CHEM 101 Chapter 1
CHEM 101 Chapter 1 Chem 101
Popular in General Chemistry 1
Popular in Chemistry
This 9 page Class Notes was uploaded by Lyna Nguyen on Friday January 29, 2016. The Class Notes belongs to Chem 101 at Texas A&M University taught by Dr. Daniel Collins in Fall 2015. Since its upload, it has received 21 views. For similar materials see General Chemistry 1 in Chemistry at Texas A&M University.
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Date Created: 01/29/16
09/01/1509/08/15 Chemistry 101 Chapter 1 What is chemistry? Definition: study of matter and changes it undergoes using energy Is a central science Physics: chemistry in motion Bio: chemistry in a cell Engineering: application of sciences Why is it hard? Terminology Words, numbers, equations Skeptic: looks at all sides and chooses the best Organic: contains carbon and hydrogen All chemists: eat, drive a car, cook Chemical intuition Biggest challenge: getting standard units, terms, and numbers Chemistry and its method Parts of Scientific Method Observation Hypothesis Data Collection Record what you do; proof Summary of data Laws and theories Hypothesis, Laws and Theories Hypothesis: tentative explanation or prediction w/ knowledge Requires both qualitative and quantitative in experiments Quantitative: numerical data Supports claims Ex: mass, temp Qualitative: non-numerical; observations Ex: color, physical appearance Law: a concise verbal or mathematical statement of a behavior or a relation that is the same in all conditions Narrow statement 1 09/01/1509/08/15 Theory: well-tested, unifying principle that explains a body of facts and the laws based on them Binds observations/data together Capable of suggesting new hypotheses Based on carefully determined and reproducible evidence “Umbrella” statement Can change w/ new facts Systematic Approach Scientific method Observation -> representation -> interpretation -> observation … (repeating cycles) Goals of Science What makes a good scientist? Patience Knowledge Hard work Luck Goals: Prediction and control Can be dangerous Understanding and Explaining Examples Dilemmas and integrity in science Results can be inconclusive Guidelines (4 rules): Results should be reproducible Research should be reviewed (detailed) Conclusions should be reasonable and unbiased Credits should be given where it is due Sustainability and Green Chemistry Began to take root 20+ years ago New ways of doing things w/ lower pollution levels Classifying matter Matter Anything that occupies space and has mass Governed by 2 things: compositions and energy States of Matter and Kinetic-Molecular Theory State: gas, liquid, solid At low temps, all matter is solid As temp increases, liquids becomes gases Kinetic-Molecular Theory of Matter 2 09/01/1509/08/15 All matter consists of small particles Solid: packed closely, regular in array, vibrate in avg. positions Liquid: random arrangement, fluid, not confined to position Gas: parts are far part, moves around, volume=container, fluid There are net forces between particles in all states Gas: small Solid/liquid: large Determines properties of matter Higher temp = faster movement Energy of motion (kinetic) acts to overcome the forces of attraction between parts Energy causes change in state Matter at the Macroscopic and Particulate Levels Macroscopic: world of experiments and observations observed by the naked eye Submicroscopic/particulate: only seen by microscope (atoms and molecules) Matte r Substance Mixtures s Heterogeneo Homogenous us Pure Substances Solutions: mixture of liquid (water) and dissolved substances Has unique properties which it can be recognized Melting/boiling point Cannot be separated into 2+ species by any physical means Physical means: used to separate a mixture into its pure components Ex: distillation, using a magnet Mixtures: Heterogeneous and homogenous 3 09/01/1509/08/15 Mixture: 2 or more pure substances that can be separated by physical techniques Retains specific identities Heterogeneous: uneven texture, not uniform throughout Ex: cement Homogenous: 2+ substances in same phase Ex: milk, soda, solder Often called solutions Uniform throughout Elements: only 1 type of atom; cannot be separated by chemical means 118 elements 82 occur naturally Ex: Au, Al, Pb, O, C, S 36 elements created by scientists Atom: smallest particle of an element that retains the characteristics chemical properties Compounds: pure substances composed of 2+ elements held together by chemical bonds at fixed proportions Referred as chemical compounds Can be changed by chemical means Ions: electrically charged atoms or groups of atoms Molecules: smallest discrete unit that retain the composition and chemical characteristics Chemical Formula: represents compound Ex: H 2 -> 2 Hydrogen atoms w/ 1 Oxygen Physical Properties: properties that can be observed and measured w/o changing the composition of a substance Ex: height, weight, color, conductivity Density: ratio of mass to volume Temperature: affects the numerical values of its properties Chemical Properties: indicates whether and sometimes how readily a material undergoes a chemical change w/ another material Ex: combustion, fire, food digestion Ex Questions: Sugar dissolving in water Physical Methane burning in air Chemical Extensive and Intensive Properties Extensive: depends on amount of substance