Happy New Year 2014! Happy New Year 2014! Warm Up: 1. NaOH = _______________ 2. MnO2 = _______________ 3. Sodium sulfate = _______ 4. Nitric acid = _____________

Ch. 8 Chemical Equations and Reactions 8.1 Describing Chemical Reactions

Chemical Reactions when a substance changes identity when a substance changes identity reactants- original reactants- original products- resulting products- resulting law of conservation of mass law of conservation of mass total mass of reactants = total mass of products total mass of reactants = total mass of products

Chemical Reactions chemical equation chemical equation represents identities and relative amounts of reactants and products in the chemical reaction represents identities and relative amounts of reactants and products in the chemical reaction uses symbols and formulas to represent chemicals uses symbols and formulas to represent chemicals Uses coefficients to balance amounts Uses coefficients to balance amounts

Hints of Chemical Rxn heat or light heat or light gas bubbles gas bubbles precipitate precipitate color change color change

Symbols Used in Equations yieldsreversible above arrow: or heatheated MnO 2 or Ptcatalyst 25°Cspecific T requirement 2 atmspecific P requirement after a formula: (s)solid (l)liquid (aq)aqueous: dissolved in water (g)gas

How to write elements... most pure elements are written as elemental symbol most pure elements are written as elemental symbol diatomic molecules diatomic molecules molecule containing only 2 atoms molecule containing only 2 atoms some elements normally exist this way (BrINClHOF twins) some elements normally exist this way (BrINClHOF twins) H 2, O 2, N 2, F 2, Cl 2, Br 2, I 2, At 2 H 2, O 2, N 2, F 2, Cl 2, Br 2, I 2, At 2 other exceptions other exceptions sulfur: S 8 sulfur: S 8 phosphorus: P 4 phosphorus: P 4

Word Equations uses names instead of formulas uses names instead of formulas Can act as bridge between word problem and actual chemical equation Can act as bridge between word problem and actual chemical equation

Example Solid sodium oxide is added to water at room temperature and forms sodium hydroxide.

Another Example Ammonia is produced by reacting excess nitrogen with hydrogen.

Counting Atoms Use Elmo Use Elmo

Balancing Equation Use Elmo Use Elmo