Chemistry: The Study of Change   Chapter 1

The Discovery Process Chemistry - The study of matter… Matter - Anything that has mass and occupies space. This desk A piece of Aluminum foil What about air? Yes it is matter.

Chemistry - The study of matter and the changes it undergoes. Chemical and physical changes Energy changes

MAJOR AREAS OF CHEMISTRY Biochemistry - the study of life at the molecular level Organic Chemistry - the study of matter containing carbon and hydrogen. Inorganic Chemistry - the study of matter containing all other elements. Analytic Chemistry - analyze matter to determine identity and composition.

Physical Chemistry - attempts to explain the way matter behaves. Not only does chemistry cover all the above fields but it’s fingers reach out into many other areas of study other sciences medical practitioners pharmaceutical industry

Chemistry: A Science for the 21st Century Health and Medicine Sanitation systems Surgery with anesthesia Vaccines and antibiotics Energy and the Environment Fossil fuels Solar energy Nuclear energy

Chemistry: A Science for the 21st Century Materials and Technology Polymers, ceramics, liquid crystals Room-temperature superconductors? Molecular computing? Food and Agriculture Genetically modified crops “Natural” pesticides Specialized fertilizers

The Study of Chemistry Macroscopic Microscopic

The scientific method is a systematic approach to research A hypothesis is a tentative explanation for a set of observations tested modified

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

Observation of a phenomenon A question A hypothesis (a potential answer) Experimentation Theory New hypothesis Further experimentation Development of new experimentation and theory

Primordial Helium and the Big Bang Theory Chemistry In Action: Primordial Helium and the Big Bang Theory In 1940 George Gamow hypothesized that the universe began with a gigantic explosion or big bang. Experimental Support expanding universe cosmic background radiation primordial helium

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. Sugar Water Gold

A mixture is a combination of two or more substances in which the substances retain their distinct identities. Homogenous mixture – composition of the mixture is the same throughout. soft drink, milk, solder Heterogeneous mixture – composition is not uniform throughout. cement, iron filings in sand

Physical means can be used to separate a mixture into its pure components. distillation magnet

114 elements have been identified 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 32 elements have been created by scientists technetium, americium, seaborgium

Elements: sulfur, arsenic, iodine, magnesium, bismuth, mercury.

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. Water (H2O) Glucose (C6H12O6) Ammonia (NH3)

Classifications of Matter

The Three States of Matter solid liquid gas

Matter and Properties Properties - characteristics of matter chemical vs. physical Three states of matter 1. gas - particles widely separated, no definite shape or volume solid 2. liquid - particles closer together, definite volume but no definite shape 3. solid - particles are very close together, define shape and definite volume

Physical or Chemical? A physical change does not alter the composition or identity of a substance. ice melting sugar dissolving in water A chemical change alters the composition or identity of the substance(s) involved. hydrogen burns in air to form water

hydrogen + oxygen  water Chemical property - result in a change in composition and can be observed only through a chemical reaction. Chemical reaction (chemical change) a process of rearranging, replacing, or adding atoms to produce new substances. hydrogen + oxygen  water reactants products

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

Measurement in Chemistry Data, Results and Units Data - individual result of a single measurement or observation. obtain the mass of a sample record the temperature of Results - the outcome of the experiment Units - the basic quantity of mass, volume or whatever being measured. A measurement is useless without its units.

ENGLISH AND METRIC UNITS English system - a collection of measures accumulated throughout English history. no systematic correlation between measurements. 1 gal = 4 quarts = 8 pints Metric System - composed of a set of units that are related to each other decimally. That is, by powers of tens

1 meter = 10 decimeters = 100 centimeters Truly systematic 1 meter = 10 decimeters = 100 centimeters Basic Units of the Metric System Mass gram g Length meter m volume liter L prefixes are used to indicate the power of ten used

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 = 1 x 103 g weight – force that gravity exerts on an object weight = c x mass on earth, c = 1.0 on moon, c ~ 0.1 A 1 kg bar will weigh 1 kg on earth 0.1 kg on moon

International System of Units (SI)

Volume – SI derived unit for volume is cubic meter (m3) 1 cm3 = (1 x 10-2 m)3 = 1 x 10-6 m3 1 dm3 = (1 x 10-1 m)3 = 1 x 10-3 m3 1 L = 1000 mL = 1000 cm3 = 1 dm3 1 mL = 1 cm3

Density – SI derived unit for density is kg/m3 1 g/cm3 = 1 g/mL = 1000 kg/m3 density = mass volume d = m V A piece of platinum metal with a density of 21.5 g/cm3 has a volume of 4.49 cm3. What is its mass? d = m V m = d x V = 21.5 g/cm3 x 4.49 cm3 = 96.5 g

