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Description
P. Chapman introduces the programme. Shot of a "Mercury in glass" thermometer connected to several monitoring devices. Ian Bousted explains the apparatus and the aims of the experiment (t...o examine thermal properties of mercury). Experiment commences: Mercury sample in the thermometer is cooled and the effect monitored with a pen recorder graph. A temperature/time curve is plotted. Chapman explains the results of the temperature/time curve. Boustead continues the experiment. A temperature/Volume curve is also plotted as the sample is cooled. Chapman explains why the volume of the mercury sample decreases as temperature falls. Diagram of an Energy Separation Curve used as an aid to the discussion. Pen recorder graph now shows volume of mercury decreasing as temperature remains constant. Boustead shows that a phase change from liquid to solid has taken place and is responsible for this behaviour. Chapman with a diagram representing the arrangement of molecules in a liquid. He uses the diagram to aid his discussion on the mechanics of phase changes. Boustead with a differential scanning calorimeter. A sample of polyethyline film is heated and its temperature shown. The calorimeter monitors temperature and energy change at point of phase transition. Boustead, with the aid of an animated diagram, explains how the apparatus works. Boustead does the experiment with a sample of polyethyline. A pen recorder graph shows the results. Chapman explains the reason for an uneven curve from the above experiment: a range of thermal energies in a material so that different parts of the material have different thermal energies and so melt at different temperatures. Chapman uses this information to interpret the temperature/time graph for a solid to liquid phase change of polyethyline. The polyethyline speciman is allowed to cool (solidify again) and its temperature/time curve is monitored. Only a single peak in this curve is seen: Boustead heats the speciman again.(results of this later) Chapman with a schematic diagram of a differential scanning calorimeters plot for iron. The temperature/time graph shows several peaks. Chapman explains why. Boustead with the calorimeter. The polyethyline sample has now been reheated and its temperature/time curve plotted. It has only a single peak. X-ray diffaction photograph of polyethyline before and after heating. This shows a significant change molecular orientation. Boustead explains why a change in orientation has occured. Shot of polyethyline under the microscope. (The sample is cooling after it's first heating cycle).
Metadata describing this Open University video programme
Module code and title: TS251, An introduction to materials
Item code: TS251; 03
First transmission date: 16-11-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:23:20
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Producer: Barrie Whatley
Contributors: I. Boustead; Peter Chapman
Publisher: BBC Open University
Keyword(s): Energy changes; Low density polythene film; Mercury; Structural changes; Temperature-time curves; Thermal analysis; Volume-temperature curves; X-ray crystallographic photos
Master spool number: 6HT/70356
Production number: 00525_5030
Videofinder number: 1554
Available to public: no