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Chapter 2 : Section 2. Objectives  Distinguish between a quantity, a unit, and a measurement standard  Name SI units for length, mass, time, volume,

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Presentation on theme: "Chapter 2 : Section 2. Objectives  Distinguish between a quantity, a unit, and a measurement standard  Name SI units for length, mass, time, volume,"— Presentation transcript:

1 Chapter 2 : Section 2

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  Quantity – magnitude, size, or amount  5 2,000, o  Units – compare what is measured with defined size  mL g feet  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 (cm 3 )  Graduated cylinder  Water displacement  Weight – measure of the gravitational pull on matter  Example : Moon has 1/6 weight Visual Concept 1 – Click HereVisual Concept 2 – Click Here

6 Metric Prefixes  Tera- T  Giga- G  Mega- M  kilo- k  hecto- h  deka- da   deci- d  centi- c  milli- m  micro- u (mu)  nano- n  pico- p

7 Derived SI units  Combination of SI base units  Examples  Aream 2 L x W  Volumem 3 L x W x H  DensityKg/m 2 mass/volume  Molar massKg/molmass/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 cm 3  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 cm 3. Calculate the density of aluminum. Write density equation Step 1: D V = m List your variables Step 2: D V m = = = ? 8.4 g 3.1 cm 3 Replace variables in the equation Step 3: 8.4 g 3.1 cm 3 = Rearrange the equation Step 4: Solve Step 5: 2.7 g/cm 3 =

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

10 Practice pg.40 # What is the density of a block of marble that occupies 310. cm 3 and has a mass of 853 g? 2. Diamond has a density of 3.26 g/cm 3. What is the mass of a diamond that has a volume of cm 3 ? 3. 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? 1.14 g 2.75 g/cm mL

11 Density of Some Common Substances Substance Density (g/cm 3 )  Air  Feathers  Wood(Oak)  Ice 0.92  Water 1.00  Bricks 1.84  Aluminum 2.70  Steel 7.80  Silver  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  Equalities  1 dollar = 4 quarters  1 kg = 1000 g  1 Km = miles 1 dollar4 quarters 4 quarter or1 dollar Visual Concept – Click Here = So: How many quarter are there in $55 ? 55 dollarsx 1 dollars 4 quarters = 220 quarters

13 Making conversions  How many miles are in 15 Km? 1. Write given value: 2. Choose conversion factor 3. Multiply top and divide bottom 11.0 miles x miles 1 km = 17.7 km Video Concept – Click Here

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

15 Practice 1 & 2 pg Express a length of m in centimeters and in kilometers. 2. Express a mass of mg in grams cm, km g Answers:


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