Chapters 1 2 Matter Density Specific Gravity Significant

Chapters 1 & 2 Matter, Density & Specific Gravity, Significant Figures et. al. , Chemical History 1

What is Chemistry? What does it have to do with me? 2

What Does It Have To Do With Me? “What does chemistry have to do with me? ” said Mr. Averageman, as he looked at a page printed with ink made by a chemical process, and tied his shoes, shoes made of leather tanned by a chemical process. He glanced through a gla pane of glass, made by a chemical process, process and saw a bakers wagon full of bread leavened by a chemical process, and a pr draper’s wagon delivering a parcel of silk, dyed by a chemical process. He put on a hat, shaped by a chemical process, and stepped out on the asphalt pavement, compounded by a chemical process, bought a daily paper with a penny refined by a chemical process. “No, ” he added, “of course not, chemistry has nothing to do with me. ” Herbert Newton Casson 1869 -1964 [Merrill Chemistry 1995 3

This is a liquid crystal molecule. 4

These are liquid crystal fibers. 5

Ever use any of these? 6

What is Chemistry and How Did We Get to This Point? l Chemistry is called the ‘central science’. l Studies the structure and properties and changes of matter. 7

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Scientific Method 9

What is Matter? l Complete ‘Is It Matter? ’ probe individually. l When instructed, share your answers and your reasoning w/ a partner (5) 10

Matter - the ‘stuff’ that everything is made of Takes up space l Has mass l Has inertia l Has energy l 11

Takes up space means that it is Three dimensional 12

Has mass indicates l l the quantity of matter present Gram units 13

Has inertia refers to l the tendency of a body to maintain its state of rest or uniform motion unless acted upon by an external force inertia 14

Has energy which means l The ability to do work l In science we say that work is done on an object when you transfer energy to that object. 15

Mass and Inertia Relationship? 16

Watch the demo! 17

What did you notice about… l l Their hands? Which was more difficult to catch? Which required greater effort to stop ? Remember that inertia is the resistance to a change in motion. 18

What can you conclude about the relationship between mass and inertia? l More mass = More inertia 19

Mass and Energy Relationship? 20

Assignment l Read “Nature of Energy” l p 516 - 518 in text 21

Many different types of energy l l l Chemical Nuclear Radiant l l Heat Light Electrical Mechanical l l Kinetic Potential 22

One form of energy can be transformed into another. chemical potential radiant electrical kinetic 23

Significant Figures, Calculations and Measurements 24

SI system of units l modern metric l l Be able to recognize the order of the prefixes. Be able to convert from one unit to another. 25

Prefix abbreviation Power of 10 Mass unit Length unit Volume unit kilo- k 1000 or 103 kilogram, kg kilometer, km kiloliter, k. L kl hecto- h 100 or 102 hectogram, hg hectometer, hm hectoliter, hlh. L deka- dk 10 dekagram, dkg dekameter, dkm dekaliter, dk. L dkl 1 gram meter liter base unit deci- d . 1 or 10 -1 decigram, dg decimeter, dm deciliter, dl d. L centi- c . 01 or 10 -2 centigram, cg centimeter, cm centiliter, clc. L milli- m . 001 or 10 -3 milligram, mg millimeter, mm milliliter, m. L 26

Kids have days they don’t care much. kilo hecto deka meter deci centi milli liter gram To change 11. 263 cg to deka grams… To change 1. 235 km to millimeters … 27

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t n a c i f i n g s i S gure i F 29

Atlantic/Pacific Rule l To determine the number of sig figs in a given value, use the Atlantic/Pacific Rule regarding decimals Pacific Ocean Atlantic Ocean 30

Significant Figures (con’t) l If the decimal is Absent, count from the Atlantic side from the first non-zero digit l If the decimal is Present, count from the Pacific side from the first non-zero digit l Do NOT stop counting until you’ve run out of digits! A bar above a zero indicates the marked zero was the estimated value in the measurement and is to be included in calculating the accuracy of the instrument and in determining the number of significant figures. l 31

How many sig figs are in each number? 408. 00 g 5 sig figs 639. 0 g 4 sig figs 0. 0058020 mm 5 sig figs 5640 m 3 sig figs 0. 002 g 1 sig fig 3, 090, 000 km 3 sig figs 32

Ice Cubes in a Bag - probe l Complete ‘Ice Cubes in a Bag’ probe individually. (5) l When instructed, share your answers and your reasoning w/ a partner (5) 33

“Matter and energy are two sides of the same physical entity. ” Albert Einstein l E = mc 2 l l l E = Energy m = Mass c = speed of light l 3 x 108 m/s 34

Law of Conservation of Mass and Energy l l matter and energy are interchangeable the total amount of matter and energy in the universe is constant 35

