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Chapter 6

Chapter 6. Chemical Reactions. Objectives 1. Recognize some signs that a chemical reaction may be taking place. Explain chemical changes in terms of the structure and motion of atoms and molecules. Describe the differences between endothermic and exothermic reactions.

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Chapter 6

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  1. Chapter 6 Chemical Reactions

  2. Objectives 1 • Recognize some signs that a chemical reaction may be taking place. • Explain chemical changes in terms of the structure and motion of atoms and molecules. • Describe the differences between endothermic and exothermic reactions. • Identify situations involving chemical energy.

  3. Reactants • A substance or molecule that participates in a chemical reaction • All of the elements, formulas, and compounds before (to the left of) the arrow in a chemical equation. • Na + Cl 

  4. Products • A substance that forms in a chemical reaction. • All of the elements, formulas, and compounds after (to the right of) the arrow in a chemical equation. •  NaCl

  5. Chemical Energy • The energy released when a chemical compound reacts to produce new compounds. • The total energy before the reaction is equal to the total energy of the products and their surroundings.

  6. Exothermic Reaction • A chemical reaction in which heat is released to the surroundings. • A + B  C + Heat • Example: A hand warmer. Burning wood. Ouch!! That’s Hot!!

  7. Endothermic Reaction • A chemical reaction that requires heat. • A + Heat  B + C • Example: Wanting wood to burn Gotta put out that fire.

  8. Section Review 1 • Page 189 • Problems 1 - 4

  9. Objectives 2 • Distinguish among five general types of chemical reactions. • Predict the products of some reactions based on the reaction type. • Describe reactions that transfer or share electrons between molecules, atoms, or ions.

  10. Synthesis Reaction • A reaction in which two or more substances combine to form a new compound. • A + B  AB • Na + Cl  NaCl Yum!!!

  11. Decomposition Reaction • A reaction in which a single compound breaks down to form two or more simpler substances. • AB  A + B • 2H2O  2H2 + O2

  12. Misc. Reactions • Electrolysis – the process in which an electric current is used to produce a chemical reaction, such as the decomposition of water. • Combustion Reaction – the oxidation reaction of an organic compound in which heat is released.

  13. Single – displacement Reaction • A reaction in which one element or radical takes the place of another element or radical in a compound. • AB + C  A +CB • 3 CuCl2 + 2 Al  2 AlCl3 + 3 Cu

  14. Double – displacement Reaction • A reaction in which a gas, a solid precipitate, or a molecular compound forms from the apparent exchange of atoms or ions between two compounds. • AB + CD  AD + CB • Pb(NO3)2 + K2CrO4  PbCrO4 + 2 KNO3

  15. Oxidation – Reduction Reaction • Any chemical change in which one species is oxidized (loses electrons) and another species is reduced (gains electrons); also called redox reaction.

  16. Radical • An organic group that has one or more electrons available for bonding.

  17. Section Review 2 • Page 197 • Problems 1,2,3,5

  18. Objectives 3 • Demonstrate how to balance chemical equations. • Interpret chemical equations to determine the relative number of moles of reactants needed and moles of products formed. • Explain how the law of definite proportion allows for predictions about reaction amounts. • Identify mole ratios in a balanced chemical equation. • Calculate the relative masses of reactants and products from a chemical equation.

  19. Chemical Equation • A representation of a chemical reaction that uses symbols to show the relationship between the reactants and the products. • Reactants  Products (yield)

  20. Mole Ratio • The relative number of moles of the substances required to produce a given amount of product in a chemical reaction. • The coefficients in front of the formulas in a balanced equation. • 2 H2O  2 H2 + O2

  21. Section Review 3 • Page 204 • Problems 1-3 Yeah! More Work.

  22. Objectives 4 • Describe the factors affecting reaction rates. • Explain the effect a catalyst has on a chemical reaction. • Explain chemical equilibrium in terms of equal forward and reverse reaction rates. • Apply Le Chatelier’s principle to predict the effect of changes in concentration, temperature, and pressure in an equilibrium process.

  23. Catalyst • A substance that changes the rate of a chemical reaction without being consumed or changed significantly. Would You hold still???? Oh No!! I’d better hurry up or he’ll get me.

  24. Enzyme • A type of protein that speeds up metabolic reactions in plants and animals without being permanently changed or destroyed.

  25. Substrate • A part, substance, or element that lies beneath and supports another part, substance, or element; the reactant in reactions catalyzed by enzymes.

  26. Chemical Equilibrium • A state of balance in which the rate of a forward reaction equals the rate of the reverse reaction and the concentrations of products and reactants remain unchanged.

  27. Section Review 4 • Page 212 • Problems 1 – 3 I’m finally done!! Wish I were there.

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