The document discusses factors that affect the rate of chemical reactions, including: 1) Collision theory - reactions only occur during collisions where particles have energy above the activation energy. 2) Higher temperatures lead to more particles with sufficient kinetic energy for reactions. 3) Increasing concentration means less space between particles, leading to more collisions and a faster reaction rate.

1. Sir. Muhammad Abdul Mageid
CIE - IGCSE Chemistry
Chapter 7 CHEMICAL REACTIONS

2. Contents
7.2 Interpreting Data
7.1 Rate (speed) of the Reaction
7.3 Photochemistry
Friday, October 9, 2020
Sir. Muhammad Abdul Mageid

3. Friday, October 9, 2020
7.1 Rate (speed) of the Reaction
Sir. Muhammad Abdul Mageid
Collision Theory
 In order for a reaction to occur reactant particles must collide .
 Not all collisions between reactants succeed in making products.
 Only those collisions with sufficient energy to break the bonds
in the reactants will lead to a reaction.
 A successful collisions is one where reactants react and products are formed
 The minimal amount of energy a collision needs to be successful is called
The Activation Energy
 If the reactants collide and have an energy less than the activation
energy, then no reaction occurs.

4. Friday, October 9, 2020
7.1 Rate (speed) of the Reaction
Sir. Muhammad Abdul Mageid
Collision Theory
 For substances to react , their particles:
1- must collide
2- must collide with enough energy to break existing bonds
 The higher the number of successful collisions
per unit time , the higher the rate of reaction
Rate of the reaction
 Is the concentration of reactant used up , or product made , in a given
time
 Units of rate : 𝒎𝒐𝒍/𝒅𝒎 𝟑
. 𝑺−𝟏

5. Friday, October 9, 2020
Temperature & Concentration
Sir. Muhammad Abdul Mageid
Diagram showing the increased kinetic energy that particles have at higher temperatures

6. Friday, October 9, 2020
Temperature & Concentration
Sir. Muhammad Abdul Mageid
Concentration
•Increasing the concentration means there are more particles per cm3, so there is
less space between the particles
•Since there are more particles then it follows that there are more collisions, hence
the rate of reaction increases