What is Chemistry The science that deals with matter, and the changes that matter undergoes.

Physical Change Physical state is altered, but composition is the same. SOLID  LIQUID Melting LIQUID  GAS Boiling GAS  LIQUID Condensing SOLID GAS Sublimation GAS  SOLID Reverse sublimation or deposition LIQUID  SOLID Freezing

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

Physical Properties Color Odor Density Hardness Solubility Melting Point Boiling Point

Chemical Change Exhibited when a substance reacts with other substances Atoms are rearranged to form a new substance Often observable such as color change or change in energy

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

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 malleability color Wolpa/Advanced Placement Chemistry 1.6

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

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 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. Heterogeneous mixture – composition is not uniform throughout. ? 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

No Calculator Vomit!! We want to use the correct number of Significant Figures! On the AP exam, you have to be within 1 sig fig in order to receive credit!

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

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

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 The speed of sound in air is about 343 m/s. What is this speed in miles per hour? 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 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

Temperature conversion factors   Celsius to Kelvin K = T in oC + 273 Kelvin to Celsius oC = T in K - 273 Celsius to Fahrenheit oF = (1.8 (T in oC)) + 32 Fahrenheit to Celsius (T in oF - 32)/1.8

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

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

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.

Example: Accuracy and Precision

Equations for Precision and Accuracy Percent Error % Error = (True value-Calculated Value) X 100 True Value You will have to find the % Error for most of your labs!