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Chemistry
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How did Chemistry Become a Science?
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The Greeks believed there were four elements.
The Beginnings early practical chemistry: household goods, weapons, soap, wine, basic medicine The Greeks believed there were four elements. ~ D D ___ D ___ earth air fire water
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Timeline Greeks (Democratus ~450 BC) Discontinuous theory of matter
ALCHEMY Issac Newton ( ) 400 BC 300 AD 1000 2000 Greeks (Aristotle ~350 BC)) Continuous theory of matter American Independence (1776)
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Allegedly, this substance would turn cheap metals into gold.
Alchemy In Europe, alchemy was the quest for the Philosopher’s Stone (the elixir, the Sorcerer’s Stone). Allegedly, this substance would turn cheap metals into gold.
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Alchemy Symbols Alchemy Symbols
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Alchemy (~500 – 1300 A.D.) the quest for the Philosopher’s Stone It was supposed to change cheap metals into gold. The Alchemist, by David Teniers Alchemical symbols for substances… . . . . . . SAND IRON GOLD SILVER COPPER transmutation: changing one substance into another In ordinary chemistry, we cannot transmute elements.
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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
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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
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What is Chemistry? the study of matter and its changes
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Areas of Chemistry Organic Inorganic Analytical Physical Biochemistry
The study of most carbon-containing compounds The study of all substances not classified as organic, mainly those compounds that do not contain carbon The identification of the components and composition of materials The five areas of chemistry listed: organic, inorganic, analytical, physical and biochemistry are the main areas of chemistry. Many people work as chemist in related fields – law, pharmaceutical, medical, agricultural, sales. The study of the properties, changes, and relationships between energy and matter The study of substances and processes occurring in living things
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Stereotypes of Chemists
Male Middle-aged White Lab coat Nerd / Geek This slide shows what the typical person envisions when they are asked to tell you what a chemist looks like. This stereotypical view is not accurate. Chemists come from all walks of life and are male and female.
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Careers in Chemistry research (new products)
production (quality control) development (manufacturing) chemical sales software engineering teaching Food science technician, Toxicologist, Forensic chemist, Nuclear medicine technologist, Firefighter, Pharmacist are other careers for chemists!
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Government Regulation of Chemicals
…to protect the… environment consumer worker Consumer Product Safety Commission, USDA, BATF, FDA OSHA EPA
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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.
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are affected by chemistry.
All fields of endeavor are affected by chemistry.
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Chemistry and Manipulating Numerical Data
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Graphs
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shows how many of something
Bar Graph shows how many of something are in each category
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shows how a whole is broken into parts
Pie Graph shows how a whole is broken into parts Percentage of Weekly Income
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shows continuous change
Line Graph shows continuous change Stock Price over Time
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Elements of a “good” line graph
axes labeled, with units use the available space title neat Hopefully, students will realize this data makes no sense. As temperature increase – the volume of a gas increases.
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How to read a graph 7 L ~4 L Interpolate - read between data points
What volume would the gas occupy at a temperature of 150 K? Extrapolate - read data beyond data points What volume would the gas occupy at a temperature of 260 K? Which do you have more confidence in? Why? 7 L (dependent variable) Hopefully, students will realize this data makes no sense. As temperature increase – the volume of a gas increases. ~4 L (independent variable)
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Graphs Line Graph Bar Graph Pie Graph
Used to show trends or continuous change Bar Graph Used to display information collected by counting Pie Graph Used to show how some fixed quantity is broken down into parts GRAPHS Each graph is used for a specific reason.
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Scientific Notation Often used to express very large or
very small numbers. Also used to maintain correct number of significant figures.
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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 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.
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6.02 x 1023 Method to express really big or small numbers.
Format is Mantissa x Base Power Decimal part of original number Decimal you moved 6.02 x 1023 We just move the decimal point around.
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Scientific Notation 5000 = 5 x 103 or 5 3 EE 5 x (10 x 10 x 10)
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. = 5 x or 5 x (10 x 10 x 10) 5 x 1000 5000 Numbers > one have a positive exponent. Numbers < one have a negative exponent. x 10n EE
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Converting Numbers to Scientific Notation
2.205 x 10-5 1 2 3 4 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.
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Form: (# from 1 to 9.999) x 10exponent
800 = 8 x 10 x 10 = 8 x 102 2531 = x 10 x 10 x 10 = x 103 = 1.4 / 10 / 10 / 10 = 1.4 x 10-3
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Change to standard form.