K = 0C + 273.15 273 K = 0 0C 373 K = 100 0C 0F = x 0C + 32 9 5 32 0F = 0 0C 212 0F = 100 0C

Conversions between Fahrenheit and Celsius 1. Convert 75oC to oF. 2. Convert -10oF to oC. 1. Ans. 167 oF 2. Ans. -23oC

Convert 172.9 0F to degrees Celsius. 0F = x 0C + 32 9 5 0F – 32 = x 0C 9 5 x (0F – 32) = 0C 9 5 0C = x (0F – 32) 9 5 0C = x (172.9 – 32) = 78.3 9 5

Chemistry In Action On 9/23/99, $125,000,000 Mars Climate Orbiter entered Mar’s atmosphere 100 km (62 miles) lower than planned and was destroyed by heat. 1 lb = 1 N 1 lb = 4.45 N “This is going to be the cautionary tale that will be embedded into introduction to the metric system in elementary school, high school, and college science courses till the end of time.”

Scientific Notation The number of atoms in 12 g of carbon: 602,200,000,000,000,000,000,000 6.022 x 1023 The mass of a single carbon atom in grams: 0.0000000000000000000000199 1.99 x 10-23 N x 10n N is a number between 1 and 10 n is a positive or negative integer

Scientific Notation Addition or Subtraction 568.762 0.00000772 move decimal left move decimal right n > 0 n < 0 568.762 = 5.68762 x 102 0.00000772 = 7.72 x 10-6 Addition or Subtraction Write each quantity with the same exponent n Combine N1 and N2 The exponent, n, remains the same 4.31 x 104 + 3.9 x 103 = 4.31 x 104 + 0.39 x 104 = 4.70 x 104

Scientific Notation Multiplication Division (4.0 x 10-5) x (7.0 x 103) = (4.0 x 7.0) x (10-5+3) = 28 x 10-2 = 2.8 x 10-1 Multiply N1 and N2 Add exponents n1 and n2 Division 8.5 x 104 ÷ 5.0 x 109 = (8.5 ÷ 5.0) x 104-9 = 1.7 x 10-5 Divide N1 and N2 Subtract exponents n1 and n2

Scientific Notation The measuring devise determines the number of significant figures a measurement has. In this section you will learn to determine the correct number of significant figures (sig figs) to record in a measurement to count the number of sig figs in a recorded value to determine the number of sig figs that should be retained in a calculation.

Significant figures - all digits in a number representing data or results that are known with certainty plus one uncertain digit.

Significant Figures Any digit that is not zero is significant 1.234 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 0.00420 g 3 significant figures

How many significant figures are in each of the following measurements? 24 mL 2 significant figures 3001 g 4 significant figures 0.0320 m3 3 significant figures 6.4 x 104 molecules 2 significant figures 560 kg 2 significant figures

Significant Figures Addition or Subtraction The answer cannot have more digits to the right of the decimal point than any of the original numbers. 89.332 1.1 + 90.432 one significant figure after decimal point round off to 90.4 3.70 -2.9133 0.7867 two significant figures after decimal point round off to 0.79

Significant Figures Multiplication or Division The number of significant figures in the result is set by the original number that has the smallest number of significant figures 4.51 x 3.6666 = 16.536366 = 16.5 3 sig figs round to 3 sig figs 6.8 ÷ 112.04 = 0.0606926 = 0.061 2 sig figs round to 2 sig figs

Significant Figures Exact Numbers Numbers from definitions or numbers of objects are considered to have an infinite number of significant figures The average of three measured lengths; 6.64, 6.68 and 6.70? 6.64 + 6.68 + 6.70 3 = 6.67333 = 6.67 = 7 Because 3 is an exact number

RECOGNITION OF SIGNIFICANT FIGURES All nonzero digits are significant. The number of significant digits is independent of the position of the decimal point Zeros located between nonzero digits are significant 4055 has 4 sig figs

Zeros to the left of the first nonzero integer are not significant. Zeros at the end of a number (trailing zeros) are significant if the number contains a decimal point. 5.700 Trailing zeros are insignificant if the number does not contain a decimal point 2000. versus 2000 Zeros to the left of the first nonzero integer are not significant. 0.00045

How many significant figures are in the following? 3.400 3004 300. Examples of Significant Figures How many significant figures are in the following? 3.400 3004 300. 0.003040

Accuracy – how close a measurement is to the true value Precision – how close a set of measurements are to each other accurate & precise precise but not accurate not accurate & not precise

You need to be able to convert between units UNIT CONVERSION You need to be able to convert between units within the metric system between the English and metric system The method used for conversion is called the Factor-Label Method or Dimensional Analysis !!!!!!!!!!! VERY IMPORTANT !!!!!!!!!!!

