Types of Reactions Science 10 Chapter 6

6.1 Exothermic vs Endothermic Reactions Exothermic: Energy-releasing rxn. (may be hot) Ex: explosion, burning wood, rusting of iron, formation of ice H 2 O (l)  H 2 O (s) + thermal energy Endothermic: Energy-absorbing rxn. (may be cold) Ex: electrolysis, baking, evaporation of water H 2 O (l) + thermal energy  H 2 O (g)

Law of the conservation of energy Energy can be converted from one form to another, but the total quantity of energy is constant. 2Na + Cl 2  2NaCl + thermal energy 10kJ + 30kJ  20kJ + 20kJ t.e. + 2Na 3 N  6Na + N 2 ? + 50kJ  20kJ + 65kJ

Modelling Chemical Reactions In a group, model one of the rxn on p. 184 #9 Write the word equation Then write the balanced equation Then draw the balanced equation using different symbols for the different atoms Share your answer with the rest of the class Do Analyze # 2 (p.184)

Check your understanding After reading p , do p. 185 # 1, 3 to 5.

6.2 Synthesis (Formation) Reactions The reaction of two or more substances to form one substance. A + B  AB Ex: 2H 2(g) + O 2(g)  2H 2 O (l) + thermal energy

Decomposition Reactions The reverse of a synthesis reaction. One reactant breaks down into two or more products. AB  A + B Ex: H 2 CO 3(aq)  CO 2(g) + H 2 O (l)

Reactions Questions After reading pages 180 to 188 complete questions 1, 3 and 4 on page 189. NOTE: Don’t forget the diatomic clown HOFBrINCl H 2, O 2, F 2, etc…

6.3 Single Displacement Reaction One element takes the place of (displaces) another element in a compound. A + BX  AX + B Ex: 2Na (s) + 2H 2 O (l)  2NaOH (aq) + H 2(g)

Activity series of metals Potassium Aluminum Zinc Lead This list is always written from the most reactive metal to the least reactive one. K + ZnNO 3  ? Pb + AlPO 4  ?

Double Displacement Reactions The cations of 2 compounds exchange places, forming 2 new compounds WX + YZ  WZ + YX Ex: NaOH + HCl  NaCl + H 2 O

Summary of Rxn’s Rxn TypeAbbreviationGeneral Rxn Double Displacement DDAB + CD  AD + CB Single Displacement SDA + BC  B + AC Synthesis (Formation) SA + B  AB DecompositionDC  A + B CombustionCAB + O 2  AO + BO

It’s your turn Read “Think about it” and “What to do” on p. 200 Do questions 1 – 6 (p ) After reading p , do p. 202 # 2 - 4

6.4 Reactions Involving Carbon Compounds Organic compounds: compounds containing carbon except CO, CO 2 and – CO 3 2- Hydrocarbon: organic compound containing only hydrogen and carbon Ex: methane, ethane, propane, butane

Complete vs Incomplete Combustion Complete combustion: enough oxygen available, blue flame, very hot and produces CO 2 and water vapor. Incomplete combustion: not enough oxygen present, orange flame, hot, and produces CO 2, water vapor, CO and C (soot).

Check your understanding After reading p , do p. 206 # 2, 5 and 6. Chapter review p # 1, 4 – 6, 9, 11 – 13.