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Chapter 6.2

Chapter 6.2. Chemical Reaction. Chemical Reactions. Process by which atoms or groups of atoms in substances reorganize into different substances Chemical bonds are broken or formed For example – 4 Fe + 3 O 2 2 Fe 2 O 3. Reactants and Products. Chemical Equation:

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Chapter 6.2

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  1. Chapter 6.2 Chemical Reaction

  2. Chemical Reactions • Process by which atoms or groups of atoms in substances reorganize into different substances • Chemical bonds are broken or formed • For example – 4 Fe + 3 O2 2 Fe2O3

  3. Reactants and Products Chemical Equation: C6H12O6 + O2CO2 + H20 (Glucose and oxygen react to form carbon dioxide and water) Reactants (starting substances): C6H12O6 + O2 Products (substances formed): CO2 + H20

  4. Balanced Equation • According to the principle of conservation of mass, matter cannot be created or destroyed • The number of atoms of each element on the reactant side must equal the number of atoms of the same element on the product side For example: 2 H2O22 H20 + O2 C6H12O6 + 6 O26 CO2 + 6 H20

  5. Energy of Reactions • Activation Energy – minimum amount of energy needed to start a chemical reaction; energy needed for reactants to form products

  6. Energy-Releasing Reaction Energy-Absorbing Reaction Activation energy Products Activationenergy Reactants Reactants Products Energy of Reactions

  7. Enzymes • Most chemical reactions proceed slowly since the activation energy is high • A catalyst is a substance that lowers the activation energy needed to start a chemical reaction • Enzymes are biological catalysts; enzymes are proteins

  8. Enzymes

  9. How Enzymes Work • Reactants, called substrates, bind to specific enzymes; the site where enzymes bind is called the active site • Once the substrate binds to the active site, it changes shape and forms the enzyme-substrate complex • The substrates react to form new products; the enzyme-substrate complex helps to break and form bonds

  10. Example of Enzyme Reaction http://blog.poolcenter.com/print.asp?articleid=6072

  11. Another View of Enzymes

  12. Enzymes Many factors can affect enzyme activity such as: • pH • Temperature • Concentration of substrates

  13. Chapter 6.3 Water and Solution

  14. Water’s Polarity • Water molecules are formed by covalent bonds between 2 hydrogens and 1 oxygen atom • Since the electrons are more strongly attracted to the oxygen, the electrons spend more time near the oxygen nucleus • The unequal distribution of electrons gives oxygen a slight negative charge • Molecules with an unequal distribution of charges are polar molecules – they have oppositely charged regions Slight Negative Charge Slight Positive Charge

  15. Water’s Polarity and Hydrogen Bonds • The two water molecules are brought together, their polar ends attract each other • This attraction between water molecules is called hydrogen bonding • It is a weak bond between the hydrogen of one atom and the oxygen of another • A water molecule can hydrogen bond with three other water molecules

  16. Hydrogen Bonding in Water http://commons.wikimedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.jpg

  17. Properties of Water Water is the UNIVERSAL SOLVENT • Because water is polar, it can dissolve many substances • For example, NaCl

  18. Properties of Water Water Expands When It Freezes • Because of hydrogen bonding, water molecules separate when freezing and water becomes less dense • Extremely important for marine organisms

  19. http://expertvoices.nsdl.org/polar/2009/02/03/teaching-about-snowflakes-a-flurry-of-ideas-for-science-and-math-integration/http://expertvoices.nsdl.org/polar/2009/02/03/teaching-about-snowflakes-a-flurry-of-ideas-for-science-and-math-integration/ http://cc.oulu.fi/~nmrwww/comp_res4.html Solid Water (Ice) Liquid Water

  20. Properties of Water Water is COHESIVE and ADHESIVE Because of hydrogen bonding, • Water is attracted to other water molecules – this is called COHESION • Water is attracted to other surfaces – this is called ADHESION

  21. Cohesion

  22. Cohesion Causes Surface Tension

  23. Adhesion

  24. Adhesion (Capillary Action) http://discovermagazine.com/2003/mar/featscienceof http://www.sciencebuddies.org/science-fair-projects/project_ideas/PlantBio_p033.shtml

  25. Mixtures • two or more substances which are combined so that each substance keeps its own chemical identity. • Water combines to form many types of mixtures

  26. Mixtures • Mixtures can be classified as • Homogeneous – a combination of substances that is uniform throughout or • Heterogeneous – a combination of substances that are physically distinct from one another

  27. Homogenous Mixtures • Same uniform appearance • Same composition throughout • Examples • Sugar water • Salt water • Water and vinegar • Air in the atmosphere

  28. Homogeneous Mixture • Solutions are a homogeneous mixture • There are two components of solution: • Solvent – a substance in which another substance is dissolved • Solute – the substance that is dissolved

  29. Heterogeneous Mixture • Visibly different substances • Components remain distinct • Examples – • Vinegar and oil • Salad (lettuce, vegetables, croutons, etc.) • Sand and water

  30. Acids and Bases Substances that release H+ ions when dissolved in water WATERH2O Substances that release OH- ions when dissolved in water ACIDS BASES

  31. pH Scale • pH scale – measurement system used to indicate the concentration of H+ ions in a solution • pH scale ranges from 0-14 • pH 7 is neutral and the concentration of H+ ions and OH- ions is equal • Acids – any compound that forms H+ ions in solution; contain pH values less than 7 (the lower the pH values, the higher the acidity) • Bases – a compound that produces hydroxide ions (OH-) in solution; contain lower concentrations of H+ ions than water and have pH value greater than 7 • Buffers • weak acids or bases that can react with strong acid or bases to prevent sudden changes in pH • For example, to buffer a strong acid, you would add a weak base H2O H+ + OH-

  32. Chapter 6.4 The Building Blocks of Life

  33. Organic Chemistry • Organic compounds are those containing CARBON • Life forms are carbon-based and therefore considered organic

  34. Macromolecules • Macromolecules – large molecules that form from joining smaller molecules together • The smaller molecules are called monomer • The larger molecules are called polymers • Four biologically important macromolecules: • Carbohydrates • Lipids • Proteins • Nucleic acids

  35. Macromolecules Monomer – smaller molecule Polymer – larger molecule formed by joining together smaller molecules

  36. Biological Macromolecules

  37. Carbohydrates

  38. Lipids

  39. Proteins

  40. Nucleic Acids

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