This preview has intentionally blurred parts. Sign up to view the full document

View Full Document

Unformatted Document Excerpt

to Introduction Chemistry Mr. Christopherson Normal Community High School www.unit5.org/chemistry Whetheryoubelieveyoucandoathing Problemscallforthourcourageandourwisdom; orbelieveyoucant, indeed,theycreateourcourageandourwisdom. youareright. itisonlybecauseofproblemsthatwegrowmentally andspiritually.Itisthroughthepainof Dontbeafraidtotakeabigstep Manufacturer Henry Ford, 1863-1947 American Car confrontingandresolvingproblems ifoneisindicated. thatwelearn. Youcantcrossachasm intwosmalljumps. M. Scott Peck, b. 1936 American Psychiatrist and Writer David Lloyd George, 1863-1945 British Prime Minister and Statesman Allthroughmylife, thenewsightsofNature mademerejoicelikeachild. Believethatlifeisworthliving, andyourbeliefwillhelpcreatethefact. Marie Curie, 1867-1934 Polish-Born French Chemist William James, 1842-1910 American Psychologist and Philospher Chemistry is the study of matter and the transformations it can undergo Matter is anything that occupies space. Matter is anything that occupies space. Chemistry witha Purpose Interactive Periodic Table 7 1 C H S 1 6 Ir O N Mn < N e 16 77 7 H 25 TheHumanElement H He 1 8 2 1 3 Li Be B C N O F Ne 3 2 4 5 6 7 8 9 10 Al Si P S Cl Ar 13 14 15 16 17 18 Na Mg 11 4 K 19 5 Ca Sc V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 23 24 35 36 I Xe 53 54 21 22 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In 39 40 41 42 49 50 Hf Ta W 72 73 74 38 Cs Ba 55 7 Ti 20 37 6 12 56 Fr Ra 87 88 25 43 26 44 Re Os 75 76 27 28 29 47 30 32 46 Ir Pt Au Hg Tl Pb 77 78 81 82 80 33 34 Sn Sb Te 45 79 48 31 51 52 Bi Po At Rn 83 84 85 86 Rf Db Sg Bh Hs Mt 104 105 106 107 108 109 La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 57 58 59 Ac Th Pa 89 90 91 60 U 92 61 62 63 64 65 66 67 68 69 70 71 Np Pu Am Cm Bk Cf Es Fm Md No Lr 93 94 95 96 97 98 99 100 101 102 103 Natural Science Physical Science Physics Chemistry Earth and Space Science Geology Astronomy Meteorology Life Science Botany Ecology Oceanography Natural science covers a very broad range of knowledge. Wysession, Frank, Yancopoulos, Physical Science Concepts in Action, 2004, page 4 Zoology Genetics Table of Contents Introduction to Chemistry Introduction / Perceptions (17 slides) Safety (21 slides) Pure vs. Applied Science (10 slides) Scientific Method (27 slides) Lab Equipment (6 slides) Alchemy vs. Chemistry (30 slides) Manipulating Numerical Data (11 slides) Conversion Factors and Unit Cancellation (6 slides) Simple Math with Conversion Factors (8 slides) Scientific Notation (18 slides) Using the Exponent Key (17 slides) Basic Concepts in Chemistry (7 slides) Metric System (10 slides) Measurement (23 slides) Essential Math (14 slides) Lecture Outline Intro. to Chemistry Lecture Outline Introduction to Chemistry student notes outline textbook questions Lecture Outline Introduction to Chemistry textbook questions Keys http://www.unit5.org/chemistry/intro.html Intro to Chemistry Copyright 2007 Pearson Benjamin Cummings. All rights reserved. World of Chemistry The Annenberg Film Series VIDEO ON DEMAND Episode 1 World of Chemistry The world of chemistry is introduced by providing highlights of key sequences and themes from programs in the series. The relationships of chemistry to the other sciences and to everyday life are presented. A Lost Child Keeping Warm Once upon a time a small child became lost. Because the weather was cold, he decided to gather material for a fire. As he brought objects back to his campfire, he discovered that some of them burned and some of them didnt burn. To avoid collecting useless substances, the child began to keep track of those objects that burned and those that did not. He proposed a possible generalization. Perhaps: Cylindrical objects burn. This procedure if one of the elementary logical thought processes by which information is systematized. It is called inductive reasoning (a general rule is framed on the basis of a collection of individual observations (or facts)). Jaffe, New World of Chemistry, 1955, page 3-4 Cylindrical Objects Burn WILL BURN WONT BURN Tree limbs Rocks Broom handles Blackberries Pencils Marbles Chair legs Paperweights Flagpoles Jaffe, New World of Chemistry, 1955, page 3-4 Using his generalization, the boy gathered more substances to burn. He collected three pieces of pipe, two ginger ale bottles, and the axle from an old car, while leaving a huge cardboard box full of newspapers. During the long cold night that followed he drew these conclusions: (1) The cylindrical shape of a burnable object may not be intimately associated with its flammability after all. (2) Even though the cylindrical rule is no longer useful, tree limbs, broom handles, pencils, and other burnables still burn . (3) Hed better bring the list along tomorrow. New idea: Perhaps Wooden objects burn. Jaffe, New World of Chemistry, 1955, page 3-4 The Six Levels Evaluation Synthesis Analysis Application Comprehension of Thought Success is a journey, not a destination. -Ben Sweetland Successful students make mistakes, but they dont quit. They learn from them. -Ralph Burns Success consist of a series of little daily efforts. -Marie McCuillough Food Elements Removed from the soil by various plants Nitrogen Phosphorus Potassium Magnesium Calcium Sulfur Pounds Per Acre 30 20 10 Corn Jaffe, New World of Chemistry, 1955, page 468 Hay Wheat Cotton Oats Potatoes Tobacco Medium alkaline S l i g h tl y alkaline Very Slightly alkaline Very Slightly acid S l i g h tl y acid Medium acid Strongly acid Strongly alkaline Table: Soybean nutrient requirements in pounds/40 bushels Nutrient Seed Plant Total Nitrogen (N) 150 30 180 Phosphorus (P2O5) 35 10 45 Potassium (K2O) 57 52 109 Calcium (Ca) 7 -- 7 Magnesium (Mg) 7 -- 7 Sulfur (S) 4 -- 4 Zinc (Zn) 0.04 -- 0.04 Iron (Fe) -- -- 1.20 Manganese (Mn) 0.05 -- 0.05 Copper (Cu) 0.04 -- 0.04 -- -- 0.008 Molybdenum (Mo) 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 Acidity / Alkalinity (pH) Most nutrients are obtained from residual sources http://www.vaes.vt.edu/tidewater/soybean/soyproduction/soyguide.html#L4 Job Skills for the Future Evaluate and Analyze Think Critically Solve Math Problems Organize and Use References Synthesize Ideas Apply Ideas to New Areas Be Creative Make Decisions with Incomplete Information Communicate in Many Modes Chemistry will develop ALL of these skills in YOU! Youve Finally Met Your Match A Description of a Burning Candle A photograph of a burning candle is shown1 in the upper right corner. The candle is cylindrical2 and has a diameter3 of about 3 cm. The length of the candle was initially about 16 centimeters4, and it changed slowly5 during observation, decreasing about 1 cm in one hour6. The candle is made of a translucent7, white8 solid9 which has a slight odor10 and no taste11. It is soft enough to be scratched with the fingernail12. There is a wick13 which extends from top to bottom14 of the candle along its central axis15 and protrudes about 5 mm above the top of the candle16. The wick is made of three strands of string braided together17. A candle is lit by holding a source of flame close to the wick for a few seconds. Thereafter the source of flame can be removed and the flame sustains itself at the wick18. The burning candle makes no sound19. While burning, the body of the candle remains cool to the touch 20 except near the top. Within about 1.5 cm of the top the candle is warm21 (but not hot) and sufficiently soft to mold easily22. The flame flickers in response to air currents23 and tends to become quite smoky while flickering24. In the absence of air currents, the flame is of the form shown in the photograph, though it retains some movement at all times25. The flame begins about 2 mm above the top of the candle26, and at its base the flame has a blue tint27. Immediately around the wick in a region about 2 mm wide and extending about 5 mm above the top of the wick28 the flame is dark29. This dark region is roughly conical in shape30. Around this zone and extending about 1 cm above the dark zone is a region which emits yellow light31, bright but not blinding32. The flame has rather sharply defined sides33 but a ragged top34. The wick is white where it emerges from the candle35, but from the base of the flame to the end of the wick36 it is black, appearing burnt, except for the last 0,5 cm, where it glows red37. The wick curls over about 3 mm from its end38. As the candle becomes shorter, the wick shortens too, so as to extend roughly a constant length above the top of the candle39. Heat is emitted by the flame40, enough so that it becomes uncomfortable in 10 to 20 seconds if one holds his finger 10 cm to the side of the quiet flame41 or 10 12 cm above the flame42. OConnor Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles 1982, page 462, Dual Perceptions Dual Perceptions Dual Perceptions Stack of Blocks Perception of Motion Unit 1 Introduction to Chemistry Internet web site: www.unit5.org/chemistry www.unit5.org/christjs Click to see VIDEO A Colorful Demonstration: The Remsen Reaction Vocabulary - Intro. to Chemistry Vocabulary - Introduction to Chemistry Vocabulary - Introduction to Chemistry Keys http://www.unit5.org/chemistry/intro.html Safety Basic Safety Rules Use common sense. No unauthorized experiments. No horseplay. Handle chemicals/glassware with respect. Safety Features of the Lab safety shower fire blanket fire extinguisher eye wash fume hood circuit breaker switch Government Regulation of Chemicals The government regulates chemicals to reduce the risk to the Consumer FDA, USDA, Consumer Product Safety Commission Worker OSHA Environment EPA Chemical Stewardship