Honors Chemistry, Chapter 2 Page 1

 Evolution of a Gas (Bubbles, Odor)  Formation of a Precipitate (Formation of Cloudiness in a Clear Solution, Solids Collecting at the Bottom or Top)  Release of Energy (Heat, Light)  Color Change Honors Chemistry, Chapter 2 Page 2

 Observing and Collecting Data Qualitative (Bubbles Formed) Quantitative (1 gram/liter of catalyst speeded the reaction by 25%) Chemists Study Systems (Region Selected for Study)  Formulate Hypothesis Generalization about Data Testable Statement Honors Chemistry, Chapter 2 Page 3

 Testing Hypothesis (Experimentation) Supported, Retained Not Supported, Discarded, Modified  Theorizing – Create a Model Model: An Explanation of How Phenomena Occur and How Data or Events are Related.  Visual  Verbal  Mathematical Honors Chemistry, Chapter 2 Page 4

Honors Chemistry, Chapter 2 Page 5 JFHICW FH VHHVLBFND FL N ZGVHFIVLB, BTV NZZVNGNLPV CY JFHICW JFDD IC FL N PNLIFINBV. – VGFP HVRNGVFI.

(Wisdom is essential in a president, the appearance of wisdom will do in a candidate. – Eric Severeid) Honors Chemistry, Chapter 2 Page 6

1. What is the purpose of the scientific method? 2. Distinguish between qualitative and quantitative observations. 3. Describe the differences between hypothesis, theories, and models. Honors Chemistry, Chapter 2 Page 7

 Measurements Are Quantitative Information  Quantity: Something That Has Size or Amount Honors Chemistry, Chapter 2 Page 8

 SI Units Are Defined in Terms of Standards of Measurement  Seven Basic Units  All Others Derived From Seven Basic Units Honors Chemistry, Chapter 2 Page 9

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Honors Chemistry, Chapter 2 Page 13 Useful Conversion Factors 1000 ml = 1 L 1 cm 3 =1 ml 1000 g = 1 kg 1000 mg=1 g 1000  g=1 mg  g=1 g 1000 mmol=1 mol

m = 1 ___a) mm b) km c) dm g = 1 ___ a) mg b) kg c) dg L = 1 ___a) mL b) cL c) dL m = 1 ___ a) mm b) cm c) dm

 ? kilometer (km) = 500 meters (m)  2.5 meter (m) = ? centimeters (cm)  1 centimeter (cm) = ? millimeter (mm)  1 nanometer (nm) = 1.0 x meter O—H distance = 9.4 x m 9.4 x cm nm O—H distance = 9.4 x m 9.4 x cm nm

Select the unit you would use to measure 1. Your height a) millimeters b) meters c) kilometers 2. Your mass a) milligramsb) grams c) kilograms 3. The distance between two cities a) millimetersb) meters c) kilometers 4. The width of an artery a) millimetersb) meters c) kilometers

 AreaAm 2  VolumeVm 3  DensityDkg/m 3 (=m/V)  Molar MassMkilograms/mol  Concentrationcmol/liter  Molar VolumeV m m 3 /mol  EnergyEjoule Honors Chemistry, Chapter 2 Page 18

 Relationship Between D, m, and V: Honors Chemistry, Chapter 2 Page 19 D m V

Strategy 1.Use density to calc. mass (g) from volume. 2.Convert mass (g) to mass (lb) Need to know conversion factor = 454 g / 1 lb First, note that 1 cm 3 = 1 mL

1.Convert volume to mass 2.Convert mass (g) to mass (lb)

Osmium is a very dense metal. What is its density in g/cm 3 if g of the metal occupies a volume of 2.22cm 3 ? 1) 2.25 g/cm 3 2)22.5 g/cm 3 3)111 g/cm 3

2) Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass = g = volume2.22 cm 3 volume2.22 cm 3 = g/cm 3 = 22.5 g/cm 3 = g/cm 3 = 22.5 g/cm 3

A solid displaces a matching volume of water when the solid is placed in water. 33 mL 25 mL

What is the density (g/cm 3 ) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? 1) 0.2 g/ cm 3 2) 6 g/m 3 3) 252 g/cm 3 33 mL 25 mL

Which diagram represents the liquid layers in the cylinder? (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) 2) 3) K K W W W V V V K

The density of octane, a component of gasoline, is g/mL. What is the mass, in kg, of 875 mL of octane? 1) kg 2) 614 kg 3) 1.25 kg

If blood has a density of 1.05 g/mL, how many liters of blood are donated if 575 g of blood are given? 1) L 2) 1.25 L 3) 1.83 L

Fractions in which the numerator and denominator are EQUAL quantities expressed in different units Example: 1 in. = 2.54 cm Factors: 1 in. and 2.54 cm 2.54 cm 1 in.

