Oscillating chemical reactions

(supervisor: Dave Langstaff)

Nature of project: experimental, data analysis

Available to full-time physicists or joint students.

Project description and methodology

Oscillating reactions are not simply a chemical curiosity; the reactions have direct analogy to biological processes, in particular the waves of excitation in neural and cardiac tissue. In this project a simple, famous oscillating reaction will be studied, that of Belousov and Zhabotinsky, as described in Strogatz (1994). This apparently impossible reaction, it was thought to violate the second law of thermodynamics, was discovered by Belousov in the 1950s and subsequently developed by the biophysicist Zhabotinsky.

The project will involve setting up the reaction in a beaker and recording pH and temperature of the reaction as it proceeds along with a video recording to observe the colour changes that take place. This data will then be reduced and compared with a system of differential equations which describe the dynamics of the chemical reactions involved.

A successful project will develop beyond the above in one/some of the following directions:
Relate time constants of ODE to reaction kinetics and predict oscillation rate for different starting temperatures.

When considering where to take your project, please bear in mind the time available. It is preferable to do fewer things well than to try many and not get conclusive results on any of them. However, sometimes it is useful to have a couple of strands of investigation in parallel to work on in case delays occur.

Additional scope or challenge if taken as a Year-4 project: If the reaction is carried out in 2D, a fascinating series of spirals and other geometric patterns develop which can be captured by video. The dynamics of the formation of different geometrical features can be studied by numerical methods, as discussed by Field, Koros and Noyes (1972) and more recently by Aliev and others (1997). The numerical models of the spiral waves and other geometric patterns can be compared with those captured by video from the experiment. An extensive literature exists describing these numerical approaches.

Initial literature for students:

  1. Strogatz, S, Nonlinear dynamics and chaos with applications to physics biology, chemistry and engineering, Perseus Books Publish
  2. Aliev, R. et al. On the phase dynamics of the BZ reaction, J. Physical Chemistry, A 101 (42) 7691 (1997)
  3. Espenson, J.H. Chemical Kinetics and Reaction Mechanisms (2nd ed., McGraw-Hill 2002) p.190 ISBN 0-07-288362-6
  4. Zhang, Dongmei; Györgyi, László; Peltier, William R. (1993).

Novelty, degree of difficulty and amount of assistance required

This project will involve laboratory-based study of a novel chemical reaction and as such will require some assistance in the materials laboratory. Reagents are available and the recipe is easily followed and provided good laboratory practice is followed there will be no safety hazards. The critical part of the project will be to capture the varied geometric patterns and categorize them and compare these patterns with those obtained from simple numerical models.

Project milestones and deliverables (including timescale)

milestoneto be completed by
In the laboratory complete set of test reactions to optimise image capture of the B-Z reaction. end of October
Capture time sequence of reaction in beakerChristmas
Develop the numerical approach, identifying reacting species and boundary conditions.end of February
Compare the images collected through the image capture with the numerical models.Easter

Students taking this project will have to submit a full risk assessment form