1. IPC 04 Chemical Reactions Energy in Reactions Chemical Equations Law of Conservation of Mass Balancing Equations Classifying Reactions

2. Law of Conservation of Mass - __________________________________! The total mass of the reactants must _________ the total mass of the products. 1CH 4 + 2O 2  1CO 2 + 2H 2 O 16 g + 64 g = 44 g+ ? g Ex: In a chemical reaction, 16 g of methane (CH 4 ) combine with 64 g of oxygen to form carbon dioxide (CO 2 ) and water (H 2 O). What is the mass of the water formed? Reactants = Products

3. Practice: 1.In a chemical reaction, 4 g of hydrogen combine with 32 g of oxygen to form water What is the mass of the product formed? 2H 2 + O 2  2H 2 O 2. If 60 g of ethane burns in 224 g of oxygen to produce 108 g of water, what is the mass of the remaining product? C 2 H 6 + O 2  CO 2 + H 2 O

4. Chemical Reaction (1) reactants - substances that _________________________. (2) products - ________substances that _________________________________. milk + vinegar  cheese

5. Energy in Reactions Exothermic means there is a ________ ___ ________. Endothermic means there is an ________ ___ _______. HOT! COLD!

6. Exothermic Reaction Heat Energy Released: energy of products is ________________ the energy of reactants.

7. Endothermic Reaction Heat Energy Absorbed: energy of products is ________________ the energy of reactants.

8. Hot Packs vs. Cold Packs Hot/cold packs are used by athletes to minimize swelling of injuries such as muscle and joint sprains. They are constructed of a pouch containing a dry chemical plus an inner pouch of water. The hot/cold pack is activated by breaking the seal on the pouch of water and shaking the pack vigorously. This action mixes the water with the chemical starting the exothermic or endothermic reaction. Hot Packs are ________________________(heat released). Cold Packs are _______________________(heat absorbed).

9. A __________________ _____________________ that produces light. –Ex. Glow sticks are made of plastic with compounds inside. When the glow stick is bent, it breaks the vial. The compounds _______________ _________________________

10. Review: Changes of Matter Chemical Changes: A change that _________________ produce a new substance. Ex: Iron rusts forming iron oxide. Physical Changes: A change that ___________________ produce a new substance. Ex: Ice melts into water.

11. Physical or Chemical Change? Silver tarnishes Sugar dissolves in water. Chopped wood Leaf changes colors. Butter melts. Chemical Physical

12. Reaction Symbols Yields or Produces Solid or precipitate Liquid Gas Aqueous (acids & bases dissolved in water) Catalyst (speeds up)  Heat Added Reversible Reaction Element or compd is added

13. Identifying a Chemical Equation: 1.Which are the reactants?________________ 2.Which are the products? ________________ 3.Which are the coefficients? ______________ 4.Which is the subscript? _________________ 5.Which is diatomic? _________________ __ Mg + O 2  __ MgO ReactantsProducts Coeff. Sub.

14. Mg (s) + O 2 (g)  MgO (s) 1 st Count the number of __________________ on both sides of the arrow. 2 nd Place a coefficient ____________________ of the compound so that the total # of atoms in the reactants _______________ the total # of atoms in the products.

15. Ex. 1: Mg + HCl  MgCl 2 + H 2 Ex. 2: KClO 3 −   KCl + O 2

16. More Practice Ex. 3: H 2 + N 2 − Pt  NH 3 Ex. 4: Al + CuSO 4  Al 2 (SO 4 ) 3 + Cu Keep Polyatomics together!

17. 1. H 2 + N 2  NH 3 2. Na + H 2 O  NaOH + H 2 3. H 2 O 2  H 2 O + O 2 4. Al(NO 3 ) 3 + Cu  Cu(NO 3 ) 2 + Al Practice

18. Combustion Reactions: Balance “CHO” Ex. 5 C 3 H 8 + O 2  CO 2 + H 2 O Ex. 6. C 5 H 10 + O 2  CO 2 + H 2 O Balance: C first H second O last If odd number of O’s, then Double all!

19. Complete combustion  __________________ Incomplete combustion  ________________ (poisonous & fatal to breathe)  Avoid carbon monoxide poisoning by keeping air filters, the furnace, and heater burners _______________________.  Do ______ stay in a closed garage while the car is running.

20. Chemical Reactions that impact the environment! What kind of reaction is this? ____________… Disfigures marble & stone. Effects plant life. Effects water life.

21. Ozone Depletion The _______ protects the Earth from harmful _________ ____ rays. These rays include deadly ________ that can cause ______ _______ in humans, and ________ the reproduction of some animals, and _________ plant life.