Key concept CCR7.1: Catalysis
Learning
focus
As students’
conceptual
understanding
progresses
they can:
A catalyst is a substance that increases the rate of reaction, without being used up, by
providing an alternative reaction pathway with a lower activation energy.
CONCEPTUAL PROGRESSION
Recognise that a
catalyst increases
the rate of formation
of new substances
by increasing the
rate of a chemical
reaction.
Recognise that
increasing the
surface area of a
solid catalyst
increases rate of
reaction between
substances in the
gas state.
Recognise that a
catalyst cannot
increase the yield
(total amount of
product) of a
chemical reaction.
Explain how
increasing
temperature
increases the rate of
reaction by
increasing the
frequency of
successful collisions.
Identify an energy
profile diagram that
shows a catalysed
reaction (with
lowered activation
energy).
Diagnostic
questions
Catalytic
converter
Honeycomb
Hydrogen
peroxide
Temperature
effect
Reaction profiles
Mystery box
Reaction
sequence
Comparing
catalysts
Colliding
molecules
Comparing
reaction profiles
Response
activities
P
Prior understanding from earlier stages of learning.
Run the slide show to activate the clickable boxes.
B
Bridge to later stages of learning.
Useful information can be found in the slide notes.
Section 1: Diagnostic questions
•
Use diagnostic questions to identify quickly where your students are in their
conceptual progression, and what preconceptions and misunderstandings
they may have.
•
Then decide how to best focus and sequence your teaching.
•
Use further diagnostic questions and response activities to move students’
understanding forwards.
A zip file containing all the resources for this key concept can be downloaded from
www.BestEvidenceScienceTeaching.org
The zip file provides:
• Teacher guidance for this key concept, including a summary of the research
evidence on relevant preconceptions and misunderstandings.
• A full set of editable and printable student sheets and teacher notes for each
diagnostic question. The teacher notes include a summary of research evidence,
guidance for using the activity, expected answers and suggestions of how to
respond to students’ misunderstandings.
Catalytic converter (1/2)
A catalytic converter is fitted to
a car’s exhaust.
A catalytic converter reduces the emissions of harmful carbon
monoxide (CO) and nitrogen monoxide (NO)
Catalytic converter (2/2)
Home
How does a catalytic converter reduce the emission of harmful carbon
monoxide and nitrogen oxide?
A
It filters out carbon monoxide and nitrogen monoxide.
B
It destroys carbon monoxide and nitrogen monoxide.
C
It makes carbon monoxide and nitrogen monoxide harmless.
D
It increases the rate of the chemical reaction that produces new
less harmful substances.
Honeycomb (1/2)
A catalytic converter is filled with a metal honeycomb structure. The
catalyst coats the inside of honeycomb.
Honeycomb (2/2)
Home
1 What is the purpose of the honeycomb
structure inside the catalytic converter?
For each statement, select one column to show what
you think.
A to increase the surface area of catalyst
B to provide structural support
C
to maximise the rate of reaction between
gases
D
to increase the number of molecules that
can bind to the catalyst
I am
sure
this is
right
I
think
this is
right
I
think
this is
wrong
I am
sure
this is
wrong
Hydrogen peroxide
Home
Hydrogen peroxide gradually decomposes (breaks
down) into water and oxygen.
Some students are discussing what effect a
catalyst will have on the reaction.
Niall: There will be
an increase in the
total volume of
oxygen produced.
Sharon: After 10
seconds more
oxygen will have
been produced.
Evie: More oxygen
will be produced per
second.
Colin: The rate
of reaction will
increase.
1 Who do you agree with, and why?
Temperature effect (1/2)
1 In industry, some products are made by reacting substances in the
gas state. The temperature of these reactions can be controlled.
a If the temperature is increased, what happens to the rate of reaction?
A
increases
B
decreases
Temperature effect (2/2)
Home
b Why does increasing the
temperature have this effect?