1.87 x 10–5 = 3.7 x 108 = 7.88 x 101 = 2.164 x 10–2 = . . 370,000,000 78.8
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Change to scientific notation.
12,340 = 0.369 = 0.008 = 1,000,000,000 = 1.234 x 104 3.69 x 10–1 8 x 10–3 1 x 109
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Essential Math of Chemistry
Essential Math of Chemistry “No human endeavor can be called science if it can not be demonstrated mathematically.” Leonardo da Vinci ( )
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The Importance of Units
Units must be carried into the answer, unless they cancel. 5.2 kg (2.9 m) (18 s)(1.3 s) = kg-m s2 0.64 4.8 kg (23 s) (5.2 s)(37 s) = kg s 0.57
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Basic Algebra x + y = z x + y = z – y – y x = z – y
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, x = z – y leaving us with…
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Basic Algebra x – 24 = 13 x – 24 = 13 +24 +24 x = 37 Solve for x.
x and 24 are connected by subtraction. Separate them using the opposite function: addition. x – 24 = 13 +24 +24 The –24 and +24 cancel on the left, leaving us with… x = 37
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( ) Basic Algebra F = k x __ 1 k F = k x (or) F = k x k x = F k __
Solve for x. F = k x ( ) __ 1 k F = k x x and k are connected by multiplication. Separate them using the opposite function: division. (or) F = k x k The two k’s cancel on the left, leaving us with… x = F k __
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( ) Basic Algebra 8 = 7 x __ 1 7 8 = 7 x (or) 8 = 7 x 7 x = 8 7 __
Solve for x. 8 = 7 x ( ) __ 1 7 8 = 7 x x and 7 are connected by multiplication. Separate them using the opposite function: division. (or) 8 = 7 x 7 The two 7’s cancel on the right, leaving us with… x = 8 7 __
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( ) Basic Algebra ___ x BA = TR H BAH = xTR 1 TR ___ BAH = xTR ___ BAH
Solve for x. ___ x BA = TR H One way to solve this is to cross-multiply. BAH = xTR 1 TR ( ) ___ Then, divide both sides by TR. BAH = xTR ___ BAH TR x = The answer is…
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( ) ____ T1 P1V1 = P2V2 T2 1 P1V1 ____ P1V1T2 = P2V2T1 T2 = P1V1
Solve for T2, where… P1 = 1.08 atm P2 = 0.86 atm V1 = 3.22 L V2 = 1.43 L T1 = 373 K ____ T1 P1V1 = P2V2 T2 1 P1V1 ( ) ____ P1V1T2 = P2V2T1 T2 = P1V1 ______ P2V2T1 T2 = (1.08 atm)(3.22 L) _____________________ (0.85 atm)(1.43 L)(373 K) = 130 K
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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?”
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SI Prefixes kilo- 1000 deci- 1/10 centi- 1/100 milli- 1/1000
Also know… 1 mL = 1 cm3 and 1 L = 1 dm3
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Conversion Factors and Unit Cancellation
Converting between two sets of units never changes the number of significant figures in a measurement. Remember, data are only as good as the original measurement, and no later manipulations can clean them up.
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A physical quantity must include:
Number + Unit
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( ) ______ How many cm are in 1.32 meters? equality: 1 m = 100 cm
(or 0.01 m = 1 cm) applicable conversion factors: ______ 1 m 100 cm ______ 1 m 100 cm or ( ) ______ 1 m 100 cm 132 cm X cm = 1.32 m = We use the idea of unit cancellation to decide upon which one of the two conversion factors we choose.
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Again, the units must cancel.
How many meters is 8.72 cm? equality: 1 m = 100 cm applicable conversion factors: ______ 1 m 100 cm ______ 1 m 100 cm or ( ) ______ 1 m 100 cm m X m = 8.72 cm = Again, the units must cancel.
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( ) ( ) ____ ______ How many kilometers is 15,000 decimeters? 10 dm
1 km 1.5 km X km = 15,000 dm =
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How many seconds is 4.38 days?
