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1 Major divisions of Chemistry General Inorganic Elements besides Carbon Analytical Methods of analysis Physical Theory and concepts Organic Carbon based compounds Biochemistry Chemistry of living things 2 Chapter 1: Measurement Units of Measurement Conversion Calculations Density 3 Measurements in chemistry See Handout Sheet of Units of Measurements 4 Units of Measurement Metric SI Common Conversions Length meter (m) 1 m = 1.09 yd Volume Mass liter (L) 1 L = 1.06 qt gram (g) 1 kg = 2.2 lb 5 Matter =The stuff things are made of. (Air, water, rocks, etc..) Matter has Mass and takes up space. =The amount of stuff (in g’s) (Bowling Ball > Balloon) Weight on earth. =Pull of Gravity on matter. 6 Mass Vs. Weight How much would you weigh on another planet? http://www.exploratorium.edu/ronh/weight/ 7 Scientific notation If a number is larger than 1 • Move decimal point X places left to get a number between 1 and 10. 1 2 3 , 0 0 0 , 0 0 0. = 1.23 x 108 •The resulting number is multiplied by 10X. 8 Scientific notation If a number is smaller than 1 • Move decimal point X places right to get a number between 1 and 10. 0. 0 0 0 0 0 0 1 2 3 = 1.23 x 10-7 •The resulting number is multiplied by 10-X. 9 Examples Write in Scientific Notation: 25 = 8931.5 = 0.000593 = 0.0000004 = 3,210. = 2.5 10 1 8.9315 10 3 5.93 10 - 4 4 10 - 7 3.210 103 Do not press this on your calculator! 10 Scientific notation 1.44939 × 10-2 = 1.44939E -2 0.0144939 On Calculator ×10 1.44939 EE (-) 2 Means ×10 Change Sign 11 Measured & Exact Numbers Exact Numbers = from counting or by definition 12 coins per package 12 coins 1 package = 1 package 12 coins 12 coins 1 dozen coins = 1 dozen coins 12 coins 12 Measured & Exact Numbers Measured Numbers = estimated using a tool All measurements contain some uncertainty. • We make errors • Tools have limits 1 2 3 4 5 6 7 8 9 cm 13 Accuracy How close are we to the true value? Truth Precision How well do our values agree? Consistency 14 Significant figures Length of object is between 6.7 and 6.8 The next digit would be a guess. 1 2 3 4 5 6 7 8 9 cm If use 6.76 then have error of + 0.01cm 15 Metric prefixes Changing the prefix alters the size of a unit. Prefix Symbol Factor (multiple) mega M 106 1,000,000 kilo k 103 1,000 100 1 deci d 10-1 0.1 centi c 10-2 0.01 milli m 10-3 0.001 16 Problem Solving Using Conversion Factors Many problems require a change of one unit to another unit by using conversion factors (fractions). unit1 × conversion factor = unit2 17 How many feet are there in 22.5 inches? The conversion factor must unit factor = unit2 accomplish two things: 1 × conversion inches × conversion factor = feet It must cancel inches. It must introduce feet 18 The conversion factor takes a fractional form. ft in = ft in 19 Putting in the measured value and the ratio of feet to inches produces: 1ft 22.5in = ft 12in = 1.875 ft = 1.88 ft 20 Convert 3.7×1015 in to miles. Inches can be converted to miles by writing down conversion factors in succession. in ft miles 3.7 10 in 15 1 mile 1 ft 10 x x = 5.8 10 miles 5280 ft 12 in 21 Convert 4.51030 cm to kilometers. Centimeters can be converted to kilometers by writing down conversion factors in succession. cm m km 1 km 1m 25 x 4.5 10 cm x = 4.5 10 km 100 cm 1000 m 30 22 Conversion of units Examples: 10.7 T = ? fl oz 62.04 mi = ? in 5 kg = ? mg 9.3 ft = ? cm 5.7 g/ml = ? lbs/qt 23 Conversion of units Examples: 10.7 T = ? fl oz 1 fl oz 10.7 T x = 5.35 fl oz 2T 62.04 mi x 62.04 mi = ? in 5.5 kg = ? mg 9.3 ft = ? cm 5280 ft 12 in x = 3.931106 in 1 mi 1 ft or 3931000 in 5.5 kg x 9.3 ft 5.7 g/ml = ? lbs/qt x 1000 g 1000 mg x = 5.5 106 mg 1 kg 1g 12 in 2.54 cm x = 280 in (not 280.) 1 ft 1 in 12 lb 1 lb 1L 5.7 g 1000 ml x x x 1.06 qt 1 qt 1 ml 454 g 1L 24 Density = Density Mass Volume 1cc = 1 cm3 = 1 ml = 1 g water g cm3 or Water 1.0 Air 0.0013 Gold 19.3 g ml Urine Bone Oil o At 4 C 1.01 - 1.03 1.7 - 2.0 0.8 - 0.9 25 Density calculation What is the density of 5.00 ml of serum if it has a mass of 5.230 g? d =m V V =m d d = 5.230 g 5.00 ml m=Vd = 1.05 g ml 26 Specific gravity density of substance g Specific Gravity = ml density of reference g ml Reference commonly water at 4oC •Specific Gravity is unitless. •At 4oC, density = specific gravity. 27 Specific gravity Hydrometer •Commonly used to test sugar in urine. •Float height will be based on Specific Gravity. 28 Density as a Conversion A liquid sample with a density of 1.09 g/mL is found to weigh 7.453 grams. What is the volume of the liquid in mLs? • Identify any conversion factors. • What is unique to the problem? 7.453 g 1.0 ml = 6.837614 ml = 6.84 ml 1.09 g •How should the answer look? 1.09 g 1 ml 1 ml 1.09 g 29