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Chemical Reactions

Chemical Reactions. I. CHEMICAL Reactions:. All the chemical reactions in our bodies are called metabolism . Breakdown and reassemble molecules in the body. Chemical bonds are broken and formed during chemical reactions. II. Writing a Chemical Equation:. YIELDS. REACTANTS. PRODUCTS.

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Chemical Reactions

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  1. Chemical Reactions

  2. I. CHEMICAL Reactions: • All the chemical reactions in our bodies are called metabolism. • Breakdown and reassemble molecules in the body. • Chemical bonds are broken and formed during chemical reactions.

  3. II. Writing a Chemical Equation: YIELDS REACTANTS PRODUCTS CH4 + 2O2  CO2 + 2H2O (methane) + (oxygen)  (carbon dioxide) + (water)

  4. II. Writing a Chemical Equation: • Coefficients = # of molecules of a compound • Ex: 6O2 = 6 molecules of Oxygen (O) • 3H2O = 3 molecules of H2O CH4 + 2O2  CO2 + 2H2O

  5. II. Writing a Chemical Equation: • Subscripts = # of atoms of an element • Ex: CH4 = 1 atom C, 4 atoms H • CO2 =1 atom of C,2 atoms O CH4 + 2O2 CO2 + 2H2O

  6. II. Writing a Chemical Equation: • How many atoms of O are in 6O2 ? 12 atoms of O!

  7. III. Balancing Chemical Equations: • In ALL chemical equations the same number of atoms of elements are on the reactant and the product side of chemical equations • Why? • Because of the Law of Conservation of Matter (atoms are never created or destroyed; they are simply rearranged!)

  8. III. Balancing Chemical Equations: • We balance equations so the Law of Conservation of Mater is NOT violated! • We must always balance equations using coefficients!!

  9. Tips for balancing equations: • Subscriptscan never be changed! • Coefficients must always be placed in FRONT of the entire compound! • Create an atom inventory

  10. Ex: Balance the following equations so the Law of Conservation of Matter is NOT violated: H2 + O2 H2O

  11. Ex: Balance the following equations so the Law of Conservation of Matter is NOT violated: CaO + KBr K2O + CaBr2

  12. Ex: Balance the following equations so the Law of Conservation of Matter is NOT violated: Al2S3 + BaCl2 AlCl3 + BaS

  13. Energy of Reactions

  14. IV. Energy of Reactions • The key to a chemical reaction is energy! • Most compounds in living things cannot undergo chemical reactions without energy

  15. Graph A IV. Energy of Reactions • Activation energy = the minimum amount of energy needed for reactants to form products in a chemical reaction • Look at Graph A: the peak in the graph represents the amount of energy that must be added to the system to make the reaction occur!

  16. IV. Energy of Reactions • All living things are chemical factories driven by chemical reactions! • Enzymes (catalysts) need to be present in order to reduce the activation energy and allow the reaction to proceed quickly.

  17. Graph B IV. Energy of Reactions • Look at Graph B: the enzyme lowers the activation energy and the product will be formed sooner!

  18. IV. Energy of Reactions • Catalyst = a substance that lowers the activation energy needed to start a chemical reaction. • Enzyme = special proteins that are biological catalysts that speed up the rate of a chemical reaction • Essential to life! • Specific to one reaction

  19. How do ENZYMES Work? • The reactants that bind to the enzyme are called substrates. • The specific location where a substrate binds on an enzyme is called the active site.

  20. How do ENZYMES Work? • The active site and substrate have complementary shapes (lock-and-key). • Enzymes are very specific for the substrates that will change!

  21. How do ENZYMES Work? • When the enzyme-substrate complex forms, chemical bonds are broken and new bonds form to produce the products. • Enzyme releases the product and the enzyme can be used again

  22. Factors That Affect Enzymes: • pH (how acidic or basic a substance is) • Temperature • most enzymes in human cells are most active at 98.6F • pH & temperature will denature (change the shape) of the enzyme so it will not be able to bond with the corresponding substrate!

  23. Examples Of Enzymes Working: • Helps with digestion • DNA replication • Enzymes in the venom of a venomous snake break down the membranes of a person’s red blood cells

  24. Examples Of Enzymes Working: • Hard green apples ripen because of the action of enzymes • Photosynthesis and cellular respiration provide energy for the cell with the help of enzymes

  25. pH, Acids, Bases

  26. V. pH, Acid, BASES: • pH= how acidic or basic a substance is • Acid= substance that forms H+ (hydrogen ions) in water HCl H+ + Cl- (pH LESS than 7) Water

  27. V. pH, Acid, BASES: • Base = substance that forms OH- (hydroxide ions) in water NaOH Na+ + OH- (pH MORE than 7) Water

  28. The pH scale: 0 7 14 N E U T R A L ACID BASE

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