<p> Chapter 2 SCIENTIFIC MEASUREMENT Types of Measurement</p><p>1. Quantitative: Use numbers to describe. -Examples: 4 feet, 10 inches</p><p>2. Qualitative: Description without numbers -Examples: extra large, hot</p><p>Accuracy: How close the measurement is to the actual value</p><p>Precision: How well can the measurement be repeated</p><p>Percent Error </p><p>Error: Accepted Value – Experimental Value</p><p>Error can be positive or negative </p><p>Percent Error = (Error ÷ Accepted Value) x 100</p><p>Significant Figures</p><p>A measurement consists of all the digits known with certainty plus one final digit, which is somewhat uncertain or is estimated. </p><p>All digits including the uncertain one are significant.</p><p>Usually, the final digit is uncertain but significant.</p><p>Significant Figures Rules</p><p>Rule #1 All non zero digits are always significant. How many significant figures in each? 274 (3) 26.632 (5) 8.987 (4) Rule # 2 All zeros between significant digits are always significant</p><p>How many significant figures in the following? 504 (3) 60002 (5) 9.077 (4)</p><p>Rule # 3 All final zeros to the right of the decimal are significant.</p><p>How many significant figures in the following: 32.0 (3) 19.000 (5) 105.0020 (7)</p><p>Rule # 4 Zeros acting as place holders are not significant.</p><p>How many significant figures in the following? 0.0002 (1) 6.02 x 10 23 (3) 800 (1)</p><p>Rule # 5 All counting numbers and constants have an infinite number of significant figures.</p><p>How many significant figures in the following</p><p>458g (3) 4085g (4) 4850g (3) 0.0485g (3) 0.004085 g (4) 40.004085 g (8)</p><p>Adding and Subtracting When you add or subtract measurements, your answers must have the same number of decimal places as the one with the fewest.</p><p>Example: 27.93 + 6.4 Calculator Answer: 34.33 Final Answer: 34.3 Practice: 12.52 + 349.0 + 8.25 = 369.76 Final answer: 369.8</p><p>74.626 – 28.34 = 46.286 final answer: 46.29</p><p>Multiplication & Division Look at the total number of significant figures.</p><p>Your answer must have the same number of significant figures as the one with the fewest.</p><p>Example: 3.6 x 653 Calculator Answer: 2350.8 Final Answer: 2400 (2 significant figures)</p><p>Practice: 3.6 x 653 = 2350.8 Final answer: 2400 (2 significant figures)</p><p>2.10 x 0.70 = 1.47 Final answer: 1.5</p><p>2.4526 / 8.4 = 0.291976 Final answer: 0.29</p><p>Metric System</p><p>A decimal system</p><p>Based on units of 10</p><p>A metric unit has two parts a prefix & base</p><p>Prefix tells you how many times to divide or multiply by 10.</p><p>Base Units Length: meter (m) Mass: grams (g) Time: seconds (s) Temperature: Kelvin or °Celsius Volume: Liter (L) Energy: Joule (J) Amount of substance: mole (mol)</p><p>Volume Base unit is liters (L) Calculated by Length x Width x Height 1 L = 1000 cm3 1000 cm3= 1000 mL</p><p>Solving Problems Analyze the problem. Determine the known and unknown.</p><p>Calculate the unknown</p><p>Solve for the unknown using a conversion factor.</p><p>Conversion Factors 1. Allow you to convert units. 2. Are defined quantities so they have unlimited significant figures</p><p>Convert 25 mg to g Identify the known and unknown Known: 25 mg Unknown: ? g</p><p>Identify the conversion factor: 1g = 1000 mg Solving Problems Set up youryour problemproblem usingusing the conversion factor.</p><p>25 mg × 1 g = 0.025 g 1000 mg</p><p>Conversion Factor</p><p>Convert the 0.45 km to mm Identify the known and unknown Known: 0.45 km Unknown: ? mm</p><p>Identify the conversion factor 1 km = 1,000,000 mm Solving Problems Set up youryour problemproblem usingusing the conversion factor.</p><p>0.45 km × 1000,000 mm = 450mm 1 km Conversion Factor Convert 35 mL to L Identify the known and unknown Known: 35 mL Unknown: ? L</p><p>Identify the conversion factor 1 L = 1,000 mL Solving Problems Set up youryour problemproblem usingusing the conversion factor.</p><p>35 mL × 1 L = 0.035 L 1,000 mL Conversion Factor</p><p>Convert 12.0 in to cm Identify the known and unknown Known: 12.0 in Unknown: ? cm</p><p>Identify the conversion factor 1 in = 2.54 cm Solving Problems Set up youryour problemproblem usingusing the conversion factor.</p><p>12.0 in × 2.54 cm = 30.5 cm 1 in Conversion Factor</p><p>Convert 65.0 mi/h to m/s Identify known & unknown Known: 65.0 mi/h Unknown: ? m/s</p><p>Identify the conversion factor.</p><p>1 hr = 3600 s 1000 m = 0.6214 mi</p><p>65 mi × 1000 m × 1 hr hr 0.6214 mi 3600 s</p><p>= 29 m/s</p><p>Density How heavy something is for its size</p><p>The ratio of mass to volume for a substance It is independent of how much you have The units are usually g/L or g/ mL or g/cm3</p><p>Density Density Formula D = M V Density Triangle M D V</p><p>When you use the circle cover up the variable you are trying to find.</p><p>Horizontal line: divide Vertical line: multiply Calculating Density 1. A piece of wood has a mass of 11.2 g and a volume of 23 mL. What is the density?</p><p>D = M ÷ V</p><p>= 11.2 g / 23 mL</p><p>= 0.48869 g/mL Using the correct number of significant figures the final answer is 0.49 g/mL 2. A piece of wood has a density of 0.93 g/mL and a volume of 23 mL. What is its mass? M = D x V = 0.93 g/mL x 23 mL = 21.39 g Using the correct number of significant figures the final answer is 21 g</p><p>Temperature</p><p>Temperature: Which way heat will flow (from hot to cold).</p><p>Heat: Energy, ability to do work.</p><p>Scientists use the Kelvin scale to measure temperature.</p><p>Kelvin: °C + 273</p><p>The Kelvin scale starts at absolute zero (- 273 °C)</p>