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Topic 1 Matter and Measurements AP Chemistry

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Wolpa/Advanced Placement Chemistry 2 How to be Successful in AP Chemistry Memorize strategies not equations! Study a lot! Work ALL the problems. Self-evaluate after test results. Make use of Tutorial. Start a Study Group

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Wolpa/Advanced Placement Chemistry 3 Chapter 1: Matter and Measurement Overview: The Study of Chemistry Classifications of Matter Properties of Matter Units of Measurement Uncertainty in Measurement Dimensional Analysis Basic Math Concepts

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Wolpa/Advanced Placement Chemistry 4 Chemistry The study of matter and the changes it undergoes

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Wolpa/Advanced Placement Chemistry 5 Matter Anything that has mass and occupies space Characterized by physical and chemical properties Law of the Conservation of Mass - matter is neither created nor destroyed in chemical reactions

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Wolpa/Advanced Placement Chemistry 6 Element An element is a pure substance composed of one type of atom. An atom is the smallest particle of an element that retains the chemical properties of the element. An element is the most basic form of matter under ordinary circumstances Simplest chemical substance Only a few elements are found in their free state (nitrogen, oxygen, gold, etc.)

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Wolpa/Advanced Placement Chemistry 7 Elements and the Periodic Table Each element is represented by a name and a symbol. (Periods/groups - alkali metals, alkaline earth metals, halogens, noble gases) The first letter is always capitalized the second (and third) are never capitalized.

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Wolpa/Advanced Placement Chemistry 8 Compound A unique substance composed of two or more elements that are chemically combined (i.e. joined intimately, not just mixed together) Pure compounds have definite compositions and properties Require complex chemical procedures to separate into simpler substances (elements) Compounds include water, table salt, sugar, etc

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Wolpa/Advanced Placement Chemistry 9 Properties of Substances Elements and Compounds are pure substances. Properties describe the particular characteristics of a substance Pure substances have definite composition and definite, unchanging properties Physical properties - can be observed without changing the substance Chemical properties - require that the substance change into another

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Wolpa/Advanced Placement Chemistry 10 Physical States The three physical states are solid, liquid and gas solids - have a definite shape and volume liquid - have a definite volume but not a definite shape gas - neither a definite volume or shape A substance exists in a particular physical state under defined conditions

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Wolpa/Advanced Placement Chemistry 11

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Wolpa/Advanced Placement Chemistry 12 Phase Changes Melting point or freezing point temperature at which a substance changes from solid to liquid Boiling point or condensation point temperature at which a substance changes from liquid to gas

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Wolpa/Advanced Placement Chemistry 13 Density ratio of the mass of a substance to the volume of that mass usually measure in g/mL for solids and liquids; g/L for gases also a conversion factor relating the mass of a substance to its volume Specific gravity is the ratio of the mass of a substance to the mass of an equal volume of water

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Wolpa/Advanced Placement Chemistry 14 Whats happening?

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Wolpa/Advanced Placement Chemistry 15 Density Calculation Equation d=m/V Example: If an object has a mass of 15.0 g and a volume of 10cm 3 whats the objects density? d = 15.0 g/ 10.0 cm 3 = 1.50 g/cm 3

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Wolpa/Advanced Placement Chemistry 16 Temperature and its Measurement Temperature - measure of the intensity of the heat of a substance Thermometer - device to measure temperature Kelvin - K - SI unit of temperature Celsius - C - commonly used unit Fahrenheit - F - only used in USA

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Wolpa/Advanced Placement Chemistry 17 The Kelvin scale The idea of negative temperatures is a problem for any mathematical treatment of temperature dependent properties. It was found that a practical minimum temperature did exist (absolute zero) which has a value of -273.15C This is defined as 0 K (no degree sign) The Kelvin degree is the same size as the Celsius degree (K = C + 273.15)

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Wolpa/Advanced Placement Chemistry 18 Temperature Scale Comparison

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Wolpa/Advanced Placement Chemistry 19 Chemical Properties Chemical properties - involve how a substance changes into another Sometimes quite difficult to determine Some examples are burning (as opposed to boiling) and color changes

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Wolpa/Advanced Placement Chemistry 20 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. 2. Heterogeneous mixture composition is not uniform throughout. ?

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Wolpa/Advanced Placement Chemistry 21 Mixtures Combinations of two or more substances Can be separated by exploiting different physical properties (filtration, distillation, crystallization, chromatography) Have chemical and physical properties that are different from the substances that make them up The percentages by mass of the components of a mixture can be varied continuously

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Wolpa/Advanced Placement Chemistry 22 Heterogeneous Vs. Homogeneous Mixtures

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Wolpa/Advanced Placement Chemistry 23 Physical means can be used to separate a mixture into its pure components.

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Wolpa/Advanced Placement Chemistry 24 Physical means can be used to separate a mixture into its pure components. (Mechanical process) magnet filtration distillation

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Wolpa/Advanced Placement Chemistry 25 Physical Change: the composition of the substance remains the same but the state changes.

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Wolpa/Advanced Placement Chemistry 26 Chemical Change: a new substance is formed.

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Wolpa/Advanced Placement Chemistry 27 Physical Properties: Identifying properties of a substance. Density Solubility Color Melting/Boiling Point Crystalline Shape Malleability, Ductility, Conductivity, Luster Etc.

