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 Ralph A. Burns, Fundamentals of Chemistry 1999, page 23 Chemical properties can ONLY be observed during a chemical reaction!

Evidence a Chemical Change Indications of a Chemical Reaction – Evolution of heat, light, and/or sound – Production of a gas – Formation of a precipitate – Color change

Formation of a solid: AgCl AgNO 3 (aq) + KCl(aq)  KNO 3 (aq) + AgCl(s)

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

Matter: Solids, Liquids, and Gases (also Plasma) 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 Interactions between Very strongStrong Essentially none particles

Conservation of Mass Reactants yield Products

Burning Magnesium Metal in an Open Container Dorin, Demmin, Gabel, Chemistry The Study of Matter, 3 rd Edition, 1990, page 77

Burning Magnesium Metal in a Closed Container Dorin, Demmin, Gabel, Chemistry The Study of Matter, 3 rd Edition, 1990, page 77

Classification of Matter MATTER (gas. Liquid, solid, plasma) PURE SUBSTANCES MIXTURES HETEROGENEOUS MIXTURE HOMOGENEOUS MIXTURES ELEMENTSCOMPOUNDS Separated by physical means into Separated by chemical means into Kotz & Treichel, Chemistry & Chemical Reactivity, 3 rd Edition, 1996, page 31

Pure Substances Element – composed of identical atoms – homogenous – EX: copper wire, aluminum foil Courtesy Christy Johannesson

Pure Substances Compound – composed of 2 or more elements in a fixed ratio by mass – properties differ from those of individual elements – homogenous – EX: table salt (NaCl) Courtesy Christy Johannesson

Mixtures Variable combination of 2 or more pure substances. Heterogeneous (uneven mix) Homogeneous (even mix) Courtesy Christy Johannesson

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

Solid, Liquid, Gas (a) Particles in solid (b) Particles in liquid (c) Particles in gas

Solid H 2 O (s) Ice Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 31

Liquid H 2 O (l) Water Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 31 In a liquid molecules are in constant motion there are appreciable intermolecular forces molecules are close together Liquids are almost incompressible Liquids do not fill the container

Gas H 2 O (g) Steam Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 31

Liquids The two key properties we need to describe are EVAPORATIONCONDENSATION EVAPORATION and its opposite CONDENSATION add energy and break intermolecular bonds EVAPORATION release energy and form intermolecular bonds CONDENSATION

ELEMENT hydrogen molecule, H 2 ELEMENT oxygen molecule, O 2 MIXTURE a mixture of hydrogen and oxygen molecules CHEMICAL REACTION if molecules collide with enough force to break them into atoms, a can take placeCOMPOUND water, H 2 O