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Chapter Objectives: Section 2.1 1. Identify the characteristics of matter and substances 2.Differentiate among the three states of matter 3.Define physical property and list several common physical properties of substances Section 2.2 4. Categorize a sample of matter as a substance or a mixture 5.Distinguish between homogeneous and heterogeneous samples of matter Section 2.3 6. Explain the difference between an element and a compound 7.Identify the chemical symbols of common elements, and name common elements, given their symbols Section 2.4 8. Differentiate between physical and chemical changes in matter 9.Apply the law of conservation of mass

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States of Matter Prentice-Hall 2002General Chemistry: Chapter 1 Slide 2 of 19

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Some Properties of Solids, Liquids, and Gases Property Solid Liquid Gas Shape Has definite shapeTakes the shape of Takes the shape the container of its container Volume Has a definite volumeHas a definite volume Fills the volume of the container Arrangement of Fixed, very closeRandom, close Random, far apart Particles Intermolecular Very strongStrong Essentially none forces

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Kinetic theory All particles have energy and move Higher temperature = faster movement At the same temperature (energy), smaller particles/atoms will move faster than heavier ones. The kinetic theory explains the differences between the states of matter: Solid has definite shape and definite volume; the particles in a solid are packed closely together (least energy) Liquid has a definite volume, but does not have a definite shape; particles are further apart than in solids (more energy) Gas does not have a definite shape and does not have a definite volume (expands as much as possible); particles are spread far apart (most energy)

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Matter Substance Definite composition (homogeneous) Substance Definite composition (homogeneous) Element (Examples: iron, sulfur, carbon, hydrogen, oxygen, silver) Element (Examples: iron, sulfur, carbon, hydrogen, oxygen, silver) Mixture of Substances Variable composition Mixture of Substances Variable composition Compound (Examples: water. iron (II) sulfide, methane, Aluminum silicate) Compound (Examples: water. iron (II) sulfide, methane, Aluminum silicate) Homogeneous mixture Uniform throughout, also called a solution (Examples: air, tap water, gold alloy) Homogeneous mixture Uniform throughout, also called a solution (Examples: air, tap water, gold alloy) Heterogeneous mixture Nonuniform distinct phases (Examples: soup, concrete, granite) Heterogeneous mixture Nonuniform distinct phases (Examples: soup, concrete, granite) Chemically separable Physically separable Classification of Matter

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Pure Substances Element composed of identical atoms EX: copper wire, aluminum foil Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

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Top Ten Elements in the Universe Percent Element (by atoms) 1.Hydrogen73.9 2.Helium24.0 3.Oxygen 1.1 4.Carbon 0.46 5.Neon 0.13 6.Iron 0.11 7.Nitrogen 0.097 8.Silicon 0.065 9.Magnesium 0.058 10.Sulfur 0.044 A typical spiral galaxy (Milky Way is a spiral galaxy)

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Pure Substances Compound composed of 2 or more elements in a fixed ratio properties differ from those of individual elements EX: table salt (NaCl) Sodium Chlorine gas used in WWI

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Pure Substances Law of Definite Composition A given compound always contains the same, fixed ratio of elements. Law of Multiple Proportions Elements can combine in different ratios to form different compounds. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

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Pure Substances For example Two different compounds, each has a definite composition. Carbon, C Oxygen, O Carbon monoxide, CO Carbon, C Oxygen, O Oxygen, O Carbon dioxide, CO 2 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

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Mixtures Variable combination of two or more pure substances. HeterogeneousHomogeneous Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

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Methods of Separating Mixtures Magnet Filter Decant Evaporation Centrifuge Chromatography Distillation

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A Distillation Apparatus liquid with a solid dissolved in it thermometer condenser tube distilling flask pure liquid receiving flask hose connected to cold water faucet

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Elements, Compounds, and Mixtures (a) an element (hydrogen) (b) a compound (water) (c) a mixture (hydrogen and oxygen) (d) a mixture (hydrogen and oxygen) Dorin, Demmin, Gabel, Chemistry The Study of Matter, 3 rd Edition, 1990, page 68 hydrogen atoms hydrogen atoms oxygen atoms

