4Parts of a Chemical Reaction Chemical Equation – Shorthand way to describe what happens in the overall chemical reaction.Reactants – Elements or compoundsthat are the “starter materials” for a reaction.Products – Elements or compoundsproduced by a chemical reaction
5Ex. Chemical equation for photosynthesis 6CO2 + 12H2O + sunlight O 2 + C6 H12O 6 + 6H2OReactants ProductsEx. Chemical equation for photosynthesis
6Types of Chemical Reactions SynthesisDecompositionCombustionSingle DisplacementDouble Displacement
8Indicators that a Rxn. occurred 1. Gives off heat , light or sound(all forms of Energy)2. Gives off a gas / bubbles3. Forms a solid precipitate4. Color change is observed
9Chemical reactions always involve the breaking of bonds in reactant molecules and the formation of new bonds in the product molecules.
10Bond Energy in Chemical Reactions What happens when bonds break and bonds form?Energy must be added to break bonds that hold the reactant molecules together. This is called activation energy (Ae). This amount of energy is what “activates” or gets the reaction started.
11Once the bonds are broken, the atoms are freed up and can make new molecules. When bonds form between the atoms to make new molecules, energy is released.
12The specific amount of energy that is needed to break a bond, or is releases when that same bond forms, is called bond energy.
13Two Categories of Chemical Reactions based on Energy Changes Exothermic ReactionsEndothermic Reactions
14Exothermic reactions release more energy than they absorb Exo – out thermic - heat
15Endothermic reactions absorb more energy than they release Endo – into thermic - heatEx. Photosynthesis
17Activation energy is the amount of energy that needs to be absorbed to start a chemical reaction.
18Connection to life:In order to stay alive, organisms need to carry out chemical reactions that require energy; therefore every organism must have a source of energy to carry out reactions.Plants trap and store energy from sunlightAnimals consume plants and other animals to produce energy