CHEM 101 1st Edition Lecture 2 Outline of Last Lecture I. Basic Concepts of ChemistryII. States of MatterIII. Levels of MatterIV. Classifying MatterV. Physical and Chemical PropertiesOutline of Current Lecture I. Kinetic and Potential EnergyII. Units of MeasurementIII.Dimensional AnalysisIV. Performing MeasurementsV. Scientific/Exponential NotationVI.Significant FiguresVII. Start of Chapter 2: The AtomCurrent Lecture- Kinetic and Potential Energyo Matter consists of atoms and molecules in motiono Kinetic energy- energy associated with motion: The motion of macroscopic objects like a thrown baseball or falling water The motion at microscopic (particulate) level (thermal energy)o Potential energy- the energy associated with changed or partially changed particles; electrostatic energy (microscopic) Results from the position of an object: Gravitational: an object held at a height, such as waterfalls (macroscopic) Energy stored in an extended spring (macroscopic) Energy stored in molecules (chemical energy, microscopic)- Units of Measuremento Science uses the système International d’ Unitès (International System of Units, SI) better known as the “Metric System”o The 7 Basic Units Measured Property Name of Unit AbbreviationMass Kilogram kgThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Length Meter mTime Second sTemperature Kelvin KAmount of Substance Mole molElectric Current Ampere ALiminous Intensity Candela cdo The base units are modified by a series of prefixes which you will need to memorize Prefix Abbreviation MeaningGiga- G 10^(9) (billion)Mega- M 10^(6)Kilo- k 10^(3)Deci- d 10^(-1)Centi- c 10^(-2)Milli- m 10^(-3)Micro- μ 10^(-6)Nano- n 10^(-9)Pico- p 10^(-12)Femto- f 10^(-15)- Temperature Unitso Fahrenheit is not an SI unit!o T(°C) = (T(°F)-32) x (5/9)°F °C KBoiling Point 212 100 373.15Freezing Point 32 0 273.15o Temperature (in science) is measured in °C and Kelvin temperature scaleso Temperature conversion: T(K)= 1K/1 °C + 273.15 °C- Length, Volume, and Masso The common units of lengths on the molecular scale are: Nanometers (1nm = 1 x 10^(-9)m) Ångstrom (1Å = 1 x 10^(-12)m) Picometers (1Å = 1 x 10^(-12)m)- Dimensional analysis o Dimensional analysis- converts one unit to another by using conversion factors (CF’s)1 unit x conversion factors = another unito The resulting quantity is equal to the original quantity, it differs only by the units Ex: 1m = 100cm Conversion Factor 1m x 100cm = 100cm 1m Ex: 1L = 1000 mL 1 mL = 1 cm^3 1L = 0.001m^31L x 1000 mL x 1 cm^3 = 1000cm^3 1L 1mLo The base unit of mass in the SI system is the kilogram, but the gram is more commonly used Ex: 1kg = 10^(3)g1mg x 1g x 1kg = 0.1 x 10^(-5)kg 1x10^(3)mg 1x10^(3)go Energy is the capacity to do work The SI unit for energy is the joule (J) Energy is also measured in calories (cal) Kilojoules (kJ) and kilocalories (kcal) are also common- 1kJ = 10^(3) J 1 kcal = 10^(3) cal- Performing Measurementso Precision- indicates how well several determinations of the same quantity agreeo Accuracy- can be expressed by the experimental error.Percent Error= Experimental value – Accepted value x 100 Accepted Value Poor precision and poor accuracy- all over the place, no consistency at all (darts all over a dart board) Good precision and poor accuracy- good consistency, but not where you want it (darts in the same region of a dart board, but not in the bulls eye where you want the darts to be) Good precision and good accuracy- good consistency exactly where you want it (darts in the same region of a dart board on the bulls eye where you want the darts to be)o The Standard Deviation is equal to the square root of the sum of the squares of the deviations for each measurement from the average divided by one less than the number of measurements (n)Standard Deviation = square root Σ(x n -x)^2 n-1 o Measurements are often reported to plus or minus the standard deviation to report the precision of a measurements- Scientific/Experimental Notationo Most often in science, numbers are expressed in a format that conveys the order of magnitude:3285 ft = 3.285 x 10^3 ft0.00215 kg = 2.15 x 10^3 kg- Significant Figures (Sig Figs or SF)o The number of digits is not relevant for exact numbers (ex: 100 cm in 1 m)o The number of digits represented in a number conveys the precision of the number (ex: from a measurement)o A mass measured to plus or minus 0.1g is far less precise than a mass measured to plus or minus 0.0001g o Rules: 1. All non zero numbers are significant 2. All zeros between non zero numbers are significant 3. Leading zeros are never significant 4. Trailing zeros are significant only if a decimal point is part of the numbero Practice: 1256 = 4 sig figs (rule 1) 1056007 = 7 sig figs (rule 1 and 2) 0.000345 = 3 sig figs (rule 1 and 3) 1780 = 3 sig figs (rule 1 and 4) 770.0 = 4 sig figs (rule 1 and 4)- Significant Figures in Calculatorso Multiplication/Division- the number of sig figs in the answer is limited by the factor with the smallest number o Addition/Subtraction- the number of sig figs in the answer is limited by the least precise number (the number with the last digit at the highest place) Ex: 23.50 ÷ 0.2001 x 17 = 1996.501749 4 SF ÷ 4 SF x 2 SF = 10 SF scientific notation = 1.996501749 x 10^3 round to 2 sig fig = 2.0 x 10^3 Ex: (26.05 + 32.1) = 58.150 = 7.5488 round to 7.5 sig figs (0.0032 +7.7) = 7.7032 Chapter 2: Atoms, Molecules, and Ions- The Atomo Protons Positive electrical charge Mass = 1.672622 x 10^(-24) g Mass = 1.007 atomic units (u)o Electrons Negative electrical charge Mass = 0.005 uo Neutrons No electrical charge Mass= 1.009 uo All atoms of the same element have the same number of protons in the nucleus, Z.o The atomic mass of one atom of an element is relative to 1 atom of anothero Current standard is based upon the carbon-12 isotope.
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