Ch 100- Fundamentals for Chemistry.ppt

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1、Ch 100: Fundamentals for Chemistry,Chapter 1: IntroductionLecture Notes,What is Chemistry?,Chemistry is often described as the “central” science Chemistry is the study of matter Matter is the “stuff” that makes up the universe, i.e. anything that has mass and occupies space The fundamental questions

2、 of Chemistry are: How can matter be described? How does one type of matter interact with other types of matter? How does matter transform into other forms of matter?,Major Developments in Chemistry I,400 BC: Democritus proposed the concept of the “atom” 300 BC: Aristotle developed 1st comprehensive

3、 model of matter 700 AD: Chinese alchemists invent gunpowder 1661: Robert Boyle proposed the concept of elements 1770-90: Lavoisier proposed the concept of compounds & the Law of Mass Conservation 1774: Priestly isolates oxygen 1797: Proust proposed the Law of Definite Proportions 1803: Dalton re-in

4、troduces the concept of the atom and establishes Daltons Laws 1869: Mendeleev creates the 1st Periodic Table 1910: Rutherford proposes the “nuclear” model of the atom 1915: Bohr proposes a “planetary” model of the hydrogen atom 1920: Schroedinger publishes his wave equation for hydrogen 1969: Murray

5、 Gell-Mann proposes the theory of QCD (proposing the existence of quarks),Major Developments in Chemistry II,Discovery of subatomic particles: 1886: Proton (first observed by Eugene Goldstein) 1897: Electron (JJ Thompson) 1920: Proton (named by Ernest Rutherford) 1932: Neutron (James Chadwick)Other

6、Important Discoveries: 1896: Antoine Henri Becquerel discovers radioactivity 1911: H. Kamerlingh Onnes discovers superconductivity in low temperature mercury 1947: William Shockley and colleagues invent the first transistor 1996: Cornell, Wieman, and Ketterle observe the 5th state of matter (the Bos

7、e-Einstein condensate) in the laboratory,Scientific Method,1. (OBSERVATION) Recognize a problem Make observation Formulate a question 2. (EXPLANATION) Make an educated guess - a hypothesis Predict the consequences of the hypothesis 3. (VALIDATION) Perform experiments to test the predictions Does exp

8、erimental data support or dispute hypothesis? 4. Formulate the simplest rule that organizes the 3 main ingredients - develop a theory,EXPLANATIONS,Bottom Line: The Scientific Attitude,All hypotheses must be testable (i.e. there must be a way to prove them wrong!) Scientific: “Matter is made up of ti

9、ny particles called atoms” Non-Scientific: “There are tiny particles of matter in the universe that will never be detected”,The Particulate Nature of Matter,Matter is the tangible substance of nature, anything with mass that occupies space At the most fundamental level, matter is discrete or particu

10、late in nature The smallest, most basic units of matter are called atoms All matter is thus comprised of individual atoms, or specific combinations of atoms called molecules Molecules can be broken apart into their constituent atoms but atoms cannot be further broken apart and still retain the prope

11、rties of matter Matter can exist in one or more physical states (or phases),States of Matter,Solid Liquid Gas,+Energy,+Energy,Solid Liquid Gas,+Energy,+Energy,State,Shape,Volume,Compress,Flow,Solid,Keeps,Shape,Keeps,Volume,No,No,Liquid,Takes,Shape of,Container,Keeps,Volume,No,Yes,Gas,Takes,Shape of,

12、Container,Takes,Volume of,Container,Yes,Yes,Classification of Matter,Matter can be classified as either Pure or Impure: Pure Element: composed of only one type of atom Composed of either individual atoms or molecules (e.g. O2) Compound: composed of more than one type of atom Consists of moleculesImp

13、ure (or mixture) Homogeneous: uniform throughout, appears to be one thing Pure substances Solutions (single phase homogeneous mixtures) Suspensions (multi-phase homogeneous mixtures) Heterogeneous: non-uniform, contains regions with different properties than other regions,Separation of Matter,A pure

14、 substance cannot be broken down into its component substances by physical means only by a chemical process The breakdown of a pure substance results in formation of new substances (i.e. chemical change) For a pure substance there is nothing to separate (its only 1 substance to begin with) Mixtures

15、can be separated by physical means (and also by chemical methods, as well) There are 2 general methods of separation Physical: separation based on physical properties Filtration Distillation Centrifugation Chemical: separation based on chemical properties,Ch 100: Fundamentals for Chemistry,Chapter 2

16、: Measurements & Calculations Lecture Notes,Types of Observations,Qualitative Descriptive/subjective in nature Detail qualities such as color, taste, etc. Example: “It is really warm outside today” Quantitative Described by a number and a unit (an accepted reference scale) Also known as measurements

