Chapter 1 The Study of Change Chemistry is all around us Health Medicine Energy Environment Materials Technology Food Agriculture Macroscopic vs Microscopic Macroscopic Microscopic 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 as the 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 VOCABULARY Types of Changes Physical Change in water Chemical Change to form water does not alter the composition or identity of a substance i e ice melting sugar dissolving alters the composition or identity of the substance s involved i e hydrogen burns in air Extensive and Intensive Property Extensive Dependent Intensive Independent temperature and color depends upon how much matter is being considered i e mass length volume does not depend upon how much matter is being considered i e density VOCABULARY Matter anything that occupies space and has mass Mass measure of the quantity of matter SI unit of mass is the kilogram kg Weight force that gravity exerts on an object Volume SI derived unit for volume is the cubic meter 1 mL 1cm3 Density SI derived unit for density is kg m3 Density Mass Volume 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 1 234 kg 4 significant figures 606 m 3 significant figures Any digit that is not zero is significant o Zeros between nonzero digits are significant o Zeros to the left of the first nonzero digit are not significant o If a number is greater than 1 then all zeros to the right of the decimal point are significant o 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 2 0 mg 2 significant figures 0 08 L 1 significant figure 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 TEMPERATURE CONVERSIONS K 0C 273 15 0C K 273 15 0F 9 5 x 0C 32 0C 0F 32 5 9 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 Empirical Shows the simplest whole number ratio of the atoms in a substance VOCABULARY Accuracy how close a measurement is to the true value Precision how close a set of measurements are to each other 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 o DO NOT use Greek prefixes Anion non mental add ide to element name VOCABULARY Molecule The aggregate of two or more atoms Diatomic molecules Contain only two atoms H2 N2 O2 Br2 HCl CO Polyatomic molecules More than two atoms Ion An atom that has a net positive or negative Monatomic Polyatomic Cation Ion with positive charge loses one or more electrons Na to Na Anion Ion with negative charge gains one or more electrons Cl to CL 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 nucleus Atomic Number The number of protons in a nucleus Mass Number Number of protons Number of neutrons Isotopes Are atoms of the same element x with different numbers of neutrons in their POLYATOMIC IONS ammonium ion NH4 1 carbonate ion chlorate ion chromate ion cyanide ion dichromate ion dihydrogen phosphate ion hydrogen carbonate bicarbonate ion hydrogen phosphate ion hydrogen sulfate bisulfate ion hydroxide ion nitrate ion nitrite ion permanganate ion phosphate ion sulfate ion sulfite ion thiocyanate ion 2 CO3 1 ClO3 CrO4 2 CN 1 2 Cr2O7 1 H2PO4 HCO3 1 HPO4 2 HSO4 1 OH 1 1 NO3 1 NO2 MnO4 1 PO4 3 SO4 2 2 SO3 1 SCN Acids o A substance that yields hydrogen H when dissolved in water Oxoacid An acid that contains hydrogen oxygen and another element Oxoanion Anions of oxoacids Rules for naming oxoanions o o 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
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