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How Science Works by Judith Hann, Dorling Kindersley, pp 192, £12.99

Children are curious to find out about the world. Some are fortunate
enough to have an adult to answer their questions imaginatively. All scientists
or engineers among us can probably remember an adult who influenced us and
sparked off our interest.

The trouble is that in many cases – as the small numbers that now opt
for a career in science or engineering witness – children switch off from
science and say that it is not for them. Somehow their curiosity about the
hows and the whys of the world becomes blocked, and with it the creative
desire to make things. Quite why, nobody knows, but one element must surely
be that the right kind of stimulus and encouragement was not present at
a critical point in the child’s development.

How Science Works aims to counter that switch off from science. It is
intended as a book for the whole family to use and enjoy, and to show how
much fun and how rewarding science can be. Its experiments and projects
are simple to carry out at home using safe, everyday ingredients, and colour
photographs take the reader through them step by step. For example, the
enzymes in biological washing powder dissolve an egg; a home-made hot-air
balloon, in which the air is heated with a hairdryer, illustrates the expansion
of a gas; and Hooke’s law for elastic materials is exploited in a model
aircraft driven with a rubber band.

In places the explanations are inadequate. For example, in the section
on gravity Hann introduces the concept of terminal velocity, defining it
as the speed where the air resistance of an object balances the pull of
gravity. There is a beautiful picture of 24 skydivers in a ring and seven
others moving in to join them, with the caption ‘Freefalling skydivers can
reduce their terminal velocity by extending their arms and legs out to increase
air resistance’. Fine so far, but what would their terminal velocity be
if they didn’t spread out their limbs? What is it when they do? Is the terminal
velocity further reduced when the skydivers come together in a ring? Any
curious child would want to know the answers – and it will be a rare parent
who will be able to supply them. Nor does the glossary at the end of the
book help. Here terminal velocity is defined as ‘The maximum velocity that
a falling object can achieve’. Unless qualified, this definition is wrong.

Some of the glossary definitions leave a lot to be desired. For example,
boiling point is defined as: ‘the maximum temperature a liquid reaches’.
How much clearer is the definition given by Chambers Science and Technology
Dictionary: ‘The temperature at which a liquid boils when exposed to the
atmosphere . . . ‘ Absolute zero is defined by Hann as -273.15 °C ,
yet elsewhere the kelvin temperature scale is described as ‘corresponding
to Celsius, but beginning at -273.15 °C’. Inconsistencies do matter
in science.

An author must decide whether to approximate or use the more accurate
figure, using both will only cause confusion.

Notwithstanding these criticisms, this book is a useful source of interesting
experiments. It is a positive attempt to convey the pleasures of scientitifc
activity. teachers too will find some ideas for class activity, making it
a book worth buying for the school library.

Antony Anderson is an electronics consultant.