Dimensional Analysis Method of Solving Problems Determine which unit conversion factor(s) are needed Carry units through calculation If all units cancel except for the desired unit(s), then the problem was solved correctly. given quantity x conversion factor = desired quantity desired unit given unit given unit x = desired unit

What does any number divided by itself equal? Let your units do the work for you by simply memorizing connections between units. For example: How many donuts are in one dozen? We say: “Twelve donuts are in a dozen.” Or: 12 donuts = 1 dozen donuts What does any number divided by itself equal? ONE! or...

What does any number times one equal? This fraction is called a unit factor What does any number times one equal? That number.

a number divided by itself = 1 We use these two mathematical facts to do the factor label method a number divided by itself = 1 any number times one gives that number back Example: How many donuts are in 3.5 dozen? You can probably do this in your head but let’s see how to do it using the Factor-Label Method.

Start with the given information... 3.5 dozen = 42 donuts Then set up your unit factor... See that the units cancel... Then multiply and divide all numbers...

Dimensional Analysis Method of Solving Problems How many mL are in 1.63 L? Conversion Unit 1 L = 1000 mL 1L 1000 mL 1.63 L x = 1630 mL 1L 1000 mL 1.63 L x = 0.001630 L2 mL

The speed of sound in air is about 343 m/s The speed of sound in air is about 343 m/s. What is this speed in miles per hour? conversion units meters to miles seconds to hours 1 mi = 1609 m 1 min = 60 s 1 hour = 60 min 343 m s x 1 mi 1609 m 60 s 1 min x 60 min 1 hour x = 767 mi hour

C. Volume 1 gallon = 4 quarts 1 quart = 2 pints Common Relationships Used in the English System A. Weight 1 pound = 16 ounces 1 ton = 2000 pounds B. Length 1 foot = 12 inches 1 yard = 3 feet 1 mile = 5280 feet C. Volume 1 gallon = 4 quarts 1 quart = 2 pints 1 quart = 32 fluid ounces Commonly Used “Bridging” Units for Intersystem conversion Quantity English Metric Mass 1 pound = 454 grams 2.2 pounds = 1 kilogram Length 1 inch = 2.54 centimeters 1 yard = 0.91 meter Volume 1 quart = 0.946 liter 1 gallon = 3.78 liters

1.3 Measurement in Chemistry Examples of Unit Conversion 1. Convert 5.5 inches to millimeters 2. Convert 50.0 milliliters to pints 3. Convert 1.8 in2 to cm2 1.3 Measurement in Chemistry

Think Metric!!!!!!! 10E-12 boos = 1 picoboo 1boo E2 = 1 boo boo 10 E1 cards = 1decacards 10 E-2 menals = 1 centimental 10 E6 phones = 1 megaphone 10 E-6 phones = 1 microphone 10 E3 joys = 1 kilo-joy

Derived Units The density of an object is its mass per unit volume, where d is the density, m is the mass, and V is the volume. Generally the unit of mass is the gram. The unit of volume is the mL for liquids; cm3 for solids; and L for gases. 2

A Density Example A sample of the mineral galena (lead sulfide) weighs 12.4 g and has a volume of 1.64 cm3. What is the density of galena?

A Density Example A sample of the mineral galena (lead sulfide) weighs 12.4 g and has a volume of 1.64 cm3. What is the density of galena? mass Density = volume

A Density Example A sample of the mineral galena (lead sulfide) weighs 12.4 g and has a volume of 1.64 cm3. What is the density of galena? mass 12.4 g Density = = volume 1.64 cm3

A Density Example A sample of the mineral galena (lead sulfide) weighs 12.4 g and has a volume of 1.64 cm3. What is the density of galena? mass 12.4 g Density = = = 7.5609 = 7.56 g/cm3 volume 1.64 cm3

cork water brass nut liquid mercury

Calculations using density: What is the density of a sample of bone with mass of 12.0 grams and volume of 5.9 cm3? A sinker of lead has a volume of 0.25 cm3. Calculate the mass in grams. The density of lead is 11.3 g/cm3. What is the volume of air in liters (density = 0.00129 g/mL) occupied by 1.0 grams.

WORKED EXAMPLES

Worked Example 1.1

Worked Example 1.2

Worked Example 1.4