Matt Chemical Reactions

Parts of the Atom Chemical Reaction Basics What part of the atoms are affected? Electrons (valence electrons) are affected in reactions because they decide how reactive is the atom. An atom with one valence electron is more reactive than an atom with seven valence electrons (Figure) Eight is the most valence electrons in an atom. These atoms are not reactive. Electrons are lost or gained in chemical reactions. Oxidized: Atom loses electrons Reduced: Atom gains electrons Figure: Valence Electrons Gray atom has 1 valence electron Green atom has 7 valence electrons http://www.visionlearning.com/library/module_viewer.php?mid=54 Volume Library 1 Chapter 7 page 17 Oxidation-reduction reactions

Events during Chemical Rx Chemical Reaction Basics What is happening during a chemical reaction? Bonds between atoms or molecules have interactions among their electrons breaking and/or forming new bonds. http://wiki.answers.com/Q/What_happens_when_a_chemical_reaction_occurs Reactants & Products Application of Law of Conservation of Mass Five Signs of a Chemical Rx Description Reactants which are the substances that go into the reaction come out as final substances called products No matter what you do to the substance in chemical reactions it will still have the same mass. Actually law: Matter cannot be created nor destroyed only rearranged. Five signs: Change of color Formation of gas Formation of precipitate (solid separates for a solution) Change of temperature Energy produced Reference http://www.nelsonthornes.com/secondary/science/scinet/scinet/reaction/change/reactant.htm http://en.wikipedia.org/wiki/Conservation_of_mass http://wiki.answers.com/Q/What_are_the_5_signs_of_a_chemical_reaction

Role of Energy in Chemical Rx Forms of Energy Potential Energy– substances have a energy due to electrons and bonds. This is the energy that bonds already have to start with for a reaction. Activation Energy– threshold energy needed to initiate a chemical Rx or energy requirement to have a chemical reactions. This is the hump need to get over. (On next slide) Types of Energy Reactions (Table) Exothermic Rx Endothermic Rx Description Chemical reactions that release energy as part of their product Chemical reactions that absorb energy to form the product Basic Concept A + B  AB + energy A + B + energy  AB Example Combustion of methane CH4 + 2O2  CO2 + 2H2O Sports “Cold pack” 2NH4NO3(5) + H2O(1) + heat  NH4+(aq) + NO3–(aq) Graphic 1.http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm 2. http://genchem.chem.wisc.edu/demonstrations/Images/06thermo/methanebubbles.jpg 3. http://dopamine.chem.umn.edu/chempedia/index.php/Cold_Packs/Hot_Packs

Energy and Chemical Reactions Exothermic reaction Graphic illustrates that a chemical reaction (x-axis) occurs when a threshold energy is achieved (“activation energy”) and a product is formed that generates heat (ΔH along y-axis) Endothermic reaction Figure depicts much energy is needed (y-axis) to “activate” the reaction (x-axis) Products of this reaction make surrounding area colder due to higher energy needs to activate the reaction http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm

Types of Chemical Reactions Synthesis Decomposition Combustion Single Replacement Double Replacement Description Two substances combine to make a single product One substance is broken down into two substances Oxygen is a reactant and products include carbon dioxide & water One element replaces another as part of a compound Two compounds “switch partners” Basic Concept A + B  AB AB  A + B CxHy + O2  CO2 + H20 A + BC  AB + C AB + YZ  AY + BZ Example Iron and sulfur yields iron (II) sulfide http://farm3.static.flickr.com/2110/1508159256_cde784b80b.jpg?v=0 Electrolysis of water to make oxygen and hydrogen gas http://img.sparknotes.com/figures/0/02480ae8fc1a41b131a3fdb5a698e9a3/lyticcell.gif Burning of naphthalene http://www.separationsnow.com/FCKeditor/UserFiles/Image/sepNOW_ezines_2006/0601_sfcdetector1.jpg Magnesium replaces hydrogen in water to yield magnesium hydroxide and hydrogen gas http://chem200.tripod.com/flame2.gif Lead (II) nitrate with potassium iodide forms lead (II) iodide and potassium nitrate http://www.nitrogenorder.org/experiment/dblreplace.shtml Chemical Formula 8 Fe + S8  8 FeS 2 H2O  2 H2 + O2 C10H8 + 12 O2  10 CO2 + 4 H20 Mg + 2 H20  Mg(OH) 2 + H2 Pb(NO3)2 + 2 KI  PbI2 + 2 KNO3 Video on Chemical Reactions http://misterguch.brinkster.net/6typesofchemicalrxn.html

Bibliography Parts of the Atom http://www.visionlearning.com/library/module_viewer.php?mid=54 Volume Library 1 Chapter 7 page 17 Oxidation-reduction reactions Events during chemical reaction wiki.answers.com/Q/What_happens_when_a_chemical_reaction_occurs http://www.nelsonthornes.com/secondary/science/scinet/scinet/reaction/change/reactant.htm http://en.wikipedia.org/wiki/Conservation_of_mass http://wiki.answers.com/Q/What_are_the_5_signs_of_a_chemical_reaction Role of Energy in Chemical Reactions http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm http://genchem.chem.wisc.edu/demonstrations/Images/06thermo/methanebubbles.jpg http://dopamine.chem.umn.edu/chempedia/index.php/Cold_Packs/Hot_Packs Energy and Chemical Reactions http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm Types of Chemical Reactions http://misterguch.brinkster.net/6typesofchemicalrxn.html