# Systems and Conversion Procedures Objectives

Chapter 3 Measurement Systems and Conversion Procedures Objectives ▪ ▪ ▪ ▪ Interpret the systems of measurement Simplify units using dimensional analysis Perform metric system conversions Perform conversions between metric and nonmetric systems © 2010 Delmar, Cengage Learning. 2 Objectives (cont’d.) ▪ Perform conversions between apothecary and household systems ▪ Perform temperature conversions between Celsius, Fahrenheit and Kelvin © 2010 Delmar, Cengage Learning. 3 Systems of Measurement ▪ United States Customary System of Measurement: • Distance: – 1 ft = 12 in – 1 yd = 3 ft – 1 mi = 5280 ft • Volume: – 8 fl oz = 1 cup – 1 pt = 2 cups – 1 qt = 2 pt – 4 qt = 1 gal © 2010 Delmar, Cengage Learning. 4 Systems of Measurement (cont’d.) ▪ Metric system: • m → meter → Length • l or L → liter → Volume • g → gram → Weight – 0.91 m = 1 yd – 3.79 L = 1 gal – 28.3 g = 1 oz © 2010 Delmar, Cengage Learning. 5 Systems of Measurement (cont’d.) Table 3.1 Metric Prefixes and Values © 2010 Delmar, Cengage Learning. 6 Basic Dimensional Analysis ▪ Algebraically changing or converting units of measure • . • . • Grams per liter © 2010 Delmar, Cengage Learning. 7 Conversions Within the Metric Systems ▪ Horizontal format: 1. Identify decimal location in the number being converted 2. Identify prefix location on horizontal diagram 3. Find the difference between the two exponents associated with each prefix © 2010 Delmar, Cengage Learning. 8 Conversions Within the Metric Systems (cont’d.) ▪ Horizontal format: 4. Conversion is moving right on the diagram: – Move decimal to the right by the amount calculated in step 3 5. Conversion is moving left on the diagram: – Move the decimal to the left by the amount calculated in step 3 Figure 3.1 Horizontal format for metric prefixes and values © 2010 Delmar, Cengage Learning. 9 Conversions Within the Metric Systems (cont’d.) ▪ Horizontal format: (cont’d.) • Convert 12 mL to microliters – Identify decimal: 12.0 – Identify prefixes in diagram – Difference is -3 –(-6) = 3 – 12 mL = 12,000 μL © 2010 Delmar, Cengage Learning. 10 Conversions Within the Metric Systems (cont’d.) ▪ Dimensional analysis: • 1 will always be placed with two-letter unit ▪ Convert: 12μL to mL • . © 2010 Delmar, Cengage Learning. 11 Conversions Between Metric and Nonmetric Table 3.2 Relationships between the U.S. System and the Metric System © 2010 Delmar, Cengage Learning. 12 Conversions Between Metric and Nonmetric (cont’d.) ▪ Convert 5 kg to oz: • Convert kg to lbs • Convert lbs to oz © 2010 Delmar, Cengage Learning. 13 Apothecary Systems ▪ Apothecary equivalents: • • • • • • • • 1 fl oz = 8 fl dr 4 mL = 1 fl dr 60 minims = 1 fl dr 1 g = 15 gr 1 gr = 60 mg 1 mL = 16 minims 1 pt = 16 fl oz 1 qt = 2 pt © 2010 Delmar, Cengage Learning. 14 Apothecary Systems (cont’d.) ▪ 50mg is how many grains? • . © 2010 Delmar, Cengage Learning. 15 Apothecary Systems (cont’d.) ▪ 250 fl dr equals how many milliliters? • . © 2010 Delmar, Cengage Learning. 16 Household Systems ▪ Household equivalents: • • • • • • • • 60 drops (gtt) = 1 tsp 1 fl oz = 30 mL 2 tbs = 1 oz 6 fl oz = 1 teacup 8 fl oz = 1 glass 16 oz = 1 lb 1 cup = 8 fl oz 5 mL = 1 tsp © 2010 Delmar, Cengage Learning. 17 Household Systems (cont’d.) ▪ You drank 3 ½ glasses of water • How many ounces did you consume? • . © 2010 Delmar, Cengage Learning. 18 Household Systems (cont’d.) ▪ How many tablespoons are in 12oz? • . © 2010 Delmar, Cengage Learning. 19 Household, Apothecary, and Metric Equivalents © 2010 Delmar, Cengage Learning. 20 Temperature Conversions ▪ Three scales to measure temperature: • Fahrenheit • Celsius • Kelvin ▪ Converting Celsius to Fahrenheit: • . or © 2010 Delmar, Cengage Learning. 21 Temperature Conversions (cont’d.) ▪ 0°C equals how many °F? • °F = (0° × 1.8) + 32°= 0° + 32° = 32° ▪ 75°F equals how many °C? • . © 2010 Delmar, Cengage Learning. 22 Temperature Conversions (cont’d.) ▪ Converting Celsius to Kelvin: • K = °C + 273.15 • 100°C K = 100° + 273.15° = 373.15° • Converting Kelvin to Fahrenheit: • °F = 1.8K − 459.67° • 300K °F = 1.8(300°) − 459.67° = 80.33° © 2010 Delmar, Cengage Learning. 23 Summary ▪ To perform metric conversions, we must be familiar with Table 3.1 ▪ Conversions within the metric system can be done using the horizontal format ▪ Apothecary system: used in calculating drug dosages ▪ Household system: used when administering medications in the home © 2010 Delmar, Cengage Learning. 24 Summary (cont’d.) ▪ The three main temperature formulas: © 2010 Delmar, Cengage Learning. 25 Chapter 4 Dilutions, Solutions, and Concentrations Objectives ▪ ▪ ▪ ▪ Perform dilutions Determine concentrations Solve dilution problems Solve problems involving percents © 2010 Delmar, Cengage Learning. 