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3.1.1. could chemistry be explained by mechanical forces?
3.1.2. what is the nature of the forces?
3.1.3. how can the forces be measured in the laboratory?
3.1.4. can heat and temperature be incorporated into the paradigm,
and if so, how?
3.2.1. is heat a substance or invisible, chaotic motion of
ultimate particles of ordinary matter ?
3.2.2. Greeks talked themselves out of the existence of atoms
so rejected kinetic theory
3.3.1. mechanical phenomenon (kinetic theory) or imponderable
fluid (caloric theory)
3.3.1.1. vibration of “corpuscles” of matter vs. substance
with unusual properties
3.3.1.2. could neither be weighed nor measured
3.3.2. Newton, Boyle, Hooke, Huygens favored mechanical theory
3.3.3. chemists wanted to know how to measure the forces and vibrations,
and what principles were involved
3.4.1. all three winners favored the caloric concept of heat
as a substance
3.4.2. view was developed mathematically and proved useful in
description of many thermal phenomena
3.4.3. Black’s calorimetric scheme fitted the caloric hypothesis
and gave it added prestige
3.4.4. kinetic interpretation remained an open alternative, but
caloric theory was more fully developed and more popular
3.5.1. Kinetic Theory and Caloric Theory
3.6.1. revived atomic theory in nineteenth century led to modern
interpretations of kinetic theory
3.6.2. resolved controversy of imponderable vs. mechanical nature
3.6.3. combined Newtonian mechanical paradigm and atomic theory
3.6.4. joined atomic and Newtonian paradigms into a larger, stronger
body of knowledge
3.6.5. required for full understanding of the nature of heat
3.6.5.1. not necessary for understanding of principles involved
in everyday matters
3.6.5.2. not necessary to deal quantitatively with heat
as a form of energy and transformation of mechanical energy into thermal energy
3.6.6. we will study details of kinetic theory later
3.6.7. next: Caloric Theory
4.2.1. language retains vestiges of concept
4.2.2. heat flows, objects soak up heat
4.2.3. leads to confusion: we speak of it as a substance
while told that it is not
4.2.3.1. metaphor
4.2.4. Lavoisier coined the term later in 1787
4.2.4.1. firmly entrenched by 1780
4.2.4.2. largely discredited by 1850
4.3.1. heat lost by one object is gained by another
4.3.2. this is true and still a basis for calorimetry
4.4.1. fluid = can flow
4.4.2. a “fluid” called caloric
4.5.1. massless
4.5.2. could not be created nor destroyed
4.5.3. all substances contain caloric and absorb or release it
4.5.4. flows from hot to cold objects or substances
4.5.5. counterbalanced attractive forces of "particles of
matter"
4.5.5.1. self repulsion caused it to flow from higher to
lower concentration
4.5.5.2. kind of like pressure in a balloon
4.6.1. caloric surrounds the particles of matter causing them
to swell
4.6.2. caloric occupied space, so gas has lots of caloric
Black, Joseph (1728-99), was a Scottish physician who was also a chemist
and physicist. He became professor of medicine at Glasgow and later of chemistry
at Edinburgh. He performed early quantitative experiments and was among the first
to emphasize the importance of such experiments to chemists. He discovered that carbon
dioxide is produced by respiration, burning of charcoal, and fermentation; that it
behaves as an acid; and that it is probably found in the atmosphere. He founded the
theory of latent heat and investigated the concept of specific heat but was unable
to fit them into place because of his belief in the phlogiston theory. These
theories of specific heat and latent heat furnished a basis for Lavoisier's caloric
theory of heat. He also invented a form of ice calorimeter.
5.1.1. studied carbon dioxide
5.2.1. unable to fit theories into place because of his belief in pholgiston and caloric
5.3.1. invented calorimeter
5.3.2. ice calorimeter was first type
5.3.3. insulated water calorimeter later
5.5.1. Measurement of Heat
Calorimeter
5.5.1.1. uses calorimeter
5.5.1.2. assumes conservation of heat
5.5.1.3. depends on change in temperature of a given amount
of a certain substance, usually water
5.5.1.4. heats units standardized by comparing with change
of temperature of water
5.5.2. heat gained or lost depends on mass, specific heat of substance
and temperature change
5.5.2.1. delta H = mc delta T
5.5.3. heat gained by one substance = heat lost by another substance
5.5.3.1. conservation of heat
5.5.3.2. assumes total transfer
5.5.3.3. assumes no “loss” to surroundings
5.5.3.4. assumes no outside work done
5.5.4. heat of combustion
5.5.4.1. bomb calorimeter
5.5.4.2. foods and fuels burned to determine usable energy
content
5.5.4.3. reported in kcal/kg or J/kg
5.5.5. heat of reaction
5.5.5.1. combustion is one type of reaction
5.5.5.2. solution, acid-base reactions, other chemical reactions
5.6.1. clarified distinction between heat and temperature
5.6.2. defined and measured specific heats of various substances
5.6.3. water tank model
5.6.3.1. heat:temperature :: size of tank: level in tank
5.6.3.2. heat is transferred, temperature is intensity of
heat
5.6.3.3. level depends on amount transferred and size of
reservoir
6.2.1. appears when work is done
6.2.2. appears when mechanical energy "disappears"
6.2.3. systems move naturally from high to low energy
6.2.4. is conserved during interactions
7.1.1. no difference in weight between hot and cold objects
7.1.2. countered by Aristotlean arguement: not ordinary
matter so not affected by gravity
7.1.3. precedent in imponderable quintessential matter (Aristotle)
7.2.1. based on friction
7.2.2. "by accident" while supervising boring of cannons
7.2.3. heat was produced as long as horses were working
7.2.4. theory held than caloric was released when metal is reduced
to chips
7.2.4.1. more heat was produced when drill bit was dull
and produced fewer chips
7.2.5. how can motion of horses create an inexhaustible supply
of caloric?
