Review of Chemistry1.doc

1、Review of ChemistryDerived QuantitiesDefinitions: A DERIVED QUANTITY is a number made by combining two or more other values.A DERIVED UNIT is a unit which is made by combining two or more other units.II.4 DensityDefinition: Mass= the quantity of matter on an objectDensity= the mass contained in a gi

2、ven volume of a substanceII.5 Significant figures and experimental uncertaintySIGNIFICANT FIGURESA. A significant figure is a measured or meaningful digit.B. An accurate measurement is a measurement that is close to the correct or accepted value; a precise measurement is a reproducible measure.C. Th

3、e number if significant figures is equal to all the certain digits plus the first uncertain digit.D. “Defined” numbers and “counting” numbers are assumed to be perfected so that they are “exempt” from the rules applying to significant figures.BE VERU CAREFU; WHEN A VLAUE APPEARS TO COINCIDE EXACTLY

4、WITH A MARKING ON A MEASURING DEVICE. The following procedure should help when such a situation occurs.THE PROCEDURE FOR CORRECTLY READING MEASURING SCALES WHEN A POINTER IS EXACTLY ON A NUMBERED DIVISION Determine the value that the measurement seems to have. Pretend you have a value in between two

5、 of the unnumbered subdivisions on your measuring device. Determine how many decimal places you could read off the measuring device at the “in-between value”. Add a sufficient number of zeroes to the actual reading to give you the correct number of decimal places for your reading.EXPERIMENTAL UNCERT

6、AINTYDefinition: The experimental uncertainty is the estimated amount by which a measurement might be in error.E. When adding an uncertainty to a measurement, the uncertainty goes after the measured value but before the unit.NOTE: If the uncertain digit is in the first decimal place, the uncertainty

7、 will be in the first decimal place also.INTERPRETATION OF UNCERTAINTIESIMPORTANT: The place value (tens, units, first decimal, etc.) of the experimental uncertainty and the first uncertain digit of a measurement must agree with each other.F. NORMALLY USE UNCERTAINTIES TO THE NEAREST 0.1 OF THE SMAL

8、LEST UNNUMBERED SUBDIVISION. If you can only estimate a value to the nearest 0.2 or even 0.5 of the smallest unnumbered subdivision, feel free to do so, but be prepared justify your decision.G. Leading zeroes are not significant.H. Trailing zeroes are all assumed to be significant and must be justif

9、ied by the precision of the measuring equipment.There are two ways to count the number of significant figures.EXPRESS THE NUMBER IN SCIENTIFIC NOTATION AND THEN COUNT ALL THE DIGITS.Or even simpler:Starting from the left side of the number, ignore all “leading zeroes” and only start counting at the

10、first NON-ZERO” digit. Once you start counting, continue until you run out of digits.I. After MULTIPLYING or DIVIDING numbers, round off the answer to the LEASR NUMBER OF SIGNIFICANT FIGURES contained in the calculation.J. after ADDING or SUBTRACTING numbers, round off the answer to the LEAST NUMBER

11、 OF DECIMAL PLACES contained in the calculation.UNIT III: THE PHYSICAL PROPERTIES ANG PHYSICAL CHANGES OF SUBSTANCESIII.1. some basic definition in scienceThe following are general characteristics of HYPOTHESES1. Hypotheses are normally single assumptions.2. Hypotheses are narrow in their scope of e

12、xplanation.3. When originally proposed, hypotheses are tentative but may become generally accepted after more complete testing.The following are general characteristic of THEORIES1. Theories are composed if one or more underlying hypotheses.2. Theories are broad in scope and may have subtle implicat

13、ion which are not foreseen when they are proposed because they provide explanation for entire “fields” of related behavior.3. Theories are sometimes called models because they often provide a concrete way to examine, predict and test the workings of nature.4. A theory cant be “proven” but at some po

14、int it may have such a tremendous record of explanation and prediction that we place a high probability in its correctness as a model capable of describing reality.5. Theories must be “falsifiable”, they must make testable prediction about the behavior of the system under NEW conditions. The followi

15、ng are general characteristics of LAWS1. Laws summarize the results of many experiments or observations and state what will happen when a specific situation occurs.2. Laws do NOT try to explain WHY something occurs.3. Laws are NOT “proven theories”, as sometimes is erroneously stated. Laws are often