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Wolpa/Advanced Placement Chemistry 28 An extensive property of a material depends upon how much matter is is being considered. An intensive property of a material does not depend upon how much matter is is being considered. mass length volume density malleability color Extensive and Intensive Properties 1.6

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Wolpa/Advanced Placement Chemistry 29 Solutions A type of homogeneous mixture Usually involves a liquid phase, but can be solid-solid, liquid-liquid, solid-liquid, etc. The pure substances can be in different phases but form a homogeneous mixture (table salt and water, for example)

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Wolpa/Advanced Placement Chemistry 30 Measurements and Units Measurement - determines the quantity, dimensions or extent of something 1.Consist of two parts a. a numerical quantity (1.23) b. a specific unit (meters) Unit - a definite quantity adapted to as a standard of measurement

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Wolpa/Advanced Placement Chemistry 31 Features of Measured Quantities When we measure a number, there are physical constraints to the measurement Instruments and scientists are not perfect, so the measurement is not perfect (i. e., it has error) The error in the measurement is related to the accuracy and the precision of the measurement

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Wolpa/Advanced Placement Chemistry 32 Accuracy and Precision Accuracy how close the measurement is to the true value (of course we have to know what the true value is) Precision is a measure of how closely individual measurements agree with one another.

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Wolpa/Advanced Placement Chemistry 33 Example: Accuracy and Precision

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Wolpa/Advanced Placement Chemistry 34 Equations for Precision and Accuracy 1. Precision 2. Accuracy Absolute Error % AE = (True value-Avg Value) X 100 True Value

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Wolpa/Advanced Placement Chemistry 35 Significant Figures Any digit that is not zero is significant 1.234 kg 4 significant figures Zeros between nonzero digits are significant 6006 m 4 significant figures Zeros to the left of the first nonzero digit are not significant 0.08 L 1 significant figure One or more final zeros to the right of the decimal point are significant 2.00 mg 3 significant figures 0.00420 g 3 significant figures 10.006000 8 sig figs AP Chemistry Exam Hint: You must be within 1 sig fig it does not need to be perfect, but sig figs DO count!

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Wolpa/Advanced Placement Chemistry 36 Counting Significant Figures Atlantic / Pacific Method a. Absent Decimal- Start on atlantic side of number & cross out all zeroes until 1 st nonzero digit is reached, remaining digits are significant b. Present decimal- start on the pacific side of the number & cross out all zeros until the 1 st nonzero digit Is reached, remaining digits are significant

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Wolpa/Advanced Placement Chemistry 37 2. Examples:

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Wolpa/Advanced Placement Chemistry 38 How many significant figures are in each of the following measurements? 24 mL2 significant figures 3001 g 4 significant figures 0.0320 m 3 3 significant figures 6.400 x 10 4 molecules 4 significant figures 560 kg2 significant figures

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Wolpa/Advanced Placement Chemistry 39 Significant Figures Addition or Subtraction The answer cannot be more accurate than any of the original numbers. 89.332 1.1+ 90.432 round off to 90.4 one significant figure after decimal point 3.70 -2.9133 0.7867 two significant figures after decimal point round off to 0.79 370 -291.33 78.67 Number is rounded to tens place round off to 80

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Wolpa/Advanced Placement Chemistry 40 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 figsround to 3 sig figs 6.8 112.04 = 0.0606926 2 sig figsround to 2 sig figs = 0.061

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Wolpa/Advanced Placement Chemistry 41 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 Because 3 is an exact number = 7

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Wolpa/Advanced Placement Chemistry 42 Scientific notation format

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Wolpa/Advanced Placement Chemistry 43 Scientific notation and significant figures 1. When using scientific notation the base must be written with the correct number of significant digits 2. All zeroes are significant when using scientific notation

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Wolpa/Advanced Placement Chemistry 44 Measurement of mass, length and volume In the United States, we use a fairly awkward system of measurement for most things - the English system Scientists use the metric and SI systems of units for the measurement of physical quantities This system using standard units based on very precisely known properties of matter and light Prefixes are used in from of the units to indicate powers of ten

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Wolpa/Advanced Placement Chemistry 45 SI Units MeasurementUnitSymbol MassKilogramkg LengthMeterM TimeSeconds TemperatureKelvinK QuantityMolemol EnergyJouleJ PressurePascalPa

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Wolpa/Advanced Placement Chemistry 46 SI Prefixes PrefixSymbolPowerPrefixSymbolPower tera-T10 12 deci-d10 -1 giga-G10 9 centi-c10 -2 mega-M10 6 milli-m10 -3 kilo-k10 3 micro- 10 -6 hecto-h10 2 nano-n10 -9 deca-da10 1 pico-p10 -12

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Wolpa/Advanced Placement Chemistry 47. Base Units Mass - the quantity of matter that a sample contains Note that weight is a measure of the attraction of gravity for a sample and it varies depending on the distance of the mass to a planet or moon Scientists often speak imprecisely of the weight of an amount of substance. They really mean mass.

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Wolpa/Advanced Placement Chemistry 48 Basic SI units/Derived units Used to generate new Units Volume - space a given quantity of matter occupies Volume - expressed in terms of length - m 3 m 3 - an inconveniently large volume, so we use liter (L; one cubic decimeter) We often use a mL (1 cubic centimeter) for more manageable amounts of matter

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Wolpa/Advanced Placement Chemistry 49 Converting between units The standard method to convert between two different units is the factor-label or dimensional analysis method Dimensional analysis converts a measurement in one unit to another by the use of a conversion factor Conversion factors are developed from relationships between units

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Wolpa/Advanced Placement Chemistry 50 The speed of sound in air is about 343 m/s. What is this speed in miles per hour? 1 mi = 1609 m1 min = 60 s1 hour = 60 min 343 m s x 1 mi 1609 m 60 s 1 min x 60 min 1 hour x = 767 mi hour meters to miles seconds to hours