Chapter 7.3 Guided Notes
1. Chemical reactions:
a. ____________________ chemical bonds in the _____________________
b. ____________________ new chemical bonds in the _____________________
2. Chemical energy: Energy stored in the ___________________________ of a substance.
a. True for both ___________________ and ____________________
3. Energy changes in _________________  determined by changes in
______________________________________.
a. Example: combustion of _________________________
i. C3H8 + 5O2  3CO2 + 4H2O
b. Bonds in reactants are ______________________ (C3H8 and O2)
i. Propane molecules have C-C and C-H ______________________
ii. Oxygen molecules have O=O ____________________________
c. Bonds in products are formed (CO2 and H2O)
i. Carbon dioxide molecules have C=O _________________________
ii. Water molecules have H-O ___________________________
4. Breaking Bonds
a. In __________________________ of propane, all chemical bonds in both
_____________________________ (propane and oxygen) must be
__________________.
b. Breaking chemical bonds requires _______________________.
i. A ________________________ provides enough energy to get the
reaction started.
5. Forming Bonds: burning propane
a. ________________________________________________________
6. Each molecule of propane __________________________ forms:
a. _________ molecules of carbon dioxide
i. 6 ______________________ (double) bonds formed
b. __________ molecules of water.
c. 8 __________________ (single) bonds formed
7. Forming of chemical bonds ____________________________ energy.
a. ___________________________________ given off because new chemical
bonds formed
8. Exothermic and Endothermic Reactions
a. During a chemical reaction, energy is either
_____________________________________________________.
9. Exothermic Reaction – Activity 3
a. _________________________________ energy to its surroundings
i. “Exo” means Energy “____________________” from the reaction
b. Energy required to break reactant bonds  ________________________ energy
________________________ as products formed
10. Exothermic reaction: chemical energy of reactants is ___________________________
chemical energy of products.
11. Chemical energy peaks before reactants ______________________ into products.
a. Peak Height = energy required to _______________ the chemical bonds of the
reactants.
i. Particles must ____________________ with enough energy to break these
bonds, or the reaction will not occur.
12. ____________________________ is an extremely exothermic reaction.
a. Example: 1 mole of propane + 5 moles of oxygen  ______________
(kilojoules) of heat is released.
i. C3H8 + 5O2  3CO2 + 4H2O + 2220 kJ
b. _____________________ = 1watt for 1 second
c. 100 watt light bulb for _______________________ needs 1 kJ
d. 44g propane releases enough energy for _______________________________
13. Endothermic Reaction – Activity 1 & 2
a. _________________________ energy from surroundings
i. “Endo” means Energy goes “______________________” the reaction
14. Energy required to ______________________ reactant bonds  ________________
than energy released by formation of products.
15. Endothermic reaction - energy of products is ___________________ energy of reactants.
16. Endothermic Reaction
a. Example: Emergency Cold Packs
i. Liquid inside the cold pack is ________________.
ii. In the water is another plastic bag or tube containing
__________________________________________ fertilizer.
iii. When you hit the cold pack, it _________________ the tube so that the
water mixes with the fertilizer.
iv. This mixture creates an ___________________ reaction -- it absorbs heat.
v. The temperature of the _____________________ falls to about 35 F for
10 to 15 minutes.
17. __________________________________ of Energy:
a. Total Energy is same _______________ and _________________ a reaction
18. ______________________________ reaction:
a. Chemical energy of reactants = _______________ + chemical energy of products.
19. ______________________________ reaction:
a. Chemical energy of reactants + _______________ = chemical energy of products.