Page 21 - Curriculum Visions Dynamic Book

Making use of changes of state
The property that water will change easily from solid to liquid to gas is extremely important. In fact, a large part of the industrial revolution, which changed us from an agricultural society to an industrial one, depended on the change of state of water, especially the change from liquid to gas and back again.
Steam engines
Behind all of the early industrial machines was the knowledge that water could be changed from liquid to gas (in the form of steam) and then back to water again.
In the late 17th century Denis Papin invented a pressure cooker, that is, he enclosed water in a container with a tightly fitting lid and then heated it. In this way he created steam under pressure, and the result was that it blew the lid off the container. From this came the idea of using steam to power a piston and cylinder engine.
One of the earliest machines to use this principle was the pumping engine. The pumping engine was developed to draw water out of deep coal mines.
In a simple steam pump water is heated in a boiler until it is turned to steam by heating the water well above its boiling point. In this way the steam is under pressure. The steam is then sent into a cylinder containing a piston.
Expanding steam moves very fast and with great force (as heat energy is converted into mechanical energy of movement). For example, expansion from a pressure of about 12 times atmospheric pressure down to about half atmospheric pressure occurs with a speed of about 1,100 metres per second.
(Above and below) Pumping engines for mines were the first steam engines.
(Below) Trevithick’s engine of 1803.
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