Types of Reactions

Science 10Chapter 6

6.1 Exothermic vs Endothermic Reactions Exothermic: Energy-releasing rxn.

(may be hot) Ex: explosion, burning wood, rusting of

iron, formation of ice H2O(l) H2O(s) + thermal energy Endothermic: Energy-absorbing rxn.

(may be cold) Ex: electrolysis, baking, evaporation of

water H2O(l) + thermal energy H2O(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 + Cl2 2NaCl + thermal energy 10kJ + 30kJ 20kJ + 20kJ

t.e. + 2Na3N 6Na + N2

? + 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. 180-182, 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: 2H2(g) + O2(g) 2H2O(l) + thermal

energy

Decomposition Reactions The reverse of a synthesis

reaction. One reactant breaks down into two or more products. AB A + B Ex: H2CO3(aq) CO2(g) + H2O(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 H2, O2, F2, 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) + 2H2O(l) 2NaOH(aq) + H2(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 + ZnNO3 ? Pb + AlPO4 ?

Double Displacement Reactions

The cations of 2 compounds exchange places, forming 2 new compounds

WX + YZ WZ + YX Ex: NaOH + HCl NaCl + H2O

Summary of Rxn’s

Rxn Type Abbreviation General Rxn

Double Displacement

DD AB + CD AD + CB

Single Displacement

SD A + BC B + AC

Synthesis (Formation)

S A + B AB

Decomposition

D C A + B

Combustion C AB + O2 AO + BO

It’s your turn Read “Think about it” and “What

to do” on p. 200 Do questions 1 – 6 (p. 200-201) After reading p. 190- 195, do p.

202 # 2 - 4

6.4 Reactions Involving Carbon Compounds Organic compounds: compounds

containing carbon except CO, CO2 and –CO3

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 CO2 and water vapor.

Incomplete combustion: not enough oxygen present, orange flame, hot, and produces CO2, water vapor, CO and C (soot).

Check your understanding After reading p. 203-205, do p. 206

# 2, 5 and 6. Chapter review p. 208-209 # 1, 4

– 6, 9, 11 – 13.