Basic Chemistry- Chemical Bond Video

Chemical Equations Chapter 10

Chemical Reactions Chemical reactions are chemical changes A change that takes place at the atomic level (a new substance if formed) Two ways: Forming/making bonds Break bonds Both forms take energy

Parts of a Chemical Reaction 2 main parts Reactants Products

Reactants These undergo the changes Can be one molecule or a bunch of single atoms 2H2 + O2 2 H2O The reactants

Products This is the result of the chemical reaction Can also be one molecule or a bunch of single atoms depending on the type of reaction that took place 2H2 + O2 2 H2O The product

Chemical Equations These chemical changes are represented by a chemical equation like you see below It shows the atoms that go through the changes and the result of that change 2H2 + O2 2 H2O The reactants The products Yields/produces Coefficient shows how many of that molecule you have The subscript shows how many of that particular atom you have

Chemical Equations Must be balanced! Because of The law of Conservation of mass (matter can never be created nor destroyed.) The total number of atoms for each element in the reactants must be EQUAL to the total number of atoms for element in the products 2H2 + O2 2 H2O

__ N2 +__ H2 ___ NH3 Balancing Equations First thing you will need to do is count the atom for each element Element Reactant Product N H

__ N2 +__ H2 ___ NH3 Balancing Equations First thing you will need to do is count the atom for each element Element Reactant Product N 2 1 H 3

__ N2 +__ H2 ___ NH3 Balancing Equations Change the coefficients to make them equal (use some guess and check) Element Reactant Product N 2 1 H 3

N2 + 3 H2 2 NH3 Balancing Equations Check to make sure the atoms are the same on both sides of the arrow Element Reactant Product N 2 H 6

Your turn Balance the equations on the board. http://funbasedlearning.com/chemistry/chemBalancer/

Types of Chemical Reactions There are three main types of chemical reactions Synthesis (combination) Decomposition Displacement (switching)

Synthesis or Combination Separate reactions will combine or bond forming a new substance A + B AB A + BC ABC Balance the following combinations: S + 02 SO3 Mg + O2 MgO Na + Cl NaCl

Decomposition Bonds are separated, a large molecule is broken up in to smaller molecules or atoms AB A+B ABC A+ BC Balance Equations 1. HgO Hg + O2 2. H2O2 O2 + H2O 3. H2CO3 H2O + CO2

Displacement (switching) The reactants are switched to make different bonds/combinations in the product AB+ C A+ BC 1. NaBr + Cl2 NaCl + Br2 2. Al + CuO Al2O3 + Cu

Energy in Reactions Energy is needed for every reaction! Depending on the way the energy is used, determines the type of reaction In order to start any type of reaction you must have a certain amount of energy Activation energy- minimum amount of energy required to start (activate) a reaction

Energy in Reactions Endothermic- heat is absorbed by the reaction (energy is absorbed) because it requires more energy Examples: Photosynthesis Evaporation/melting Electrolysis

Energy in Reactions Exothermic- heat is released by the reaction (energy is released) Examples: Combustion Freezing Flames rusting

Reaction Rate Chemical reactions take different amounts of time depending on the type of reaction Catalyst- increases the rate of reaction by lowering the activation energy required Enzyme- type of catalyst (biological) Inhibitor- slows down reactions