17、 Notes on Measurements: Described with a value (number) & a unit (reference scale) Both the value and unit are of equal importance! The value indicates a measurements size (based on its unit) The unit indicates a measurements relationship to other physical quantities Example: “The temperature is 85o

18、F outside today”,Application of Scientific Notation,Writing numbers in Scientific Notation Locate the Decimal Point Move the decimal point to the right of the non-zero digit in the largest place The new number is now between 1 and 10 Multiply the new number by 10n where n is the number of places you

19、 moved the decimal point Determine the sign on the exponent, n If the decimal point was moved left, n is + If the decimal point was moved right, n is If the decimal point was not moved, n is 0 Writing Scientific Notation numbers in Conventional form Determine the sign of n of 10n If n is + the decim

20、al point will move to the right If n is the decimal point will move to the left Determine the value of the exponent of 10 Tells the number of places to move the decimal point Move the decimal point and rewrite the number,Measurement Systems,There are 3 standard unit systems we will focus on: 1. Unit

21、ed States Customary System (USCS) formerly the British system of measurement Used in US, Albania, and a couple other countries Base units are defined but seem arbitrary (e.g. there are 12 inches in 1 foot) 2. Metric Used by most countries Developed in France during Napoleons reign Units are related

22、by powers of 10 (e.g. there are 1000 meters in 1 kilometer) 3. SI (LSysteme Internationale) a sub-set set of metric units Used by scientists and most science textbooks Not always the most practical unit system for lab work,Measurements & the Metric System,All units in the metric system are related t

23、o the fundamental unit by a power of 10 The power of 10 is indicated by a prefix The prefixes are always the same, regardless of the fundamental unit When a measurement has a specific metric unit (i.e. 25 cm) it can be expressed using different metric units without changing its meaning Example: 25 c

24、m is the same as 0.25 m or even 250 mm The choice of measurement unit is somewhat arbitrary, what is important is the observation it represents,Measurement, Uncertainty & Significant Figures,A measurement always has some amount of uncertainty Uncertainty comes from limitations of the techniques used

25、 for comparison To understand how reliable a measurement is, we need to understand the limitations of the measurement To indicate the uncertainty of a single measurement scientists use a system called significant figures The last digit written in a measurement is the number that is considered to be

26、uncertain Unless stated otherwise, the uncertainty in the last digit is 1 Examples: The measurement: 25.2 cm uncertainty: 0.1 cm The measurement: 25.20 cm uncertainty: 0.01 cm The measurement: 25.200 cm uncertainty: 0.001 cm,Rules for Counting Significant Figures,Nonzero integers are always signific

27、ant Zeros Leading zeros never count as significant figures Captive zeros are always significant Trailing zeros are significant if the number has a decimal point Exact numbers have an unlimited number of significant figuresRules for Rounding Off If the digit to be removed is less than 5, the precedin

28、g digit stays the same equal to or greater than 5, the preceding digit is increased by 1 In a series of calculations, carry the extra digits to the final result and then round off Dont forget to add place-holding zeros if necessary to keep value the same!,Exact Numbers,Exact Numbers are numbers that

29、 are assumed to have unlimited number of significant figures are considered to be known with “absolute” certainty. You do not need to consider or count significant figures for exact numbers. The following are considered exact numbers for CH100: Counting numbers, such as: The number of sides on a squ

30、are The number of apples on a desktop Defined numbers such as those used for conversion factors, such as: 100 cm = 1 m, 12 in = 1 ft, 1 in = 2.54 cm 1 kg = 1000 g, 1 LB = 16 oz 1000 mL = 1 L; 1 gal = 4 qts. 1 minute = 60 seconds Numbers or constants defined in equations, such as: y = 3x + 15 (both t

31、he “3” and the “15” are exact numbers),Converting between Unit Systems,Converting units from one unit system to another (especially within the Metric system) can appear daunting at first glance. However, with a little guidance, and a lot of practice, you can develop the necessary skill set to master

32、 this process. To begin, here is a simple mnemonic to guide you through the unit conversion process: Eliminate Replace Relate All unit conversions, regardless of how complex they appear, involve these 3 simple steps. In the following sections, you will be stepped through the unit conversion process

33、using these 3 words as a guide.,Example: Unit Conversion,Convert 25.0 m to cmConvert 1.26 g to kg,Metric Prefixes,Mass,Mass is the quantity of matter in a substance Mass is measured in units of grams Mass does not reflect how much volume something has The kilogram (kg) unit is the preferred unit of

