Temperature. — The rate of motion of these particles is
proportional to the intensity of the heat. This heat in-
tensity may be measured by a thermometer and is called
temperature. There will be a heat not sensible by the ther-
mometer, and known as latent heat. Because of this latent
heat the temperature of a body does not indicate the amount
of heat contained in it any more than the height of a body
would alone determine its weight.
Latent Heat. — The amount of latent heat is dependent on
the property of the body to ^absorb heat without showing
any change in temperature. As an example, may be noted
the heat necessary to evaporate water by rapid boiling while
all the time the temperature of the water remains imchanged.
The radiant energy of the sun — supposed to be the source
of all possible energy in matter, may be shown by concen-
trating the sun's rays on white paper by means of a convex
lens; and noting the charred effect or even the flame pro-
duced if the sunshine is bright enough.
It is computed that were the sun to be extinguished, all
terrestrial life, in less than a month, would cease to exist.
This radiant energy, coming as it does in waves produced by
molecular motion in the ether, is stored up in animal and
vegetable life to be liberated when consumed either as food
or as fuel.
34 HANDBOOK OF DOMEJSTIC SCIENCE
During this consumption the compounds are changed into
much simpler products, potential energy being liberated as
work or as heat.
Method. — Discuss the source of all heat — the sun.
ExPEKiMENT 1. Eub two sticks together briskly or rub
two pieces of ice together.
ExPEKiMENT 2. Place cold water in a large flask. Drop
into it a cube of litmus or a crystal of potassium permanga-
nate. Apply heat from underneath. The flask may stand
on asbestos mat over gas flame. Let the pupil watch the
motion in the liquid.
Experiment 3. Apply cloth wet in boiling water to neck
of bottle, in which a glass stopper is tightly fitted, or loosen
cover of Mason fruit jar in same way.
Experiment 4. Concentrate the sun's rays with convex
lens upon black paper "or paper smoked by gas or candle
flame ; concentrate rays upon white paper. Note the effect
on each. Explain the absorbing power of lampblack or any
other black substance.
Experiment 5. Apply heat from gas flame to one end of
brass or steel wire on which, at regular intervals, are fastened
small shot held in position Avith warm parafiin. As the heat
is transmitted the melting of the fat causes shot to fall.
Let the pupils perform these experiments individually if
this is possible. Be sure not only that they see the result,
but also that they understand the deductions to be made
from these results, and above all the general principles thus
illustrated.
Combustion
Facts. — The liberation of energy when accompanied by
the evolution of light and heat, or heat alone, is known as
combustion. In the restricted sense combustion is produced
whenever the oxygen of the air unites with another element
or compound with consequent evolution of heat. The heat
THE KITCHEN 35
and light obtained from combustion is a result of oxidation
of carbon or hydrogen or both. These, therefore, are the
essential elements in fuels. The oxygen present in some
fuels, as in wood, is inert in the sense that it may not take
an active part in the production of heat.
Page 19
Presented as published in 1900. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
AI-modernized reading of the original text
Temperature. — The rate of motion of these particles is proportional to the intensity of the heat. This heat intensity may be measured by a thermometer and is called temperature. There will be a heat not sensible by the thermometer, and known as latent heat. Because of this latent heat the temperature of a body does not indicate the amount of heat contained in it any more than the height of a body would alone determine its weight.
Latent Heat. — The amount of latent heat is dependent on the property of the body to ^absorb heat without showing any change in temperature. As an example, may be noted the heat necessary to evaporate water by rapid boiling while all the time the temperature of the water remains imchanged. The radiant energy of the sun — supposed to be the source of all possible energy in matter, may be shown by concentrating the sun's rays on white paper by means of a convex lens; and noting the charred effect or even the flame produced if the sunshine is bright enough.
It is computed that were the sun to be extinguished, all terrestrial life, in less than a month, would cease to exist. This radiant energy, coming as it does in waves produced by molecular motion in the ether, is stored up in animal and vegetable life to be liberated when consumed either as food or as fuel.
During this consumption the compounds are changed into much simpler products, potential energy being liberated as work or as heat.
Method. — Discuss the source of all heat — the sun.
ExPEKiMENT 1. Eub two sticks together briskly or rub two pieces of ice together.
ExPEKiMENT 2. Place cold water in a large flask. Drop into it a cube of litmus or a crystal of potassium permanganate. Apply heat from underneath. The flask may stand on asbestos mat over gas flame. Let the pupil watch the motion in the liquid.
Experiment 3. Apply cloth wet in boiling water to neck of bottle, in which a glass stopper is tightly fitted, or loosen cover of Mason fruit jar in same way.
Experiment 4. Concentrate the sun's rays with convex lens upon black paper "or paper smoked by gas or candle flame ; concentrate rays upon white paper. Note the effect on each. Explain the absorbing power of lampblack or any other black substance.
Experiment 5. Apply heat from gas flame to one end of brass or steel wire on which, at regular intervals, are fastened small shot held in position with warm paraffin. As the heat is transmitted the melting of the fat causes shot to fall.
Let the pupils perform these experiments individually if this is possible. Be sure not only that they see the result, but also that they understand the deductions to be made from these results, and above all the general principles thus illustrated.
Combustion
Facts. — The liberation of energy when accompanied by the evolution of light and heat, or heat alone, is known as combustion. In the restricted sense combustion is produced whenever the oxygen of the air unites with another element or compound with consequent evolution of heat. The heat
and light obtained from combustion is a result of oxidation of carbon or hydrogen or both. These, therefore, are the essential elements in fuels. The oxygen present in some fuels, as in wood, is inert in the sense that it may not take an active part in the production of heat.