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Chapter 3: Matter – Properties and Changes Properties of Matter States of Matter From Creative Commons Introduction to Chemistry: General, Organic, and Biological, Chapter 8 under a Creative Commons by-nc-sa 3.0 license. http://2012books.lardbucket.org/books/introduction-to-chemistry-general-organic-and-biological/s11-solids-liquids-and-gases.html Instead of the old definite volume definite shape definitions, visualize the particles in solids, liquids, and gases From Wikipedia. http://en.wikipedia.org/wiki/State_of_matter Notice that in the solid to liquid transition, bonds are weakened and the material becomes fluid. In the liquid to gas transition, bonds are broken and particles are free. Where does the energy go in the gas to plasma transition? Answer: electrons are stripped from atoms creating a positive ion, hence ionization. Properties of Matter Physical properties: can be observed or measured without changing the chemical identity (or composition) of the sample Intensive properties are independent of sample size (density, temperature, color) Extensive properties are dependent on sample size (mass, volume, heat) Physical changes alter the substance without changing its chemical identity such as phase changes or dissolution Chemical properties: ability of a substance to change the chemical identity (or composition) of the sample If a substance is not combustible, this is considered a chemical property Chemical changes always alter the chemical identity or composition of a substance Law of Conservation of Mass: mass reactants = mass products (Antoine Lavoisier) matter is neither created nor destroyed in a chemical reaction – it is conserved (See Example Problem 3.1 on page 78 of the text) Example: Practice Problem 5 on page 78 of the text Use the data in the table to answer the following questions: Aluminum and Liquid Bromine Reaction Substance Before Reaction After Reaction Aluminum 10.3 g 0.0 g Liquid Bromine 100.0 g 8.5 g Compound 0.0 g How many grams of bromine reacted? How many grams of compound were formed? Ans: 100.0 g – 8.5 g = 91.5 g Ans: 10.3 g + 91.5 g = 101.8 g Mixtures Homogeneous (or solution): constant composition throughout, only a single phase Heterogeneous: individual substances remain distinct, multiple phases with phase boundaries or interface layers Indicators of a chemical reaction 1. Energy evolution (heat / light / temperature change) 2. Evolution of a gas 3. Formation of a precipitate 4. Color change 5. Odor Separating mixtures: can be accomplished by physical means Filtration Crystallization From: Wikipedia http://en.wikipedia.org/wiki/Recrystallization_%28chemistr y%29 Sublimation From: Wikipedia http://en.wikipedia.org/wiki/Deposition_%28physics%29 Chromatography From: WikiLectures http://www.wikilectures.eu/index.php/Filtration Distillation Used by permission: https://uk.vwr.com/app/Header?tmpl=/chromatography/t hinlayer_chromatography%20.htm From: Wikipedia http://en.wikipedia.org/wiki/Simple_distillation#Simple_dis tillation Elements and Compounds Element: a pure substance that cannot be separated into simpler substances by chemical or physical means The smallest particle of an element is the atom The periodic table lists the 92 naturally occurring elements and man-made elements occurring after uranium Examples of element names and symbols: sodium (Na) and chlorine (Cl) Periodic table s p d f Rows are called periods or series Columns are called groups or families Compound: a pure substance composed of two or more types of elements that can be decomposed by chemical means Electrolysis is often used to decompose compounds into elements Law of Definite Proportions: the elements which compose a compound always occur in the same proportions by mass mass of element / mass of compound ) x 100% Percent mass = ( Example: Find the mass percent of sodium in sodium chloride (NaCl) Na = 23.0 g Cl = 35.5 g %Cl = ( 35.5 g / 58.5 g ) x 100% = 60.7% NaCl = 58.5 g Na represents the remainder = 39.3% Law of Multiple Proportions: if two compounds are formed by the same elements and the same mass is used for the first element, the ratio of the masses of the second element will occur as a small, whole number ratio Example: Water (I) and hydrogen peroxide (II) (I) H : O = 11.1 g : 88.9 g (divide both by 11.1 g gives) 1 : 8 (II) H : O = 5.9 g : 94.1 g (divide both by 5.9 g gives) 1 : 16 Note that the oxygen masses now have a ratio of 8 : 16 or 1 : 2
