15P2
Fri 15 May
L15
§4.5
Week 4 · Lesson 12 of 17

Rate of reaction: collision theory — application and consolidation

You've now met collision theory and the two requirements for a successful collision (sufficient energy + correct orientation). Today you put them to work — running through the textbook Learning Ladder questions for §4.5 to make sure you can predict, explain, and justify the rate of any reaction in terms of collision theory.
Learning Intentions + Success Criteria

LITo apply collision theory to predict and justify rate changes.

SC: I can:

  1. 01I can predict whether a change (pressure, temperature, concentration, or agitation) speeds up or slows down a reaction.
  2. 02I can justify the prediction with collision theory (frequency of collisions and/or proportion that are successful).
  3. 03I can sketch a successful and an unsuccessful collision and label the orientation.
01

Engage

5 min
Quick recap · from last class
L14 · §4.5 Rate of reaction: collision theory — the two requirements for a successful collision

Try these 2questions before today's new content. Click an answer for instant feedback — your teacher will walk through them with you.

ClickView video · school login↗
What Factors Affect Reaction Rate?
Replay if you want a quick recap before today's practice.

This is your application and consolidation lesson for §4.5. You'll work through the textbook Learning Ladder questions on p.101. Have the textbook open in front of you for the whole period.

Predict · your turn
Write before you watch

Before we start: which idea from §4.5 do you feel LEAST confident about — the two requirements (energy + orientation), the meaning of activation energy, or applying collision theory to predict a rate change? Write down the one you most want to nail today.

02

Explicit

10 min

Recap — the two tools you'll use today

The two requirements for a successful collision:

  1. Sufficient energy — at least the activation energy (Eₐ) is needed to break the reactant bonds so new bonds can form.
  2. Correct orientation — the bonding sites of the two particles must face each other when they collide.

If either requirement fails, the particles bounce apart without reacting.

The factors that can affect reaction rate (from §4.5; explored in detail in §4.6):

  • concentration
  • surface area
  • pressure
  • temperature
  • catalysts
  • agitation (stirring).

Agitation means stirring or shaking the reactants so fresh particles keep meeting each other. It does not change the energy of each collision by itself; it mainly increases mixing, so particles collide with new reaction partners more often.

03

Apply

35 min

Work the textbook Learning Ladder questions in order. Write each answer in your book; type the short ones below for self-check.

Question 1Identify the two requirements
Your turnShort answer · Have a go first
Identify two things that must occur for a chemical collision to be successful.
Question 2Predict the effect of pressure
Your turnShort answer · Have a go first
Propose what would happen to the rate of a reaction if you were to increase the pressure within a given volume.
Question 3Justify with collision theory
Your turnShort answer · Have a go first
Justify your response to Question 2 with reference to collision theory.
Question 4Diagram a successful and unsuccessful collision
Your turnShort answer · Have a go first
When H+ and OH- ions collide with enough force, it might result in a successful collision to form water (H2O). Using labelled diagrams, show how the ions would be aligned during a (a) successful collision, and (b) unsuccessful collision.
04

Catch

5 min
05

Reflect

5 min
Your turnReflect · One thing you learned

Look back at the idea you flagged at the start as 'least confident'. After today's practice, do you feel solid on it? If not — what specifically still doesn't make sense?

Success criteria — where are you right now?

Next class (Fri 15 May, P3): §4.6 begins — concentration and temperature, the first two factors that affect reaction rate.