present; size dependent Ex: mass and volume, energy, length 4 09/01/1509/08/15 Intensive: do NOT depend on amount Ex: density, temp, color Useful in identifying material Physical and Chemical Changes Physical changes: changes in physical properties Identity of substance is sustained No new chemicals Ex: melting, dissolving Chemical changes: 1 or more substances (reactants) are transformed into 1 or more other substances (products) Alter composition; “reaction” Chemical equation: representation of chemical reaction Left: reactants Right: products Ex: hydrogen burns air to form water Energy: Some basic principles Defined as the capacity to do work Kinetic energy: motion Potential energy: results from an object’s position or state and included height, springs, and chemical bonds Ex: chemical, position Types of energy Radiant: comes from the sun/primary source Thermal: associated w/ motion of atoms/molecules Chemical: stored w/in bonds of chemical substances Nuclear: stored w/in collection of neurons and protons in the atom Can be converted Conserved most of the time Ex: chemical -> kinetic Law of Conservation of Energy Correct title: First Law of Thermodynamics Thermodynamics: movement of energy Defined as “energy can neither be created nor destroyed Total energy of the universe is constant Math Review: Measurements, quantitative Measurements and importance: Length: ruler (m) Mass: balance (g, kg) Volume: beaker, flask, bottle (oL,oL) Temperature: thermometer ( F, C, K) Critical Parts: number and unit 5 09/01/1509/08/15 SI units: created by the General Conference of Weights and measurements; standard units 2 major parts: base unit and prefix Base unit: tells us what it is Prefix: tells us size of it Mass vs. Weight Mass: measure of what is there SI: kilograms 3 1kg=1000g=1x10 g=2.21lbs Weight: force gravity exerts on an object Weight=c*mass Volume 3 SI: cubic meter (m ) 1 cm =(1x10 ) =1x10 m -6 3 3 1 cm =1mL=1cc Density 3 3 3 Density = kg/m -> 1g/cm (solids) =1g/mL OR 1000kg/m (volume/liquids) =m/v 1g/L = .001 g/mL (gases) Most universal Intensive Energy SI: Joules 2 2 Mechanical energy: 1J=1 kg*m /s Calories: old energy unit 1 calorie (cal) = 4.184 joules (J) 1 dietary cal = 1000 cals Temperature Celsius: o Freezing point: 0 C Boiling point: 100 Co o Room temp: 20 C Body temp: 37 C o Kelvin Absolute zero: lowest temperature o o 0 C = 273.15K = 32 F 100 C = 373.15K = 212 F o Conversion K= C+273.15 F=(9/5)x C+32 6 09/01/1509/08/15 Making measurements Precision: of measurement indicates how well several determinations of the same quantity agree How close data is to each other Multiple and reproducible results Accuracy: agree of a measurement w/ the accepted value of the quantity Correct value; “true value” Expressed as percent error Experimental Error Error in measurement = experimentally determined value – accepted value Percent error=(Error in measurement/accepted value)*100% Standard deviation Defined: equal to the square root of the sum of the square of the deviations for each measurement from the average, divided by one less than the number of measurements Steps: Average calculated Difference b/w measurement and average Determinate errors: caused by faulty instruments or human errors Ex: incorrect record keeping Indeterminate (random errors): uncertainties in a measurement Mathematics in chemistry Exponential or scientific notation Fixed notation: full number (324) Way of presenting very large/small numbers n N x 10 N: digit term Between 1-10; +/- N: power Integer; +/- Significant figure rules Any digit that is not 0 is significant 0 b/w 2 other sigfigs are significant 0 place holders are not significant 0 to the right of a nonzero number and to the right of a decimal are significant In numbers less than 0, only zeros after nonzero sigfigs are significant Significant Figures in Calculations Ambiguous: prefer 1 sigfig; use scientific notation 7 09/01/1509/08/15 Exact numbers: numbers from definition or numbers of objects are considered to have an infinite number of sigfigs Ex: numbers of trials, data Sigfig calculation rules Rule 1: fewest decimal places when adding/subtracting Rule 2: fewest sigfigs when multiplying/dividing Rule 3: When rounded off, the last digit to be retained is increased by one inly if the following digit is 5 or greater Truncation: chop off Round off at end of calculations Problem Solving by Dimensional Analysis Dimensional analysis (factor-label): general problem-solving approach that uses dimensions/units Steps 1) Determine which unit conversion factors are needed Conversion factor: equivalence of a measurement in 2 different units Number in original [new/old]=new unit 2) Carry units 3) Desired unit/target unit should be the only thing left Given*conversion factor=desired factor Graphs and Graphing Standard straight line Y=mx+b DO NOT CONNECT DOTS Problem Solving and Chemical Arithmetic Step 1: state the problem Step 2: what do you know? Step 3: strategy (sketch, pictures, roadmap) Step 4: solution (execute plan) REMEMBER UNITS Step 5: think about answer Step 6: check your understanding Problem Solving Tips Answer the question Read the entire problem Equations, tables, and unit analysis Know how to get data Time management Is your answer reasonable? Check calculator mistakes 8 09/01/1509/08/15 9
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