Because of this, chemical rxn… l are always accompanied by changes in energy (E) l l l E given off - exothermic E used – endothermic Cannot gain or lose l mass of reactants = mass of products 36

A thought experiment… l You have just made lemonade. You taste it and find that you pucker when you drink it. l What should you do to ‘fix’ the lemonade? 37

l l “Add sugar” . . . qualitative solution “Add 1 cup of sugar”. . . quantitative solution l l *has Numeral *has UNIT 38

Mass v. Weight l l Mass – amount of matter present Weight – measure of the pull of gravity on the mass. 80 kg 39

Mass v. Weight l The gravitational force on the moon is 1/6 th that of the earth. l weight is less on the moon. 13. 3 kg 40

Basic unit l original measurement 41

Derived unit l - result of a mathematical function performed on basic units l volume of a box [l x w x h], § speed [distance/time] 42

! g n i r u as e M 43

Measuring l Compares a feature of an object to a standard l For example: l l l the length of a book is compared to the standard length of a ruler the mass of a jar of pickles is compared to the standard mass of a gram Measurement tools we will often use in the lab: l l l Balance (measures mass) Graduated cylinder (measures volume) Meter stick (measures length) 44

When reading an instrument… l Consider all forms of error that could occur l l l Human error (we all make mistakes) Equipment error Changing environmental conditions l l Ex: Pressure No instrument is 100% accurate 45

All measurements MUST have… l l l Number value Unit Indicator of the degree of accuracy l Significant figures indicate the degree of accuracy l The number of digits in the measurement shows the degree of precision of the measuring instrument, which shows how accurate the measurement is 46

When taking a measurement, remember: l l Read all numbers from the instrument PLUS one additional ESTIMATE When reading a measurement from a digital readout, treat the last number on a digital readout as an estimate 47

Significant Figures l All of the numbers that can be directly read from an instrument PLUS one additional estimated number l l For digital instruments such as the electronic balance, the last digit IS the mechanically estimated value Significant figures reflect the precision of an instrument, which shows the accuracy of a measurement 48

Accuracy l l Nearness to an accepted value Measured in ERROR ABSOLUTE ERROR EA = O – A ü EA – absolute error ü O – observed; may be individual or experimental average ü A – accepted value RELATIVE ERROR (Percent Error) ER = (EA A) 100 or Percent error = experimental value – accepted value X 100 accepted value 49

Precision l l l Repeatability; consistency; closeness of multiple measurements to each other Measured in DEVIATION ABSOLUTE DEVIATION DA = OI - M ü l OI – individual observed trial ü M – average of all trials RELATIVE DEVIATION DR = (DA M) 100 50

Accuracy vs. Precision (con’t) l Two archers are taking target practice. Here are their shots… l Which of these archers is accurate and which is precise? 51 How do you know? ?

Measuring & Calculating Activity 52

Measuring the Mass ~Digital v. Triple Beam Balances~ l Always use weighing paper or a glass container – never put Digital Balances Triple Beam Balances chemicals or hot objects directly on the balance § Turn the scale on and be sure it reads 0. 0 • Use the zero adjust knob until the pointer g before placing anything on it to be rests at zero if it is not already. (The massed. pointer must be at zero before use) §Mass the container / paper to be used in the weighing. § Press the Tare button to bring the scale back to 0. 0 g. §Add the substance to be weighed to the container / paper. §No estimation is necessary: the last • Pre-weigh the paper or glassware that the solid or liquid will be in. After recording that mass, put the solid or liquid into the glassware and remass the glassware. • Mass of Glassware & Substance – Mass of Glassware = Mass of Substance • Adjust the sliding weights on the various scales as necessary 53 • Be sure to estimate to the hundreths place

Measuring the Volume ~Graduated Cylinders~ l l The lowest curvature of the liquid level in a graduated cylinder is the meniscus To read the volume of liquid in a graduated cylinder, you need to carefully read the BOTTOM of the meniscus at eye level l If you read the markings on the top of the meniscus, your reading will be incorrect! l If you read the meniscus from an angle and not at eye level, your reading will either be too high or too low l Don’t forget, when taking a measurement, you want to read all of the numbers from the instrument PLUS one estimated number (can be a zero) 54

Evaluation l Measurement Using Significant Figures 55

DENSITY l l l derived unit mass per volume D = m/V Density § § = mass of orange volume of orange = __x_grams 4/3 π r 3 56

Units of Density l l g/cm 3 - unit of density for solids and liquids g/L - unit of density for gases 57

Density Example : A brick [ingot ] of silver is 3 cm x 4. 5 cm x 7. 5 cm. What is the density of silver if the brick is massed at 1062 g? l m = 1062 g l v = 3 cm x 4. 5 cm x 7. 5 cm l = 101. 25 cm 3 l D = 1062 g 101. 25 cm 3 = 10. 49 g/cm 3 l 58

