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UNITS OF MEASUREMENT

Chapter 2 : Section 2. UNITS OF MEASUREMENT. Objectives. Distinguish between a quantity, a unit, and a measurement standard Name SI units for length, mass, time, volume, and density Distinguish between mass and weight Perform density calculations

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UNITS OF MEASUREMENT

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  1. Chapter 2 : Section 2 UNITS OF MEASUREMENT

  2. Objectives • Distinguish between a quantity, a unit, and a measurement standard • Name SI units for length, mass, time, volume, and density • Distinguish between mass and weight • Perform density calculations • Transform a statement of equality to a conversion factor

  3. Units of measurement • Units – compare what is measured with defined size • mL g feet • Quantity – magnitude, size, or amount • 5 2,000,000 0.030o • Quantity has no meaning without the unit • 5 mL 100 g 2,000,000 feet

  4. SI Measurement • Le Systeme International d’Unites • Adopted 1960 as world-wide agreed upon standards • Base units

  5. Some SI Base Units • Mass – measure of the amount of matter in an object • Grams (g) • Electronic scale or triple beam balance • Volume – amount of space an object takes up • Liters L • V = L X W X H (cm3) • Graduated cylinder • Water displacement Visual Concept 1 – Click Here Visual Concept 2 – Click Here • Weight – measure of the gravitational pull on matter • Example : Moon has 1/6 weight

  6. Metric Prefixes • Tera- T 1012 1 000 000 000 000 • Giga- G 109 1 000 000 000 • Mega- M 106 1 000 000 • kilo- k 103 1000 • hecto- h 102 100 • deka- da 10 10 • - - - - • deci- d 10-1 0.1 • centi- c 10-2 0.01 • milli- m 10-3 0.001 • micro- u (mu) 10-6 0.000 001 • nano- n 10-9 0.000 000 001 • pico- p 10-12 0.000 000 000 001

  7. Derived SI units • Combination of SI base units • Examples • Area m2 L x W • Volume m3 L x W x H • Density Kg/m2 mass/volume • Molar mass Kg/mol mass/mole Speed : 2 measurements distance divided by time

  8. Volume and Density • Volume = Length x Width x Height • 1 cm x 1 cm x 1 cm = 1 cm3 • Density = mass / Volume • Sample Problem 2-1 • A sample of aluminum metal has a mass of 8.4 g. The volume of the sample is 3.1 cm3. Calculate the density of aluminum. Step 1: m 8.4 g D = = Step 4: = 2.7 g/cm3 Write density equation 3.1 cm3 V Replace variables in the equation D = ? Step 2: m = 8.4 g Step 5: List your variables Solve V = 3.1 cm3 Step 3: Rearrange the equation

  9. Rearranging Equations m D = V Solve for m: m x D = V V x V Step 1: Multiply both sides by V Step 3: Step 2: Rewrite the equation = D x V so: m V’s will cancel out leaving m by itself and on top m Solve for V: D = V Step 3: Step 1: m Rewrite the equation Multiply both sides by V x D = V V x V Step 2: m D = V x Divide both side by D D D m = V so: D

  10. Practice pg.40 #1-3 • What is the density of a block of marble that occupies 310. cm3 and has a mass of 853 g? • Diamond has a density of 3.26 g/cm3. What is the mass of a diamond that has a volume of 0.351 cm3? • What is the volume of a sample of liquid mercury that has a mass of 76.2 g, given that the density of mercury is 13.6 g/mL? 2.75 g/cm3 1.14 g 5.60 mL

  11. Density of Some Common SubstancesSubstanceDensity(g/cm3) • Air 0.0013 • Feathers 0.0025 • Wood(Oak) 0.6 - 0.9 • Ice  0.92  • Water  1.00 • Bricks  1.84 • Aluminum  2.70 • Steel  7.80 • Silver  10.50 • Gold  19.30 

  12. Conversion Factors • Ratio derived from the equality between two different units that can be used to convert from one unit to the other Visual Concept – Click Here • Equalities • 1 dollar = 4 quarters • 1 kg = 1000 g • 1 Km = 0.6213 miles • 1 dollar4 quarters • 4 quarter or 1 dollar So: How many quarter are there in $55 ? = 4 quarters 55 dollars x 220 quarters = 1 dollars

  13. Video Concept – Click Here Making conversions • How many miles are in 15 Km? • Write given value: • Choose conversion factor • Multiply top and divide bottom 1 km 11.0 miles x = 17.7 km 0.6213 miles

  14. Sample Problem 2.2 Express a mass of 5.712 grams in milligrams and in kilograms. 1000 mg 5.172 g x 5172 mg = 1 g 1 kg 5.172 g x = 0.005172 kg 1000 g

  15. Practice 1 & 2 pg. 42 • Express a length of 16.45 m in centimeters and in kilometers. • Express a mass of 0.014 mg in grams. Answers: 1. 1645 cm, 0.01645 km 2. 0.000 014 g

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