Temperature and Reaction Rates
Temperature
If the temperature of the reaction increases, so does the average rate of the reaction.
In the temperature and reaction rate experiment make sure the learners do not shake the test tubes. Shaking gives energy to the reaction and affects the rate. The test tubes should be left as still as possible once the effervescent tablets have been added.
Plastic bottles, such as those shown in the picture, can be used instead of test tubes.
Optional Experiment: Temperature and reaction rate
Aim
To determine the effect of temperature on reaction rate.
Apparatus
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Two effervescent tablets (e.g. Cal-C-Vita)
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An ice-bath, two test tubes
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Two balloons, two rubber bands
Method
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Half fill two large test tubes with water. Label them A and B.
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Break two effervescent tablets in two or three pieces and place them in the two balloons.
Fit one of these balloons tightly to test tube A and one to test tube B, being careful not to drop the contents into the water. You can stand the test tube in a beaker to help you do this.
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Place only test tube A into an ice-bath and leave to equilibrate (come to the same temperature). Approximately 10 minutes should be enough.
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At the same time lift the balloons on test tubes A and B so that the tablets go into the water. Do not shake either test tube.
\(\text{CO}_{2}\)(g) is released during this reaction.
Observe how quickly the balloons increase in size and write down your observations (which increases in size faster).
Results
Note (write down) your observations.
Questions and discussion
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Which balloon expanded faster?
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Suggest a reason for the difference in rates.
Conclusions
The balloon on test tube B will expand faster. This is because the higher temperature (room temperature rather than an ice bath) leads to an increase in the average rate of \(\text{CO}_{2}\) gas production.
The video below shows how much pressure can build up when \(\text{CO}_{2}\)(g) is released during the reaction of an effervescent tablet with water.
Optional Video: Water + Effervescent Tablets Reactions
The higher the temperature, the greater the average kinetic energy of the particles, which means that the particles are moving faster.
Therefore:
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particles moving faster means more collisions per unit time (collision theory)
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particles with higher kinetic energy are also more likely to react on colliding as they have enough energy for the reaction to occur (see Section 7.4 on the mechanism of reaction).
Optional Video: Temperature
This lesson is part of:
Energy and Chemical Reactions