Chemistry: The Study of Change Chang & Goldsby 12 th edition

Transcription

1 Chemistry: The Study of Change Chang & Goldsby 12 th edition modified by Dr. Hahn Chapter 1

2 Chemistry: A Science for the 21 st Century (2) Materials and Technology Polymers, liquid crystals photovoltaic cells light to electricity Food and Agriculture Genetically modified crops tobacco leaf and tobacco horn worm 2

3 The Study of Chemistry Macroscopic (real visible world) Microscopic (chemists view of rusting) 3

4 The Scientific Method The scientific method is a systematic approach to research. observation hypothesis law theory A hypothesis is a tentative explanation for a set of observations. Tested modified 4

5 The Scientific Method (2) A law is a concise statement of a relationship between phenomena that is always the same under the same conditions. Force = mass acceleration A theory is a unifying principle that explains a body of facts and/or those laws that are based on them. Atomic Theory 5

6 Defining Chemistry Chemistry is the study of matter and the changes it undergoes. Matter is anything that occupies space and has mass. A substance is a form of matter that has a definite composition and distinct properties. 6

7 Mixtures A mixture is a combination of two or more substances in which the substances retain their distinct identities. 1. Homogenous mixture composition of the mixture is the same throughout (sugar water, sweet tea) 2. Heterogeneous mixture composition is not uniform throughout iron filings in sand 7

8 Mixtures (2) Physical means can be used to separate a mixture into its pure components. magnet (iron filing & sand) distillation (water & ethanol) 8

9 Elements An element is a substance that cannot be separated into simpler substances by chemical means. 114 elements have been identified 82 elements occur naturally on Earth gold, aluminum, lead, oxygen, carbon, sulfur 32 elements have been created by scientists technetium, americium, seaborgium 9

10 Elements (2) (memorize listed, except crossed out in red) Copyright McGraw-Hill Education. Permission required for reproduction or display. Table 1.1 Some Common Elements and Their Symbols Name Symbol Name Symbol Name Symbol Aluminum Al Fluorine F Oxygen O Arsenic As Gold Au Phosphorus P Barium Ba Hydrogen H Platinum Pt Bismuth Bi Iodine I Potassium K Bromine Br Iron Fe Silicon Si Calcium Ca Lead Pb Silver Ag Carbon C Magnesium Mg Sodium Na Chlorine Cl Manganese Mn Sulfur S Chromium Cr Mercury Hg Tin Sn Cobalt Co Nickel Ni Tungsten W Copper Cu Nitrogen N Zinc Zn 10

11 Compounds A compound is a substance composed of atoms of two or more elements chemically united in fixed proportions. Compounds can only be separated into their pure components (elements) by chemical means. 11

12 The Classification of Matter Matter can be classified according to its composition: elements, compounds, and mixtures.

13 A Comparison: The Three States of Matter 13

14 Solid Matter solid has a fixed volume and rigid shape. Example: Ice, aluminum, diamond

15 Liquid Matter Liquids have fixed volume but not fixed shape & assume the shape of its container. Example: water, alcohol, gasoline

16 They are free to move relative to one another. Gaseous Matter These qualities make gases compressible so gases have no fixed volume and shape.

17 Types of Changes A physical change does not alter the composition or identity of a substance. ice melting A chemical change alters the composition or identity of the substance(s) involved. sugar dissolving in water hydrogen combines with oxygen to form water 17

18 Physical and Chemical Changes

19 Extensive and Intensive Properties An extensive property of a material depends upon how much matter is being considered. mass length volume An intensive property of a material does not depend upon how much matter is being considered. density temperature color 19

20 Matter Matter - anything that occupies space and has mass mass measure of the quantity of matter SI unit of mass is the kilogram (kg) 1 kg = 1000 g = g weight force that gravity exerts on an object weight = cc mass on earth, cc = 1.0 on moon, cc ~ kg bar will weigh 1 kg on earth 0.1 kg on moon 20

21 International System of Units (SI) Copyright McGraw-Hill Education. Permission required for reproduction or display. Table 1.2 SI Base Units Base Quantity Name of Unit Symbol Length meter m Mass kilogram Kg Time second s Electrical current ampere A Temperature kelvin K Amount of substance mole mol Luminous intensity candela cd 21

22 Prefix Multipliers The International System of Units uses the prefix multipliers shown in the next table with the standard units. These multipliers change the value of the unit by the powers of 10 (just like an exponent does in scientific notation). For example, the kilometer has the prefix kilo meaning 1000 or 10 3.

