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?

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.

The construction of cook stoves is at present in a transition stage and drawings are not given in this text, as it is hoped soon that the construction of stoves will be materially changed. The loss of heat and the attendant waste of fuel in heating an ordinary oven is very great. It is said that only about seven per cent of the heat is utilized. Modern stoves are now being constructed with non-conducting substances around the air chambers which surround the ovens so that the waste of heat is much reduced. An oven thermometer should be placed on every oven to substitute a scientific means of regulation for the old-fashioned dependence on "luck" when baking. With gas and electric stoves a thermostat should shut off heat when a certain temperature has been attained, the baking being then completed by the retained heat of the oven.

Cooking is the art of preparing food for the nourishment of the human body by the aid of heat. We cook food to make it more palatable, more digestible, and to destroy any harmful bacteria which it may contain.

The processes of cooking may be classed as:

1. Boiling.

a. Cooking directly in water.

b. Steaming.

(1) Moist, cooking in a steamer.

(2) Dry, cooking in double boiler.

2. Roasting.

a. Roasting in front of open fire.

b. Roasting in hot oven.

3. Broiling.

a. Broiling over red-hot coals or gas flame.

b. Pan-broiling in very hot pan (without fat).

4. Frying.

a. Deep frying.

b. Sauteing, or frying in small amount of fat.

Boiling:

Experiment 11

Put cold water in glass beaker or stewpan. Heat. With thermometer note temperature at which small bubbles form on the bottom and sides of the beaker and rise to the surface. What are these bubbles? Where do they break ? Note temperature at which larger bubbles rise; and also note temperature when the surface of the water is completely agitated. What are these large bubbles ? Where do they break ? What is the temperature of simmering water ? of boiling water ? How is the heat of the fire conveyed to the water? How is the heat conveyed through the water? Note the deposit left on the pan after the water has boiled away; what is this deposit? Give two reasons why boiled water tastes flat. Why should water be freshly boiled for tea and coffee? How can you improve the taste of water which has been boiled ?