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Chapter 16 and 17

Chapter 16 and 17. Chemical Bonding and Chemical Reactions. Chemical Bonding. The force that holds two atoms together Unites atoms in a molecule Atoms bond so they will become more stable . Their outer rings will resemble the noble gases. Ionic Bonds. Ion

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Chapter 16 and 17

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  1. Chapter 16 and 17 Chemical Bonding and Chemical Reactions

  2. Chemical Bonding • The force that holds two atoms together • Unites atoms in a molecule • Atoms bond so they will become more stable. Their outer rings will resemble the noble gases.

  3. Ionic Bonds • Ion • Atom that has lost or gained an electron • Is now positive or negatively charged • Ionic Bond • Attraction that holds oppositely charged ions close together • Positive Na ion and negative Cl ion are attracted to one another.

  4. Ionic Bond

  5. Covalent Bonds • Chemical bond that forms between nonmetal when they share electrons • Electrons move back and forth between the outer energy levels of each atom to maintain the covalent bond

  6. Molecule • The neutral particle formed when atoms combine • 2 Types: • Element or Compound • Element—Molecule formed from 1 type of atom • Compound—Molecule formed from 2 or more types of atoms

  7. Symbols for Compounds • Compounds can be described using element symbols and numbers • Subscripts (small numbers) after the letters tell how many of that element are in a molecule. • Example: H2O contains 2 Hydrogen atoms and 1 oxygen atom.

  8. Chemical Formula • Combination of chemical symbols and numbers that shows which elements are present in a compound and how many atoms of each element are present. • Examples: • Ammonia: NH3 • Silver Tarnish: Ag2S • Hydrogen Gas: H2

  9. Chapter 17 Chemical Reactions

  10. Physical or Chemical Change? • Physical Change • Affects the physical appearance of a substance • Changes in state • Changes in shape or size • Chemical Change • Produces a new substance during a chemical reaction • Produces gas, light, change in heat, precipitate, change in color, sound • Oxidation, Burning

  11. Physical or Chemical Change?

  12. Chemical Equations • Describes the reactants and products in a chemical reaction using symbols and numbers • Reactants • Substances that exist before the reaction begins • Products • Substances that form as a result of the reaction

  13. Writing Chemical Equations • Reactants Products • 2H2 + O2 2H20 • Hydrogen + Oxygen Water • 2 Ag + H2S Ag2S + H2 • Silver + Hydrogen Sulfide Silver Sulfide + Hydrogen

  14. Conservation of Mass • Matter is not created or destroyed • Every atom that appears on the reactant side of the reaction also appears on the product side of the reaction

  15. Balancing Equations • Ag + H2S Ag2S + H2 • H2 + O2 H20

  16. pH Scale • Scale used to measure the strength of an acid or base. • 1---6.5 is considered an acid (battery acid) • Releases H+ ions in a solution • 7 is considered neutral (water) • 7.5—14 is considered a base (lye, soap) • Releases OH– ions in a solution

  17. pH Scale

  18. Energy in Chemical Reactions • Endothermic Reaction • Reaction that absorbs heat energy (gets colder) • 2H20 + energy 2H2 + O2 • Exothermic Reaction • Reaction that releases heat energy (gets warmer) • CH4 + 2O2 CO2 + H2O + energy

  19. Activation Energy • Minimum amount of energy need to start a chemical reaction • Example—burning of gasoline

  20. Catalyst • A substance that speeds up a chemical reaction • Are not changed permanently or used up during a chemical reaction • Enzymes • Special Catalysts that speed up chemical reactions in cells.

  21. Inhibitor • Substance that slows down a chemical reaction • Makes the formation of a certain amount of product take longer

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