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Matter Flowchart Examples: graphite pepper sugar (sucrose) paint soda Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem element heterogeneous mixture compound solution homo. mixture homogeneous mixture

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Properties & Changes in Matter Physical vs. Chemical Extensive vs. Intensive

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C. Johannesson Physical vs. Chemical Properties Physical Property can be observed without changing the identity of the substance Chemical Property describes the ability of a substance to undergo changes in identity Bromine Aluminum Sodium

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C. Johannesson Physical vs. Chemical Properties Examples: melting point Flammable Density Magnetic tarnishes in air physical chemical physical chemical

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C. Johannesson Physical vs. Chemical Physical Change changes the form of a substance without changing its identity properties remain the same Steel rusting: Chemical ChangeSteel rusting: changes the identity of a substance products have different properties 4 Fe + 3 O 2 2 Fe 2 O 3

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C. Johannesson Physical vs. Chemical Signs of a Chemical Change change in color or odor formation of a gas (not from boiling!) formation of a precipitate (solid) from two liquids change in light or heat

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C. Johannesson Physical vs. Chemical Changes Examples: rusting iron dissolving in water burning a log melting ice grinding spices chemical physical chemical physical

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C. Johannesson Extensive vs. Intensive Extensive Physical Property depends on the amount of matter present Examples: mass, volume, heat Intensive Physical Property depends on the identity of substance, not the amount color, melting point, boiling point, odor, density, temperature

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C. Johannesson Extensive vs. Intensive Examples: boiling point volume mass density conductivity intensive extensive intensive

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Physical and Chemical Properties Examples of Physical Properties Boiling point Color SlipperinessElectrical conductivity Melting point TasteOdorDissolves in water Shininess (luster) SoftnessDuctilityViscosity (resistance to flow) Volatility HardnessMalleabilityDensity (mass / volume ratio) Examples of Chemical Properties Burns in air Reacts with certain acidsDecomposes when heated Explodes Reacts with certain metalsReacts with certain nonmetals Tarnishes Reacts with waterIs toxic Chemical properties can ONLY be observed during a chemical reaction!

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Physical & Chemical Changes Limestone, CaCO 3 crushing PHYSICAL CHANGE Crushed limestone, CaCO 3 heating CHEMICAL CHANGEPyrex CO 2 CaO Lime and carbon dioxide, CaO + CO 2

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Pyrex O2O2 H2OH2OPyrex H2O2H2O2 Light hastens the decomposition of hydrogen peroxide, H 2 O 2. The dark bottle in which hydrogen peroxide is usually stored keeps out the light, thus protecting the H 2 O 2 from decomposition. Sunlight energy H H O O

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Chemical Properties and Chemical Change Chemical change or chemical reaction transformation of one or more atoms or molecules into one or more different molecules. Chemical change or chemical reaction transformation of one or more atoms or molecules into one or more different molecules. Burning hydrogen (H 2 ) in oxygen (O 2 ) gives H 2 O.Burning hydrogen (H 2 ) in oxygen (O 2 ) gives H 2 O.

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2 H 2 O2O2 O2O2 2 H 2 O + + + + E E Copyright 2007 Pearson Benjamin Cummings. All rights reserved.

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The Zeppelin LZ 129 Hindenburg catching fire on May 6, 1937 at Lakehurst Naval Air Station in New Jersey.

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Hydrogen is the most effective buoyant gas, but is it highly flammable. The disastrous fire in the Hindenburg, a hydrogen-filled dirigible, in 1937 led to the replacement of hydrogen by nonflammable helium.

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Packing of NaCl Ions Electron Microscope Photograph of NaCl

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Dissolving of Salt in Water NaCl(s) + H 2 O Na + (aq) + Cl - (aq) Cl - ions Na + ions Water molecules

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Thermal Expansion Most objects e-x-p-a-n-d when heated Large structures such as bridges must be built to leave room for thermal expansion All features expand together COLD HOT Cracks in sidewalk.