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Computer simulations of gas molecules in collision and the monitoring of reactions by absorption of visible light are examined.
Metadata describing this Open University video programme
Module code and title: ST285, "Solids, liquids and gases"
Item code: ST285; 05
First transmission date: 31-03-1973
Published: 1973
Rights Statement:
Restrictions on use:
Duration: 00:23:19
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Producer: Barrie Whatley
Contributor: Robert A. Ross
Publisher: BBC Open University
Keyword(s): Collision rate; Computer simulation; Energy barrier curve; Exchanges of energy; Experimental apparatus; Histogram of speeds; Iodine; Reaction rate; Speed distribution
Footage description: R.A. Ross introduces the unit which will look at the collision of molecules in a gas. He explains the difficulty of calculating the exchanges of energy which occur on collision for a sample of a gas large enough to do real experiments on. Shots of computer simulation of 60 gas molecules in motion. Ross explains that the computer can plot a histogram of speeds of molecules - the number of molecules with a speed within a given range. Shot of such a computer plotted histogram. Ross explains why better results could be obtained with a larger sample. \/hat is the effect of the initial speed of the molecules on the speed distribution? Shots of computer plotted histogram, this time with a higher initial speed. The two distributions are compared. Computer simulation of gas molecules shows the frequency of collision of one molecule and then of all 60 molecules. Ross compares the collision rate and observed reaction rate of two gases. Reaction rate is much lower that the collision rate. This is due, he says to a minimum energy requirement before a reaction can start. The computer simulates and compares collision rates and collision energies on a histogram. This shows that most collisions occur at small energies. The computer then simulates and compares collision rates with collision energy for those molecules which have at least the minimum activation energy. The simulation is done again, this time with an increase in temperature of the gas. A greater number of collisions have more than minimum activation energy and this is in line with experimental results. Ross now looks at the reaction H2 + I2 =2HI. Computer simulation of the molecules of Hg and I2 in collision shows the reaction. Ross with the energy barrier curve for the above reaction. He follows the progress of this reaction over the energy barrier. Ross explains the traditional way in which a reaction such as H H2 + l2 = 2HI was followed in the laboratory. He then explains a method by which the reaction can be monitored continuously, based on the light absorbing qualities of the iodine. Shots of the experimental apparatus which will monitor the reaction in this way. Ross points out the components and explains how the experiment will be done. He uses mag board diagrams as an aid. Ross sums up the programme.
Master spool number: 6HT/70903
Production number: 00525_1063
Videofinder number: 682
Available to public: no