Chapter 1 The Study of Change Chemistry is all around us Health Medicine Energy Environment Materials Technology Food Agriculture Macroscopic vs Microscopic Macroscopic Microscopic as the rusting of a nail can be seen by the naked eye easily observable needs a microscope or tool to be seen a process that is not seen such Hypothesis a tentative explanation for a set of observations This involves the testing and modifying the hypothesis many times Law a concise statement of a relationship between phenomena that is always the same under the same conditions Always true such as Force Mass x Acceleration Theory a unifying principle that explains a body of facts and or those laws that are based on them Chemistry the study of matter and the changes it undergoes Matter anything that occupies space and has mass Substance a form of matter that has a definite composition and distinct properties Mixture 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 i e soft drink lemonade water Heterogeneous mixture composition is not uniform throughout i e trail mix chicken noodle soup cement Physical means used to separate a mixture into its pure components Element a substance that cannot be separated into simpler substances by chemical means Compound a substance composed of atoms of two or more elements chemically united in fixed proportions Can only be separated into their pure components elements by chemical means Types of Changes melting sugar dissolving in water hydrogen burns in air to form water Chemical Change Physical Change Extensive Dependent Extensive and Intensive Property length volume Intensive Independent density temperature and color does not alter the composition or identity of a substance i e ice alters the composition or identity of the substance s involved i e depends upon how much matter is being considered i e mass does not depend upon how much matter is being considered i e Scientific Notation 568 762 Move decimal left 0 00000772 Move decimal to right o o o o o Addition or Subtraction 1 Write each quantity with the same exponent n 2 Combine N1 and N2 3 The exponent n remains the same o Multiplication 1 Multiply N1 and N2 2 Add exponents n1 and n2 o Division 1 Divide N1 and N2 2 Subtract exponents n1 and n2 Significant Figure Rules Any digit that is not zero is significant o 1 234 kg 4 significant figures Zeros between nonzero digits are significant o 606 m 3 significant figures Zeros to the left of the first nonzero digit are not significant o 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 o 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 o 0 00420 g 3 significant figures Addition or Subtraction o The answer cannot have more digits to the right of the decimal point than any of the original numbers Multiplication or Division o The number of significant figures in the result is set by the original number that has the smallest number of significant figures Exact Numbers o Numbers from definitions or numbers of objects are considered to have an infinite number of significant figures Dimensional Analysis Method of Solving Problems Determine which unit conversion factor s are needed Carry units through calculation If all units cancel except for the desired unit s then the problem was solved correctly Chapter 2 Atoms Molecules and Ions The Periodic Table Vertical column are called Groups Horizontal rows are called Periods Group 1A Alkali Metals Group 2A Alkali Earth Metals Group 7A Halogens Group 8A Noble Gases Formulas Molecular Shows the exact number of atoms of each element in the smallest unit of a substance Shows the simplest whole number ratio of the atoms in a substance Empirical Ionic Compounds Consist of a combination of anions and cations Usually the same as empirical The sum of the charges in each formula unit must equal zero Chemical Nomenclature o Often a metals and nonmetal o Anion non mental add ide to element name o DO NOT use Greek prefixes Molecular Compounds Nonmetals or nonmetals metalloids Common names H2O NH3 CH4 Element furthest to the left in a period and closest to the bottom of a group on periodic table is placed first in formula If more than one compound can be formed from the same elements use prefixes to indicate number of each kind of atom Last element name ends in ide 2 1 NH4 CO3 ClO3 1 CrO4 2 CN 1 Cr2O7 POLYATOMIC IONS ammonium ion carbonate ion chlorate ion chromate ion cyanide ion 2 dichromate ion H2PO4 dihydrogen phosphate ion 1 hydrogen carbonate bicarbonate ion HCO3 1 hydrogen phosphate ion HPO4 2 HSO4 hydrogen sulfate bisulfate ion 1 OH 1 hydroxide ion NO3 nitrate ion 1 nitrite ion NO2 1 1 permanganate ion MnO4 phosphate ion PO4 3 sulfate ion sulfite ion thiocyanate ion SO4 2 SO3 2 1 SCN Acids A substance that yields hydrogen H when dissolved in water Oxoacid o An acid that contains hydrogen oxygen and another element Oxoanion o Anions of oxoacids o Rules for naming oxoanions 1 When all the H ions are removed from the ic acid the anion s name ends with ate 2 When all the H ions are removed from the ous acid the anion s name ends with ite 3 The names of anions in which one or more but not all the hydrogen ions have been removed must indicate the number of H ions present Base A substance that yields hydroxide ions OH when dissolved in water Hydrates Compounds that have a specific number of water molecules attached to them Chapter 3 Mass Relationships in Chemical Reactions Average Atomic Mass The weighted average of all of the naturally occurring isotopes of the element Mole Mol A unit to count numbers of particles The amount of a substance that contains as many elementary entities as there are atoms in exactly 12 00 grams of 12C Molar Mass or molecular weight The mass of 1 mole of anything in grams The sum of the atomic masses in amu in a molecule Example SO2 1S 32 07 amu 2O 2 16 00 amu 64 07 amu Formula Mass The sum of the atomic masses in amu in a formula unit of an ionic compound Example NaCl 1 Na 22 99 amu 1 Cl 35 45 amu 58 44 amu 1 formula unit NaCl 58 44 amu 1 mole NaCl 58 44 g NaCl Percent Composition n x molar mass of element molar mass of compound 1 mole of the compound n is the number of moles of the element in CHEMISTRY STUDY GUIDE 1045 Exam 2 Chapters 3 7
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