34、mass in the SI system. 1 kilogram is equal to the mass of a platinum-iridium cylinder kept in a vault at Sevres, France. 1 kg has the weight equivalent (on Earth) of 2.205 lbConservation of Mass: The total quantity of mass is never created nor destroyed during a chemical process,Distinguishing Mass

35、vs. Weight,Mass is a fundamental property of matter, it is the amount of “stuff” in an object Mass represents an objects inertia (tendency to resist change in motion) Mass is the same everywhere in the universe SI Units of mass are kilograms (kg),Weight is the effect (or force) of gravity on an obje

36、cts mass Weight depends on location (& local gravity) Weight is not a fundamental property of matter SI units of weight are newtons (N) USCS units are pounds (lb),The terms mass and weight are commonly used interchangeably but they are fundamentally different! The following are some important differ

37、ences between mass and weight:,Volume,Volume is the 3-dimensional space that an object occupies Volume Units: The SI unit for volume is the cubic meter, or m3 (meters x meters x meters) The more common metric unit of volume is the Liter (L)In the laboratory, the milliliter (mL) is often more conveni

38、entNote: mass and volume are not the same thing (try not to confuse them). Two objects with the same volume (e.g. a pillow & a sack of potatoes can have different masses and vice versa),Density,Density is a property of matter representing the mass per unit volume For equal volumes, a denser object h

39、as greater mass For equal masses, a denser object has smaller volume Commonly used units: Solids = g/cm3 (Note: 1 cm3 = 1 mL) Liquids = g/mL Gases = g/L Useful Notes on Density: Volume of a solid can be determined by water displacement Density of matter in various states: solids liquids gases (excep

40、tion: water) In a heterogeneous mixture, the denser matter will tend to sink to the bottom,Manipulating the Density Equation,Ch 100: Fundamentals for Chemistry,Chapter 3: Elements & Compounds Lecture Notes,Chemical Symbols & Formulas,Each element has a unique chemical symbol Examples of chemical sym

41、bols: Hydrogen: H Oxygen: O Aluminum: Al Each molecule has a unique chemical formula The chemical formula of a molecule indicates the chemical symbol for each of the elements present The # of atoms of each element present in the molecule Examples of chemical formulas: Elemental oxygen: O2 (2 O atoms

42、 per molecule) Water: H2O (2 H atoms & 1 O atom) Aluminum sulfate: Al2(SO4)3 (2 Al, 3 S & 12 O atoms),The Periodic Table,All of the known elements are arranged in a chart called the Periodic Table Each element in the Periodic Table is identified by both its chemical symbol and its Atomic Number The

43、elements are organized left-to-right and top-to-bottom according to their Atomic Number The elements are arranged by similarity of chemical properties The columns are called Groups Elements of each group typically have similar properties The rows are called Periods, and reflect the periodicity of ch

44、emical properties as atomic number increases,The Periodic Table of Elements,Elements and the Periodic Table,The elements can be categorized as: Metals The leftmost elements in the periodic table Roughly 70% of all of the elements are metals Nonmetals The rightmost elements of the periodic table Semi

45、metals (metalloids) The elements that reside along the “stair step” between the metals and nonmetals in the Periodic Table The properties of semimetals are not quite metallic or non-metallic, but rather somewhere in between,Dmitri Mendeleev (1834-1907),Russian born chemist Considered one of the grea

46、test science teachers of his era He organized the known elements of his time into the first “periodic table” Elements were organized by chemical properties (& by weight) - called periodic properties Surprisingly, his periodic table predicted the existence of 3 new elements (which were subsequently d

47、iscovered),Ch 100: Fundamentals for Chemistry,Chapter 4: Properties of Matter Lecture Notes,Physical & Chemical Properties,Physical Properties are the characteristics of matter that can be changed without changing its composition These characteristics are directly observable or measurable Types of P

48、hysical Properties: Extrinsic Physical Properties are unique to objects (i.e. size, shape, mass, etc.) Intrinsic Physical Properties are unique to substances (i.e. density, conductivity, color, etc.) Chemical Properties are the characteristics of a substance that determine the tendency of the matter

49、 to transform in composition as a result of the interaction with other substances, the influence of energy or both These are characteristics that describe the behavior of matter,Physical & Chemical Changes,Physical Changes are changes that do not result in a change the fundamental composition of the

50、 substanceTypical Examples: Physical State Changes: boiling, melting, condensing, etc. Shape, Size or Texture Changes Chemical Changes involve a change in the fundamental composition of the matterNotes on Chemical Change: Production of a new substance(s) Referred to as chemical reactions The basic representation: Reactants Products Note: Both physical and chemical changes will likely produce an alteration of appearance, the key is to discern the type of change that has occurred,