Chemistry

How did Chemistry Become a Science? http://en.wikipedia.org/wiki/History_of_chemistry

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

Timeline Greeks (Democratus ~450 BC) Discontinuous theory of matter ALCHEMY Issac Newton (1642 - 1727) 400 BC 300 AD 1000 2000 Greeks (Aristotle ~350 BC)) Continuous theory of matter American Independence (1776)

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.

Alchemy Symbols Alchemy Symbols

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.

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

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

What is Chemistry? the study of matter and its changes

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

Government Regulation of Chemicals …to protect the… environment consumer worker Consumer Product Safety Commission, USDA, BATF, FDA OSHA EPA

Chemistry and Manipulating Numerical Data

Graphs

Graphs Bar Graph Pie Graph Line Graph Used to display information collected by counting Pie Graph Used to show how some fixed quantity is broken down into parts Line Graph Used to show trends or continuous change GRAPHS Each graph is used for a specific reason.

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.

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)

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.

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. 602000000000000000000000

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. 5000 = 5 x 103 or 5 3 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

Converting Numbers to Scientific Notation 0 . 0 0 0 0 2 2 0 5 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.

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. 1.87 x 10–5 = 3.7 x 108 = 7.88 x 101 = 2.164 x 10–2 = 000000187000000 . . 0.0000187 370,000,000 78.8 0.02164

Change to scientific notation. 12,340 = 0.369 = 0.008 = 10,000,000 = 1.234 x 104 3.69 x 10–1 8 x 10–3 1 x 107

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 (1452-1519)

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 g (23 s) (5.2 s)(37 s) = g s 0.57

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…

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

( ) 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 __

( ) 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 __

( ) 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…

( ) ____ 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

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?”

SI Prefixes kilo- 1000 deci- 1/10 centi- 1/100 milli- 1/1000 Also know… 1 mL = 1 cm3 and 1 L = 1 dm3

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.

A physical quantity must include: Number + Unit

( ) ______ 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.

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 0.0872 m X m = 8.72 cm = Again, the units must cancel.

( ) ( ) ____ ______ How many kilometers is 15,000 decimeters? 10 dm 1 km 1.5 km X km = 15,000 dm =

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

Simple Math with Conversion Factors

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

( ) ( ) ( ) ( ) 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 = 0.00412 m2 ( ) ______ 100 cm 1 m 2 X m2 = 41.2 cm2 = 0.00412 m2

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

Basic Concepts in Chemistry

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.

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

carbon dioxide methane + oxygen  + water CH4(g) + 2 O2(g)  CO2(g) + H2O(g) 2 

sodium hydroxide sodium + water  hydrogen + 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

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 CO2 + H2O O2 + C6H12O6