Government Regulation worker OSHA environment EPA The government regulates chemicals to protect the FDA USDA FAA CPSC consumer Thalidomide Prescription drug for morning sickness Drug can be made in two ways Put together same material in more than one way. A = good drug (stops morning sickness) B = bad drug (birth defects) Side-effect from bad drug Stopped development in fetus Short arms; flipper-babies Happy & Sad Balls Cis-isomer Sad ball Trans-isomer Happy ball Mercury Poisoning One tiny drop of mercury shatters lives and science Karen Wetterhahn, a chemistry Professor at Dartmouth College, died of mercury poisoning after spilling just one drop in a laboratory on Aug. 14, 1996. The mercury penetrated her skin through gloves. LYME, N.H. (AP) It was just a drop of liquid, That night, Leon drove her to the emergency just a tiny glistening drop. It glided over her glove room. It was Monday, Jan. 20, 1997, five months like a jewel. since she had spilled the drop in the lab. Scientist Karen Wetterhahn knew the risks: The Just a single drop of liquid. Yet somehow it had bad stuff kills if you get too close. penetrated her skin. She took all the precautions working with merBy the weekend, Karen couldn't walk, her speech cury in her Dartmouth College lab wearing pro- was slurred and her hands trembled. Leon paced the tective gloves and eye goggles, working under a house. "Virus" seemed an awfully vague diagnosis, ventilated hood that sucks up chemical fumes. for symptoms that were getting worse every day. So on that sunny day in August, when she acci"It's mercury poisoning," Dr. David Nierenberg dentally spilled a drop, she didn't think anything of said. "We have to start treatment immediately." it. She washed her hands, cleaned her instruments Leon hung up with relief. At last, they understood and went home. the problem. Now maybe they could fix it. It was just a drop of liquid, just a tiny glistening It seemed impossible to believe that anything drop. could be wrong with Karen Wetterhahn, one of At first, friends thought she had caught a stomach those quietly impressive individuals whose lives bug on her trip to Malaysia. It wasn't until she seemed charmed from the start. started bumping into doors that her husband, Leon Serious and hardworking, she excelled at every Webb, began to worry. Karen, always so focused, thing she turned to science or sailing or skiing. always so sure of her next step, was suddenly falling She grew up near Lake Champlain in upstate New down as if she were drunk. York in a family so close that when she and her only In 15 years together, she had never been sick, nev- sister became mothers, they named their daughters er stopped working, never complained. Leon was after each other: Charlotte and Karen. stunned when she called for a ride home from work. Karen was always the brilliant one of the family, Over lunch a few days later, Karen confided to her the one who would do great things. And she did, bebest friend, Cathy Johnson, that she hadn't felt right coming the first woman chemistry professor at for some time. Words seemed to be getting stuck in Dartmouth, running a world-renowned laboratory her throat. Her hands tingled. It felt like her whole on chromium research, devoting herself to her body was moving in slow motion. work. "Karen," Johnson said as she drove her back to It was important work, the kind that could lead to the college, "we've got to get you to the hospital." cures for cancer and AIDS. Karen thrived on it. She "After work," Karen promised, walking unsteadi- loved nothing more than experimenting with a ly into the Burke chemistry building for the last chemical, figuring out its bad side and how it breaks time. down living things. Lead Poisoning (Plumbism) LD50 = mg / kg Small children may accidentally ingest lead-based paints that peel off from window sills and walls. Lead accumulates near bone joints lighter color on X-ray is lead. Effects: slow mental development, lack of concentration Safety Symbols SAFETY CLOTHING This symbol is to remind you to wear a laboratory apron over your street clothes to protect your skin and clothing from spills. SAFETY GOGGLES This symbol is to remind you that safety goggles are to worn at all times when working in the laboratory. For some activities, your teacher may also instruct you to wear protective gloves. GLOVES This symbol is to remind you to wear gloves to protect your hands from contact with corrosive substances, broken glass, or hot objects. HEATING This symbol indicates that you should be careful not to touch hot objects with your bare hands. Use either tongs or heat-proof gloves to pick up hot objects.. FIRE This symbol indicates the presence of an open flame. Loose hair should be tied back or covered, and bulky or loose clothing should be secured in some manner. DANGEROUS VAPORS This symbol indicates the presence of or production of poisonous or noxious vapors. Use the fume hood w hen directed to do so. Care should be taken not to inhale vapors directly. When testing an odor, use a wafting motion to direct the vapor toward your nose. EXPLOSION This symbol indicates that the potential for an explosive situation is present. When you see this symbol, read the instructions carefully and follow them exactly.. POISON This symbol indicates the presence of a poisonous substance. Do not let such a substance come in contact with your skin and do not inhale its vapors. ELECTRICAL SHOCK This symbol indicates that the potential for an electrical shock exists. Read all instructions carefully. Disconnect all apparatus when not in use. RADIATION This symbol indicates a radioactive substance. Follow your teacher's instructions as to proper handling of such substances.. CORROSIVE SUBSTANCE This symbol indicates a caustic or corrosive substance - most frequently an acid. Avoid contact with skin, eyes, and clothing. Do not inhale vapors. DISPOSAL This symbol indicates that a chemical should be disposed of in a special way. Dispose of these chemicals as directed by your teacher. BREAKAGE This symbol indicates an activity in which the likelihood of breakage is greater than usual, such as working with glass tubing, funnels and so forth. HYGIENE This symbol is to remind you to always wash your hands after completing a laboratory investigation. Never touch your face or eyes during a laboratory investigation. Safety Symbols Eye Protection Required Heat Protection Clothing Protection Required Glassware Safety Hand Protection Required Laboratory Hygiene Chemical Safety Sharp Object Hazard Caustic Substance Waste Disposal Safety Equipment Safety Goggles Fire Extinguisher Type A Type B Type C Safety Shower Chemical Burns Flammable Health Reactive Special Chemical burns on feet. Skin burned by chemicals DANGER Laboratory Safety Rules SAFETY in the Science Classroom Obey the safety contract Use common sense No unauthorized experiments Wear safety glasses Safety is an attitude! Dont take anything out of lab Read and follow all instructions Material Safety Data Sheet (MSDS) Gives information about a chemical. Lists Dos and Donts. Material Safety Data Sheet Material Safety Data Sheet questions Acetone MSDS Material Safety Data Sheet questions Keys http://www.unit5.org/chemistry/intro.html Chemical Exposure acute exposure a one-time exposure causes damage chronic exposure damage occurs after repeated exposure How Toxic is Toxic? Chemicals may cause harm in many different ways. Flammable Explosive Radioactive Corrosive Irritant Toxic Chronic toxicity: low doses repeated over a long period of time Acute toxicity: immediate effect of a substance as a result of a single dose Lethal Dose 50% LD50 Toxicity Which is more toxic? http://lansce.lanl.gov/training/FST2004/images04/chemicals1.gif Toxicity Which is more toxic? Chemical A: LD50 = 3.2 mg/kg Chemical B: LD50 = 48 mg/kg Chemical A is more toxic because less of it proves fatal to half of a given population. LD50 the lethal dosage for 50% of animals on which the There are various ways an LD50 can be chemicalFor example, acetone has the is tested expressed. following LD50s: ORL-RAT LD50: 5,800 mg/kg IHL-RAT LD50: 50,100 mg/m3-h SKN-RBT LD50: 20 g/kg Knowledge = Safety Material Safety Data Sheet (MSDS) Acute Exposure Lists hazards, special handling instructions, and risks associated with a material. Supplied by manufacturer. Single episode can cause great damage Chronic Exposure Many episodes over a period of time cause damage Carcinogen causes cancer Mutagen causes mutations (genetic defects) Tetragen causes birth defects Neurotoxin severely poisonous and toxic Science Basic research leads us to a greater understanding of how the natural world operates. Applied research aims to develop useful applications from the knowledge gained from basic research. The Functions of Science pure science science the search for knowledge; facts applied using knowledge in a practical way Science attempts to establish cause-effect relationships. ? Pure Science The search for facts about the natural world. In science, we often try to establish a cause-effect relationship. - Driven by curiosity: the need to know, explore, conquer something new. - Applied Science The practical application of scientific discoveries. Also known as technology - Used to improve our lives - Cell phones Biodegradable garbage bags Corning Glass NASAs Problem Design a material that is clear and can withstand extreme differences in temperature without failing (cracking). Corning Glass FAILEDbut SUCCEEDED at making great cookware that can withstand extremes in temperature. Design a face shield to protect and provide clear vision. Fertilizers (5-15-10) Nitrogen (N) Promotes vegetative growth, making the plants lush and green Excess nitrogen: few blooms (flowers) Phosphorous (P) Gives energy and vitality Promotes rapid maturity and flowering Potassium (K) Promotes strong plant growth and deep roots Helps plants become more disease-resistant Fertilizers help plants produce more food. Table Sugar = sucrose (glucose + fructose) HOCH2 O HOCH2 O OH HO O HO CH2OH OH OH Formula: C12H22O11 [C12(H2O)11] Dehydration of Sucrose: C12H22O11 + 11 H2SO4 12 C + 11 H2SO4.H2O saccharin A compound, C7H5NO3S, that is several hundred times sweeter than can sugar and is used as a calorie-free sweetener. risk-benefit analysis weigh pros and cons before deciding Because there are many considerations for each case, 50/50 thinking rarely applies. How does scientific knowledge advance? 