General Chemistry PDF

GENERAL CHEMISTRY General, Organic and Biochemistry 8th Edition Copyright The McGraw-...

GENERAL CHEMISTRY General, Organic and Biochemistry 8th Edition Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 1.1 The Discovery Process Chemistry: the study of matter and its chemical and physical properties – Matter - Anything that has mass and occupies space – What about air? Yes, it is matter the chemical and physical changes matter undergoes As matter undergoes change, it will gain or lose energy. Energy - the ability to do work to accomplish some change 2 Three States of Matter 1. Gas - particles widely separated, no definite shape or 1.2 The Categorization of volume 2. Liquid - particles closer together, definite volume but no definite shape 3. Solid - particles are very close together, definite shape 4 and definite volume Matter Three States of Water (a) Solid (b) Liquid (c) Gas 3 1  Physical property - is observed 5 1.2 The Categorization of without changing the composition or identity of a substance Physical change - produces a Matter recognizable difference in the appearance of a substance without causing any change in its composition or identity - conversion from one physical state to another - melting an ice cube 4 1.2 The Categorization of Chemical property - result in a change in composition and can be 5 observed only through a chemical reaction Matter Chemical reaction (chemical change) - a chemical substance is converted in to one or more different substances by rearranging, removing, replacing, or adding atoms. hydrogen + oxygen  water reactants products 5 Intensive properties - a property of matter that is independent of the 1.2 The Categorization of quantity of the substance 6 - Color - Melting Point and Freezing Point Matter - Density - Temperature Extensive properties - a property of matter that depends on the quantity of the substance - Mass - Volume - Length/Height 6 2  Composition of Matter 1.2 The Categorization of Matter Pure substance - a substance that has only one component 7 Mixture - a combination of two or more pure substances in which each substance retains its own identity, not undergoing a chemical reaction 7 Composition of Matter 1.2 The Categorization of Matter Element - a pure substance that cannot be changed into a simpler form of matter by any chemical reaction 7 Compound - a pure substance resulting from the combination of two or more elements in a definite, reproducible way, in a fixed ratio 8 Composition of Matter 1.2 The Categorization of Matter Mixture - a combination of two or more pure substances in which each substance retains its own identity 7 Homogeneous mixture - uniform composition, particles well mixed, thoroughly intermingled Heterogeneous mixture – nonuniform composition, random placement 9 3  1.3 The Units of Measurement Units - the basic quantity of mass, volume or whatever quantity is being measured – A measurement is useless without its units English system - a collection of functionally unrelated units – Difficult to convert from one unit to another – 1 foot = 12 inches = 0.33 yard = 1/5280 miles Metric System - composed of a set of units that are related to each other decimally, systematic – Units relate by powers of tens 10 Metric System Units Time - metric unit is the second Mass - the quantity of matter in an object 1.3 The Units of – not synonymous with weight Measurement – standard unit is the gram (g) – The pound (lb) is the common English unit. 1 lb = 454 g Length - the distance between two points – standard unit is the meter (m) – The yard is the common English unit. – 1 yd = 0.91 m Volume - the space occupied by an object – standard unit is the liter (L) – The quart is the common English Unit – 1 qt = 0.946 L 11 Metric System Prefixes Basic units are the units of a quantity without any metric prefix. Prefix Abbreviation Meaning Decimal Equivalent Equality with major metric units (g, m, or L are represented by x in each ) mega M 106 1,000,000. 1 Mx  106 x kilo k 103 1,000. 1 kx  103 x deka da 101 10. 1 dax  101 x deci d 10 1 0.1 1 dx  101 x centi c 10 2 0.01 1 cx  102 x milli m 10 3 0.001 1 mx  103 x micro μ 10 6 0.000001 1 μx  106 x nano n 10 9 0.000000001 1 nx  109 x 12 12 4  Significant figures - all digits in a number representing data or results that are known with certainty plus one uncertain digit 1.4 The Numbers of Measurement 13 Recognition of Significant Figures 1.4 The Numbers of All nonzero digits are significant Measurement 7.314 has four significant digits The number of significant digits is independent of the position of the decimal point 73.14 also has four significant digits Zeros located between nonzero digits are significant 60.052 has five significant digits 14 Use of Zeros in Significant Figures 1.4 The Numbers of Zeros at the end of a number (trailing zeros) are Measurement significant if the number contains a decimal point. 