EXPERIMENT 8. — Place rods of wood, metal, and glass on an
asbestos mat over a gas burner with the ends of the rods extending
beyond the mat. The metal rod will soon become hot, while the
other two will not be appreciably heated. Metals are good con-
12 DOMESTIC SCIENCE
ductors of heat and cold, glass and wood are poor conductors. Air
is a very poor conductor.
The conduction of heat consists of the transfer of motion from
molecule to molecule.
NOTE. — Students make a list of good conductors ; of poor con-
ductors.
Why are wooden handles placed upon teakettles, flat-irons,
etc. ? Why is the handle of a kettle sometimes made in the form
of a spiral ? Why is the outer portion of an ice cream freezer made
of wood ? Why is the inner can made of metal ? What is the prin-
ciple upon which a fireless cooker is constructed? a thermos
bottle ? How should the oven of a stove be constructed ?
Convection:
EXPERIMENT 9. — Partly fill a glass beaker with water, add one
half teaspoon of sawdust, and heat slowly. A movement will be
seen in the sawdust, indicating that the heat sets up currents in
the water which have an upward direction immediately over the
flame. The water nearest the flame becomes heated and expands ;
this makes it lighter and it rises, while the cold water of the top
takes its place, thus causing the currents noted. This method of
heat transference, which takes place in liquids and in gases, is
called convection. There are convection currents in the atmosphere,
caused by the unequal heating of the earth by the sun. The air
over a heated portion of the earth rises, and the cool air rushes in
to take its place.
NOTE. — What is the principle of heating a building with a hot-
water system ? How should a room be ventilated ?
Radiation :
EXPERIMENT 10. — When you hold your hand in front of a fire,
heat travels directly from the fire to the hand. This method of
heat transference, in which heat travels in straight lines, or radiates
through the atmosphere, is known as radiation.
NOTE. — How is heat transferred in making toast ? in broiling ?
Is there loss of heat from radiation in the ordinary cook stove ?
AIR AND COMBUSTION 13
NOTE. — Students examine the stoves and ranges in use in the
domestic science laboratory. Make drawings of them, showing the
principle of heat conveyance and the system of dampers used for
admitting oxygen to the fire and for controlling the heat currents.
Bring a detailed drawing of the stove used at home. Test various
parts of the school oven with paper or flour, showing in what part
of the oven the heat is the most intense. Examine also and make
drawings of
1. Gas burners and their mixers.
2. Fireless cookers.
3. Electric stoves.
4. Kerosene stoves.
5. Gasoline stoves.
Discuss the evolution of the cook stove. Catalogues showing
modern stoves, including gas stoves, electric stoves, etc., should be
shown to students or be collected by them.
Page 6
Presented as published in 1913. 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
EXPERIMENT 8. — Place rods of wood, metal, and glass on an asbestos mat over a gas burner with the ends of the rods extending beyond the mat. The metal rod will soon become hot, while the other two will not be appreciably heated. Metals are good con-
ductors of heat and cold, glass and wood are poor conductors. Air is a very poor conductor.
The conduction of heat consists of the transfer of motion from molecule to molecule.
NOTE. — Students make a list of good conductors ; of poor conductors.
Why are wooden handles placed upon teakettles, flat-irons, etc. ? Why is the handle of a kettle sometimes made in the form of a spiral ? Why is the outer portion of an ice cream freezer made of wood ? Why is the inner can made of metal ? What is the principle upon which a fireless cooker is constructed? a thermos bottle ? How should the oven of a stove be constructed ?
Convection:
EXPERIMENT 9. — Partly fill a glass beaker with water, add one half teaspoon of sawdust, and heat slowly. A movement will be seen in the sawdust, indicating that the heat sets up currents in the water which have an upward direction immediately over the flame. The water nearest the flame becomes heated and expands ; this makes it lighter and it rises, while the cold water of the top takes its place, thus causing the currents noted. This method of heat transference, which takes place in liquids and in gases, is called convection. There are convection currents in the atmosphere, caused by the unequal heating of the earth by the sun. The air over a heated portion of the earth rises, and the cool air rushes in to take its place.
NOTE. — What is the principle of heating a building with a hotwater system ? How should a room be ventilated ?
Radiation :
EXPERIMENT 10. — When you hold your hand in front of a fire, heat travels directly from the fire to the hand. This method of heat transference, in which heat travels in straight lines, or radiates through the atmosphere, is known as radiation.
NOTE. — How is heat transferred in making toast ? in broiling ? Is there loss of heat from radiation in the ordinary cook stove ?
NOTE. — Students examine the stoves and ranges in use in the domestic science laboratory. Make drawings of them, showing the principle of heat conveyance and the system of dampers used for admitting oxygen to the fire and for controlling the heat currents. Bring a detailed drawing of the stove used at home. Test various parts of the school oven with paper or flour, showing in what part of the oven the heat is the most intense. Examine also and make drawings of
1. Gas burners and their mixers.
2. Fireless cookers.
3. Electric stoves.
4. Kerosene stoves.
5. Gasoline stoves.
Discuss the evolution of the cook stove. Catalogues showing modern stoves, including gas stoves, electric stoves, etc., should be shown to students or be collected by them.