Introduction to energy

Target Language or Knowledge:

A useful definition is that energy is something that is needed to make things happen. Energy can make things move or change. Energy makes things happen!
There are many different forms of energy. Some types of energy involved _stored_ energy, but other types of energy are involved in making things _happen._ Stored energy is called _potential_ energy. That energy is available to make things happen. Energy associated with something moving or changing in some way can be called _'active_ energy' (e.g. the light energy associated with exploding fireworks).
What is conservation of energy?
The Law of Energy _Conservation_ . Energy may change form but the amount of energy stays _constant._ Energy must come from some- where (it is never created out of _nothing)._ Energy can never be _destroyed;_ it can only be transformed from one form to another.
Some of the energy becomes useful energy for the purpose of the appliance. Some energy becomes waste energy which cannot be used.
Using an actual example, a 100 watt light bulb uses 100 _joules_ of electrical energy per second and _wastes_ 90 joules as thermal energy. So: _ Useful_ Energy = 100 J - 90 J = 10 J
conductors of energy include all metals. Insulators are most often non metal substances.
Conduction of thermal energy occurs mostly in _solids._ The energy travels from the _hotter_ end of an object along to the cooler end. All objects are made of tiny particles of matter - atoms or molecules (small groups of atoms bonded together). In a solid the particles are in _fixed_ positions. They can only _vibrate._ The more thermal energy the particles have, the _faster_ they vibrate. This vibrating movement jostles neighbouring particles, and they begin to vibrate more, gaining thermal energy
Energy transformations or changes are taking place around us all of the time. In an energy transformation energy is changed from one type to another or into several different types.
Energy transformations occur: stored chemical energy in the food you eat is transformed into thermal energy in your body to keep you warm. electrical energy to _sound_ energy in a speaker b) electrical energy to thermal energy in a _heater_ c) electrical energy to light energy in a _light_ bulb d) electrical energy to _kinetic_ energy in a CD player e) _elastic_ energy to kinetic energy in a windup toy f) chemical energy to light energy in a _torch_
Complete these stories
When your car is moving it has _kinetic_ energy. This energy comes from the burning of _petrol_ in the motor. The petrol contains _stored_ chemical energy. This petrol was refined from oil. The chemicals in oil were originally produced by microscopic plants which lived in the sea. These plants obtained their energy from _radiant_ energy coming from the _Sun_