Matter and Energy Properties of Matter

Chemistry of Matches P 4 S 3 + KClO 3 P 2 O 5 + KCl + SO 2 tetraphosphorus trisulfide potassium chlorate diphosphorus pentaoxide potassium chloride sulfur dioxide  The substances P 4 S 3 and KClO 3 are both present on the tip of a strike anywhere match. When the match is struck on a rough surface, the two chemicals (reactants) ignite and produce a flame. Charles H.Corwin, Introductory Chemistry 2005, page 182 Safety matches The products from this reaction are P 2 O 5, KCl, and SO 2,the last of which is responsible for the characteristic sulfur smell. Strike anywhere matches The substances P 4 S 3 and KClO 3 are separated. The P 4 S 3 is on the matchbox cover. Only when the chemicals combine do they react and produce a flame.

block of wood: length = 2.0 m width = 0.9 m height = 0.5 m block of wood: force = 45 N pounds = 1 kilogram 10 Newton (9.8 N)

Force versus Pressure Area = 0.9 m x 2.0 m = 1.8 m 2 Area = 0.5 m x 2.0 m = 1.0 m 2 Area = 0.5 m x 0.9 m = 0.45 m 2 block of wood: length = 2.0 m width = 0.9 m height = 0.5 m 25 N/m 2 45 N/m N/m 2 Herron, Frank, Sarquis, Sarquis, Schrader, Kulka, Chemistry, Heath Publishing,1996, page Section 6.1

Pressure Which shoes create the most pressure?

During a “physical change” a substance changes some physical property… During a “physical change” a substance changes some physical property… H2OH2O

…but it is still the same material with the same chemical composition. H2OH2O gas solid liquid

Chemical Property: The tendency of a substance to change into another substance. caused by iron (Fe) reacting with oxygen (O 2 ) to produce rust (Fe 2 O 3 ) Steel rusting: 4 Fe + 3 O 2 2 Fe 2 O 3

Chemical Change: Any change involving a rearrangement of atoms.

Chemical Reaction: The process of a chemical change...

During a “chemical reaction” new materials are formed by a change in the way atoms are bonded together. During a “chemical reaction” new materials are formed by a change in the way atoms are bonded together.

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!

The formation of a mixture The formation of a compound Chemical Change Physical Change

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

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