For this segment of my ISU I read about the different
theories of how humans’ understanding of what heat was has changed over time.
Since the chapter tied into what we were talking about in class and I was
reading from my grade 11 textbook, I was able to fully understand everything I
was reading and did not require further research or discussion. Furthermore, during
this segment I was advised to not to worry about applying the different theories
to the Stirling Engine. Thusly, I will not be talking about the Stirling Engine
in this post.
The very first concept of what matter consisted of was
created thousands of years ago. They believed that all matter consisted of 4
elements; earth, air, fire and water. Under this theory all matter consisted of
these elements and under certain conditions the matter would “release” its
fire.
This belief held until 400 years ago when a German scientist
presented a new theory. His theory presented that heat was a fluid known as Phlogiston.
His theory stated that Phlogiston or heat flowed from, into or out of the
substance. This theory lasted about 100 years to the mid-1700s when scientists
discovered combustion required Oxygen.
With their newest belief of heat proven wrong scientists
searched for a new answer. The result was Caloric Theory. This theory stated
that “Caloric” or heat was an invisible “massless” substance that existed in
all materials and could not be created or destroyed. It stated that “Caloric”
had a self-repulsive force which caused Caloric to flow from high concentration
to low concentration. This theory was able to explain almost all observations,
but still failed to explain what heat was. Caloric Theory could not explain why
rubbing two cold objects together could create heat. This question remained
unanswered until the discovery of the particle.
By the 1900s scientists had discovered the particle. Particle
theory suggested that all matter is composed of particles that are always in
motion. The current heat theory, the Kinetic Molecular Theory was created from
this discovery. This theory is able to explain all currently observed
phenomenon associated with heating and cooling objects and contains multiple
laws of thermodynamics. The theory stats that particles in hot objects move
more rapidly thus have more kinetic energy than cooler objects. This means that
heat is not a substance but the transfer of thermal energy. According to the
theory, thermal energy is the kinetic energy of the particles of a substance
and is transferred from particles colliding with slower-moving particles.
When reading about how thermal energy is transferred between
particles I used an analogy to understand it on a larger scale. I thought of two
cars of equal mass and size. One car is moving at 10km/h, while the second car
is moving at 90km/h. The 90km/h car collides with the car moving at 10km/h. As
a result the 10km/h car speeds up while the 90km/h car slows down. This same
event occurs in a microscopic scale during the transfer of thermal energy –
fast particles collide with slower particles speeding up the slower particles
while slowing down the fast particles. A thermal equilibrium occurs when the
fast particles have collided with the slow particles enough so that the fast
particles and the slow particles are the same speed. At this point the temperatures
of the two objects are identical. As I said at the beginning of this post, the
readings for this segment where straight forward and I had no problem
understanding the different theories proposed in the textbook.
Sources:
Dick G, Geddis A, James E, McCaul T, McGuire B, Poole R, Holzer B. (2001). Physics 11. Toronto, ON: McGraw-Hill Ryerson Limited.
No comments:
Post a Comment