16、 stated before any theory exists as to WHY the law is true.III.2 THE PHYSICAL PROPERTIES OF MATTERDefinition: MATTER= anything that has mass and occupies space.(a) Solids are rigid, do not readily change their shape, and experience very small changes in volume when heated or subjected to pressure.(b

17、) Liquids conform to the shapes of their containers and experience only slight changes in volume when heated or subjected to pressure.(c) Gases conform to the shapes of their containers and experience drastic changes in volume when heated or subjected to pressure.An investigation of: vapor pressure,

18、 evaporation rate, viscosity, and gas compressibility.III.3 The classification of matter1. A HOMOGENEOUS substance is substance consisting of only one phase.Examples: air, water, salt water, a piece of iron.2. A HETEROGENENOUS substance is a substance consisting of more than one phase.Examples: a hu

19、man being, a pencil. gravel3. A PURE SUBSTANCE is a substance that is homogeneous and has an unchangeable composition.Examples: sugar, water, copper, iron4. A MIXTURE is a system made up of two or more substance, such that the relative amounts of each substance can be VARIED.Examples: salt dissolved

20、 in water, alcohol dissolved in water“Mixture” is a general term which includes both heterogeneous mixtures (better known as “mechanical mixtures”) and homogeneous mixtures (better known as “solution”).5. A MECHANICAL MIXTURE is a heterogeneous mixture of two or more substances.Examples: gravel, san

21、d and iron filings, a pencilNote: ALL HETEROGENEOUS substances are MECHANICAL MIXTURES, and vice ideas.6. A SOLUTION is a homogeneous mixture of two or more substances.There are several different types of solutions.Types of solution ExampleGas-in-gas solution Air (oxygen, nitrogen, etc.)Gas-in-liqui

22、d solution Soda popLiquid-in-liquid solution Water and alcoholSolid-in-liquid solution Salt waterSolid-in-liquid solution Alloys (metals melted together)7. As defined previously, an ELEMENT is a substance which cannot be separated into simpler substances as a result of any chemical process. In other

23、 words, an element is a pure substance in which all the atoms are of the same types.8. A COMPOUND is a pure substance made of two or more types of atoms. Only one type of molecule is present in a compound.The difference in physical properties between different classifications of matter.III.4 The phy

24、sical separation of substancesA. Hand SeparationB. FiltrationC. EvaporationD. DistillationE. Solvent ExtractionF. RecrystallizationG. Gravity SeparationH. Paper, column, and thin chromatographyA SYNOPSIS OF SEPARATION METHODSA. Mechanical MixturesMIXTURE METHOD WHEN TO USE METHODHand separation Larg

25、e chunks present among other solidsGravity The density of the desired solids is much different from the density of the other solidsSolvent extraction One solid preferentially dissolves in a particular solventSOLID in SOLIDChromatography The solids are colored, present in small amounts and are solubl

26、e in some solvent or mixture of solventHand separation A few large pieces of solid are present in the liquidGravity separation Solid particles are present in a small amount of liquidLIQUID in LIQUIDFiltration Solid particles are present in a large amount of liquidB. SolutionsMIXTURE METHOD WHEN TO U

27、SE METHODEvaporation The solid is wanted and the liquid is notDistillation The liquid is wanted; the solid may or may not be wantedSolvent extraction An immiscible added solvent preferentially dissolves at least one but not all of the solids presentRecrystallization One dissolved solid is much less

28、soluble than the others present (if any); the liquid is not wantedSOLID in SOLIDChromatography Small amounts or more than one colored solid are present; the liquid present is not wantedLIQUID in LIQUID Distillation Two or more liquids are present and have different boiling temperaturesSolvent extrac

29、tion An immiscible added solvent preferentially dissolves at least one but not all of the liquids presentIII.5 Phase changesIMPORTANT: Chemical changes are frequently accompanied by physical changes. For example, hydrogen gas and oxygen gas react to form liquid water. Therefore, a reference to a che

30、mical change implies that the primary change is chemical, but a physical change may occur as a result. On the sloping portions of the graph- all the heat is used to warm the substance so the temperature rises. On the level portions of the graph- the substance contains so much heat energy that it can