1. curiosity 2. good observations 3. determination 4. persistence Aluminum Mining Charles Martin Hall 1850s: aluminum sold for $500 / pound Developed method to extract aluminum from bauxite Halls method 1 pound Al costs 30 cents 4-6 pounds bauxite + current = 1 lb Al The Scientific Method Guiding Questions Scientific explanations must meet certain criteria: they should be logical, respect the rules of evidence, be open to criticism, report methods and procedures, and make knowledge public. Scientific experiments are conducted after much thought about what may be causing the phenomena in order to isolate important factors. In order to isolate these factors careful planning, including addressing safety issues, must be taken into consideration before attempting experiments. In order to draw a valid conclusion from an experiment, all variables except for that which is being tested must be controlled. Measurements communicate not only a magnitude and the system of measurement (unit) but also information about the tool used to make the measurement through precision (significant figures) and uncertainty Pseudosciencedefinitely NOT the Scientific Method Checkbook Activity Checkbook Activity-Scientific Method Checkbook Activity-Scientific Method Keys http://www.unit5.org/chemistry/intro.html Fundamental Properties of Models A model does not equal reality. Models are oversimplifications, and are therefore often wrong. Models become more complicated as they age. We must understand the underlying assumptions in a model so that we dont misuse it. World of Chemistry The Annenberg Film Series VIDEO ON DEMAND Episode 4 - Modeling The Unseen Scientific investigators need to explain things beyond the realm of ordinary perception. The models used by scientists often represent flights of intuition and invention. Focusing on some examples of models used in chemistry, this program emphasizes one classic example that explains the behavior of gases. Scientific Method Scientific Method Scientific Law Scientific Method and Law Theories and Laws Why Dinosaurs Disappeared The Hellenic Market Four-Element Theory Drunken Goldfish Science and Morality Using the scientific method requires that one be a good observer. observation uses the five senses inference involves a judgment or assumption The Skeptical Chemist In The Sceptical Chymist (1661) Boyle stated that scientific speculation was worthless unless it was supported by experimental evidence. Robert Boyle This principle led to the development of the scientific method. observation what you sense or measure vs. inference involves a judgment My mother the eye doctor My mother the eye doctor Observation or Inference? The adult isholding on apiece ofReds. mother of the batter. (an eye doctor). One playerisofincatcher.abat.is talking. The adult written thethecatchers opposite teams. Namesmotherholdinga a note anpaper. The of are isholdingcalleduniforms.the One playerteamsthepicture thefrom mask. The piece thewearing The the is ofthe batter umpire. is optometrist or opthalmologist One players apaper is bat are on Data Observations are also called data. There are two types of data. qualitative data descriptions; no numbers quantitative data measurements; must have numbers and UNITS Parts of the Scientific Method Identify an unknown. Make a hypothesis (a testable prediction). Experiment to test the hypothesis. Draw a valid conclusion. Hypotheses A tentative explanation for the observations May not be correct, but it puts the scientists understanding of the system being studied into a form that can be tested Copyright 2007 Pearson Benjamin Cummings. All rights reserved. Experiments Tests the validity of the hypothesis Are systematic observations or measurements made under controlled conditions, in which the variable of interest is clearly distinguished from any others If experimental results are reproducible, they are summarized in a law. Copyright 2007 Pearson Benjamin Cummings. All rights reserved. A Scientific Experiment variable procedure any factor that the order of could influence events the result in an Experiments must experiment; be controlled; they must have two set-ups that must differ the recipe by only one variable. The conclusion must be based on the data. A Controlled Experiment? Introduction to Qualitative Analysis Introduction to Qualitative Analysis Introduction to Qualitative Analysis Keys http://www.unit5.org/chemistry/intro.html Scientific Method Observations Hypothesis Experimentation Controlled (one variable changed at a time) Collect data (quantitative and qualitative) Analyze data (graph, statisticstrends) Form valid conclusion. After many experimentsform a theory. Fundamental Properties of Models A model does not equal reality. Models are oversimplifications, and are therefore often wrong. Models become more complicated as they age. We must understand the underlying assumptions in a model so that we dont misuse it. Scientific Law vs. Scientific Theory A law states what happens. Law of A theory tries to explain why Gravity or how something happens. Theory of Gravity Atomic Theory Collision Theory of Reactions Experiments Law A verbal or mathematical description of a phenomenon that allows for general predictions Describes what happens and not why Unlikely to change greatly over time unless a major experimental error is discovered Theory Attempts to explain why nature behaves as it does Is incomplete and imperfect, evolving with time to explain new facts as they are discovered Copyright 2007 Pearson Benjamin Cummings. All rights reserved. Theory vs. Natural Law Scientific theory Natural law analyze additional data Hypothesis analyze initial observations Experiment Make observation Scientific Method Ask question Develop hypothesis Test hypothesis with further experiments Test hypothesis with an experiment Revise hypothesis Analyze data and draw conclusions Hypothesis IS supported Wysession, Frank, Yancopoulos, Physical Science Concepts in Action, 2004, page 8 Hypothesis is NOT supported Develop theory Question First What does the scientist want to learn more about? Then Research Scientific Method An Overview Gathering of information Next An Educated guess of an answer to the question Hypothesis Then Written and carefully followed step-by-step experiment designed to test the hypothesis Procedure/ Method Next Information collected during the experiment Data And And Written description of what was noticed during the experiment Observations Finally Conclusion Was the hypothesis correct or incorrect? Broad Questions Pe pe rform rim en ts S Qu pec es ific t io ns firm Con lts u Res Ex e Narrow th Focus Ref le Find ct on ings e ns ak tio M rva e bs O te ca s i un her mt om th O Ci W Learn What Is Known t men s u Doc tation ec Ex p Wheel of Scientific Inquiry Copyright 2007 Pearson Benjamin Cummings. All rights reserved. Stages In The Scientific Method FORMULATING HYPOTHESES OBSERVING collecting data measuring experimenting communicating organizing and analyzing data classifying inferring predicting communicating TESTING predicting experimenting communicating collecting data measuring Data do not support hypothesis revise or reject hypothesis PUBLISH RESULTS THEORIZING constructing models predicting communicating Results confirmed by other scientists validate theory. communicating Reviewing Concepts What is Science? How does the scientific process start and end? How are science and technology related? What are the branches of natural science? Explain the advantages and disadvantages of subdividing science into many different areas. Why do scientists seek to discover new laws of the universe? Reviewing Concepts Using a Scientific Approach What is the goal of scientific methods? How does a scientific law differ from a scientific theory? Why are scientific models useful? What are three types of variables in a controlled experiment? Does every scientific method begin with an observation? Explain. Scientific Law Charless Law V1V2 = T1T2 Observations Experiments Scientific Law Laws of nature never change. Theories and Laws The Earth is flat Speeding kills (Audubon, Germany); seat belts save lives LAW: 65 mph and wear seat belt No explanation of whybut the theory is if you drive at 120 mph and crash, an ambulance wont need to be called (only next of kin). Galileo Galilei (15641642) Among other things, rolled spheres down inclined planes. h h h Galileo nearly formulated concept of inertia. Why Dinosaurs Disappeared A theory Sun blocked Dinosaurs Earth Meteor Dust Cloud Evidence Ice Age - Glaciers RIP Meteor Crater Moon is formed The Original Metric Reference 1/10,000,000 = 1 meter H2O 1/10 m = 1 kilogram H2O 1 kg 1/10 m 1/10 m Length Mass Volume = 1 liter The Hellenic Market ~ ~ Fire Water Earth Air Four Element Theory FIRE Plato was an atomist Thought all matter was composed of 4 elements: Earth Water Fire Air Ether (close to heaven) Dry Hot AIR EARTH MATTER Wet Cold WATER Relation of the four elements and the four qualities