The Conservation of Energy
- Energy is the capacity of something to do work:
- If something contains a store of energy it is able to do work
- If something does not store energy then it will not work
- The law of conservation of energy states that:
- Energy cannot be created or destroyed, it can only change from one form to another
- What this means is that the total amount of energy in a closed system remains constant, although how much of each form there is may change
Some examples:
- A falling object (in a vacuum): Gravitational potential energy → Kinetic energy
- A gas cooker: Chemical → Internal (Heat)
- An LED (Light Emitting Diode): Electrical → Light
Conservation of Energy in Multiple Stages
- Many processes involve several steps before energy ends up in its final form
For example:
- A fossil fuel power station takes chemical energy (the fuel) and uses it to produce electrical energy, but the individual steps are:
Chemical → Internal (heat) → Kinetic (steam) → Kinetic (turbine and generator) → Electrical
Types of Energy
- Energy can exist in a number of forms
For your IGCSE examination you are expected to know about the following:
Worked example showing how energy is stored and transferred
Exam Question: Types of Energy
Energy Transfer
- In addition to the six forms of energy mentioned above, there are four ways in which energy can be transferred from one form to another:
Exam Question: Energy Transfer
Energy Dissipation
- When energy is transferred from one form to another, not all of the energy will end up in the desired form (or place)
- This lost energy often ends up being dissipated (spreading out into the environment), usually in the form of heat, light or sound
Diagram showing the forms of energy transfers and stores
Exam Tip
The classification of energy into forms and transfers, as mentioned above, is a fairly new approach and so there is a chance that you may have been taught this topic slightly differently or have come across different approaches elsewhere.
Don’t worry if this is the case, but you will need to become familiar with the above classification as there is a very good chance that it will be used in your examinations.