31、not absorb more heat and stay in the same phase. The added heat is used, for example, to break up the solid and allow a liquid to form. All the heat is used to change phase so the temperature doesnt change and the graph levels off.Special note: When 1g of candle wax is burned about 10000 joules of h

32、eat are produced; when 1g of liquid wax solidifies about 40joules of heat are produced. This is typical of the differences between the energy involved in physical changes (for example, the solidification of wax) and chemical changes (for example, the burning of wax). In general: the amount of heat i

33、nvolved in a physical change is much less than the amount involved in a chemical change.III.6 The role of kinetic energy in physical changes(a) Rotational energy- causes a molecule to rotate around one of its axes; bond lengths and bond angles dont change(b) Vibration energy- changes the bond length

34、s and/or angles between atoms in a molecule(c) Translational energy- causes the molecule to travel in a straight line from place to place, but has no effect on bong lengths and angles.PRACTICAL APPLICATIONS OF KNIETIC ENERGY CHANGES1. MICROWAVE OVENS supply energy which causes the water molecules in

35、 food and liquids to vibrate.2. IN INFRARED (IR) SPECTROSCOPY, molecules absorb infrared (heat) energy. (“Infrared” is pronounced “infra-red”.) IR energy is just energy with less energy than red light; if white light is passed through a prism, the light energies are spread out as shown below.Every d

36、ifferent molecule has its own “fingerprint”; by comparing the spectrum of an “unknown” molecule with the spectra of known molecules the unknown can be identified.UNIT IV: INORGANIC NIMENCLATUREIV.1 the chemical elementsSome comments about the elements may help you to learn their names and symbols.a)

37、 The first letter in the symbol is ALWAYS in upper case (capitals). Second letters, if present, are ALWAYS in lower case.Example: Pt, Te, Be, Clb) Many elements just use the first two letters of the elements name as the elements symbol.Example: Al, Bi, Lic) When the first two letters have already be

38、en used with some other element, the first and the third letters are used.Example: Ar=argon; As=arsenic (cant use Ar); At=astatine (cant use As)d) Elements which were known in ancient times or which have name taken from substances known in ancient times have symbols derived from their Latin names.El

39、ement Latin name SymbolAntimony Stibium SbCopper Cuprum CuGold Aurum AuIron Ferrum FeLead Plumbum PbMercury Hydragyrum HgPotassium Kalium KSilver Argentium AgSodium Natrium NaTin Stannum Sne) A few elements have single letter symbols.Example: B, C, F, H, I, K, N, O, P, S, U, V, Wf) Some elements and

40、 their elements frequently cause problems with students. The following might be of some help things straight.IV.2 naming inorganic compoundsIMPORTANT: Metals form POSITIVE ions.Nonmetals form NEGATIVE ions (Hydrogen is generally an exception).Naming monatomic ionsA. naming monatomic metal ions: use

41、the name of the metal and add the word “ion”Example: Sodium metal (Na) form the sodium ion (Na+)Aluminum metal (Al) forms the aluminum ion (Al3+)The stocking System of naming metal ion: If a metal ion has more than one possible charge, the charge is indicated by a Roman numeral, in parentheses, imme

42、diately following the name.Example: Fe3+=iron (III) ion, Fe2+=iron (II) ion, U6+=uranium (VI) ion, U3+= uranium (III) ionB. naming monatomic non-metal ions: take off the original ending of the elements name and put on an “ide” ending.Element name Element symbol Ion name Ion symbolFluorine F Fluoride

43、 F-Chlorine Cl Chloride Cl-Bromine Br Bromide Br-Iodine I Iodide I-Oxygen O oxide O2-Sulphur S Sulphide S2-Nitrogen N Nitride N3-Phosphorus P Phosphide P3-Naming polyatomic ionsConstructing the formula of an ionic compound, given the name of the compoundConstructing the name of an ionic compound, gi

44、ven the formula of the compoundNaming hydratedNaming compounds by using the prefix-naming systemSome common acidsIV.3 Extension: the colors of the some common aqueous ionsIon Color Ion Color Ion ColorFe2+ Pale green MnO4- Purple Cr2O72- Bright orangeFe3+ Dull yellow Ni2+ Bright green Cu2+ Blue(*)Co2+ Pink-red(*) CrO42- Bright yellow Mn2+ Very pale pink(*)