9th Grade Chapter 7 Lesson 1

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  • 1. Pgs. 155-162 For Student Use Only 9 th Grade Chapter 7 Lesson 1
  • 2. Question 1 What is a chemical reaction?
    • A. Can results from molecules colliding with each other
    • C. Molecules can combine or break apart
    • B. Starts with chemical changes
    • D. A chemical change resulting from a collision between atoms or molecules
  • 3. Key
    • 1) A,B,C,D
  • 4. Chemistry is Everywhere
    • Student generated ideas:
    • Explain which pictures could be showing a chemical reaction. Explain why you chose that picture.
    • Pic 2= because if you mix different chemicsls you can get different colors
    • Pic. 4: shows molecules combinig and breaking apart
    • Pic 5= fire is putting in enerrgy to create a reaction by helping milescules combine
  • 5. Chemistry is Everywhere
    • Chemical Reactions
      • Original substances are changed into something different
      • Reactants= chemical substances that undergo changes
      • Products= things that are produced in the chemical reaction
    • Reaction of sulfuric acid and sugar. The acid dehydrates the sugar forming a pillar of carbon (black) and steam.
    http://www.scienceclarified.com/images/uesc_09_img0486.jpg
  • 6. Chemistry is Everywhere
    • Student generated ideas:
    • Write any chemical equations you can think of with the help of the pictures over to the side.
  • 7. Chemistry is Everywhere
    • Chemical Equations:
    • The reactants are on the left side of the equation
    • The products are on the right side of the equation
      • 2H 2 + O 2 = 2H 2 O
    • Coefficient tells how many molecules of the substance are in the reaction
    • Subscript tells how many atoms of molecules are present
    H 2 + Cl 2   -->   2 HCl http://www.personal.kent.edu/~cearley/ChemWrld/balance/balance.htm
  • 8. Chemistry is Everywhere
    • Student generated ideas:
    • What type of chemical reactions take place in baking a cake?
  • 9. Chemistry is Everywhere
    • Chemical Reactions:
    • Law of conservation of mass:
      • The total mass of the reactants is equal to the total mass of the products
      • Atoms are conserved in chemical reactions and have to be balanced
    http://www.winsite.com/info/images/1500000035527/methane.gif
  • 10. Chemistry is Everywhere
    • Student generated ideas:
    • How do you plan to balance equations? What do you need to know to balance equations?
  • 11. Chemistry is Everywhere
    • Balancing Chemical Equations:
    • RULES:
      • 1. Remember that only the coefficients on an equation NOT the molecular formulas may be adjusted
      • 2. Balance the element with the largest subscript first
      • 3. In an equation involving a pure element and one or more compounds balance the pure element last
    http://www.winsite.com/info/images/1500000035527/methane.gif
  • 12. Energy is everywhere
    • List all the ways that chemistry will produce energy in the pictures to the side.
  • 13. Chemistry is Everywhere
    • Energy in Chemical Reactions:
    • Activation Energy: Energy put into the reaction to make the reaction happen
    • Exothermic reaction- releases energy
    • Endothermic reaction- produce energy
  • 14. Chemistry is Everywhere
    • Energy in Chemical Reactions:
    • 2 nd law of thermodynamics states:
      • Energy and matter always tend to head toward less usable energy and greater disorder (called entropy- amount of disorder or decay)
      • Also- in every physical and chemical reaction, some of the energy cannot be used again
  • 15. Energy is everywhere
    • Based on the pictures what is one factor that affects reactions.
  • 16. Chemistry is Everywhere
    • Factors that affect chemical reactions:
    • Temperature: an increase in temperature will usually speed up a rxn (reaction) (due to more kinetic energy and colliding of particles)
    • Concentration: increased concentration increases the rate of rxn- (more particles to collide)
  • 17. Chemistry is Everywhere
    • Factors that affect chemical reactions:
    • Surface Area: the surface area of the of the reactants increases the speed of the reaction (more area for molecules to collide)
    • Catalysts: a substance that speeds up a reaction without being permanently changed (this lowers the amount of activation energy)