35 Rate of reaction graphs 14-16

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 assessment.

## Learning objectives

Students will be able to:

1. interpret graphs which show how the rate of reaction is affected by temperature and by the concentration and surface area of reactants.

## 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 everyone contributes.

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.

## Resources

### Props

 A Rate of reaction graphs sheet for each student An Information sheet for each student A mini whiteboard for each student

### Equipment

For the demonstration

• Marble chips
• Hydrochloric acid (Irritant)
• Conical flask with side arm
• Eye protection.

## Safety notes

It is the responsibility of the teacher to carry out an appropriate risk assessment for the demonstration.

• Wear eye protection.

The graph which is most likely to be produced from experiment 2 is Graph C
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 Graph A
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 Graph D
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 Graph B
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.