Available online
Description
Phase changes and pressure-volume-termperature relationships are examined.
Phase changes and pressure-volume-termperature relationships are examined.
| Module code and title: | ST285, "Solids, liquids and gases" |
|---|---|
| Item code: | ST285; 00 |
| First transmission date: | 20-01-1973 |
| Published: | 1973 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:23:15 |
| + Show more... | |
| Producer: | Tony Jolly |
| Contributors: | Barrie Jones; Robert Ross; Alan Walton |
| Publisher: | BBC Open University |
| Keyword(s): | Carbon dioxide; Dry ice; Liquid nitrogen; Open/closed systems; Phase changes; Pressure/volume/graph; Pressure/volume/relationships |
| Footage description: | Alan Walton with a large block of ice. He explains that the ice is not in equilibrium (some is melting and vaporising), and points out the problem of measuring its quantity. Walton shows a piece of equipment which could take such a measurement. Bob Ross introduces his experiment to measure the temperature, pressure and volume of CO2. He shows the equipment which he will use and points out the individual components. Ross explains the temperature/pressure/volume relationship of CO2. Walton with a large 3 dimensional graph which has Pressure, Temperature, Volume as its axes. He explains how values are plotted. Ross changes pressure of the CO2 in his apparatus and takes new temp., press., volume readings. Walton plots these new values on his 3 dimensional graph. Walton then places another plot on his graph and explains that it must be the graph for a solid. Shots of a steel ball being heated over a burner. Walton plots a new reading on the graph. Pressure/volume axes have changed very little. Walton labels this area of the graph the "solid" area. Ross heats the CO2 gas in his apparatus with a hairdryer. Walton plots the new readings on the graph. Temperature and volume changed but pressure remained constant. Walton labels this area of the graph the "gaseous" area. Ross with a syringe apparatus from which temperature, pressure, volume readings can be taken. Walton labels the liquid area of the graph. He then labels areas of solid/liquid and liquid/gas equilibrium. He points out that the only area left is a solid/gas area which suggests that a phase change from one to the other is possible without an intermediate liquid phase. Dry ice (CO2 solid) is heated in a test tube. There is a solid/gas phase change without liquid phase. Walton introduces a discussion on scale of volume changes. Barrie Jones pours liquid nitrogen into a balloon. There is a volume change on the order of 1000. Walton points out those areas on the graph where solids, liquids and gases are in equilibrium. Barrie Jones with lab. apparatus which can induce solid, liquid and gaseous phases in specimen. He points out individual components of the apparatus and explains their functions. Jones performs and experiment with this apparatus. Pressure is changed and volume changes. Both liquid and gaseous nitrogen are together in equilibrium. Walton shows the position on the graph. Jones makes pressure drop even lower. Solid begins to form on top of the liquid nitrogen. An equilibrium mixture of solid, liquid and gaseous nitrogen has been formed. Walton plots this state on his 3 dimensional PVT graph. Jones explains that this property is not unique to nitrogen. He does the experiment again this time with water. Walton relates this to the solid/liquid/gas line on his graph. He then discusses some other possibilities for his graph. Jones investigates the critical point of CO2. He shows and explains his experimental apparatus. Jones heats liquid CO2. Walton shows what is happening to the CO2 on his graph. Shots of the CO2 liquid in the tube. As temperature rises and approaches the critical point, it becomes more difficult to see the division between liquid and gas. It appears to be neither liquid nor gas. Walton shows why this might be so. He uses his graph as an aid. The experiment is shown again. Walton explains how temperature/pressure/volume relationships can be represented on 2 dimensions graphs if one of the variables is kept constant. Walton sums up. |
| Master spool number: | 6HT/70875 |
| Production number: | 00525_1057 |
| Videofinder number: | 677 |
| Available to public: | no |
