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Diffusion in gases, liquids and solids is discussed and demonstrated experimentally.
Metadata describing this Open University video programme
Module code and title: ST285, "Solids, liquids and gases"
Item code: ST285; 08
First transmission date: 19-05-1973
Published: 1973
Rights Statement:
Restrictions on use:
Duration: 00:24:29
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Producer: Tony Jolly
Contributors: Ian Lowe; Alan Walton; Graham Weaver
Publisher: BBC Open University
Keyword(s): Applications; Common physical principles; Computer animated film; Diffusion in gases; Diffusion in liquids; Diffusion of solids; Graphics; Physics; Random walk
Footage description: Ian Lowe introduces the programme Shots of Alan Walton doing a bromine diffusion experiment. (from S100/05, sequence 3). Ian Lowe discusses diffusion of molecules in a gas. He does an experiment which diffuses NH3 and HC1 through the air. A white cloud forms where the two gases meet. Lowe next sets up an experiment which monitors the diffusion of NH3 and HC1 under controlled conditions. (The experiment takes some time and results are shown later in the programme) Graham Weaver examines transport phenomena in liquids. He performs an experiment which monitors convection of potassium permanganate through water. Weaver next performs an experiment which monitors the diffusion of dye stuffs through water. The water is held in a transparent sponge. Micrographs of the sponge show the pores. Weaver shows the results of an experiment which determined the effect of temperature on diffusion through liquids. The readings from this experiment are shown in graphical form. Back to Ian Lowe's diffusion of NH3 and HC1 experiment. A white cloud has formed where the two gases met and interacted. The experiment shows that diffusion is a slow process. Back to Graham Weaver and his temperature/diffusion graph. He explains how the readings were plotted and demonstrates that diffusion depends on activation energy. Back to Ian Lowe's diffusion of NH3 and HC1 experiment. He explains diffusion in terms of the kinetic theory of gases. Lowe writes the equation on a board and applies it to the experiment. The calculation is confirmed by the experimental results. Lowe with a giant model of a fly. He explains how a fly's growth is limited by its respiratory system which depends on diffusion. Graham Weaver tosses a die to demonstrate one method of determining random numbers. He then briefly discusses the home experiment in which students determine how far a molecule might be expected to move in a series of random steps. Computer simulation shows molecules moving in a series of random steps from a central point of origin. Their final position after a set number of steps is plotted. The number of points at each of several distances from the origin is counted and plotted on a graph resulting in a distribution of distances from the origin curve. Back to Graham Weaver's dye stuff diffusing in jelly experiment. He shows three test tubes in which dye stuffs have been diffusing for 6, 24 and 96 hours respectively. The results correspond to the random step experiment which was computer simulated above. Ian Lowe begins discussion of diffusion in solids. He explains how it takes place using a diagram of atoms in a solid as an aid. Graham Weaver lists some examples of diffusion in solids. He shows a piece of steel from a caterpillar track which has been case hardened. The diffusion of carbon can be clearly seen. Weaver uses the sample to show that temperature is much more important than time for diffusion in solids. Ian Lowe sums up.
Master spool number: 6HT/70814
Production number: 00525_1032
Videofinder number: 685
Available to public: no