Graphic courtesy of Ken Costello @ www.chemistryland.com Some Early Ideas on Matter Anaxagoras Suggested every substance had its own kind of seeds that clustered together to make the substance, much as our atoms cluster to make molecules. Empedocles Aristotle (Greek, born in Sicily, 490 B.C.) Suggested there were only four basic seeds earth, air, fire, and water. The elementary substances (atoms to us) combined in various ways to make everything. Democritus (Greek, born 500 B.C.) (Thracian, born 470 B.C.) Actually proposed the word atom (indivisible) because he believed that all matter consisted of such tiny units with voids between, an idea quite similar to our own beliefs. It was rejected by Aristotle and thus lost for 2000 years. (Greek, born 384 B.C.) Added the idea of qualities heat, cold, dryness, moisture as basic elements which combined as shown in the diagram (previous page). Hot + dry made fire; hot + wet made air, and so on. OConnor Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles 1982, page 26, Drunken Goldfish Fighting fish Uneducated worms appear to acquire knowledge by eating educated worms. Goldfish immersed in 3.1% alcohol will overturn within 6 to 8 minutes. Because of this tendency to fall over when drunk, the goldfish is a good model for research on the effects of alcohol. When preliminary studies indicated that goldfish tended to forget things when drunk, and that Siamese Fighting Fish became more aggressive after a little drink or two, their attraction as experimental animals became irresistible. Rats are more attracted to other rats than to tennis balls. Disco music Conclusions must be supported by data to be valid. Hartston, Drunken Goldfish & Other Irrelevant Scientific Research, page 53 Evidence must be reproducible Theory A single comprehensive idea that has stood up to repeated scrutiny The Scientific Attitude This attitude is one of inquiry, experimentation, honesty, and a faith that all natural phenomena can be explained. Science and Morality Science must operate in the realms or morality that society believes in Joseph Mengele Atomic Bomb Cloning of humans Stem cell research Scientific Method and Law Combustion & Phlogiston Phlogiston Theory Combustion Theory Burning Magnesium Metal in an Open Container Burning Magnesium Metal in a Closed Container Lighting a Bunsen Burner Flame Temperature Distribution Phlogiston Theory Phlogiston theory of burning (a) When an object burns it gives off a substance called phlogiston. (b) When the space surrounding the burning object is filled with phlogiston, the object will no longer be able to burn. Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 4 (a) (b) phlogiston phlogiston Combustion Theory Modern theory of burning (c) When an object burns, it uses up a substance (oxygen) in the surrounding space. (d) When the space surrounding the burning object has too little oxygen in it, the object will no longer be able to burn. Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 4 Antoine Lavoiser (c) (d) oxygen Phlogiston Theory of Burning 1. Flammable materials contain phlogiston. 2. During burning, phlogiston is released into the air. 3. Burning stops when object is out of phlogiston, Burning Magnesium Metal in an Open Container strip of magnesium metal white powder Before burning After burning Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 77 strip of magnesium metal white powder Burning Magnesium Metal in an Open Container strip of magnesium metal white powder Before burning white powder strip of magnesium metal After burning Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 77 mass increased Mg didnt LOSE phlogiston but gained oxygen! Burning Magnesium Metal in a Closed Container nichrome wire connected to a battery strip of magnesium metal Before burning white powder After burning 2 Mg + O2 2 MgO Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 77 mass conserved The Bunsen Burner Oxidizing flame Hottest part M i x t r e Barrel o f G A S a n d A I R Collar Air Spud Gas The Bunsen Burner Oxidizing flame Hottest part M i x t r e Barrel o f G A S a n d A I R Collar Air Spud Gas Robert Bunsen Lighting a Bunsen Burner gas valve outer, transparent, dim blue cone air adjustment gas adjustment Always light match BEFORE turning on gas. inner, less transparent, brighter, greenish-blue cone Flame Temperature Distribution Bunsen / Tirrill Burner Flame 1540oC 1550oC 1560oC 1540oC 1470oC 1560oC 520oC 1450oC 350oC 300oC 1640oC 1660oC Meker Burner Flame 1660oC 1660oC 1670oC 1670oC 1720oC 1720oC 1680oC 1720oC 1775oC The Bunsen / Tirrill burner and Meker burner differ not only in the higher maximum temperature produced, but also in heat distribution within the flame. Laboratory Equipment Laboratory Equipment Chemistry How did Chemistry Become a Science? http://en.wikipedia.org/wiki/History_of_chemistry Alchemy vs. Chemistry The Alchemist The Alchemists Dream Zinc Pennies Alchemy vs. Chemistry Pure Science Applied Science Aluminum Mining Corning Glass Fertilizers (5-15-10) Areas of Chemistry Stereotypes of Chemists A Career in Chemistry Forensic Scientist The Scope of Chemistry Starting Salaries The Alchem ist Frankly, Id be satisfied if I could turn gold into lead! The Alchemists Dream COPPER SILVER GOLD Zinc coated Brass = Copper + Zinc Penny into Gold - Alchemist Dream Zinc Pennies Copper was used to make bullet shells in WW II. By 1943, the supply of copper metal was in short supply. The US government did not want to waste copper on making pennies. Before 1982, all pennies were solid copper (except 1943). A shortage of copper drove the price of copper up in the early 1980s. If melted down, the copper could be sold for more than one cent. Pennies were made with steel metal. They looked silver. After 1982, pennies were made from zinc. A thin coating of copper was pressed on the zinc. Dem ocrat vs. Republican Alike Different politicians left Topic liberal support 'little man' Different Democrat right Topic un ethical ? Republican conservative support big business Alchem vs. Chemistry y Alike Different Different Topic Topic Alchemy Chemistry I think youve crossed that thin line between transmuting and cooking. Paracelsus Man consisted of three elements SALT represented the body SULFUR the soul MERCURY the spirit He thought he could rearrange the amounts of the elements to change man. He desired immortality and searched for a mystical elixir of life. The Beginnings early practical chemistry: household goods, weapons, soap, wine, basic medicine The Greeks believed there ___ ___ were four elements. earth air fire water ~ Timeline Greeks (Democratus ~450 BC) Discontinuous theory of matter ALCHEMY 400 BC 300 AD Issac Newton (1642 - 1727) 1000 2000 Greeks (Aristotle ~350 BC)) Continuous theory of matter American Independence (1776) Alchemy In Europe, alchemy was the quest for the Philosophers Stone (the elixir, the Sorcerers Stone). Allegedly, this substance would turn cheap metals into gold. transmuta changing one substance into another tion Philosophers Stone COPPER GOLD In ordinary chemical reactions, we cannot transmute elements into different elements. Early Ideas on Elements Robert Boyle stated... A substance was an element unless it could be broken down to two or more simpler substances. Air therefore could not be an element because it could be broken down in to many pure substances. Robert Boyle Alchemy After that 'chemistry' was ruled by alchemy. They believed that that could take any cheap metals and turn them into gold. Alchemists were almost like magicians. elixirs, physical immortality Alchemy Symbols Alchemy Alchemical symbols for substances GOLD SILVER COPPER . .. .. . ........ . IRON SAND transmutation: changing one substance into another In ordinary chemistry, we cannot transmute elements. Alchemy (~500 1300 A.D.) the quest for the Philosophers Stone It was supposed to change cheap metals into gold. Alchemical symbols for substances GOLD SILVER COPPER IRON The Alchemist, by David Teniers . .. .. ........ .. SAND transmutation: changing one substance into another In ordinary chemistry, we cannot transmute elements. Contributions of alchemists: lab apparatus / procedures how to make some alloys properties of some elements Alchemy was practiced in many regions of the world, including China and the Middle East. Alchemy arrived in western Europe around the year 500 C.E. Modern chemistry evolved from alchemy. Contributions of alchemists: Information about elements - the elements mercury, sulfur, and antimony were discovered - properties of some elements Develop lab apparatus / procedures / experimental techniques - alchemists learned how to prepare acids. - developed several alloys - new glassware What is Chemistry? the study of matter and its changes Chemistry C H E M Y ST E RY CHEM-IS-TRY CHEMASTERY CH E M I SE R Y Chemistry CHEMYSTERY CHEM-IS-TRY CHE MASTE RY CHEMISERY Areas of Chemistry Organic The study of most carbon-containing compounds Inorganic The study of all substances not classified as organic, mainly those compounds that do not contain carbon Analytical The identification of the components and composition of materials Physical The study of the properties, changes, and relationships between energy and matter Biochemistry The study of substances and processes occurring in living things Areas of Chemistry organic the study of carboncontaining compounds inorganic everything except carbon e.g., compounds containing metals physical measuring physical properties of substances e.g., the melting point of gold biochemistry the chemistry of living things Stereotypes of Chemists Male Middle-aged White Lab coat Nerd / Geek Careers in Chemistry research (new products) production (quality control) development (manufacturing) chemical sales software engineering teaching Careers in Chemistry research (new products) production (quality control) development (scale up manufacturing processes) chemical sales software engineering Pharmacist teaching The skills you will develop by an earnest study of chemistry will help you in any career the field. chemistry: study of matter and its changes Areas of Chemistry organic: the study of carbon-containing compounds inorganic: studies everything except carbon (e.g., metals) biochemistry: the chemistry of living things physical: measuring physical properties of substances Biological Compounds Biological Compounds Proteins Carbohydrates Lipids Nucleic Acids a polymer composed of amino acids a simple sugar or a polymer composed of simple sugars a fat, an oil, a wax, or a steroid a polymer composed of a sugar, an organic base, and phosphoric acid Biochemical compounds can be classified as one of the following: protein, carbohydrate, lipid, or nucleic acid. Corwin, Introductory Chemistry, 2005, page 551 Government Regulation of Chemicals to protect the environment EPA consumer Consumer Product Safety Commission, USDA, BATF, FDA worker OSHA A Career in the Field of Chemistry Research Chemist Chemist who works in Development Production Chemists and Technicians Other Jobs for Chemists Chemical sales, software engineering, patent law, teaching The skills you will develop by an earnest study of chemistry will help you in any career field. The Scope of Chemistry -- petroleum products gasoline, oil, diesel fuel, heating oil, asphalt -- synthetic fibers nylon, polyester, rayon, spandex -- pharmaceuticals medicines, cancer drugs, VIAGRA 1 in 10,000 new products gets FDA approval -- bulk chemical manufacturing #1 chemical = sulfuric acid (H2SO4) All fields of endeavor are affected by chemistry. The Scope of Chemistry bulk chemical manufacturing acids, bases, fertilizers petroleum products fuels, oils, greases, asphalt pharmaceuticals 1 in 10,000 new products gets FDA approval synthetic fibers nylon, polyester, rayon, spandex Research Basic Research Carried out for the sake of increasing knowledge Driven by curiosity or a desire to know Roy Plunkett discovers Teflon is a nonstick material Applied Research Carried out to solve a specific problem Safer refrigerant that does not harm ozone layer Technological Development Production and use of products that improve our quality of life Computer chips, biodegradable materials, catalytic converters for automobiles Forensic Scientist Arson is suspected in the burning of this house. Use science to solve crimes Arson investigation DNA fingerprinting Luminol test for blood Gasoline, paint, and bottled gas are extremely volatile. The Scope of Chemistry The chemical industry has a large effect on our lives. bulk chemical manufacturing synthetic fibers petroleum products pharmaceuticals ALL fields of endeavor are affected by chemistry. Starting Yearly Salaries Chemist BS MS PhD $45,400 $53,500 $66,000 vs. Communications BS MS PhD Related Occupations: Chemical Engineering, biological scientist, chemical technologist, physicists, medical scientists Physician Resident Earning $30,753 - $41,895 $120,000 - $240,000 1998 Average Salaries All fields of endeavor are affected by chemistry. World of Chemistry The Annenberg Film Series VIDEO ON DEMAND Episode 1 - The World of Chemistry The relationships of chemistry to the other sciences and to everyday life are presented. The world of chemistry is introduced by providing highlights of key sequences and themes from programs in the series. The relationships of chemistry to the other sciences and to everyday life are presented. Running Time: 28:38 Chemistry and Manipulating Numerical Data Numbers Measurements v v science is based on measurements all measurements have: - magnitude - uncertainty - units v v mathematics is based on numbers exact numbers are obtained by: - counting - definition Graphs Bar Graph shows how many of something are in each category Chemistry Grades 10 8 6 4 2 0 A B C D F Unit 1 Test Honors Chemistry Introduction to Chemistry 1st Hour 2nd Hour 5th Hour 6th Hour 8th Hour 55 Bs 27 As 35 Cs Avg: 40.9 + 4.0 83.8 + 8.0 % 5 Ds 50 45 40 35 30 This is also about what the quarter grades will look like. September 14, 2007 Pie Graph shows how a whole is broken into parts Percentage of Weekly Income 40% 15% Entertainment (40%) Food (25%) Clothing (20%) Savings (15%) 20% 25% Line Graph shows continuous change Stock Price over Time Share Price ($) 60 50 40 30 20 10 0 Jan Feb Mar Month Apr Elements of a good line graph axes labeled, with units use the available space title neat Volume (L) Temp. v. Vol. for a Gas at Constant Pressure 10 9 8 7 6 5 4 3 2 1 0 120 140 160 180 200 Temp. (K) 220 240 How to read a graph Temp. v. Vol. for a Gas at Constant Pressure What volume would the gas occupy at a temperature of 150 K? 7 L Extrapolate - read data beyond data points What volume would the gas occupy at a temperature of ~4 L 260 K? Which do you have more confidence in? Why? Volume (L) Interpolate - read between data points (dependent variable) 10 9 8 7 6 5 4 3 2 1 0 120 140 160 180 200 Temp. (K) (independent variable) 220 240 Graphs Line Graph 80 Used to show trends or continuous change Bar Graph 60 40 20 0 1st 2nd 3r d Qtr Qt r Qt r Used to display information collected by counting 4th Qt r Pie Graph Used to show how some fixed quantity is broken down into parts Line Graph How does the mass of a penny change with age? B A Mass (g) Mass (g) Age (Year of Penny) Age (Year of Penny) D C Mass (g) Mass (g) Age (Year of Penny) Age (Year of Penny) Bar Graph Descriptive title Chemistry Grades Number of Students 70 Legend 60 50 A B C D 40 30 20 10 0 Axis labeled (with units) 1st Qtr 2nd Qtr 3rd Qtr 4th Qtr Pie Graph Pie Graphs Calcium 3% Iron 5% Aluminum 8% Other 9% Oxygen 49% Silicon 26% Earth's Crust Oxygen Silicon Other Aluminum Iron Calcium Graphing Graphing Graphing Keys http://www.unit5.org/chemistry/intro.html Reviewing Concepts Presenting Scientific Data How do scientists organize data? How can scientists communicate experimental results? What does a given point represent on a line graph? The density of copper is 8.92 g/cm3. If you plotted the volume in cubic centimeters, what would the slope of the line be? Conversion Factors and Unit Cancellation A physical quantity must include: Number + Unit Calculation Corner: Unit Conversion 1 foot = 12 inches Calculation Corner: Unit Conversion 1 foot = 12 inches 1 foot 12 inches = 1 Calculation Corner: Unit Conversion 1 foot = 12 inches 1 foot 12 inches 12 inches 1 foot = 1 = 1 Calculation Corner: Unit Conversion 1 foot 12 inches 12 inches 1 foot Conversion factors Calculation Corner: Unit Conversion 1 foot 12 inches 12 inches 1 foot Conversion factors ( 3 feet )( 12 inches 1 foot ) = 36 inches How many cm are in 1.32 meters? equality: 1 m = 100 cm (or 0.01 m = 1 cm) applicable conversion factors: 1m ______ 100 cm X cm = 1.32 m or ( 100 cm ______ 1m ) 100 cm ______ = 132 cm 1m We use the idea of unit cancellation to decide upon which one of the two conversion factors we choose. How many meters is 8.72 cm? equality: 1 m = 100 cm applicable conversion factors: 1m ______ 100 cm X m = 8.72 cm or ( 100 cm ______ 1m ) 1m ______ = 0.0872 m 100 cm Again, the units must cancel. How many feet is 39.37 inches? equality: 1 ft = 12 in applicable conversion factors: 1 ft ______ 12 in X ft = 39.37 in or 12 in ______ 1 ft () ____ = 3.28 ft 1 ft 12 in Again, the units must cancel. How many kilometers is 15,000 decimeters? X km = 15,000 dm ( )( 1m ____ 10 dm ) 1 km ______ = 1.5 km 1,000 m How many seconds is 4.38 days? X s = 4.38 d ( )( 24 h ____ 1d )( ) 60 min _____ 1h 60 s ____ 1 min = 378,432 s If we are accounting for significant figures, we would change this to 3.78 x 105 s Real Life Chemistry Real Life Chemistry Real Life Chemistry Keys http://www.unit5.org/chemistry/intro.html Simple Math with Conversion Factors Example Problem Measured dimensions of a rectangle: length (L) = 9.70 cm width (W) = 4.25 cm Find area of rectangle. L A=L. W = (9.70 cm)(4.25 cm) = 41.2 cm 2. cm W Convert 41.2 cm2 to m2. 1m X m2 = 41.2 cm2 ______ = 0.412 m2 ( 100 cm ) WRONG! = 0.412 cm.m Recall that 41.2 cm2 = 41.2 cm.cm X m2 = 41.2 cm.cm ( )( 1m ______ 100 cm ) 1m ______ 100 cm = 0.00412 m2 ( ) 1m X m2 = 41.2 cm2 ______ 2 = 100 cm 0.00412 m2 Convert 41.2 cm2 to mm2. Recall that 41.2 cm2 = 41.2 cm.cm ( 10 mm _____ 1 cm X mm2 = 41.2 cm.cm )( 10 mm _____ 1 cm ) = 4,120 mm2 X mm2 = 41.2 cm2 ( ) 10 mm 2 = _____ 1 cm 4,120 mm2 Measured dimensions of a rectangular solid: Length = 15.2 cm Width = 3.7 cm Height = 8.6 cm Find volume of solid. H L V=L.W.H = (15.2 cm)(3.7 cm)(8.6 cm) = 480 cm 3 W Convert to m3. cm.cm.cm 2 3 ( )( ( X m3 = 480 cm ) 1m _____ 100 cm 1m _____ )( 100 cm ) 1m _____ = 100 cm or 1m X m3 = 480 cm3 _____ 3 = 100 cm 0.000480 m3 or X m3 = 480 cm3 ( 3 ) 1m _________ = 4.80 x 10-4 m3 3 1000000 cm Convert to m3... Measured dimensions of a rectangular solid: Length = 15.2 cm 0.152 m Width = 3.7 cm 0.037 m Height = 8.6 cm 0.086 m H Find volume of solid. L V=L.W.H = (0.152 m)(0.037 m)(0.086 m) = 0.000480 m 3 W Convert to mm3. By what factor do mm and cm differ? 1 cm = 10 mm 10 By what factor do mm2 and cm2 differ? 1 cm)2 = (10 mm)2 (1 cm2 = 100 mm2 100 By what factor do mm3 and cm3 differ? 1 cm3 = (10 mm3 (1 cm)3= 1000mm)3 1,000 Conversion Factors Conversion Factors Conversion Factors Keys http://www.unit5.org/chemistry/intro.html Scientific Notation Often used to express very large or very small numbers. Also used to maintain correct number of significant figures. Form:(# from 1 to 9.999) x 10exponent 800 = 8 x 10 x 10 = 8 x 102 2531 = 2.531 x 10 x 10 x 10 = 2.531 x 103 0.0014 = 1.4 / 10 / 10 / 10 = 1.4 x 10-3 Change to standard form. . . 