Write conversion factors that relate each of the following pairs of units: 1. Liters and mL 2. Hours and minutes 3. Meters and kilometers

Conversion factor 2.5 hr x 60 min = 150 min 1 hr 1 hr cancel By using dimensional analysis / factor-label method, the UNITS ensure that you have the conversion right side up, and the UNITS are calculated as well as the numbers!

 Express 4.5 kg as grams  Begin by Expressing as a Fraction: 4.5 kg 1  Identify Conversion Factor: 1 kg = 1000 grams  Express as a Fraction: Honors Chemistry, Chapter 2 Page 33 1 kg 1000 g 1 = or g 1 kg

 Write Equation Including Proper Factor  Cancel Units  Multiply Numbers to Get Final Result Honors Chemistry, Chapter 2 Page kg 1000 g x = 4500 g 1 1 kg

Honors Chemistry, Chapter 2 Page 35 Factor Label Steps 1.Express as a Fraction 2.Identify Conversion Factor 3.Express Conversion Factor as Two Fractions 4.Select Proper Factor (units in denom.) 5.Write Equation Including Proper Factor 6.Cancel Units 7.Multiply Numbers to Get Final Result

1. Distinguish between a quantity, a unit, and a measurement standard. 2. Name SI units for length, mass, time, volume, and density. 3. Distinguish between mass and weight. 4. Perform a density calculation. 5. Transform a statement of equality to a conversion factor (factor label method). Honors Chemistry, Chapter 2 Page 36

 Accuracy – The Closeness of Measurements to the Correct or Accepted Value  Precision – The Closeness of a Set of Measurements Honors Chemistry, Chapter 2 Page 37

Honors Chemistry, Chapter 2 Page 38 Accuracy vs. Precision XX High Precision High Accuracy High Precision Low Accuracy

Honors Chemistry, Chapter 2 Page 39 Accuracy vs. Precision X Low Precision Low Accuracy Low Precision High Accuracy (on average)

Value accepted - Value experimental %Error = Value accepted X 100 Honors Chemistry, Chapter 2 Page 40

 All the Digits Known With Certainty Plus One Final Digit Which is Somewhat Uncertain Honors Chemistry, Chapter 2 Page 41 | I I I I | I I I I | I I I I | I I I I |

1. Zeros Appearing Between Nonzero Digits are Significant 2. Zeros Appearing in Front of All Nonzero Digits are Not Significant 3. Zeros Appearing to the Right of the Decimal Point And at the End of the Number are Significant Honors Chemistry, Chapter 2 Page 42

Honors Chemistry, Chapter 2 Page 43 Rules for Significant Figures 4. Zeros at the End of a Number but to the Left of the Decimal Point May or May Not be Significant. If a Zero Has Not Been Measured or Estimated but is Just a Placeholder, it is Not Significant. A Decimal Point Placed After Zeros Indicates They are Significant.

If the Digit Following the Last Digit to be Retained is: > 5Then Round Up < 5Then Round Down 5 Followed by non Zero Digits Then Round Up Honors Chemistry, Chapter 2 Page 44

Honors Chemistry, Chapter 2 Page 45 Rules for Rounding If the Digit Following the Last Digit to be Retained is: 5 Followed by Non-Zero Digit(s), and Preceeded by an Odd Digit Round Up 5 Followed by Non-Zero Digit(s), and Preceeded by an Even Digit Leave Unchanged

 When Adding or Subtracting Decimals, the Answer Must Have the Same Number of Digits to the Right of the Decimal Point as There are in the Measurement Having the Fewest Digits to the Right of the Decimal Point. Honors Chemistry, Chapter 2 Page 46

Honors Chemistry, Chapter 2 Page 47 Significant Figures With Multiplication/Division When Multiplying or Dividing, the Answer Can Have no More Significant Figures Than are in the Measurement with the Fewest Number of Significant Figures. (Conversion Factors Have Unlimited Digits of Accuracy.)

The numbers reported in a measurement are limited by the measuring tool The numbers reported in a measurement are limited by the measuring tool Significant figures in a measurement include the known digits plus one estimated digit Significant figures in a measurement include the known digits plus one estimated digit

RULE 1. All non-zero digits in a measured number are significant. Only a zero could indicate that rounding occurred. Number of Significant Figures cm4 5.6 ft lb___ m m___

RULE 2. Leading zeros in decimal numbers are NOT significant. Number of Significant Figures mm oz lb____ mL mL ____

RULE 3. Zeros between nonzero numbers are significant. (They can not be rounded unless they are on an end of a number.) Number of Significant Figures 50.8 mm min lb____ m m ____

RULE 4. Trailing zeros in numbers without decimals are NOT significant. They are only serving as place holders. Number of Significant Figures 25,000 in. 2 25,000 in yr yr3 48,600 gal____ 48,600 gal____ 25,005,000 g ____

