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Important things to remember in chemistry MEMORIZE the starred pages Introduction and Measurement Chemistry is • the study of matter and the changes it undergoes (transformations) • the study of reactions and interactions among different types of matter • the study of connections between macroscopic and submicroscopic events • the science that seeks to understand the behavior of matter by studying the behavior of atoms and molecules Memorize for week 1 3 Memorize for week 1 International System of Units (SI) 4 Memorize for week 2 5 6 A Comparison of Temperature Scales K = 0C + 273.15 273 K = 0 0C 373 K = 100 0C 0C = 5 x (0F – 32) 9 0F = 9 x 0C + 32 5 32 0F = 0 0C 212 0F = 100 0C 7 Significant Figures • Any digit that is not zero is significant 1.234 kg 4 significant figures • Zeros between nonzero digits are significant 606 m 3 significant figures • Zeros to the left of the first nonzero digit are not significant 0.08 L 1 significant figure • If a number is greater than 1, then all zeros to the right of the decimal point are significant 2.0 mg 2 significant figures • If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant 0.00420 g 3 significant figures http://www.roch.edu/people/tebrown/pages/sigfig2.htm 8 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 = 6.67333 = 6.67 = 7 3 Because 3 is an exact number 9 CALCULATIONS with Significant Figures Addition or Subtraction The answer cannot have more digits to the right of the decimal point than any of the original numbers. 89.332 +1.1 90.432 3.70 -2.9133 0.7867 one significant figure after decimal point round off to 90.4 two significant figures after decimal point round off to 0.79 10 CALCULATIONS with 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 figs round to 3 sig figs 6.8 ÷ 112.04 = 0.0606926 = 0.061 2 sig figs round to 2 sig figs 11 Dimensional Analysis Method of Solving Problems 1. Determine which unit conversion factor(s) are needed 2. Carry units through calculation 3. If all units cancel except for the desired unit(s), then the problem was solved correctly. given quantity x conversion factor = desired quantity given unit x desired unit given unit = desired unit 12 A law is a concise statement of a relationship between phenomena that is always observed and measured to be the same under the same conditions. Ex. Law of Acceleration Force = mass x acceleration A natural law compactly summarizes patterns in a large amount of data that often apply only under special conditions and are descriptions of nature, not facts or explanations Ex. Law of Gravity – “What goes up, must come down” m1 m2 ForceGravity = G _________ 2 d A scientific law is a statement that summarizes all past observations and predicts future observations Ex. Law of Conservation of Mass – “In a chemical reaction, matter is neither created nor destroyed.” CH4 + 2 O2 --> CO2 + 2 H2O A law allows you to predict future observations 13 Atoms, Molecules and Ions Elements and compounds: names and formula writing Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Our definitions • Atom: smallest, independent, uncharged, unique unit of matter ex. An atom of hydrogen, H H • Molecule: two or more atoms bonded together chemically; electrically neutral ex. A molecule of hydrogen gas H2 H-H • Ion: an atom that has acquired a charge, either positive (+), called cation or negative (-), called anion ex. Hydrogen ion H+ • Polyatomic ion: a group of atoms bonded to each other but carrying an over-all charge, either positive (+) or negative (-) ex. Hydroxide anion, OH- O-H - These terms are used to describe matter on the basis of the particles they are made up of 15 Orbital: The pathway of an electron • It is the region in space where the probability of finding an electron is greatest • Every set of orbitals is also known as an energy level; • It is related to the period (horizontal row) in the periodic table and represents the relative distance from the nucleus • An orbital can contain a maximum of 2 electrons per individual orbital • Electrons have a specific amount of energy and can give off or absorb energy as they enter or leave an orbital • The basic shape is a sphere but becomes more complex as more space is available father from the nucleus • An orbital is not physical material but is defined by the presence of an electron http://winter.group.shef.ac.uk/orbitron/AOs/1s/index.html Types of compounds and how they are named 17 Memorize for week 3 Memorize these names of common negative ions and their charges 18 Memorize these Common Polyatomic Ions and their charges Memorize for week 3 Name Formula Name Formula acetate carbonate hydrogen carbonate (aka bicarbonate) hydroxide nitrate nitrite chromate dichromate ammonium C2H3O2– CO32– hypochlorite chlorite ClO– ClO2– OH– NO3– chlorate perchlorate sulfate sulfite NO2– CrO42– ClO3– ClO4– SO42– SO32– hydrogen sulfate (aka bisulfate) HSO4– Cr2O72– NH4+ hydrogen sulfite (aka bisulfite) HSO3– Tro, Chemistry: A Molecular Approach HCO3 – 19 Periodic Pattern of Polyatomic Ions -ate groups 3A BO 4A -3 3 5A 6A -2 3 -1 NO 3 -2 SiO 3 -3 PO 4 CO AsO -3 4 -2 SO 4 ClO -2 SeO 4 -1 BrO 3 TeO Tro, Chemistry: A Molecular Approach 20 7A -2 4 -1 3 -1 IO 3 Memorize for week 3 21 Memorize for week 3 22 23 24 Memorize for week 3 25 Naming = Nomenclature All Compounds metal nonmetal nonmetal nonmetal has H @ start or H that can be donated