Science -- Your Future, Scotland's Future
SCI-FUN Roadshow Exhibits -- Steam Engine
SCI-FUN Roadshow Exhibits -- Steam Engine
In this exhibit you learn about how steam is used to generate power.

When water evaporates into steam, it expands. This expansion means that we can push machinery. This movement can be harnessed and used in many ways.

In a steam engine, water is boiled and the steam is pushed into alternate ends of a cylinder containing a piston. Because steam expands, it pushes the piston back and forth as it is put into each end of the cylinder. This drives a crank which turns a wheel. The movement of this wheel is then used to drive machinery or generate electricity.

The heat to boil the water can be generated in different ways. We can burn things to create heat, such as fossil fuels, i.e. coal, oil and gas, or biomass, such as wood, animal waste or alcohol made from plants. Heat can also be generated from nuclear reactors. We can also harness the heat from inside the Earth's crust, called geothermal energy.

Many years ago, steam was used to directly power factories and transportation. In the 19th Century, steam powered mills were built all over Britain, particularly in the North of England, and were used primarily to spin and weave cotton. Around the same time, mass long distance transport became available, as the railway network was built. Trains were, at that time, also powered by steam and required men shovelling coal into the furnace as the train chugged along. In those days, people did not have electricity in their homes.

Nowadays steam is used to generate electricity, which is used to power our homes, businesses, schools, public services and railway system. (Most cars and aeroplanes are powered by internal combustion engines, which also burn fuel to produce heat and move machinery, but don't use steam as an intermediate.) Using electricity, rather than using steam directly, gives us a lot more flexibility on how and when we use power. Indeed, much of modern technology uses electronic logic, rather than mechanical movement, so steam power would not be suitable.

But, although there isn't a steam engine in every train any more, we are still reliant on steam to keep them going.

1 When water _________ into steam, it _________.
2 How does steam push a piston back and forth?
3 Name three ways that we can generate heat to make steam.
4 When was the railway network built in Britain?
5 What kind of engine powers cars and aeroplanes?
6 What appliances in your home do you think could be powered by steam? Look for things which are mechanical, not electronic.

1 Watch steam expand as you heat it. Put some water into a microwave-safe bowl or mug and stretch cling film over it, making sure you form a seal all the way around. Put it into the microwave on full power for a minute (you may need more time), and watch through the window. You should see the cling film expand as the water evaporates and the steam expands; it might even pop. Make sure you wear oven gloves to take it out of the microwave and allow it to cool before removing the cling film.
2 Can you get steam to turn a turbine? Get a toy windmill or make one from card. Hold it above a pan or kettle full of boiling water. Because hot steam rises, it will turn the windmill.