A. Which answers contain 3 significant figures? 1) ) ) 4760 B. All the zeros are significant in 1) ) ) x 10 3 C. 534,675 rounded to 3 significant figures is 1) 535 2) 535,000 3) 5.35 x ) 535 2) 535,000 3) 5.35 x 10 5

In which set(s) do both numbers contain the same number of significant figures? 1) 22.0 and ) 22.0 and ) and 40 3) and 150,000

State the number of significant figures in each of the following: A m B L C g D m E. 2,080,000 bees 3 5 7

A calculated answer cannot be more precise than the measuring tool. A calculated answer cannot be more precise than the measuring tool. A calculated answer must match the least precise measurement. A calculated answer must match the least precise measurement. Significant figures are needed for final answers from Significant figures are needed for final answers from 1) adding or subtracting 1) adding or subtracting 2) multiplying or dividing

The answer has the same number of decimal places as the measurement with the fewest decimal places one decimal place two decimal places answer 26.5 one decimal place

The answer has the same number of decimal places as the measurement with the fewest decimal places one decimal place two decimal places answer 26.5 one decimal place

In each calculation, round the answer to the correct number of significant figures. A = 1) ) ) 257 B = 1) ) ) 40.7

Round (or add zeros) to the calculated answer until you have the same number of significant figures as the measurement with the fewest significant figures.

A X 4.2 = 1) 9 2) 9.2 3) B ÷ 0.07 = 1) ) 62 3) 60 C X = X ) 11.32) 11 3) 0.041

. l I.... I 3....I.... I 4.. cm First digit (known)= 2 2.?? cm Second digit (known)= ? cm Third digit (estimated) between Length reported=2.75 cm or2.74 cm or2.74 cm or2.76 cm

In 2.76 cm… Known digitsandare 100% certain Known digits 2 and 7 are 100% certain The third digit 6 is estimated (uncertain) The third digit 6 is estimated (uncertain) In the reported length, all three digits (2.76 cm) are significant including the estimated one In the reported length, all three digits (2.76 cm) are significant including the estimated one

. l I.... I 9....I.... I 10.. cm What is the length of the line? 1) 9.6 cm 2) 9.62 cm 3) 9.63 cm How does your answer compare with your neighbor’s answer? Why or why not?

. l I.... I I.... I 5.. cm What is the length of the line? First digit 5.?? cm Second digit 5.0? cm Last (estimated) digit is 5.00 cm

Always estimate ONE place past the smallest mark!

 Move the Decimal Point Left or Right Until the Mantissa is Greater Than or Equal to 1.0 and Less Than 10  Express the Number as: M x 10 n Where n Represents the Number of Places the Decimal Point was Moved, Positive if the Decimal is Moved Left and Negative if the Decimal is Moved Right Honors Chemistry, Chapter 2 Page 67

 Scientific notation is a way of expressing really big numbers or really small numbers.  For very large and very small numbers, scientific notation is more concise.

 A number between 1 and 10  A power of 10 N x 10 x

 Place the decimal point so that there is one non-zero digit to the left of the decimal point.  Count the number of decimal places the decimal point has “moved” from the original number. This will be the exponent on the 10.  If the original number was less than 1, then the exponent is negative. If the original number was greater than 1, then the exponent is positive.

 Given: 289,800,000  Use: (moved 8 places)  Answer: x 10 8  Given:  Use: 5.67 (moved 4 places)  Answer: 5.67 x 10 -4

 Simply move the decimal point to the right for positive exponent 10.  Move the decimal point to the left for negative exponent 10. (Use zeros to fill in places.)

 Given: x 10 6  Answer: 5,093,000 (moved 6 places to the right)  Given: x  Answer: (moved 4 places to the left)

 Express these numbers in Scientific Notation: 1) ) ) ) 2 5)

 Y = kX  Example Mass vs. Volume Data for Aluminum  Slope of the Line (k) is the Density Honors Chemistry, Chapter 2 Page 75

Honors Chemistry, Chapter 2 Page 76

Honors Chemistry, Chapter 2 Page 77

 Y = mX + b = slope x Volume + intercept  Slope = 2.69 g/cm 3  Intercept = 0.09 grams (!) (Actually Zero)  From Table of Densities: Sample is Aluminum (Al) Honors Chemistry, Chapter 2 Page 78

 k = XY or Y = k/X  As X Increases, Y Decreases  Example: Pressure-Volume Data Honors Chemistry, Chapter 2 Page 79

Honors Chemistry, Chapter 2 Page 80

Honors Chemistry, Chapter 2 Page 81

Honors Chemistry, Chapter 2 Page 82 Chapter 2, Section 3 Review 1.Distinguish between accuracy and precision. 2.Determine the number of significant figures in a measurement. 3.Perform mathematical operations (+,-,x,/) involving significant digits. 4.Convert measurements into scientific notation. 5.Distinguish between inversely proportional and directly proportional relationships.