For each statement select one column to
show what you think.
A There are more collisions between particles.
B
There are more frequent collisions between
particles.
C
More particles are moving faster and bounce
off each other.
D
More particles are moving fast enough to
react when they collide.
I am
sure
this is
right
I
think
this is
right
I
think
this is
wrong
I am
sure
this is
wrong
Reaction profiles (1/2)
The decomposition (break down) of
hydrogen peroxide takes place naturally,
but very slowly.
A reaction profile can be drawn for the
reaction.
Manganese dioxide acts as a catalyst and
increases the rate of reaction.
Reaction profiles (2/2)
1 Which is the reaction profile for the reaction with a catalyst?
Reaction with no
catalyst
A
B
C
D
Home
Section 2: Response activities
•
Response activities encourage students to talk and think about what they’re
thinking (metacognition).
•
This challenges students’ misunderstandings, facilitates meaning-making,
and develops and consolidates their scientific understanding.
A zip file containing all the resources for this key concept can be downloaded from
www.BestEvidenceScienceTeaching.org
The zip file provides:
• Teacher guidance for this key concept, including a summary of the research
evidence on relevant preconceptions and misunderstandings.
• A full set of editable and printable student sheets and teacher notes for each
response activity. The teacher notes include a summary of research evidence,
guidance for using the activity and expected answers.
Mystery box
Each diagram shows
three gases entering a
box.
The diagrams also show
which gases leave each
box.
A
B
Which diagram could
show the gases entering
and leaving a catalytic
converter?
C
Home
Reaction sequence (1/2)
A catalytic converter catalyses the reaction between carbon
monoxide.
carbon monoxide + oxygen → carbon dioxide
2CO(g) + O2(g) → CO2 (g)
The inside surface of a catalytic converted is covered with a platinum,
palladium or rhodium catalyst.
Reaction sequence (2/2)
Home
1 The reaction can be modelled using spheres.
a Sequence the diagrams in the correct order to show how the
reaction takes place.
b Write a description of what is happening in each diagram.
c Suggest one way in which the catalyst helps to increase the rate of
reaction.
Comparing catalysts (1/2)
The graph shows the volume of oxygen produced during the
catalysed decomposition of hydrogen peroxide.
The experiment is
repeated but using a
better catalyst.
Comparing catalysts (2/2)
Home
1 For a reaction with a better catalyst, write down the letter of the
point on the graph that shows the following:
a. the volume of oxygen
produced after 10
seconds
b. the final volume of
oxygen produced after
90 seconds
c. the time at which the
maximum volume of
oxygen is produced
(when the reaction
stops)
2 Sketch the curve of a
graph to show the volume of
oxygen produced with a
better catalyst.
Colliding molecules (1/3)
The effect of increasing temperature on rate of reaction is often
explained using a model in which particles collide to form a new
product.
This model can be represented using simple diagrams.
Colliding molecules (2/3)
This representation shows two substances (in the gas state) reacting.
1 State two ways in which this representation helps to explain how
increasing temperature increases the rate of reaction.
2 State two ways in which this representation does not help to explain
how increasing temperature increases the rate of reaction.
Colliding molecules (3/3)
Home
3 A more advanced version of the model shows molecules of the reacting
substances.
State two ways in which this representation helps to explain better the
effect of temperature on rate of reaction.
Comparing reaction profiles (1/4)
Worked example
Use the reaction profile diagrams to work out which reaction has the
larger activation energy.
Comparing reaction profiles (2/4)
Step 1
Extend the reactants line.
Comparing reaction profiles (3/4)
Step 2
Draw an arrow, on each reaction profile, from the extended reactants line
to the top of the curve.
Step 3
Compare the length of the arrows.
The arrow is longer in reaction A. Reaction A has a larger activation
energy.
Comparing reaction profiles (4/4)
Home
Practice question
Use the reaction profile diagrams to work out which reaction has the
larger activation energy.