000000187000000 1.87 x 105 = 0.0000187 3.7 x 108 = 370,000,000 7.88 x 101 = 78.8 2.164 x 102 = 0.02164 Change to scientific notation. 12,340 = 1.234 x 104 0.369 = 3.69 x 101 0.008 = 8 x 103 1,000,000,000 = 1 x 109 Using the Exponent Key on a Calculator EE EXP EE or EXP means times 10 to the How to type out 6.02 x 1023: How to out 6.02 x 1023: 6 0 . Dont do it like this 6 2 2 3 WRONG! 0 . EE EE 2 yx 2 3 WRONG! or like this 6 0 . or like this: 6 . 0 2 x 1 0 EE 2 3 TOO MUCH WORK. 2 x 1 0 yx 2 3 Also, know when to hit your () sign before the number, after the number, or either one. Example: 1.2 x 105 2.8 x 1013 Type this calculation in like this: 1 . 2 EE 5 2 8 EE 1 3 . Calculator gives 4.2857143 09 = or 4.2857143 E09 This is NOT written 4.39 But instead is written 4.3 x 109 or 4.3 E 9 7.5 x 10-6 - 8.7 x 10-4 4.35 x 106 1.23 x 10 -3 = -6.525 x 10-9 report -6.5 x 10-9 (2 sig. figs.) = 5.3505 x 103 or 5350.5 report 5.35 x 103 (3 sig. figs.) 5.76 x 10 -16 9.86 x 10 -4 = 5.84178499 x 10-13 8.8 x 1011 3.3 x 1011 = 2.904 x 1023 6.022 x 10 23 - 5.1 x 10-8 report 5.84 x 10-13 (3 sig. figs.) report 2.9 x 1023 (2 sig. figs.) = -3.07122 x 1016 report -3.1 x 1016 (2 sig. figs.) Scientific Notation Scientific Notation Converting Numbers to Scientific Notation How to Use a Scientific Calculator Scientific Notation We often use very small and very large numbers in chemistry. Scientific notation is a method to express these numbers in a manageable fashion. Thus 0.000 000 1 cm can be written 1 x 10-7 cm. Lets see why Scientific notation expresses a number as the product of two factors, the first falling between 1 and 10 and the second being a power of 10. Method to express really big or small numbers. Format is Mantissa x Decimal part of original number Base Power Decimal you moved 6.02 x 1023 We just move the decimal point around. 602000000000000000000000 Scientific Notation Numbers are written in the form M x 10n, where the factor M is a number greater than or equal to 1 but less than 10 and n is a whole number. 5000 = 5 x 103 or 5 x (10 x 10 x 10) 5 x 1000 5000 5 3 Numbers > one have a positive exponent. Numbers < one have a negative exponent. xEE 10n Converting Numbers to Scientific Notation 0.00002205 1 2 3 4 2.205 x 10-5 5 In scientific notation, a number is separated into two parts. The first part is a number between 1 and 10. The second part is a power of ten. How to Use a Scientific Calculator Divide: (5.44 x 107) . .(8.1 x 104) 671.604938 00 5.44 04 8.1 54400000. 07 How to enter this on a calculator: EE 5.44 7 . . 8.1 4 EE ENTER 4 EXP = OR EXP 5.44 7 . . 8.1 671.6049383 rounded to 6.7 x 102 Davis, Metcalfe, Williams, Castka, Modern Chemistry, 1999, page 52 Rule for Multiplication Calculating with Numbers Written in Scientific Notation When multiplying numbers in scientific notation, multiply the first factors and add the exponents. Sample Problem: Multiply 3.2 x 10-7 by 2.1 x 105 (3.2) x (2.1) = 6.72 6.72 x 10-2 (-7) + (5) = -2 or 10-2 Exercise: Multiply 14.6 x 107 by 1.5 x 104 2.19 x 1012 Rule for Division Calculating with Numbers Written in Scientific Notation When dividing numbers in scientific notation, divide the first factor in the numerator by the first factor in the denominator. Then subtract the exponent in the denominator from the exponent in the numerator. Sample Problem: Divide 6.4 x 106 by 1.7 x 102 . (6.4). (1.7) = 3.76 3.76 x 104 (6) - (2) = 4 or 104 Exercise: Divide 2.4 x 10-7 by 3.1 x 1014 7.74 x 10-22 Rule for Addition and Subtraction Calculating with Numbers Written in Scientific Notation In order to add or subtract numbers written in scientific notation, you must express them with the same power of 10. Sample Problem: Add 5.8 x 103 and 2.16 x 104 (5.8 x 103) + (21.6 x 103) = 27.4 x 103 Exercise: Add 8.32 x 10-7 and 1.2 x 10-5 2.74 x 104 1.28 x 10-5 Using Scientific Notation for Expressing the Correct Number of Significant Figures Measurement Number of significant figures it contains 25 g 2 0.030 kg 2 1.240560 x 106 mg 7 6 x 104 sec 1 246.31 g 5 20.06 cm 4 1.050 m 4 Measurement Number of significant figures it contains 0.12 kg 2 1240560. cm 7 6000000 kg 1 6.00 x 106 kg 3 409 cm 3 29.200 cm 5 0.02500 g 4 Scientific Notation Scientific Notation Scientific Notation Keys http://www.unit5.org/chemistry/intro.html Basic Concepts in Chemistry chemical any substance that takes part in, or occurs as a result of, a chemical reaction All matter can be considered to be chemicals or mixtures of chemicals. chemical reaction a rearrangement of atoms such that what you end up with products differs from what you started with reactants Combustion of a Hydrocarbon carbon + water dioxide methane + oxygen CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g) sodium + water hydrogen + sodium hydroxide 2 Na(s) + 2 H2O(l) H2(g) + 2 NaOH(aq) Law of Conservation of Mass total mass = total mass of reactants of products Rmass = Pmass Click Black Snake Demonstration The Law of Conservation of Mass total mass of reactants = total mass of products H2SO4 Sugar Dehydration of sugar with the addition of sulfuric acid. During chemical reactions, no measurable change in total mass occurs. for Video Basic Concepts in Chemistry sodium + water hydrogen + sodium hydroxide 2 Na(s) + 2 H2O(l) H2(g) + 2 NaOH(s) Lets visualize whats happening at the particle level What happens to the particles during a chemical reaction? Is there a change in energy associated with a chemical change? They are NOT created or destroyed; they are merely rearranged Yes: heat, light, sound perhaps not easily noticed Basic Concepts in Chemistry sodium + water hydrogen + sodium hydroxide 2 Na(s) + 2 H2O(l) H2(g) + 2 NaOH(s) Lets visualize whats happening at the particle level What happens to the particles during a chemical reaction? Is there a change in energy associated with a chemical change? They are NOT created or destroyed; they are merely rearranged Yes: heat, light, sound perhaps not easily noticed Synthesis taking small molecules and putting them together, usually in many steps, to make something more complex Sunlight Oxygen Carbon Dioxide Glucose Water Photosynthesis CO2 + H2O O2 + C6H12O6 World of Chemistry The Annenberg Film Series VIDEO ON DEMAND Episode 3 - Measurement The Foundation of Chemistry Accuracy and precision are fundamental properties to modern chemistry. The distinction between the two terms and their importance in establishing measurement standards in commerce and science are explained. (Running Time: 28:38) from Industry Week, 1981 November 30 TheMetricSystem No Cussing! The following 4-Letter words are forbidden here: Inch Mile Foot Pint Yard Acre And we never swear the BIG F (useoC) Please keep it clean and Metric SI System The International System of Units Derived Units Commonly Used in Chemistry Area and Volume: Derived Units Prefixes in the SI System Map of the world where red represents countries which do not use the metric system A Common System for Trade English system of measurement originated in 1215 with the signing of the Magna Carta. It attempted to bring uniform measurements to world trade. In 1790, the French government appointed a committee of scientists to develop a universal measuring system. It took ~10 years, and they unveiled the Metric system. length meter mass gram volume liter L time second s m g The International System of Units Quantity Name Symbol Length meter m Mass kilogram kg Time second s Amount of substance mole mol Thermodynamic temperature Kelvin K Electric current amperes amps Luminous intensity candela cd Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 16 The Original Metric Reference H2O 1 kg = 1 liter 1/10,000,000 Earth Volume = 1 meter Length 1/10 m H2O 1/10 m 1/10 m Mass = 1 kilogram The Official Standard Meter The Official Standard Kilogram Derived Units Commonly Used in Chemistry Quantity Area Volume Force Pressure Energy Power Voltage Frequency Electric charge Name square meter cubic meter newton pascal joule watt volt hertz coulomb Symbol m2 m3 N Pa J W V Hz C Area and Volume: Derived Units Area = length x width = 5.0 m x 3.0 m = 15 ( m x m) = 15 m2 Volume = length x width x height = 5.0 m x 3.0 m x 4.0 m = 60 ( m x m x m) = 60 m3 Prefixes in the SI System The Commonly Used Prefixes in the SI System Prefix Power of 10 for Meaning Scientific Notation Symbol _______________________________________________________________________ mega- M 1,000,000 106 kilo- k 1,000 103 deci- d 0.1 10-1 centi- c 0.01 10-2 milli- m 0.001 10-3 micro- 0.000001 10-6 nano- n 0.000000001 Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 118 10-9 Measurement 100 mL Graduated Cylinder Units of Measuring Volume Reading a Meniscus Units for Measuring Mass Quantities of Mass SI-English Conversion Factors Accuracy vs. Precision Accuracy Precision Resolution SI units for Measuring Length Comparison of English and SI Units Reporting Measurements Measuring a Pin Practice Measuring Measurement 100 mL Graduated Cylinder Units of Measuring Volume Reading a Meniscus Units for Measuring Mass Quantities of Mass SI-English Conversion Factors Accuracy vs. Precision Accuracy Precision Resolution SI units for Measuring Length Comparison of English and SI Units Reporting Measurements Measuring a Pin Practice Measuring 100 mL Graduated Cylinder Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 119 Instruments for Measuring Volume Graduated cylinder Syringe Buret Pipet Volumetric flask Units of Measuring Volume 1 L = 1000 mL 1 qt = 946 mL Timberlake, Chemistry 7th Edition, page 3 Reading a Meniscus 10mL 10 line of si ght t oo h igh proper line of sight line graduated cylinder low t too h of sig 8 oo h ing t read igh reading correct 6 read ing