Chemical Reaction – process that produces a chemical change

1. Chemical Reactions Compound – a substance containing two or more chemically combined elements and having properties different from those elements Carbon dioxide Sodium chloride Sulfuric acid Chemical Reaction – process that produces a chemical change

2. Recall Physical Change – the original substance still exist, it has only changed form; Size, shape, state of matter Evaporation Ice melting Cutting something in two Chemical Change – a new substance is produced that has properties different from those of the original substance, and there is a change in energy; Food digesting Wood rotting Cooking pancakes

3. Chemical Equations Chemical Equation – shows at a glance reactants, products, physical state, proportions of each substance present

4. Reactants and Products Reactants – substances that exist before the reaction begins (left side) Products – substances that form as a result of the reaction (right side) The arrow reads as yields (produces)

5. Chemical Name – common name Acetic acid + sodium hydrogen bicarbonate Sodium acetate + water + carbon dioxide Formula – indicates the elements that make up the compound and the number of atoms of each element present in the compound…chemical symbols used to represent a compound

6. Counting Atoms Subscripts –tell the number of atoms of each element of the compound H2O 2 atoms of hydrogen, 1 atom of oxygen CO2 NaCl H2SO4

7. Molecule – the smallest particle of a compound that still keeps all the properties of the compound; it is made of atoms 2H20 4Ag2S 2 molecules of H2O 4 molecules of Ag2S

8. Law of Conservation of Mass Law of Conservation of Mass (by Antoine Lavoiser)- atoms are never lost or created, just reordered The mass of the products = the mass of the reactants

9. Types of Reactions Chemical reactions release or absorb energy; the energy comes from bonds breaking and forming Exothermic – reactions release energy; Energy can be released in the form of light, sound, or heat 2H2 + O2 2H2O + energy Endothermic – reactions absorb energy; Energy can be absorbed in the form of electricity if products are less stable than reactants 2H2O + energy 2H2 + O2

10. Specific Heat • the amount of energy needed to change the temperature of 1 kg of a substance by 1 degree C…specific heat is a substance's resistance to temperature change • Example: Water heats up and cools down MUCH SLOWER than land. This is what causes land and sea breezes.

11. Rates of Reaction • Reaction Rate • tells how much something changes over time • tells how fast a reaction occurs • measures how fast reactants disappear or how fast products form

12. What effects reaction rate? Temperature: raising temps = speeds up reactions, lowering temps = slows down reactions Concentration: the more molecules present, the faster a reaction occurs Surface area: the larger the surface area, the faster a reaction occurs Catalyst : substance that speeds up a chemical reaction by providing surface area and reducing activation energy required. Enzymes are a type of catalyst in our bodies that help to break down proteins.

13. Vocabulary Activation energy – the specific amount of energy needed to start a chemical reaction Energy is used to break bonds between reactants & form new bonds in products Inhibitors – make the formation of a certain product take longer EX BHT, butyl hydroxytoluene, slows the spoiling of cereal

14. Balancing Equations Chemical equations must be balanced 1) Count atoms, T table 2) only add molecules, never change subscripts Ag + H2S Ag2S + H2 R P Na + AlCl3 NaCl + Al KBr + Cl2 KCl + Br2 H2O2 H2O + O2