Transformation of chemical energy
Identifying energy transformations Chemical energy at work
Other chemical transformations

Click for larger image There is a basic law in science that energy cannot be created or destroyed. What happens when a firework explodes in spectacular fashion in the sky? It seems at first sight that everything disappears, except for a charred case you might find on the ground. In fact, the energy stored in the firework has been changed to other forms - it has been transformed.

Identifying energy transformations
Let's see if we can identify some of the energies involved in this transformation sequence. From the moment the fuse is lit, thermal and light energy are apparent, but this is minor compared with the energy about to be released! With a whoosh, the whole thing is rocketed into the sky, leaving a trail of sparks - sound, light and thermal energy. The big explosion follows, with a thunder and crash of almost deafening sound! Finally, a cascade of brilliant colors fall towards the ground, with the remnant of the case.

Firework energy

So far you will have noticed at least four forms of energy: light, sound, thermal and kinetic (energy of movement). Where does all this energy come from? To answer this question, you need to go back to the firework itself. It must have all of this energy stored, ready to be released. It has great potential as you have seen, so this stored energy is called potential energy.

Chemical energy at work
Click for larger image The type of potential energy stored in this case is more commonly known as chemical energy. It is this stored energy that is finally transformed into all the other forms of energy that go to make up the dramatic display. All the materials in the Universe are made up of atoms, ions, molecules or bits of atoms, most of them are fairly stable but some are readily able to chemically react, releasing the energy stored in them.

Some of the chemical energy stored in the fireworks is converted to kinetic energy to send the rocket skyward; some compresses the air rapidly, producing sound and still more energy is transformed into light of many colors.

Other chemical transformations
Chemicals like petrol and LPG have lots of stored chemical potential energy that can propel cars, for example, by being transformed into other forms of energy. An explosion increases the pressure of gas that pushes pistons in the car engine (kinetic energy) then, by a series of gears, turns the car's wheels, and moves the car forward. Again, the chemical energy is transformed into thermal energy, sound and the kinetic energy of movement.

Click for larger image An electric cell (battery) is another type of chemical energy store. This time, it supplys energy to electrons. This stored electrical energy can be transformed into sound, thermal, light or kinetic energy depending on the components in the circuit. For example, a torch transforms electrical energy to light energy, with some of the energy being "wasted" as thermal energy - you can observe these effects if you touch a small torch light globe that has been operating for a while. (Be careful - mains light globes can get very hot indeed.)

Energy transformation in a torch
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