23 Prefix Multipliers memorize the red arrow ones

24 SI Prefixes to memorize Kilo K 10 3 centi c 10-2 milli m 10-3 Larger exponential number move decimal Smaller exponential number move decimal Kilo move centi move milli move

25 Density Density SI derived unit for density is kg m 3 1 g cm 3 = 1 g ml = 1000 kg m 3 usual unit of density is density = mass volume dd = mm VV 25

26 Densities of Some Substances Table 1.4 Densities of Some Substances at 2222 Substance Density (g/cm 3 ) Air* Ethanol 0.79 Water 1.00 Graphite 2.2 Table salt 2.2 Aluminum 2.70 Diamond 3.5 Do not memorize. Iron 7.9 Lead 11.3 Mercury 13.6 Gold 19.3 Osmium 22.6 *Measured at 1 atmosphere. Osmium (Os) is the densest element known 26

27 Example 1.1 Gold is a precious metal that is chemically unreactive. It is used mainly in jewelry, dentistry, and electronic devices. A piece of gold ingot with a mass of 301 g has a volume of 15.6 cm 3. Calculate the density of gold. (d = mass/volume) Both class end here 8/9/17 W

28 Example 1.1(2) Solution We are given the mass and volume and asked to calculate the density. Therefore, from Equation (1.1), we write dd = mm VV = 301 g 15.6 cm 3 = 19.3 g cm 3

29 Example 1.2 The density of mercury, the only metal that is a liquid at room temperature, is 13.6 g/ml. Calculate the mass of 5.50 ml of the liquid. (density = mass / volume)

30 Example 1.2 (2) Solution We are given the density and volume of a liquid and asked to calculate the mass of the liquid. We rearrange Equation (1.1) to give mm = dd VV = 13.6 g ml = 74.8 g 5.50 ml

31 A Comparison of Temperature Scales K = K = K = 100 = = =

32 Example 1.3 (a) Solder is an alloy made of tin and lead that is used in electronic circuits. A certain solder has a melting point of What is its melting point in degrees Fahrenheit? = o C o F (b) Mercury, the only metal that exists as a liquid at room temperature, melts at Convert its melting point to kelvins. K = o C K

33 Example 1.3 (2) Solution These problems require that we carry out temperature conversions, so we need Equations (usually provided somewhere on exam or quiz). Keep in mind that the lowest temperature on the Kelvin scale is zero (0 K); therefore, it can never be negative. a) This conversion is carried out by writing = b) The melting point of mercury in kelvins is given by K 1 = K

34 Scientific Notation The number of atoms in 12 g of carbon: 602,200,000,000,000,000,000, The mass of a single carbon atom in grams: N is a number between 1 and 9 N 10 nn n is a positive or negative integer 34

35 Scientific Notation (2) move decimal left nn > = move decimal right nn < = Addition or Subtraction 1. Write each quantity with the same exponent n 2. Combine N 1 and N 2 3. The exponent, n, remains the same = = end class 8/11 10 am class 35

36 Scientific Notation (3) Multiplication 1. Multiply N 1 and N 2 2. Add exponents nn 1 and nn = = = Division 1. Divide N 1 and N 2 2. Subtract exponents nn 1 and nn = =

37 Significant Figures Any digit that is not zero is significant kg 4 significant figures Zeros between nonzero digits are significant 606 m 3 significant figures Zeros to the left of the first nonzero digit are not significant 0.08 L 1 significant figure If a number is greater than 1, then all zeros to the right of the decimal point are significant 2.0 mg 2 significant figures If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant g 3 significant figures 37

38 Example 1.4 Determine the number of significant figures in the following measurements: (a)478 cm (b)6.01 g end class 8/11 9 am class (c)0.825 m (d)0.043 kg (e) atoms (f)7000 ml