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Energy
In any physical or chemical reaction energy is either released or absorbed. In
order to have a good understanding of chemistry you will need to know some
basic information about energy and how it relates to physical and chemical
reactions. We will begin learning about energy by looking at definitions and
the different types of energy. We will then look at how energy can be
converted from one form to another.
Basic Definitions
Energy - is defined as the ability to do work
Work - for scientists, work is done on an object when a force (a push or pull)
causes an object
to move some distance. Mathematically, work = force x distance
Example: If you push your car down the street you are doing work on the car
since you are applying a force and moving the car a distance.
Forms of Energy
When dealing with macroscopic (relatively large) particles, the energy that they
possess is called mechanical energy. There are two main types of mechanical
energy found in macroscopic particles. They are:
Kinetic Energy - Kinetic energy is energy of motion. All moving objects
have kinetic energy. The faster they are moving or the greater their mass, the
more kinetic energy they possess. The formula for kinetic energy is: 1/2 mass
x velocity2
Example: A truck and a car moving down the street both have kinetic energy
because they are in motion and they have mass. If they are moving at the same
speed, the truck will still possess more kinetic energy than the car if it has a
greater mass.
Potential Energy - Potential energy is stored energy that is available to do
work at a later time.
Example: A wound up spring in a watch has potential energy as long as it
remains wound up. When it is released, it is able to perform work on the gears
in the watch. When the spring is completely unwound it will have released its
potential energy.
There are other forms of energy found in submicroscopic (extremely small)
particles. These forms are referred to as nonmechanical energy. They include:
electrical energy
nuclear energy
energy)
heat energy
sound energy
magnetic energy
radiant energy (electromagnetic
chemical energy
These forms of nonmechanical energy are actually forms of kinetic and
potential energy found in submicroscopic particles. The energy found in these
particles is because of the movement of atoms and molecules. Whether energy
is mechanical or nonmechanical, it all has the capacity to do work.
Energy is constantly being converted from one form to another all around us.
For example, the chemical energy found in gasoline is converted into kinetic
energy to move your car when it is burned. It is also converted into heat energy
from the burning of the gasoline and electrical energy to run the electrical
systems in your car, and sound energy to run your radio. Scientists have found
that no matter how many energy conversions occur, the total amount of energy
always remains the same. This is true according the following basic principle in
science:
Law of Conservation of Energy - energy is neither created or destroyed, it is
only converted from one form to another.
Einstein's Theory of Relativity seems to be a contridiction to this basic
principle. Einstein stated that mass and energy were related and that whenever
an object released energy it also lost mass. He theorized that mass was being
converted into energy. If this is the case, it seems that energy is being created.
In normal reactions the amount of matter that is converted into energy is so
small that it cannot be measured. It would require a nuclear reaction that
releases tremendous amounts of energy before you can actually see a change in
the amount of mass. If the Law of Conservation of Energy is to remain true,
we would have to include mass as a form of energy also.