Conversion Factors 19 Conversion Factors • The volcanic explosion that destroyed Krakatau on August 17, 1883, released an estimated 4.3 cubic miles (mi3) of debris into the atmosphere. In SI units, how many cubic meters (m3) were released? 20 Conversion Factors • How many meters are there in a marathon race (26 miles and 385 yd)? • How large, in cubic centimeters, is the volume of a red blood cell if the cell has a circular shape with a diameter of 6.0 x 10–6 m and a height of 2.0 x 10–6 m? 21 Interesting Conversion Problem 22 Interesting Conversion Problem 23 Interesting Conversion Problem 24 Interesting Conversion Problem • A test rat weighs 512 g • The rat begins to eat Bayer Aspirin tablets 1 at a time. • How many tablets (on average) will have been consumed when the rat dies? 25