SPECIFIC GRAVITY l comparative value of a substance to a standard S. G. = density / standard l Standard Values solids/liquids - 1. 0 g/cm 3 [density of water] gases - 1. 29 g/L [density of air] l l 59

What is the density and specific gravity of mercury (Hg) with a mass of 300. 0 g and a volume of 22. 1 m. L? l l l D = m v = 300. 0 g 22. 1 m. L D = 13. 6 g/m. L l l l SG = Density Std SG = 13. 6 g/m. L 1. 0 g/cm 3 SG = 13. 6 60

Very Important Equality to Remember !!! 1 gram = 1 ml =1 cm 3 Water @ 4 o. C and standard pressure. 61

g n i t a l u lc a C 62

When you solve a math calculation, is there a ‘right’ answer? 63

Calculate the mass of a silver ingot, which measures 1. 14 cm x 2. 35 cm x 1. 88 cm and has a density of 10. 49 g/cm 3. l l Group A Solve this calculation rounding the answers to 3 numbers after each step. l l Group B Solve this calculation saving all numbers and rounding only once at the very end. Ans. 1. 14 cm x 2. 35 cm x 1. 88 cm = 5. 04 cm 3 Ans. 1. 14 cm x 2. 35 cm x 1. 88 cm = 5. 03652 cm 3 10. 49 g = mass 5. 04 cm 3 52. 9 g = mass 10. 49 g = mass 5. 03652 cm 3 52. 8 g = mass 64

What would you predict will happen if… l The calculation had more steps in it? l The calculations had much larger or much smaller numbers? 65

Now we see the need for having procedures for getting the same answer(s). 66

Sig Fig Rules for Addition/Subtraction l l l Step #1: Perform the math Step #2: Determine which number you are adding or subtracting has the least number of decimal places Step #3: Round your answer to show the same number of decimal places as the term in the problem with the fewest decimal places 67

Addition/Subtraction Example Step 1 5. 6079 m 3. 14 m + 6. 704 m 15. 4519 m Step 2 3. 14 has the fewest decimal places of any of the numbers in the calculation Step 3 Final answer should be rounded to match this number of decimal places [in this case, there should be two decimal places] Answer: 15. 45 m 68

Sig Fig Rules for Multiplication/Division l Step #1: Perform the math l Step #2: Determine which term in the calculation has the fewest number of significant figures l Step #3: Round your answer to match that number of significant figures. Double check your units. 69

Multiplication/Division Example 8. 563 cm x 9. 23 cm x 3. 487 cm = ? 4 3 4 Step 1 (Perform the math): 8. 563 cm x 9. 23 cm x 3. 487 cm = 275. 60024 cm 3 Step 2 (Round answer to least number of sig figs): Answer: 276 cm 3 Step 3 (Double check to make sure your units make sense) 70

Scientific Notation Review l l If a number is larger than the thousands place, or if the number is smaller than the thousandth place put into scientific notation l Numbers, when written in scientific notation, have only ONE DIGIT to the left of the decimal place. This is the acceptable and correct way of writing numbers in scientific notation. l Examples: How would you write the following expressions in scientific notation? Standard Form Scientific Notation Form 14, 890 0. 456 0. 007532 71

Scientific Notation Review l l If a number is larger than the thousands place, or if the number is smaller than the thousandth place put into scientific notation l Numbers, when written in scientific notation, have only ONE DIGIT to the left of the decimal place. This is the acceptable and correct way of writing numbers in scientific notation. l Examples: How would you write the following expressions in scientific notation? Standard Form Scientific Notation Form 14, 890 1. 489 x 104 0. 456 or 4. 56 x 10 -1 0. 007532 7. 532 x 10 -3 72

Changing a Number into Scientific Notation l l l If the exponent increases, the number before the x 10 (known as the mantissa) decreases by the number of decimal places the power is changed If the exponent decreases, the mantissa increases by the number of decimal places the power is changed. Example: 2. 71 x 102 to 103 l l The exponent is increased by 1 power of 10, so the mantissa is decreased by 1 decimal place 0. 271 x 103 73

Try these… l 3. 561 x 106 to 104 l 3. 0100 x 10 -2 to 10 -5 l 6. 211 x 1022 to 1025 74

Try these… l 3. 561 x 106 to 104 l l 3. 0100 x 10 -2 to 10 -5 l l Answer: 356. 1 x 104 Answer: 3010. 0 x 10 -5 6. 211 x 1022 to 1025 l Answer: 0. 006211 x 1025 75

