||Rate of reaction graphs
In this activity, pre‑drawn graphs are chosen by students
to match the most likely outcomes from different reaction conditions for
the reaction between calcium carbonate and hydrochloric acid. The graphs
are a prop to help students check and reinforce what they have learnt
about factors affecting rates of reaction, including concentration,
temperature and surface area of solid reactants.
The resource would be particularly useful for checking on learning
towards the end of teaching this topic or when revising for an external
Students will be able to:
- interpret graphs which show how the rate of reaction is affected by
temperature and by the concentration and surface area of reactants.
Sequence of activities
||Add some marble chips to hydrochloric acid in a
conical flask with a side arm and draw attention to the gas evolved.
Issue mini whiteboards.
Set up a discussion, first asking the students to write down:
- the factors which can affect the rate of reaction.
Ensure that the effect of concentration of reactant, temperature
and surface area of a solid reactant are identified.
Continue the discussion by asking them to write down:
- what determines how much product is produced during a reaction.
Ensure that the amount of the reactant that is used up is
After discussing this, share the learning objectives with students.
||Now ask the students to draw:
- the apparatus they would use to collect and record the volume of
gas produced over a period of time.
As they share their answers, ensure that they discuss methods of
collecting and measuring the gas evolved using a syringe or an
inverted burette in a trough of water.
||Explain that they are going to:
- be given details about the conditions for six different
experiments in which marble chips were added to hydrochloric acid
and some graphs showing the volume of gas produced over a period of
- select which graph is most likely to be produced in the
- Graph A is produced when 1 g of small lumps of calcium
carbonate is added to 100 cm3 of 1 mol dm-3
hydrochloric acid at 20 °C
- the same graph might be produced by more than one set of
||Give each student a Rate of reaction graphs
sheet and an Information sheet and allow time for them
to explain their choices on their Rate of reaction graphs
Circulate and support students:
- allowing them time to explain their choices
- prompting those who need help to focus on the amount of gas
produced and the rate at which it is produced.
||Arrange students into groups of three to:
- share their answers
- discuss similarities and differences in their choices
- review their ideas in the light of discussions with their peers
- record changes in their ideas.
||Bring students together in a plenary.
Select groups to explain the choices that they have made.
Encourage other groups to challenge or to add to these
Allow time for the students to reflect again on what they have
written on their sheet.
||Take in the Rate of reaction graphs sheet.
Write comments or questions to highlight the achievement that has been
demonstrated. Suggest which aspects of the topic require further
attention and where the student can find resources that will help
Assessment for learning commentary
To make the learning objectives meaningful there is an extended initial
stage, with a passive demonstration but also with a discussion where
After matching the graphs, students are given several opportunities to
review their ideas and organise their knowledge.
With the written feedback, students are helped so that they can
recognise what they need to do, to deal with any shortcomings in their
understanding of how these graphs represent changes.
||A Rate of reaction graphs sheet for each
||An Information sheet
for each student
||A mini whiteboard for each student
For the demonstration
- Marble chips
- Hydrochloric acid (Irritant)
- Conical flask with side arm
- Eye protection.
It is the responsibility of the teacher to carry out an appropriate
risk assessment for the demonstration.
The graph which is most likely to be produced from experiment 2 is
The concentration of the acid is the same as in
experiment 1 so the rate or reaction will be the same. There is, however,
twice as much calcium carbonate used so the volume of carbon dioxide
collected will be twice that collected in experiment 1.
The graph which is most likely to be produced from experiment 3 is
The only difference in the conditions compared
with experiment 1 is that there is twice as much acid. This will not make
any difference to the graph as it is the marble chips that are used up,
not the acid, so the graph will be the same.
The graph which is most likely to be produced from experiment 4 is
The acid is twice as concentrated compared with
experiment 1 so the rate of reaction will be faster. The amount of calcium
carbonate used up is the same so the volume of carbon dioxide produced
will be the same.
The graph which is most likely to be produced from experiment
5 is Graph D
The temperature is higher than it is in
experiment 1 so the rate of reaction will be higher. The amount of calcium
carbonate is the same so that the volume of carbon dioxide produced will
be the same.
The graph which is most likely to be produced from experiment 6 is
The concentration of the acid is twice what it is
in experiment 1 so the rate of reaction will be higher. The amount of
calcium carbonate is twice what it is in experiment 1 so that the volume
of carbon dioxide will also be twice that produced in experiment 1.