t oo lo w Units for Measuring Mass 1 kg = 2.20 lb Timberlake, Chemistry 7th Edition, page 3 Units for Measuring Mass 1 kg (1000 g) 1 lb 1 lb 0.20 lb ChristophersonScales Made in Normal, Illinois USA 1 kg = 2.20 lb 1024 g 1021 g Quantities of Mass Giga- Mega- 1018 g 1015 g 1012 g Ocean liner 109 g 106 g Kilo- 103 g base 10-6 g nano- 10-9 g pico- 10-12 g femto- 10-15 g atomo- 10-18 g Average human 1.0 liter of water 10-3 g micro- Indian elephant 100 g milli- 10-21 g 10-24 g Kelter, Carr, Scott, Chemistry A Wolrd of Choices 1999, page 25 Earths atmosphere to 2500 km Grain of table salt Typical protein Uranium atom Water molecule Factor Name Symbol Factor 10-1 decimeter dm 101 10-2 centimeter cm 10-3 millimeter 10-6 Name Symbol decameter 102 dam hectometer hm mm 103 kilometer km micrometer m 106 megameter Mm 10-9 nanometer nm 109 gigameter Gm 10-12 picometer pm 1012 terameter Tm 10-15 femtometer fm 1015 petameter Pm 10-18 attometer am 1018 exameter Em 10-21 zeptometer zm 1021 zettameter Zm 10-24 yoctometer ym 1024 yottameter Ym Scientific Notation: Powers of Ten Rules for writing numbers in scientific notation: Write all significant figures but only the significant figures. Place the decimal point after the first digit, making the number have a value between 1 and 10. Use the correct power of ten to place the decimal point properly, as indicated below. a) Positive exponents push the decimal point to the right. The number becomes larger. It is multiplied by the power of 10. b) Negative exponents push the decimal point to the left. The number becomes smaller. It is divided by the power of 10. c) 10o = 1 Examples: 3400 = 3.20 x 103 0.0120 = 1.20 x 10-2 Nice visual display of Powers of Ten (a view from outer space to the inside of an atom) viewed by powers of 10! Multiples of bytes as defined by IEC 60027-2 SI prefix Name Symbol Binary prefixes Multiple Name Sy mb ol Multipl e kilobyte kB 103 (or 210) kibibyte KiB 210 megabyte MB 106 (or 220) mebibyte MiB 220 gigabyte GB 109 (or 230) gibibyte GiB 230 terabyte TB 1012 (or 240) tebibyte TiB 240 petabyte PB 1015 (or 250) pebibyte PiB 250 exabyte EB 1018 (or 260) exbibyte EiB 260 zettabyte ZB 1021 (or 270) yottabyte YB 1024 (or 280) A yottabyte (derived from the SI prefix ) Metric Article Metric Article (questions) Metric Article (questions) Keys http://www.unit5.org/chemistry/intro.html SI-US Conversion Factors Relationship Conversion Factors Length 2.54 cm = 1 in. 2.54 cm 1 in and 1 m = 39.4 in. 39.4 in 1m and 946 mL = 1 qt 946 mL 1 qt and 1 qt 946 mL 1 L = 1.06 qt 1.06 qt 1L and 1L 1.06 qt and 1 lb 454 g and 1 kg 2.20 lb 1 in 2.54 cm 1m 39.4 in. Volume Mass 454 g = 1 lb 1 kg = 2.20 lb 454 g 1 lb 2.20 lb 1 kg Accuracy vs. Precision Good accuracy Good precision Poor accuracy Good precision Poor accuracy Poor precision Systematic errors: reduce accuracy (instrument) Random errors: reduce precision (person) Accuracy vs. Precision Good accuracy Good precision Poor accuracy Good precision Random errors: reduce precision Poor accuracy Poor precision Systematic errors: reduce accuracy Accuracy Precision v v v reproducibility check by repeating measurements poor precision results from poor technique v v v correctness check by using a different method poor accuracy results from procedural or equipment flaws. Types of errors Instrument not zeroed properly Reagents made at wrong concentration Temperature in room varies wildly Person running test is not properly trained Errors Systematic Errors in a single direction (high or low) Can be corrected by proper calibration or running controls and blanks. Random Errors in any direction. Cant be corrected. Can only be accounted for by using statistics. Accuracy Precision Resolution not accurate, not precise accurate, not precise not accurate, precise accurate and precise accurate, low resolution time offset [arbitrary units] 3 2 1 0 -1 -2 -3 subsequent samples Accuracy Precision Resolution not accurate, not precise accurate, not precise not accurate, precise accurate and precise accurate, low resolution time offset [arbitrary units] 3 2 1 0 -1 -2 -3 subsequent samples Standard Deviation The standard deviation, SD, is a precision estimate based on the area score: SD = ( xi x )2 i where xi is the i-th measurement x is the average measurement N is the number of measurements. y 0 One standard deviation away from the mean in either direction on the horizontal axis (the red area on the graph) accounts for around 68 percent of the people in this group. Two standard deviations away from the mean (the red and green areas) account for roughly 95 percent of the people. Three standard deviations (the red, green and blue areas) account for about 99 percent of the people. x N 1 SI Prefixes kilodecicentimilli- 1000 1/10 1/100 1/1000 Also know 1 mL = 1 cm3 and 1 L = 1 dm3 SI System for Measuring Length The SI Units for Measuring Length Unit Symbol Meter Equivalent _______________________________________________________________________ kilometer km meter m decimeter dm 0.1 m or 10-1 m centimeter cm 0.01 m or 10-2 m millimeter mm 0.001 m or 10-3 m micrometer m 0.000001 m or 10-6 m nanometer nm 0.000000001 m or 10-9 m Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 118 1,000 m or 103 m 1 m or 100 m Comparison of English and SI Units 1 inch 2.54 cm 1 inch = 2.54 cm Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 119 Reporting Measurements Using significant figures Report what is known with certainty Add ONE digit of uncertainty (estimation) Davis, Metcalfe, Williams, Castka, Modern Chemistry, 1999, page 46 Measuring a Pin Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 122 Practice Measuring 0 cm 2 3 4 5 4.5 cm 0 cm 1 2 3 4 5 4.54 cm 0 cm Timberlake, Chemistry 7th Edition, page 7 1 1 2 3 4 5 3.0 cm Implied Range of Uncertainty 3 4 5 6 Implied range of uncertainty in a measurement reported as 5 cm. 3 4 5 6 Implied range of uncertainty in a measurement reported as 5.0 cm. 3 4 5 6 Implied range of uncertainty in a measurement reported as 5.00 cm. Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 32 20 ? 15 mL ? 1.50 x 101 mL 15.0 mL 10 Reading a Vernier A Vernier allows a precise reading of some value. In the figure to the left, the Vernier moves up and down to measure a position on the scale. This could be part of a barometer which reads atmospheric pressure. The "pointer" is the line on the vernier labeled "0". Thus the measured position is almost exactly 756 in whatever units the scale is calibrated in. 756 http://www.upscale.utoronto.ca/PVB/Harrison/Vernier/Vernier.html If you look closely you will see that the distance between the divisions on the vernier are not the same as the divisions on the scale. The 0 line on the vernier lines up at 756 on the scale, but the 10 line on the vernier lines up at 765 on the scale. Thus the distance between the divisions on the vernier are 90% of the distance between the divisions on the scale. Reading a Vernier A Vernier allows a precise reading of some value. In the figure to the left, the Vernier moves up and down to measure a position on the scale. 770 5 760 756 Vernier Scale 10 This could be part of a barometer which reads atmospheric pressure. The "pointer" is the line on the vernier labeled "0". Thus the measured position is almost exactly 756 in whatever units the scale is calibrated in. 0 750 http://www.upscale.utoronto.ca/PVB/Harrison/Vernier/Vernier.html If you look closely you will see that the distance between the divisions on the vernier are not the same as the divisions on the scale. The 0 line on the vernier lines up at 756 on the scale, but the 10 line on the vernier lines up at 765 on the scale. Thus the distance between the divisions on the vernier are 90% of the distance between the divisions on the scale. If we do another reading with the vernier at a different position, the pointer, the line marked 0, may not line up exactly with one of the lines on the scale. Here the "pointer" lines up at approximately 746.5 on the scale. 760 10 5 750 If you look you will see that only one line on the vernier lines up exactly with one of the lines on the scale, the 5 line. This means that our first guess was correct: the reading is 746.5. 0 What is the reading now? 740 http://www.upscale.utoronto.ca/PVB/Harrison/Vernier/Vernier.html 741.9 If we do another reading with the vernier at a different position, the pointer, the line marked 0, may not line up exactly with one of the lines on the scale. Here the "pointer" lines up at approximately 746.5 on the scale. 760 10 5 750 If you look you will see that only one line on the vernier lines up exactly with one of the lines on the scale, the 5 line. This means that our first guess was correct: the reading is 746.5. 0 What is the reading now? 740 http://www.upscale.utoronto.ca/PVB/Harrison/Vernier/Vernier.html 756.0 760 10 5 0 Here is a final example, with the vernier at yet another position. The pointer points to a value that is obviously greater than 751.5 and also less than 752.0. Looking for divisions on the vernier that match a division on the scale, the 8 line matches fairly closely. So the reading is about 751.8. 