Adding/Subtracting Numbers in Scientific Notation l l When adding or subtracting numbers in scientific notation, the numbers must be in the same power of 10 to round answer properly, so the form may need to be TEMPORARILY manipulated to solve the calculation, but the answer must be restored to the accepted form. Use rules for significant figures for your final answer 76

Adding/Subtracting Numbers in Scientific Notation Ex: [2. 71 x 102 L] + [7. 10 x 103 L] + [1. 2 x 103 L] = ? 0. 271 x 103 L 7. 10 x 103 L + 1. 2 x 103 L 8. 571 x 103 L v v 1. 2 has the fewest number of decimal places in the calculation Round the answer to match this number of decimal points Answer: 8. 6 x 103 77

Multiplying/Dividing Numbers in Scientific Notation l l Numbers can be to any power of 10 and still be able to be multiplied or divided without first manipulating the number Example: [2. 15 x 105 cm] x [5. 030 x 10 -2] = ? v First, input the numbers into your calculator v Calculator shows either 10814. 5 cm 2 or 1. 08145 x 104 cm 2 v 2. 15 has the fewest significant figures, so your answer should be rounded to match that same number of sig figs 78 Answer: 10800 cm 2 or 1. 08 x 104 cm 2

l l ASSIGN: Density & Specific Gravity II 79

Accuracy & Precision Revisited 80

Accuracy vs. Precision (con’t) l Remember the two archers taking target practice. l Which of these archers is accurate and which is precise?

Accuracy l l l Nearness to an accepted value Measured in ERROR ABSOLUTE ERROR ü ü EA – absolute error O – observed; may be individual or experimental average ü l EA = O – A A – accepted value RELATIVE ERROR (Percent Error) ER = (EA A) 100 or Percent error = experimental value – accepted value X 100 accepted value

Precision l l l Repeatability; consistency; closeness of multiple measurements to each other Measured in DEVIATION ABSOLUTE DEVIATION DA = OI - M ü l OI – individual observed trial ü M – average of all trials RELATIVE DEVIATION DR = (DA M) 100

Determine the accuracy and precision for the EXPERIMENT Trial 1 Amount of Product (g/m. L) 3. 92 2 3. 97 3 3. 95 Accepted Value 3. 96 84

l O = 3. 95 g/m. L [3. 92 g/m. L + 3. 97 g/m. L + 3. 95 g/m. L ] ÷ 3 Ea= 3. 95 g/m. L-3. 96 g/m. L = -. 01 g/m. L l Er = -. 01 g/m. L x 100 = -. 25% 3. 96 g/m. L l l M = 3. 95 g/m. L [3. 92 g/m. L + 3. 97 g/m. L + 3. 95 g/m. L ] ÷ 3 Da = +/-. 03 + +/-. 02 + 0 = +/-. 017 g/m. L 3 l Dr = +/-. 017 g/m. L x 100 = +/-. 42% 3. 95 g/m. L l 85

In the Lab, you should be able to… l l convert between units of measure using the SI System, determine whether your data is accurate, precise, both, or neither, report data in the correct number of significant figures, and work with numbers in scientific notation.

l l ASSIGN: Accuracy and Precision w. s. ACTIVITY: Accuracy & Percision in Measurements Lab 87

What is Chemistry and How Did We Get to This Point? l CHEMICAL HISTORY An Internet Activity Research four eras that made a significant contribution to chemistry. Egyptian Era Dark Ages Pilgrim Era Am. Revolution l Content will be included on the Ch. 1 -2 test 88

INTERNET SITES l Egyptian Era http: //www. zompist. com/ver sci. htm l Scroll down to ‘Science’ l l Choose ‘Chemical History’ l Scroll down to the ‘Egyptian, Mesopotamian’ section l What contribution did chemistry make to the Egyptians? What are some products they produced? l 89

INTERNET SITES l l l Dark Ages http: //www. rsc. org/Publishing /Current. Awareness/index. as p In the ‘site search’ box type – alchemical symbols l l l Choose first selection What is the purpose(s) of alchemy? With what other practices was alchemy associated? 90

INTERNET SITES l l l Pilgrim Era http: //www. jimloy. com/p hysics/phlogstn. htm. Cho ose #5 Phlogiston. l l What was the phlogiston theory? What were it’s beliefs? 91

INTERNET SITES American Revolution l l library. thinkquest. org/C 006439/scientists/ Choose Robert Boyle l l Also choose Antoine Lavoisier l l l What did Robert Boyle contribute to our modern concept of "element". Why was Lavoisier's weighing of substances important? Why is Lavoisier remembered as the "father" of chemistry http: //www. ehow. com/info_8233221_disco veries-inventions-advances-1700 s. html l What was were the major advances in chemistry during this time period? 92