7.3.1. motion causes heating through friction
7.3.2. heating continues so long as motion continues
7.3.3. not the first to think so
7.3.3.1. F. Bacon (1620): "Heat itself . . . is motion
and nothing else.”
7.3.3.2. Boyle and Hooke expressed similar thought
7.3.3.3. Newton thought “corpuscles” of matter in motion
could explain temperature
7.3.4. no one able to explain how heat in the form of motion was
conserved
7.4.1. experiments were not convincing enough to caloric followers
8.1.1. amount of heat is proportional to amount of mechanical
energy dissipated
8.1.2. if there is a quantitative proportionality then we might
be justified in assuming that mechanical energy and heat are different forms of the
same thing
8.1.3. Rumford had failed to establish the quantitative relationship
convincingly
8.2.1. J = 4.18 Joule/cal
Here are two brief online biographies of Joule:
http://www.stemnet.nf.ca/~cfowler/joule.htm
http://www.salford.org.uk/joule/joule.htm
9.1.1. water should be warmer at bottom than at top due to loss
of potential energy
9.1.2. attempts to measure temperature differences failed
9.3.1. Faraday invented motors and generators in 1810s
9.3.2. Joule hoped to replace steam power with electric power
in family brewery
9.3.2.1. cost of zinc consumed in batteries was greater
than cost of coal
9.4.1. heat measured by calorimetry
9.4.2. measured heat developed by electric current from chemical
reactions in batteries
9.4.2.1. discovered/invented in 1803
9.4.3. measured heat from electric current produced by electrical
generator
9.4.3.1. source of generator current is mechanical work
to turn it
9.4.4. stated Joule’s law
9.4.4.1. heating produced by an electric current is proportional
to the square of the current
9.4.5. friction between moving cast iron plates
9.4.6. various liquids heated by rotating paddles
At this London Science Museum site you can view a photograph of Joule's churn.
9.4.7. liquid forced through small tubes by mechanical pressure
9.5.1. called the mechanical equivalent of heat
9.5.2. 1 calorie = 4.18 Joules (1 kcal = 4180 J)
9.5.3. joules and calories are different units for same quantity
9.5.4. input in work (joules) appears as heat (calories)
9.6.1. established through 40 years of extensive experimentation
9.6.2. includes not only mechanical energy
9.6.3. added heat, electrical energy and chemical energy to work/energy
equation
10.1.1. mechanical energy (kinetic and potential)
10.1.2. electrical energy
10.1.3. elastic energy
10.1.4. chemical energy
10.1.5. thermal energy
10.1.6. radiant energy
10.1.7. (nuclear energy)
10.4.1. solar energy evaporates water and lifts it high in
atmosphere
10.4.1.1. increases potential energy of water
10.4.1.2. condensation releases latent heat
10.4.2. precipitation collects in streams and flows downhill
10.4.2.1. water has both kinetic and potential energy
10.4.2.2. some energy is used for erosion and friction
10.4.3. stream is dammed to create energy difference due to water
level
10.4.3.1. potential energy is converted to kinetic energy
as it falls between levels
10.4.3.2. kinetic energy of water is transferred to turbine
by doing work on it
10.4.3.3. kinetic energy of turbine is converted to electrical
energy by generator
10.4.4. electrical energy is transmitted through wires as current
and magnetic field
10.4.5. final use of energy depends upon the type of transformation
at the user end
10.6.1. fascinated by Lavoisier's suggestion that animal heat
is generated by regulated combustion
10.6.1.1. slow combustion of food
10.6.2. noticed that venous blood is redder in tropics
10.6.3. noticed that animals in tropics did not consume as much
oxygen as in colder climates
10.6.4. related heat of metabolism to heat loss and work performed
by body
10.7.1. such battles are common in history of science
10.7.2. Newton’s calculus vs. Leibnitz’s for example
10.7.3. Joule gets the energy unit named after him, Mayer doesn’t
In this lesson we have considered a number of the aspects of heat as a
form of energy, from the historical and physical perspective.
The focus is that mechanical energy, although the model for energy and conservation
in general is only one of many forms of energy, including heat.
Loke momentum, energy can be transferred from one object to another.
Unlike momemtum, there are many different forms of energy, and it can be transformed
from one type to the other even in the same object.
The principle of conservation of energy, as stated by Joule and Mayer, suggests
that the total amount of energy in the universe remains constant although it may
change forms many imes.
11.1. Contributions of Black, Rumford, Joule
11.2. Caloric theory vs. energy theory of heat
11.3. Question remains as to how heat fits into Newtonian paradigm.
11.4. There are many different forms of energy
11.4.1. mechanical
11.4.2. chemical
11.4.3. thermal
11.4.4. electrical
11.4.5. radiant
11.4.6. nuclear
11.5. Energy can be transformed back and forth between the various types
11.6. Much of our modern technology is devoted to energy transformations
11.7. When energy is transformed none is lost, all can be accounted
for in one form or another
11.8. The amount of energy in a closed system remains constant
11.9. Energy can neither be created nor destroyed.
11.10. Conservation of energy vs. energy conservation
Now we are ready to undertake our studies of the nature of matter and see how that
will tie in with our studies of physics., and how the two separate fields of study
will merge into one solid and interrelated paradigm.We will do that in the next lesson.