750 740 In fact, the 8 line on the vernier appears to be a little bit above the corresponding line on the scale. The 8 line on the vernier is clearly somewhat below the corresponding line of the scale. So with sharp eyes one might report this reading as 751.82 0.02. This "reading error" of 0.02 is probably the correct error of precision to specify for all measurements done with this apparatus. http://www.upscale.utoronto.ca/PVB/Harrison/Vernier/Vernier.html How to Read a Thermometer (Celcius) 10 5 50 0 0 5 100 5 4.0 oC 10 0 8.3 oC 64 oC 0 3.5 oC Record the Temperature (Celcius) 60oC 50oC 5oC 25oC 100oC 100oC 40oC 4oC 20oC 80oC 80oC 30oC 3oC 15oC 60oC 60oC 20oC 2oC 10oC 40oC 40oC 10oC 1oC 5oC 20oC 20oC 0oC A 6oC 0oC 0oC 0oC 0oC 30.0oC B 3.00oC C 19.0oC D 48oC E 60.oC Measurements Metric (SI) units Length Mass Volume Density Timberlake, Chemistry 7th Edition, page 40 Prefixes Uncertainty Conversion factors Significant figures Problem solving with conversion factors MEASUREMENT Using Measurements I II III Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Accuracy vs. Precision Accuracy - how close a measurement is to the accepted value Precision - how close a series of measurements are to each other ACCURATE = Correct PRECISE = Consistent Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Percent Error Indicates accuracy of a measurement % error = experimental literature literature your value accepted value Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem 100 Percent Error A student determines the density of a substance to be 1.40 g/mL. Find the % error if the accepted value of the density is 1.36 g/mL. % error = 1.40 g/mL 1.36 g/mL 1.36 g/mL % error = 2.9 % Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem 100 Significant Figures Indicate precision of a measurement. Recording Sig Figs w Sig figs in a measurement include the known digits plus a final estimated digit 2.35 cm Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Significant Figures Counting Sig Figs (Table 2-5, p.47) w Count all numbers EXCEPT: Leading zeros -- 0.0025 Trailing zeros without a decimal point -- 2,500 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Significant Figures Counting Sig Fig Examples 1. 23.50 23.50 4 sig figs 2. 402 402 3 sig figs 3. 5,280 5,280 3 sig figs 4. 0.080 4. 0.080 2 sig figs Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Significant Figures Calculating with Sig Figs w Multiply/Divide - The # with the fewest sig figs determines the # of sig figs in the answer. (13.91g/cm3)(23.3cm3) = 324.103g 4 SF 3 SF 3 SF 324 g Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Significant Figures Calculating with Sig Figs (cont) w Add/Subtract - The # with the lowest decimal value determines the place of the last sig fig in the answer. 3.75 mL .75 mL + 4.1 mL 4.1 mL 7.85 mL 7.9 mL 224 g 24 + 130 g 13 0 354 g 350 g Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Significant Figures Calculating with Sig Figs (cont) w Exact Numbers do not limit the # of sig figs in the answer. Counting numbers: 12 students Exact conversions: 1 m = 100 cm 1 in any conversion: 1 in = 2.54 cm Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Significant Figures Practice Problems 5. (15.30 g) (6.4 mL) 4 SF 2 SF = 2.390625 g/mL 2.4 g/mL 2 SF 6. 18.9 g - 0.84 g 18.06 g 18.1 g Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Scientific Notation 65,000 kg 6.5 104 kg Converting into scientific notation: w w w Move decimal until theres 1 digit to its left. Places moved = exponent. Large # (>1) positive exponent Small # (<1) negative exponent Only include sig. figs. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Scientific Notation Practice Problems 7. 2,400,000 g 2.4 106 g 8. 0.00256 kg 2.56 10-3 kg 9. 7 10-5 km 0.00007 km 10. 6.2 104 mm 62,000 mm Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Scientific Notation Calculating with scientific notation (5.44 107 g) (8.1 104 mol) = Type on your calculator: 5.44 EXP EE 7 8.1 EXP EE 4 EXE ENTER = 671.6049383 = 670 g/mol = 6.7 102 g/mol Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Proportions Direct Proportion yx y x Inverse Proportion 1 y x y Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem x Reviewing Concepts Measurement Why do scientists use scientific notation? What system of units do scientists use for measurements? How does the precision of measurements affect the precision of scientific calculations? List the SI units for mass, length, and temperature. Rules for Counting Significant Figures 1. Nonzero integers always count as significant figures. 2. Zeros: There are three classes of zeroes. a. c. e. Leading zeroes precede all the nonzero digits and DO NOT count as 2 significant figures. Example: 0.0025 has ____ significant figures. Captive zeroes are zeroes between nonzero numbers. These always 4 count as significant figures. Example: 1.008 has ____ significant figures. Trailing zeroes are zeroes at the right end of the number. Trailing zeroes are only significant if the number contains a decimal point. 3 Example: 1.00 x 102 has ____ significant figures. Trailing zeroes are not significant if the number does not contain a decimal 1 point. Example: 100 has ____ significant figure. 3. Exact numbers, which can arise from counting or definitions such as 1 in = 2.54 cm, never limit the number of significant figures in a calculation. Ohn-Sabatello, Morlan, Knoespel, Fast Track to a 5 Preparing for the AP Chemistry Examination 2006, page 53 Significant figures: Rules for zeros Leading zeros are not significant. Leading zero 0.421 three significant figures Captive zeros are significant. Captive zero 4012 four significant figures Trailing zeros are significant. Trailing zero 114.20 five significant figures Significant Figures Number of Quantity Certain Uncertain Significant Digits Digits Figures 14.379 g 6.02 mL 1437 60 120.580 m 1 2 0 5 8 7.5 g 7 9 (thousandths) 5 2 (hundredths) 3 0 (thousandths) 5 (tenths) 6 2 0.037 g 3 7 (thousandths) 2 0.0370 g 37 0 (ten-thousandths) 3 *The position of the decimal point has nothing to do with the number of significant figures. Ralph A. Burns, Fundamentals of Chemistry 1999, page 52 Significant Digits Significant Digits Significant Digits Keys http://www.unit5.org/chemistry/intro.html How to pick a lab partner ? Essential Math of Chemistry No human endeavor can be called science if it can not be demonstrated mathematically. Leonardo da Vinci (1452-1519) Math Review Math Review Math Review Keys http://www.unit5.org/chemistry/intro.html Mathematics of Chemistry Mathematics of Chemistry (key) Mathematics of Chemistry (key) Keys http://www.unit5.org/chemistry/intro.html The Importance of Units Units must be carried into the answer, unless they cancel. 5.2 kg (2.9 m)= 0.64 kg-m (18 s)(1.3 s) s2 4.8 kg (23 s) = 0.57 kg s (5.2 s)(37 s) Basic Algebra Solve the following for x. x+y=z x and y are connected by addition. Separate them using subtraction. In general, use opposing functions to separate things. x+y=z y y The +y and y cancel on the left, leaving us with x=zy Basic Algebra Solve for x. x and 24 are connected by subtraction. Separate them using the opposite function: addition. x 24 = 13 x 24 = 13 +24 +24 The 24 and +24 cancel on the left, leaving us with x = 37 Basic Algebra Solve for x. x and k are connected by multiplication. Separate them using the opposite function: division. F=kx () () 1 1 __ __ F=kx k k (or) The two ks cancel on the left, F=kx k k leaving us with __ F x= k Basic Algebra Solve for x. x and 7 are connected by multiplication. Separate them using the opposite function: division. 8=7x () () 1 1 __ __ 8=7x 7 7 (or) The two 7s cancel on the right, 8=7x 7 7 leaving us with __ 8 x= 7 Basic Algebra Solve for x. One way to solve this is to cross-multiply. Then, divide both sides by TR. The answer is ___ = ___ BA TR x H BAH = xTR () () ___ BAH = xTR ___ 1 1 TR TR BAH x = ___ TR Solve for T2, where P1V1 P2V2 ____ = ____ P1 = 1.08 atm T1 T2 P2 = 0.86 atm ____ P1V1T2 = 1 ____ 1 V1 = 3.22 L P1V1 P2V2T1 P1V1 V2 = 1.43 L T1 = 373 K P2V2T () () T2 ______ 1 P1V = 1 (0.85 atm)(1.43 L)(373 K) _____________________ T2 = = 130 K (1.08 atm)(3.22 L) A General Procedure for Solving Problems Read the problem carefully and make a list of the knowns and the unknowns Look up all needed information Your lecture notes will have much, if not all, of the needed information Work out a plan and, following your plan, obtain an answer by carrying out the required math. Check over your work This is best done by estimating your answer Ask yourself: Does the answer seem reasonable? How to Succeed in Chemistry Learn the language Use the illustrations Review your notes frequently Work as many problems as possible Do NOT cram for exams. Hollow Penny Data Table Post-1982 Pre-1982 Post-1982 Initial mass 3.086 g 2.354 g 2.329 g Final mass 3.067 g 2.304 g 0.130 g with scratches IN GOD WE TRUST Score side of penny in 3 locations Place penny in HCl acid overnight Percent Composition LIBERTY 1982 What metal disappeared from the penny...copper or zinc? www.usmint.gov THE END This PowerPoint has been made possible through LOTS of my free time! KEYS - Intro. to Chemistry Worksheet - vocabulary Worksheet - material safety data sheet (acetone) Activity - checkbook activity Worksheet - graphing Worksheet - real life chemistry Worksheet - conversion factors Worksheet - scientific notation Worksheet - metric article (questions) Worksheet - significant digits Worksheet - math review Worksheet - math of chemistry Worksheet - article on the metric system Lab introduction to qualitative analysis Textbook - questions Outline (general) Resources - Intro. to Chemistry Worksheet - vocabulary Worksheet - material safety data sheet (acetone) Activity - checkbook activity Worksheet - graphing Worksheet - real life chemistry General Chemistry PP Worksheet - conversion factors Worksheet - scientific notation Worksheet - metric article (questions) Episode 1 - The World of Chemistry Worksheet - significant digits Episode 3 Measurement: The Foundation of Chemistry Worksheet - math review Episode 4 - Modeling The Unseen Worksheet - math of chemistry Worksheet - article on the metric system Lab introduction to qualitative analysis Textbook - questions Outline (general) ... View Full Document

End of Preview

Sign up now to access the rest of the document