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THE FIRST LAW OF THERMODYNAMICS
Energy is conserved
The First Law of Thermodynamics is the Law of Conservation of Energy.
This law states that energy cannot be created, nor can it be destroyed. This
seems hard to believe, especially given that you have to keep filling your car's
gas tank, but the energy of the universe is constant. However, that energy can
change forms: electricity, light, heat, and sound are all different forms of
energy.
One important aspect of this law to keep in mind is that the transfer of energy
from one form to another, or from one substance to another, is an inefficient
process. Some useful energy (energy that can be used to perform work, such as
moving an automobile or linking together nucleotides to make a DNA strand) is
always lost during the procedure. This useful energy doesn’t just disappear;
rather, it becomes energy that cannot be utilized by the process.
So when the gasoline that runs your engine is burned to move your car, some
of it helps move the pistons, which is useful, but some ends up heating up the
engine block, which is not useful. In chemical reactions, some useful energy
is always lost to an increase in the random movement and vibrations of the molecules
involved. This loss of useful energy is sometimes referred to as nature’s
energy tax.
Example 1: Metabolism
Animals oxidize the food they eat, much like a car burns gasoline
(combustion is an oxidative process). What property of our bodies is related to
nature's energy tax?
Answer:
Our body uses the energy stored in food very efficiently, but like an automobile,
much of it is wasted as heat. This is why our body temperature is generally
elevated when compared to the outside temperature, and on cold days you can
witness nature's energy tax in the form of the steam forming with each breath
you take.
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