Humans use language to communicate. This is an obvious statement, but what is language and how do we use it? Language is basically a set of symbols with associated meanings. These symbols are delivered using a set of rules for stringing the symbols together to generate additional meaning. Humans use mostly sounds to represent these symbols, although as an Italian I can communicate common meanings by only using a range of hand gestures! We string together phonetic sounds to make words, and we
Author(s): The Open University

• The phase of a material is characterised by its physical state (e.g. solid, liquid or gas), a distinctive arrangement of the atoms, and its chemical composition.

• Material properties can change suddenly as the temperature increases or decreases, corresponding to changes of phase and the degree of order associated with the arrangement of atoms.

• Shape memory alloys are examples of a wide range of useful engineering materials t
Author(s): The Open University

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

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

Referencing is not only useful as a way of sharing information, but also as a means of ensuring that due credit is given to other peopleâ€™s work. In the electronic information age, it is easy to copy and paste from journal articles and web pages into your own work. But if you do use someone elseâ€™s work, you should acknowledge the source by giving a correct reference.

Taking someone's work and not indicating where you took it from is termed plagiarism and is regarded as an infringemen
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

Books are a good source of information. The publishing process (where a book is checked by an editor before publishing, and often reviewed by another author) means that books are reliable sources of information, although they may need to be evaluated for bias. A growing number of books can be found online.