2 Dilutions ▪ It is common to dilute solutions with water or saline • Formula relating the two volumes and two concentrations: ▪ When preparing solutions: • One is constantly mixing a concentrated solution (concentrate) with a solvent (diluent) – Decreases concentration © 2010 Delmar, Cengage Learning. 3 Dilutions (cont’d.) ▪ Parts concentrate + parts diluent = total volume • Solution contains 1 μL serum and 6 μL saline – Ratio 1:6 – Ratio of serum to total volume would be 1:7 – Ratio of saline to total volume would be 6:7 – Dilutions represent parts of concentrate in total volume (1:7) © 2010 Delmar, Cengage Learning. 4 Dilutions (cont’d.) ▪ Make a 1 in 9 dilution of insulin in water • Total volume must be 225 mL ▪ What volume of insulin is needed? • Cross multiplying gives: 9x = 225 • x = 25 • 25 μL insulin is needed © 2010 Delmar, Cengage Learning. 5 Dilutions (cont’d.) ▪ What volume of diluent is needed? • From the first part, we need 25 mL insulin – Insulin + diluent = total volume – 25 + x = 225 – Subtracting 25 from both sides: x = 200 – 200 mL diluent is needed © 2010 Delmar, Cengage Learning. 6 Concentrations ▪ Amount of a substance in a given volume • Original concentration × dilution = final concentration • Find the final concentration if a saline solution consisting of 10% NaCl is diluted using a 1/8 dilution –. © 2010 Delmar, Cengage Learning. 7 Concentrations (cont’d.) ▪ Find the final concentration: • A saline solution consisting of 50% dextrose is diluted using a 1/10 dilution • . © 2010 Delmar, Cengage Learning. 8 Concentrations and Volumes of Two Solutions ▪ When a solution is diluted: • Concentration of resulting solution will decrease • Formula used to find volumes and concentrations of original and resulting solutions: © 2010 Delmar, Cengage Learning. 9 Concentrations and Volumes of Two Solutions (cont’d.) ▪ There are 12cc of a 2.5% solution • Solution added to water makes a total of 75cc • What is the concentration of the 75 cc solution? –. – 0.004 × 100% = .4% © 2010 Delmar, Cengage Learning. 10 Concentrations and Volumes of Two Solutions (cont’d.) © 2010 Delmar, Cengage Learning. 11 Percents ▪ A percent weight per unit weight, % w/w, is defined as: • . • Solute is the substance being dissolved © 2010 Delmar, Cengage Learning. 12 Percents (cont’d.) ▪ Make 150 grams of a 20% w/w NaCl solution • . x = 20g 100x = 3,000 x = 30 © 2010 Delmar, Cengage Learning. 13 Percents (cont’d.) ▪ A percent volume per unit volume, % v/v, is defined as: • . • 5% v/v solution means that 5% of the entire solution is the solute © 2010 Delmar, Cengage Learning. 14 Percents (cont’d.) ▪ Make 50 mL of a 60% v/v solution of hydrogen-peroxide in water • . • x = 60 x = 30 • 30 mL hydrogen-peroxide added to 20 mL water = 50-mL solution with a 60% v/v © 2010 Delmar, Cengage Learning. 15 Percents (cont’d.) ▪ How many milliliters of alcohol are in 40mL of a 60% v/v solution? • . 100x = 2,400 • x = 24 • There is 24mL alcohol in 40mL of a 60% v/v solution © 2010 Delmar, Cengage Learning. 16 Percents (cont’d.) ▪ A percent weight per unit volume, % w/v, is defined as: • That is, 5% w/v means that a 100-mL solution would contain 5g solute © 2010 Delmar, Cengage Learning. 17 Percents (cont’d.) ▪ How would you make 350mL of a 12% w/v morphine solution? • . x = 12 100x = 4,200 x = 42 © 2010 Delmar, Cengage Learning. 18 Percents (cont’d.) ▪ How would you make 200mL of a 70% w/v lidocaine solution? • . x = 70 100x = 14,000 x = 140 © 2010 Delmar, Cengage Learning. 19 Percents (cont’d.) ▪ How many grams of NaCl are in 25mL of a 0.9% w/v NaCl solution? • A 0.9% w/v NaCl solution is called a normal saline solution • . 100x = 22.5 x = .225 © 2010 Delmar, Cengage Learning. 20 Percents (cont’d.) ▪ How many grams of NaOH (sodium hydroxide) are in 6dL of a 20% w/v NaOH solution? • Convert dL to milliliters: • . 100x = 12,000 x = 120 © 2010 Delmar, Cengage Learning. 21 Percents (cont’d.) ▪ A 500-cc solution contains 50g Tylenol • What is the percentage of Tylenol? • . 500x = 5,000 x = 10 © 2010 Delmar, Cengage Learning. 22 Summary ▪ Parts concentrate + parts diluent = total volume • Dilutions represent parts of concentrate in total volume • Original concentration × dilution = final concentration • Dilution factor is the reciprocal of dilution © 2010 Delmar, Cengage Learning. 23 Summary (cont’d.) ▪ When a concentration and volume of a solution change as a result of adding a diluent: • Used to find volume and concentration of original and resulting solutions ▪ Percent weight per unit weight, % w/w: © 2010 Delmar, Cengage Learning. 24 Summary (cont’d.) ▪ A percent weight per unit volume, % w/v: ▪ A percent volume per unit volume, % v/v: © 2010 Delmar, Cengage Learning. 25

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