Chemical Reactions

Chemical Change Physical Change

Chemical Change Reactants Products Signs of a chemical change Color change Production of a gas Formation of a precipitate Energy change Exothermic vs. endothermic Occurs as bonds are broken or formed

Chemical Formulas Shows the number of atoms of each element in a compound Subscripts below the symbol indicate the number of atoms Use the distributive property for subscripts outside parentheses Determine the number of each type of atom in the following compounds H2O 4. (NH4)3PO4 C12H22O11 5. Pb(ClO3)4 Ca(CO3)2 6. Ba3(AsO4)2

Chemical Formulas: Covalent Compounds Number of atoms Prefix 1 mono- (not used for first element) 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hepta- 8 octa- 9 nona- Prefixes indicating the number of each atom are used in naming molecules Ex: carbon tetrachloride P2O5 CO dinitrogen trioxide dinitrogen pentoxide S3Cl7

Chemical Formulas: Covalent Compounds Write the prefix for the number indicated. 9 7 8 6 Write the name or the formula. NO 8. dinitrogen tetroxide SiO2 9. sulfur hexafluoride P3Cl5 10. dihydrogen monoxide

Chemical Formulas: Ionic Compounds To write the formula: Determine the charge on the ions using the PT. Some charges are written on transition metals Balance the charges to make a neutral compound. Add subscripts to indicate the number of each element. Examples: barium fluoride aluminum oxide Do “Forming Compounds”

Chemical Equations Reactions are written for chemical changes Use correct chemical formulas Reactants Products Due to the Law of Conservation of Mass, the number of atoms of each element on the reactant side = number of atoms of each element on the product side Use coefficients to balance equations Do not change subscripts (they’re determined by neutralizing charges when writing formulas) Use “balancing chemical equations” handout

Reaction Types Synthesis- makes one product __________ + _________ _________ A + B AB AB + C ABC Decomposition- one reactant _________ __________ + _________ ABC AC + B AB A + B (How are synthesis and decomposition related?) Use paper clips!

Reaction Types Single Replacement- one element replaces another that is in a compound Element + compound compound + element _______ + ______ _____ + _____ AB + C A + CB AB + C AC + B Double Replacement- 2 compounds switch ions Compound + compound compound + compound AB + CD AD + CB Positive ions are always written 1st !