Chapter 1Lecture Notes PowerPoint Presentationby

Alberto A. Alvarez, Jr.MSIP Grant No. P120A80073-98 U.S. Department of Education1

ObjectivesUnits of Measure Length Mass Volume Temperature Density Significant Figures Scientific Notation Rounding Off Dimensional AnalysisWow, this is a heavy load for only one chapter!!!

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Key TermsChemistry is the study of matter, its composition, structure, and changes in its composition. Matter is anything that has mass and occupies space. Mass is the amount of matter in a material.3

The amount of space occupied by a material is called its volume. An amount or quantity is identified by number and a unit of measure. 14.2 cm 75 ft. 0.62 kg 6.39 sec

A unit of measure is a word that names a physical quantity of a defined size. meter pound inch centigram4

Length is a measure of the distance between two points.

Length is measured with a ruler.

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deci = 1/10decimeter = 1/10 of a meter

centi = 1/100centimeter = 1/100 of a meter

milli = 1/1000millimeter = 1/1000 of a meter

kilo = 1000kilometer = 1000 meters6

The basic unit of length in the English system is the foot foot. The basic unit of length in the metric system is the meter meter. 1 meter = 3.281 feet7

A conversion factor is a numerical relationship between two units of measure of the same type (dimension).1 lb. = 16 oz. 1 ft. = 12 in. 1 hr. = 60 min.

Length Conversion Factors1 ft. = 12 in. 1 yd. = 3 ft. 1 mi. = 5280 ft. 1 in. = 2.54 cm 1 m = 10 dm 1 m = 100 cm 1 m = 1000 mm 1000 m = 1 km8

A conversion problem is a calculation whereby one unit of measure is changed to another unit of the same dimension.

Example 1 7.82 ft. = in.

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Example 2The distance from the earth to the sun is 93,000,000 miles. How many yards is this?

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Factor label is a procedure for solving conversion problems.Write down the given data. Multiply by a fraction which has the given unit in the denominator and the unit asked for in the numerator, provided that you know the conversion factor between the two units. If you do not know the conversion factor, change to another unit and repeat step 2. Place the numbers in the fractions and do the arithmetic.

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Example 3 Express the quantity 4.53 x 10-5 km as centimeters.

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Significant FiguresSignificant figures are the digits that are calibrated on a measuring instrument. Rules for Determining Significant Figures 1. Nonzero digits are always significant. 2. Captive zeros, zeros between two nonzero digits, are significant. 3. Leading zeros, zeros that precede all the nonzero are not significant. always digits

4. Trailing zeros, zeros that are at the right end of a number, (a) are not significant (b) unless the number contains a decimal point in which case they are significant. 5. Exact numbers are assumed to have an infinite number of significant figures.13

Example 4Identify the number of significant figures in each measurement. 378.285 m 90380 L 0.03805 mi. 783.00 g 78300 cm314

Operations with Significant FiguresFor multiplication or division the number of significant figures in the result is the same as the number that has the least number of significant figures.

For addition and subtraction the result has the same number of decimal places as the least precise measurement in the calculation.15

Example 6Record the answers to the following calculations to the correct number of significant figures. 78.58353 - 3.298 + 123.3335 - 2.17

196.9(0.0033)/8.30898

0.0035826(173.353 + 0.3538 + 2.78)16

Significant FiguresExact NumbersNumbers from definitions or numbers of objects are considered to have an infinite number of significant figures

The average of three measured lengths; 6.64, 6.68 and 6.70? 6.64 + 6.68 + 6.70 = 6.67333 = 6.67 = 7 3 Because 3 is an exact number McGraw-Hill Permission17

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Exact Numbers conversion factors should never limit the number of significant figures reported in answer 12 inches = 1 foot

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Rules for Rounding Off1. Identify the significant figures that you are to round off to. 2. Write down all leading zeros, if any. 3a.If the next digit to the significant figures is less write down the significant figures. than five,

b.If the next digit is 5 or more, add one the significant figures and write that down. 4. Other digits that are to the left of the decimal point must be recorded as zeros. 5. Other digits that are to the right of the decimal point are dropped (not recorded).19

Example 5Round off the following numbers as indicated. Round off to 3 & 2 significant figures. 1.) 7825.3826

2.) 0.0037748

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Scientific NotationA number is in scientific notation if it is written in the form:

