Matter and Measurements Chapter 1 Matter and Measurements

How to be Successful in 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 Wolpa/Advanced Placement Chemistry

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 (see Appendix A) Wolpa/Advanced Placement Chemistry

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

Wolpa/Advanced Placement Chemistry 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 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry 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.) Wolpa/Advanced Placement Chemistry

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. Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry 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 Wolpa/Advanced Placement Chemistry

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 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry 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 Wolpa/Advanced Placement Chemistry

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Wolpa/Advanced Placement Chemistry 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 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry 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 it’s volume Specific gravity is the ratio of the mass of a substance to the mass of an equal volume of water Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry What’s happening? Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry Density Calculation Equation d=m/V Example: If an object has a mass of 15.0 g and a volume of 10cm3 what’s the objects density? d = 15.0 g/ 10.0 cm3 = 1.50 g/cm3 Wolpa/Advanced Placement Chemistry

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 Wolpa/Advanced Placement Chemistry

Relationships between temperature scales Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry 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 -273.15°C This is defined as 0 K (no degree sign) The Kelvin degree is the same size as the Celsius degree (K = °C + 273.15) Wolpa/Advanced Placement Chemistry

Temperature Scale Comparison Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry 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 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry 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 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry Types of Mixtures Phase - one physical state with distinct boundaries and uniform properties Heterogeneous mixture - nonuniform mixture containing two or more phases with definite boundaries between the phases (e.g. ice and water) Homogeneous mixture - same throughout and contains only one phase (substances are mixed at the atomic or molecular level) Wolpa/Advanced Placement Chemistry

Heterogeneous Vs. Homogeneous Mixtures Wolpa/Advanced Placement Chemistry

Heterogeneous Vs. Homogeneous Mixtures Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry 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) Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry Alloys important solid solutions of two or more metals dental fillings (silver and mercury) stainless steel (iron, chromium and nickel) Wolpa/Advanced Placement Chemistry

Mixtures separated by: Filtration: Mixture consists of a solid and liquid; liquid distributing components between a mobile separated by filtration. Wolpa/Advanced Placement Chemistry

Separation of Mixtures cont. Distillation: Liquid mixture is boiled; components in the mixture boil off at different temperatures. Chromatography: Separates mixtures by and stationary phase. Wolpa/Advanced Placement Chemistry

Putting it All Together Wolpa/Advanced Placement Chemistry

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 Wolpa/Advanced Placement Chemistry

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 Wolpa/Advanced Placement Chemistry

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 - the degree to which the measurement is reproducible 1. expressed through how we write the number – significant figures Wolpa/Advanced Placement Chemistry

Example: Accuracy and Precision Wolpa/Advanced Placement Chemistry

Equations for Precision and Accuracy Percent Relative error % RE = Avg. Dev / Avg Value X 100 2. Accuracy Absolute Error % AE = (True value-Avg Value) X 100 True Value Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry Significant figures Significant figure – a digit that is either reliably known or estimated Assume that the last digit is uncertain ex: in the number 1.23, there are three significant figures and assume that the last digit, the 3, is uncertain Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry Reading Scales Estimate measurement to one digit beyond the smallest scale division Wolpa/Advanced Placement Chemistry

Counting Significant Figures Atlantic / Pacific Method a. Absent Decimal- Start on “atlantic” side of number & cross out all zeroes until 1st 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 1st nonzero digit Is reached, remaining digits are significant Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry 2. Examples: Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry Practice Count the significant figures in each of the following measurements: 1.0895 14000 12.0 5.020 1010300 17.190 0.00181 9101968 0.1980 0.00002700 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry Examples Round each of the following measurements to 3 significant figures 16.892 14670 0.01335 1.9220 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry Practice Round each of the following measurements to 2 significant figures 7.711 0.000188 5.01 13500 0.0985 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry Practice Round each of the following measurements to 2 significant figures 7.711 0.000188 5.01 13500 0.0985 Wolpa/Advanced Placement Chemistry

Significant digits in calculations Addition and subtraction – answer is expressed to the same number of significant figures as the number in the calculation with the fewest digits to the right of the decimal point ex. 10.6871 +1.42 12.1071 = 12.11 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry 2. In multiplication or division - the answer is expressed to the same number of significant digits as the number with the fewest significant digits ex. 2.34  3.225 = 7.5465 = 7.55 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry Calculation Practice 6.378 + 0.0025 = 22.37 x 3.10 x 85.75 = 22.4420 + 56.981 = 91.68 - 19.1 = 16.2 500,000 / 5.002 = Wolpa/Advanced Placement Chemistry

Scientific notation -Expressing very large and small numbers Using scientific Notation - Numbers are expressed with one nonzero digit to the left of the decimal point multiplied by 10 raised to an appropriate power 1. The base is the number with all of the appropriate significant digits 2. The exponent is the power of ten the base is multiplied by Wolpa/Advanced Placement Chemistry

Scientific notation format Wolpa/Advanced Placement Chemistry

Scientific notation and calculators 1. Calculators handle scientific notation by only inputting the exponent, using an EXP or EE key a. enter the base as you would a regular number, then press EXP or EE, then enter the exponent Wolpa/Advanced Placement Chemistry

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 Wolpa/Advanced Placement Chemistry

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 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry SI Units Measurement Unit Symbol Mass Kilogram kg Length Meter M Time Second s Temperature Kelvin K Quantity Mole mol Energy Joule J Pressure Pascal Pa Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry SI Prefixes Prefix Symbol Power tera- T 1012 deci- d 10-1 giga- G 109 centi- c 10-2 mega- M 106 milli- m 10-3 kilo- k 103 micro-  10-6 hecto- h 102 nano- n 10-9 deca- da 101 pico- p 10-12 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry . 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. Wolpa/Advanced Placement Chemistry

Basic SI units/Derived units Used to generate new Units Volume - space a given quantity of matter occupies Volume - expressed in terms of length - m3 m3 - 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 Wolpa/Advanced Placement Chemistry

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 Wolpa/Advanced Placement Chemistry

Wolpa/Advanced Placement Chemistry Conversion factors Unit factors - factors that relate a quantity in a certain unit to 1 of another unit e.g. 103 m = 1 km The conversion factor is created by divided both sides by the same quantity 103 m = 1 = 1 km 103 m 103m Wolpa/Advanced Placement Chemistry

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Wolpa/Advanced Placement Chemistry Dimensional Analysis Multiplying a quantity in one unit by an appropriate conversion factor converts the number into the new unit Note that conversion factors are exact relationships Exact relationships have unlimited precision, so they can be ignored for the purposes of decided the number of significant digits in a calculation Wolpa/Advanced Placement Chemistry

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