chapter 1 matter, energy, and the origins of the universe
TRANSCRIPT
Chemistry
• Chemistry is the science of matter: its composition, structure, and properties.
• Matter is anything that occupies space and has mass.
• Mass is a property that defines the quantity of matter in an object.
For the first exam you should know the names and elemental symbols for all elements through Krypton (Kr, # 36).
Classes and Properties of Matter
• Types of Matter
1. Pure Substances have the same physical and chemical properties throughout.
2. Mixtures are composed of two or more substances (elements or compounds) in variable proportions.
All matter is made up of either pure substances or more commonly, mixture of pure substances.
A mixture contains more than one pure substance.
Elements and Compounds
• Most elements are not found in the world in the pure form. They are found in compounds.
• Hydrogen is found in water, H2O, and other hydrogen containing compounds.
• The law of constant composition states that every sample of a compound always contains the same elements in the same proportions.
Pure Substances
• Two Groups
1. An element is the simplest kind of material with unique physical and chemical properties.
2. A compound is a substance that consists of two or more elements linked together in definite proportions.
Types of Mixtures
• In homogeneous mixtures the constituents are distributed uniformly throughout the sample.
• In heterogeneous mixtures the individual components can be seen as separate substances.
Separating Mixtures
• No chemical reactions are needed to isolate the constituents in a mixture.
Filtration
Distillation
Exam I (2007)
• Which of the following is not a pure substance?
a. nitrogen gas b. dry ice
c. distilled water d. filtered seawater
e. iron
An Atomic View
• An atom is the smallest particle of an element that retains the chemical characteristics of that element.
• A molecule is a collection of atoms chemically bonded together having constant proportions.
Chemical Formulas
• Chemical bonds link atoms together to make molecules.
• Chemical formulas use symbols to represent atoms with subscripts to identify the number of each atom present.
Chemical Reactions
• Chemical reactions show the transformation of one or more substance into different substances.
• Chemical equations use chemical formulas to express the identities and quantities of substances involved in a reaction
Properties of Matter
• Intensive property - a characteristic that is independent of the amount of substance present.Examples: color, hardness, etc.
• Extensive property - a characteristic that varies with the quantity of the substance present.Examples: length, width, mass, etc.
Properties of Matter
• Two Additional Categories of Properties
1. Physical Properties are characteristics that can be observed without changing into another substance. Examples: Luster, Hardness, Color, etc.
2. Chemical Properties are characteristics that can be observed only by reacting with another substance. Examples: Carbonates produce a gas when added to
acidic solutions
State of Matter
• Solids have definite shapes and volumes.
• Liquids occupy definite volumes, but do not have definite shapes.
• Gases have neither a definite shape nor volume.
Making Measurements
• Accurate measurements are essential for our ability to characterize the physical and chemical properties of matter.
• Standardization of the units of measurements is essential.
SI Base Units
Quantity Unit NameUnit
Abbreviation
Mass Kilogram kg
Length Meter m
Temperature Kelvin K
Time Second s
Electrical Current Ampere A
Amount of Substance
Mole mol
Luminosity Candela cd
The text adds “Joule” to this list. Is this correct?
English-Metric Conversions
• 1 in = 2.54 cm Length
• 1 lb = 453.6 g Mass
• 1qt = 946.4 mL Volume
• 1BTU = 1054-1060 J
• ton of cooling =12,000BTU/hr
Measurements in Scientific Studies
• A measurement always has some degree of uncertainty. A digit that must be estimated is called uncertain.
Accuracy versus
Precision in making
Measurements.
These terms are commonly misused by even working engineers
Accurate and precise
Precise but inaccurate
Imprecise and inaccurate
Rules for Counting Significant Figures - Overview
• Nonzero integersNonzero integers• ZerosZeros
leading zerosleading zeros captive zeroscaptive zeros trailing zerostrailing zeros
• Exact numbersExact numbers
Rules for Counting Significant Figures - Details
• Nonzero integers always count Nonzero integers always count as significant figures.as significant figures.
• 34563456 has 4 sig figs.has 4 sig figs.
Rules for Counting Significant Figures - Details
• ZerosZeros
Leading zeros do not count as Leading zeros do not count as significant figures.significant figures.