M x 10n

Where M is a number between 1 and 10 and n is an integer. 725,000 0.00029

= =21

Rules for Writing Scientific Notation1. Identify the significant figures and write them down. 2. Write the decimal point between the first two digits. 3. Write X 10. 4. Determine the exponent by counting the number of places the decimal was moved.A.) If the number is greater than 1, the exponent is positive. B.) If the number is less than 1, the exponent is negative. C.) If the decimal point is not moved, the exponent is zero.22

Example 7Record the following in scientific notation to the correct number of significant figures. 48.5(168.292)(0.022) 16.92(0.03962)-5

=

(5.82 + 10.00042)

= =23

(4.20 x 10-2)(0.0003338) 5972.3

Mass is the quantity of matter in a material. Mass is measured balance. with a balance24

The basic unit of mass in the English system is the pound pound. The basic unit of mass in the metric system gram. is the gramThe gram is the amount of matter in one cubic centimeter (cm3) of water at 4 oC.1 cm 1 cm 1 cm

1 cm3 water =

1 gram25

Mass Conversion Factors 1 lb. = 16 oz. 2000 lb. = 1 ton 1 lb. = 453.6 g 1 g = 1000 mg 1000 g = 1 kg26

Examples8. If you weigh 164 lb., what is your weight in kilograms?164 lb. = ? kg

9. How many grams make an ounce?1 oz. = ? g

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Volume is a measure of the space a material occupies.Liquid volume is measured directly with a container (pipette, burette, cylinder, volumetric flask, etc). Solid volume is calculated by water displacement or with a formula based on linear dimensions.28

The basic unit of liquid volume in the English system is the quart quart. The basic unit of liquid volume in the metric system is the liter liter. For a solid, the unit of volume is a cubic unit of distance, such as cubic centimeters (cm3), cubic feet (ft3), etc.1 cm 1 in. 1 ft.

1 cm3

1 in.3

1 ft.3

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A liter is the amount of liquid that occupies a container one cubic decimeter in capacity.

1 liter liquid 1 dm3

1 dm

1 dm 1dm30

Volume Conversion Factors

1 qt. = 2 pt. 4 qt. = 1 gal. 1.057 qt. = 1 L 1 L = 1000 mL 1 dm3 = 1 L 3 1 mL = 1 cm

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Example 10 72.5 L = pt.

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Example 11How many liters are in a cubic foot? 1 ft.3 = L

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Volume FormulasRectangular Solid V = lwh Cylinderr h34

Cube V = l3w

h l

l

V = 4Tr3/3

V = Tr2h

Sphere

r

Example 12The length of a chemistry book is 10.25 in. What is its volume, in cm3, if the book is 8.25 inches wide and 1.75 inches thick?

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Example 13The diameter of a baseball is 7.50 cm. What is its volume?

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The density of a material is the ratio (quotient) between its mass and volume.

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Example 14What is the density of a liquid if 45.8 mL of the liquid weigh 40.0 grams?

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Example 15What is the mass of a metal sample if it displaces the water in a cylinder from 50.7 mL to 64.4 mL? The density of the metal is 2.70 g/mL.

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Example 16What is the density of a rectangular piece of wood whose mass is 108.95 g, if it is 12.5 cm long, 7.1 cm wide, and 2.7 cm thick?

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Percentage error is a ratio used to indicate the accuracy of the measurements made by a person.

== accepted value = observed value41

Lab errors that are less than 5% are acceptable for this course. A large percentage error indicates inaccurate measurements. A small percentage error indicates accurate measurements.42

Example 17The density of aluminum is 2.70 g/cc. If a student determines that the density of an aluminum sample is 2.61 g/cc, what is his percentage error?

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Temperature is that property of matter that determines whether heat can be transferred from one body to another.

Temperature ScalesFahrenheit Celsius Kelvin

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The Three Major Temperature Scales

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Example 18The temperature in Lisbon, Portugal is often 17 oC at about noon. What is this temperature in oF?

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Example 19Normal body temperature for a human is considered to be 98.6 oF. What is this temperature in oC?

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Accuracy how close a measurement is to the true value Precision how close a set of measurements are to each other

accurate & precise

precise but not accurate McGraw-Hill Permission

not accurate & not precise48

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Practice Exercise Answers: www.southtexascollege.edu/business/faculty/ecortez

Dr. Cortez Permission49