CHMG-141: General & Analytical Chemistry I 8/29 in-class Group members: Piece #1: Complete the following conversion problem: 777 mi 2 5280 ft = 777 mi mi = 4.1026 10 6 mi ft 1 mi = 2.166 10 10 ft 2 5280 ft 1 mi Piece #2 My back yard is 50 feet wide x 60 feet long. What is its area in square feet? 50 ft 60 ft = 3000 ft 2 = 3.0 10 3 ft 2 (correct sig figs) Piece #3 My back yard is 50 feet wide x 60 feet long. There are 12 inches in 1 foot. What is its area in square inches? 3000 ft ft 12 in 12 in 1 ft 1 ft = 4.32x105 in 2 = 4.3x10 5 in 2
Piece #4 My back yard is 50 feet wide x 60 feet long. There are 12 inches in 1 foot. There are 2.54 cm in 1 inch. What is its area in square centimeters? 4.32x10 5 2.54 cm 2 in 1 in 2.54 cm 1 in = 2.787x10 6 cm 2 = 2.8x10 6 cm 2 Piece #5 My back yard is 50 feet wide x 60 feet long. I dig up my entire back yard to a depth of 8 inches. What is the volume of the hole in cubic centimeters? V = A h 2.54 cm 8 in = 20.32 cm = 2 1 in 0.32 cm V = 2.787x10 6 cm 2 (2 0.32 cm) = 5.66x10 7 cm 3 = 6x10 7 cm 3 Piece #6 My back yard is 50 feet wide x 60 feet long. I dig up my entire back yard to a depth of 8 inches. What volume of water (cm 3 ) would be required to fill the hole? Volume of water = Volume of hole 6x10 7 cm 3
Piece #7 1 L = 1.057 qts. 1 L is 1000 ml. A ml is a cm 3. There are 2 pints in a quart. There are 4 quarts in a gallon. How many cm 3 are in 1 pint? 1 pint 1 qt 1 L 2 pint 1.057 qt 1000 ml 1 cm 3 1 L 1 ml = 473 cm3 5x10 2 cm 3 Piece #8 I put 1.00 pints of water on a balance and find that it weighs 458.8 grams. What is the density of water in units of g/cm 3? 458.8 g 1 pint 1 pint 473 cm g = 0.968 3 cm 3 Piece #9 My back yard is 50 feet wide x 60 feet long. I dig up my entire back yard to a depth of 8 inches. What mass of water (in grams) would be required to fill the hole? 5. 66 x10 7 0.968 g 3 cm cm 3 = 5.48x10 7 g 5x10 7 g
Puzzle #1: A sheet of aluminum (Al) foil has a total area of 1.000 ft 2 and a mass of 423.6 g. What is the thickness of the foil in micrometers? Density of Al = 2.699 g/cm 3 [Please write your answer in proper scientific notation with the correct number of significant figures.] 423.6 g 1 cm3 1 in 1 in 1 in 1 ft 1 ft 1 ft 2.699 g 2.54 cm 2.54 cm 2.54 cm 12 in 12 in 12 in = 0.005542 53ft 3 5.543 10 3 ft V = Ah 0.005542 53 ft 3 = (1.000 ft 2 )h h = 0.005542 53 ft 3 (1.000 ft 2 ) h = 0.005542 53 ft = 0.005543 ft = 5.543x10 3 ft 12 in 2.54 cm 1 ft 1 in 1 m 100 cm 1 μm 10 6 m = 1689μm
Significant Figures in Calculations: 1) Multiplication and Division: The number of significant figures of a result is equal to the smallest number of significant figures in any factor or divisor. 2) Addition & Subtraction: Values must be converted to common units before adding or subtracting (that includes powers of ten). The result has the precision of the least precise value in the calculation. 3) In multi-step calculations retain all figures in your calculator until the end, then use order of operations to determine the significant figures for the result. 4) Conversion factors always have less uncertainty than data.
Piece #1 How many significant figures in a measurement of 2. feet? ONE Piece #2 There are EXACTLY 12 inches in 1 foot. How many significant figures are in the conversion factor? 12 inches 1 foot INFINITE Piece #3 Using scientific notation and the correct number of significant figures, how many inches are in 2. feet? 2 ft 12 in 1 ft = 24 in 2 101 in (1 sig fig)
Piece #4 I measure a patio brick and find that it is 2. feet long. What is the range of possible values (in feet) for the actual length of the brick? 2 ft +/- 0.5 ft Piece #5 I put 3 patio bricks (2 feet long each) next to each other with no gap in between them. What is the range of possible values for the total length of the 3 bricks (in feet)? 6 ft +/- 1.5 ft Piece #6 What is the range of possible values, in inches, for each patio brick? 2x10 1 inches +/- 5 inches Piece #7 What is the range of possible values, in inches, for the 3 patio bricks? 6x10 1 inches +/- 15 inches
Latin Prefixes Prefix Factor n (nano) 10-9 μ (micro) 10-6 m (milli) 10-3 c (centi) 10-2 d (deci) 10-1 k (kilo) 10 3 M (Mega) 10 6 G (Giga) 10 9