How can we explain a sudden switch of behaviour at a particular temperature? There must be two competing influences (say X and Y) that depend differently on temperature. Figure 23 indicates how a unique temperature (a so-called critical temperature, Tc) arises,
Author(s): The Open University

The third category of thermal effects identified in Section 2 are those associated with sudden changes. Here are some technically important examples where things change suddenly at a particular temperature:

• Pure water boils at 100 Â°C (at atmospheric pressure).<
Author(s): The Open University

The final trick I want to show you with Arrhenius's law is how to extract the constants rï»¿0 and Eï»¿a from experimental data. If the Arrhenius equation (Section 4.3.1) is â€˜turned inside outâ€™ by taking natural logarithms of both sides it becomes:

Author(s): The Open University

This is a long section and needs to be studied carefully. Keep your eye on the overall goal of seeking useful thermal effects on which to base devices.

This section continues the discussion of heat at an atomic level. You will need this background to appreciate the characteristics of processes activated by thermal energy â€“ for example, the softening of glass in a gas flame, the diffusion of atoms through solids, the electrical conductivity of ceramics, and many chemical reactions. Suc
Author(s): The Open University

• Thermometers sense temperature. They are transducers providing observable and quantifiable signals in variables other than temperature. Thermometers are calibrated to give numbers in accord with an internationally agreed scale. Various attributes influence the selection of an instrument for a task.

• Temperature can determine the rate at which certain physical and chemical changes proceed, and whether some changes can occur at all.

• <
Author(s): The Open University

Whether it's to wash clothes, make a cup of tea, or just make it safe to drink, water often has to be heated â€“ sometimes to boiling point. There are many ways to do this, but a very common means is some form of electric water-boiler, such as a kettle or an urn. In all but the crudest ones, a device is fitted to ensure that heating does not continue once the boiling point of water is reached.

In deciding on the type and design of such a device, we can suppose that a company manufacturi
Author(s): The Open University

RSS (â€˜Really Simple Syndicationâ€™ or â€˜Rich Site Summaryâ€™) newsfeeds supply headlines, links, and article summaries from various websites. By using RSS â€˜feedreaderâ€™ software you can gather together a range of feeds and read them in one place: they come to you, rather than you having to go out and look for breaking news. The range of RSS feeds on offer is growing daily. There is probably a feed to cover all aspects of your life where you might need the latest information, and you may
Author(s): The Open University

The process of keeping up-to-date in your chosen subject area is useful for your studies and afterwards, for your own personal satisfaction, or perhaps in your career as part of your continuing professional development.

There are a great many tools available that make it quite easy to keep yourself up to date. You can set them up so that the information comes to you, rather than you having to go out on the web looking for it. Over the next few pages, you will be experimenting with some
Author(s): The Open University

The date when information was produced or published can be an important aspect of quality. This is not quite as simple as saying that 'good' information has to be up to date.

## Activity 9

Here is an example of a news item from an on
Author(s): The Open University

Contingency theories are based on the idea that there is no single best style of leadership but that the most effective style depends upon the circumstances. The aspects of the circumstances identified as significant are:

• the leader's characteristics and style (thus absorbing the two earlier theories).

• the subordinates' expectations and experience.

• the nature of the task and the organisational environment.

• Author(s): The Open University

Next on the list of priorities in the functioning of groups is the process of group development. One popular conception of the way in which groups â€˜gelâ€™ and become effective was first suggested by Tuckman (1965) and then extended by Tuckman and Jensen (1977). Tuckman originally identified four stages in this development process, which he named â€˜formingâ€™, â€˜stormingâ€™, â€˜normingâ€™ and â€˜performingâ€™. These stages (see Author(s): The Open University

The hierarchical structure described above divides groups of people along largely functional lines: people working together carry out the same or similar functions. A functional team is a team in which work is carried out within such a functionally organised group. This can be project work. In organisations in which the functional divisions are relatively rigid, project work can be handed from one functional team to another in order to complete the work. For example, work on a new product can
Author(s): The Open University

Our tendency to form groups is a pervasive aspect of organisational life. As well as formal groups, committees and teams, there are informal groups, cliques and cabals.

Formal groups are used to organise and distribute work, pool information, devise plans, coordinate activities, increase commitment, negotiate, resolve conflicts and conduct inquests. Group working allows the pooling of people's individual skills and knowledge, and helps compensate for individual deficiencies. It has been
Author(s): The Open University

It is some 20 years since the Topper project was conceived by Peter Bean, Technical Director of Rolinx and Ian Proctor, the designer of the original GRP boat. Sales initially were excellent, especially to sailing schools and clubs where there was much demand for a small, light and very safe sailing boat for children. But after that, the market became saturated, sales were heavily dependant on individuals and families, so decreased despite attempts to export the boat to the USA and Israel, for
Author(s): The Open University

Nowadays ethylene is the most important building block for the chemical industry, particularly as a monomer in its own right, as a co-monomer with other vinyls, and as a source of vinyl monomers. It is the prime source for ethylene oxide, which is another major source of polymers, glycols and ethers. They can also be used to build up more complex C4 molecules and aromatics.

Some of the ways in which the ethylene molecule is modified to create other chemicals and polymers are
Author(s): The Open University

There are some limitations to the concept of the repeat unit when applied to crosslinked polymers, the thermosets. This is because of the complexity of the crosslinking reactions, the way molecules link together chemically during thermoset processing. For example, phenolic resins (the basis for materials like Bakelite) are prepared initially as prepolymers, i.e. polymers of low molecular mass (ca. 1000) by reaction between phenol and formaldehyde (
Author(s): The Open University

The increasing control of polymer structure by fine-tuned catalysis of polymerization opened up an enormous area for commercial exploitation, and new polymers are still being produced in this way (such as the metallocene polymers). A revolution of equal magnitude has occurred with polymers containing functional groups, for example, the nylons, polyesters and polyurethanes, resulting in polymers ranging from quite simple structures like aramid fibre to relatively complex repeat units like thos
Author(s): The Open University

A second type of isomerism occurs with diene monomers, and is present in both NR and butadiene rubbers (BR). It occurs because the single double bond in the final polymer can exist in two ways: a cis form and a trans form. The repeat unit shown in Table 3 for NR does less than justice to the two-di
Author(s): The Open University

The first step is to develop a picture (called in soft systems terminology a rich picture) that encapsulates all the elements that people think are involved in the problem. Once the rich picture has been drawn, the analyst will attempt to extract â€˜issuesâ€™ and key tasks.

Issues are areas of contention within the problem situation. Key tasks are the essential jobs that must be undertaken within the problem situation.

Author(s): The Open University