4.70 has three significant digits Trailing zeros are NOT significant if the number does not contain a decimal point. 100 has one significant digit; 100. has three Zeros to the left of the first nonzero integer are not significant. 0.0032 has two significant digits 15 5  Scientific Notation Used to express very large or very small numbers easily 1.4 The Numbers of and with the correct number of significant figures Measurement Represents a number as a power of ten Example: 4,300 = 4.3  1,000 = 4.3  103 When a number is exceedingly large or small, scientific notation must be used to input the number into a calculator: 0.000000000000000000000006692 g must be entered into calculator as: 6.692 x 10−24 16 To convert a number greater than 1 to scientific notation, the original decimal point 1.4 The Numbers of is moved x places to the left, and the resulting number is multiplied by 10x Measurement The exponent x is a positive number equal to the number of places the decimal point moved 6200 = 6.2  103 What if you want to express the above number with three significant figures? = 6.20  103 17 To convert a number less than 1 to scientific 1.4 The Numbers of notation, the original decimal point is moved x places to the right, and the resulting number is Measurement multiplied by 10–x The exponent x is a negative number equal to the number of places the decimal point moved 0.0062 = 6.2  10–3 18 6  Rules for Rounding Off Numbers 1.4 The Numbers of When the number to be dropped is less than 5 the preceding number is not Measurement changed When the number to be dropped is 5 or larger, the preceding number is increased by one unit Round the following number to 3 significant figures: 3.34966  104 =3.35  104 19 Significant Figures in Calculation of Results 1.4 The Numbers of Rules for Addition and Subtraction The result in a calculation cannot have greater Measurement significance than any of the quantities that produced the result Consider: 9 37.68 liters 6.71862 liters 108.428 liters 152.82662 liters correct answer 152.83 liters 20 Rules for Multiplication and Division 1.4 The Numbers of The answer can be no more precise than the least precise number from which the answer is derived Measurement The least precise number is the one with the fewest significant figures 4.2  103 (15.94)  2.9688692  10 8 (on calculator) 2.255  10  4 Which number has the fewest significant figures? 4.2  103 has only 2 The answer is therefore, 3.0  10-8 21 7  Exact and Inexact Numbers 1.4 The Numbers of Inexact numbers have uncertainty by definition Measurement Exact numbers are a consequence of counting A set of counted items (beakers on a shelf) has no uncertainty Exact numbers by definition have an infinite number of significant figures 22 1.6 Unit Conversion You must be able to convert between units: - within the metric system - between the English and metric system The method used for conversion is called the Dimensional Analysis To convert from one unit to another you must know the conversion factor, which is the relationship between the two units. 23 Temperature - the degree of “hotness” of an object Conversions Between Fahrenheit and Celsius ToC = ToF − 32 1.8 ToF = 1.8 x ToC + 32 Kelvin Temperature Scale As molecular speed increases, the Kelvin temperature proportionately increases. (Equations given on the equation sheet) TK = ToC + 273.15 24 8 1.7 Additional Experimental Density and Specific Gravity Density 12 – the ratio of mass to volume Quantities – an intensive property – use to characterize a cork substance as each substance water has a unique density brass – Units for density include: g/mL mass m g/cm3 d  volume V liquid mercury g/cc 25 1.7 Additional Experimental Specific Gravity Values of density are often related to a standard Specific gravity - the ratio of the density of the Quantities object in question to the density of pure water at 4oC = 1.000 g/mL Specific gravity is a unitless term because the 2 units cancel Often the health industry uses specific gravity to test urine and blood samples density of object (g/mL) specific gravity  density of water (g/mL) 26 9