____ ( ) ( ) _____ ( ) ____ 24 h 1 d 1 h 60 min 1 min 60 s X s = 4.38 d 378,432 s = If we are accounting for significant figures, we would change this to… 3.78 x 105 s
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Simple Math with Conversion Factors
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Example Problem Measured dimensions of a rectangle:
length (L) = 9.70 cm width (W) = 4.25 cm L W Find area of rectangle. A = L . W = (9.70 cm)(4.25 cm) = 41.2 cm 2 . cm
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( ) ( ) ( ) ( ) Convert 41.2 cm2 to m2. ______ ______ ______ ______
X m2 = 41.2 cm2 = 0.412 m2 WRONG! = 0.412 cm.m Recall that… 41.2 cm2 = 41.2 cm.cm ( ) ______ ( ) ______ X m2 = 41.2 cm.cm 100 cm 1 m 100 cm 1 m = m2 ( ) ______ 100 cm 1 m 2 X m2 = 41.2 cm2 = m2
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( ) ( ) ( ) Convert 41.2 cm2 to mm2. _____ _____ _____
Recall that… 41.2 cm2 = 41.2 cm.cm ( ) _____ ( ) _____ X mm2 = 41.2 cm.cm 1 cm 10 mm 1 cm 10 mm = 4,120 mm2 2 ( ) _____ 1 cm 10 mm X mm2 = 41.2 cm2 = 4,120 mm2
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Measured dimensions of a rectangular solid:
Length = 15.2 cm Width = 3.7 cm Height = 8.6 cm H W Find volume of solid. L V = L . W . H = (15.2 cm)(3.7 cm)(8.6 cm) = 480 cm 3
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( ) ( ) ( ) ( ) ( ) Convert to m3. _____ _____ _____ _____ _________
cm.cm.cm ( ) _____ ( ) _____ ( ) _____ 100 cm 1 m X m3 = 480 cm 3 2 100 cm 1 m 100 cm 1 m = or ( ) _____ 100 cm 1 m 3 X m3 = 480 cm3 = m3 or 1 m cm ( ) _________ 3 X m3 = 480 cm3 4.80 x 10-4 m3 =
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Convert to m3... Measured dimensions of a rectangular solid:
Length = 15.2 cm Width = 3.7 cm Height = 8.6 cm 0.152 m 0.037 m 0.086 m H W Find volume of solid. L V = L . W . H = (0.152 m)(0.037 m)(0.086 m) = m 3
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Convert to mm3.
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By what factor do mm and cm differ? 10
100 By what factor do mm3 and cm3 differ? 1,000 1 cm = 10 mm (1 cm)2 = (10 mm)2 1 cm2 = 100 mm2 (1 cm)3 = (10 mm)3 1 cm3 = 1000 mm3
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Using the Exponent Key on a Calculator
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EE or EXP means “times 10 to the…”
How to type out 6.02 x 1023: How to type out 6.02 x 1023: 6 EE . 3 2 6 EE . 3 2 Don’t do it like this… WRONG! 6 y x . 3 2 WRONG! …or like this… x 1 6 . 2 EE 3 …or like this: TOO MUCH WORK. y x 3 2 x 1 6 .
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Also, know when to hit your (–) sign…
…before the number, …after the number, …or either one.
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Example: 1.2 x 105 2.8 x 1013 = 1 . 2 EE 5 3 8 Type this calculation in like this: –09 Calculator gives… E–09 or… This is NOT written… 4.3–9 4.3 x 10–9 4.3 E –9 or But instead is written…
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= x 10-9 report -6.5 x 10-9 (2 sig. figs.) = x 103 or report 5.35 x 103 (3 sig. figs.) = x 10-13 report 5.84 x (3 sig. figs.) = x 1023 report 2.9 x 1023 (2 sig. figs.) = x 1016 report -3.1 x 1016 (2 sig. figs.)
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Basic Concepts in Chemistry
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any substance that takes part in, or occurs as a result of,
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.
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a rearrangement of atoms such that
chemical reaction a rearrangement of atoms such that “what you end up with” products differs from “what you started with” reactants
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Combustion of a Hydrocarbon
dioxide methane + oxygen + water CH4(g) + 2 O2(g) CO2(g) + H2O(g) 2
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sodium hydroxide sodium + water hydrogen + 2 Na(s) + 2 H2O(l) H2(g) + 2 NaOH(aq)
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Law of Conservation of Mass
total mass = total mass of reactants of products Rmass = Pmass
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taking small molecules and putting them
Synthesis taking small molecules and putting them together, usually in many steps, to make something more complex Sunlight Carbon Dioxide Oxygen Glucose Water Photosynthesis CO H2O O C6H12O6
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