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Chemistry 11 Ch 2.3 notes Name: __________________ Blk: ______ Date: ________ Ch 2.3: Derived Quantities & Metric Conversions Derived Quantities A derived quantity is a number made by combining two or more other values. A derived unit is a unit which is made by combining two or more units. A derived quantity is usually found in formulas as a variable. Steps to Solve for Derived Quantities: 1. Rearrange equation as in math. 2. The units that remain in the final answer are combined as the derived unit. Examples: 1) Density a) What is density? How do you measure density? b) What is the density of water at 4oC? 2) A rock has a mass of 0.2 kg and a volume of 400 mL. a) What is the density of the rock? b) Density is usually measured in grams per millilitre. What is its density in g/mL? 3) Express 6g/L into kg/mL Convert g --> kg & Convert L --> mL 4) Convert 3.00 g/cm2 into kg/m2 Practice Problems: 1. At 25oC, hydrogen molecules travel at an average speed of 1.77 x 103 m/s. Express this speed in kilometers per hour. 2. Convert a velocity of 60.0 miles per hour to kilometers per hour. (1 mile = 5280 ft, 1 ft = 12 in, 1 in = 2.54 cm) 3. Convert a tire pressure of 30.0 lb/in2 to kilograms per square centimeter. (1kg = 2.205 lb) 4. Convert 7.00 kg/cm3 into kg/m3 Challenge: 5. The equation for gas law is PV = nRT, where P = Pressure, V = Volume, n = mol, R = Gas constant and T = Temperature in Kelvin (273 K = 0 ºC). Given P = 1atm, V = 22.4L, n = 1mol, and T = 273K, subsitite the numbers for the variables and solve for R, the gas constant and its derived unit. 6. Find the derived value and unit for the kinetic energy (KE) of hydrogen gas at 0oC, using the equation KE = ½ mv2, where m = 3.35 x 10-27 kg and v = 1692 m/s. Assignment: Hebden p. 26 #31-37, 39 2