• 0.0486 has 3 sig figs.0.0486 has 3 sig figs.
Rules for Counting Significant Figures - Details
• ZerosZeros
Captive zeros always count asCaptive zeros always count assignificant figures.significant figures.
• 16.07 has 4 sig figs.16.07 has 4 sig figs.
Rules for Counting Significant Figures - Details
• ZerosZeros
Trailing zeros are significant onlyTrailing zeros are significant onlyif they come after a decimal point.if they come after a decimal point.
• 9.300 has 4 sig figs.9.300 has 4 sig figs.
Practice How many significant figures are in the How many significant figures are in the
following numbers?following numbers?
0.04550 g
100 lb
101.05 mL
350.0 g
Rules for Counting Significant Figures - Details
• Exact numbers have an infinite Exact numbers have an infinite number of significant figures.number of significant figures.
• 1 inch = 2.541 inch = 2.54 cm, exactlycm, exactly
Rules for Significant Figures in Mathematical Operations
• Addition and Subtraction: number Addition and Subtraction: number of sig figs in the result depends on of sig figs in the result depends on the number of decimal places in the the number of decimal places in the least accurate measurement.least accurate measurement.
• 6.8 + 11.934 = 18.734 6.8 + 11.934 = 18.734 18.7 (3 sig figs) 18.7 (3 sig figs)
Rules for Significant Figures in Mathematical Operations
• Multiplication and Division: number Multiplication and Division: number of sig figs in the result equals the of sig figs in the result equals the number in the least precise number in the least precise measurement used in the calculation.measurement used in the calculation.
• 6.38 6.38 2.0 = 12.76 2.0 = 12.76 13 (2 sig figs) 13 (2 sig figs)
Creation of Matter
• The Big Bang Theory Explosion of a cosmic “egg” produced an
expanding universe (Astronomer Georges Lemaitre).
Powell Hubble demonstrated that the universe is expanding by observing the light emitted by distant stars.
Scientific Method• A hypothesis is a
tentative and testable explanation for an observation or a series of observations.
• A scientific theory is a general explanation of widely observed phenomena that have been extensively tested.
Particle amu grams Charge
Neutron 1.00867 1.67494E-24 0
Proton 1.00728 1.67263E-24 +1
Electron 5.48580E-4 9.10939E-28 -1
10n 1
1p + 0-1e
Page 33
BigBang
Changing Units(Unit conversion Factors)
• A unit conversion factor is a fraction in which the numerator is a quantity equal or equivalent to the quantity in the denominator, but expressed in different units.
• 1kg = 1000g• Conversion factors: 1000g and 1kg
1kg 1000g
Unit Conversion Examples
1. Change 18.0 mL to Liters
2. Express 2.63 pounds in milligrams
3. Express a volume of 1.250 L in m3
Density
• Density is the mass of substance Density is the mass of substance per unit volume of the substance:per unit volume of the substance:
density = mass
volume
Using Densities
A density can be used to convert masses into volumes.A density can be used to convert masses into volumes.
8.533 g of Iron 1 mL = 1.08 mL8.533 g of Iron 1 mL = 1.08 mL 7.87 g of Fe 7.87 g of Fe
Exam I (2007)
• If the concentration of mercury in the water of a Berkeley pit mine-lake is 0.25 mg per liter of waste water, what is the total mass of Hg in the “lake”? Assume that The Pit has a surface area of 1.00 square mile and an average depth of 700. ft (and rising).
Practice
The lowest temperature measured on the Earth is -128.6oF recorded at Vostok, Antarctica in July 1983. What is this temperature in oC and in Kelvin?
ChemTour: Big Bang
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This animation explores the concept of the early formation of matter and radioactive decay rates within the context of the Big Bang.
ChemTour: Significant Figures
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This ChemTour reviews the rules for assigning significant figures and walks students through sample calculations.
ChemTour: Scientific Notation
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This ChemTour explains how to use scientific notation to express very large and very small numbers, and how to easily convert back and forth between decimal numbers and scientific notation.
ChemTour: Dimensional Analysis
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Students learn to keep track of the units associated with numerical values. The ChemTour includes worked examples and interactive Practice Exercises.