(Study pages 1-29) Water

To show that ordinary water has gases dissolved in it. See experiment on page 2. The gas dissolved in water is not exactly of the same composition as air. It usually contains more oxygen and more carbon dioxide than ordinary atmospheric air, varying somewhat with the sources of the water. This dissolved gas enables fish and other marine animals to live. A fish cannot live in water that has lost its dissolved air by being boiled. It is drowned just as human beings are, because of lack of oxygen.

Water of Crystallization

Make crystals as described on page 5. A certain definite amount of water is present in the crystals which varies with each substance. Clear crystals are pure or nearly so. The "mother liquor" remaining after the crystals are formed contains most of the impurities; thus crystallization is a method of purification.

The water in the crystals of washing soda may be shown by heating some in a tin dish. The crystals will melt and on continued heating, steam will be given off. Not all crystals contain water of crystallization, - for example, common salt, cane sugar.

Boiling Point

It is almost impossible to convince any "domestic" that water boiling furiously is no hotter than when it is just barely boiling. It is instructive to prove this with a thermometer. Also observe that the "simmering" temperature is very nearly the same as the water when boiling, so that cooking may be done nearly as rapidly by simmering and with far less fuel.

Latent Heat

This is a somewhat perplexing phenomenon. We all recognize that steam is hot, but that it contains a much greater supply of heat than hot water is not so easy to realize. The following may make this a little clearer: In a small sauce pan or dish put about two tablespoonfuls of water. Heat it to the boiling point and then continue the boiling until it has all boiled away. Note (i) how long it takes to raise the water to the boiling point, and (2) how much time is required to convert it all into steam.

To start the boiling, the water is raised from about 6o°F. to 2120 F., or through 1520. In converting the water into steam, there is no rise in temperature, but the heat has to be applied for a much longer period. On page 12 is the statement that "966 times as much heat is required to change a given quantity of water into steam as to raise it one degree F. " but the water in this experiment was raised 1500. As 966 divided by 152 equals 6 (plus), we might expect that it would take six times as long to boil the water away as to raise it to the boiling point. Of course no exact results can be expected in this experiment, as not all the heat applied is absorbed by the water and used in boiling it, but the experiment will show that the steam must contain a great deal of heat.

A similar experiment will show the latent heat contained in water in reference to ice. If a teaspoonful of ice cold water and an amount of snow or ice which when melted would make a teaspoonful, each be added to a glass of water of the same temperature, it will be found that the pulverized ice or snow lowers the temperature much more than the teaspoonful of ice-cold water. That is to say, a great deal more heat would have to be added to the "ice and water mixture, " to bring it back to the original temperature, than to the "ice cold water and water mixture. "

Oxygen in the Air

To show that the atmosphere contains a gas which is used up in combustion, attach a candle an inch and a half long to the bottom of a saucer with some of the melted wax. Pour about one-fourth of a glass of water into the dish, light the candle and invert the glass (one with straight sides) over the lighted candle. The flame will grow dim and soon be extinguished and the water will rise about one-fifth way up the glass. This shows a number of things. In burning, the carbon of the hydrocarbons of which the candle is made unites with the oxygen, making the gas carbon dioxide. This takes up the same volume as the oxygen out of which it was formed, but the water quickly dissolves the carbon dioxide and the pressure of the atmosphere on the water outside the glass forces it up into the partial vacuum formed.

The nitrogen of the air remains, but this will not "support combustion," and so the candle is extinguished.

Manufacturing Water

That the burning of a candle produces water as well as carbon dioxide may be shown by placing the flame against a window pane. A film of moisture may be seen, also, when a lamp having a cold chimney is first lighted. The burning of a match will show water when it is placed against a cold surface, but this experiment is not so conclusive, for the wood may contain moisture. The candle contains no moisture, so the water must have been manufactured by the burning.

Atmospheric Pressure

We have had one example of the result of atmospheric pressure in the candle experiment. The working of a siphon is an interesting example. Take a small rubber tube, fill it with water, pinch both ends, put one end in a glass of water, and lower the other end into an empty glass at a foot lower level; release the pressure of the fingers, and the water will run from the tube, apparently going "up hill" over the edge of the glass. The explanation may be found in any text book on physics. This is a good way to empty wash tubs, etc., using a piece of rubber hose.

Carbon Dioxide

Light a splinter of wood and let it burn in a wide-mouthed bottle until it is extinguished. Add a tablespoonful of clear lime water (obtained at any drug store, or add a small lump of lime to warm water in a fruit jar, stir well, cover and let settle over night), close the bottle, and shake the lime water around. It will grow milky from the formation of carbonate of lime (calcium), with which we are more familiar in the forms of chalk, marble, and clam shells.

Again with any sort of a tube (a straw), blow into a little clear lime water. It will grow milky, showing that the breath contains carbon dioxide. If you will continue to blow into the lime water for a long time, the milkiness will be seen to disappear. This is because the carbonate of lime is dissolved by the excess of carbon dioxide in the water, after the lime water (hydrate of lime) is all changed into carbonate of lime. This point comes up in connection with hard water and laundry work.

Flash Point of Kerosene

The flash point of a sample of kerosene may be determined approximately by placing about two teaspoonfuls in a cup, then adding hot water to a bowl of water in which the cup containing the oil is placed. Stir the kerosene with a thermometer, and apply a lighted taper to the surface of the oil from time to time as the temperature of the oil rises. A quick flash over the surface of the kerosene will show the flash point. Read the temperature indicated by the thermometer.

References: Chemistry of Daily Life, by Lassar-Conn. Chapter I, Atmosphere, Combustion. ($1.50, postage 12c.)

Story of a Lump of Coal, by Martin. (35c, postage 6c.) Air and Water as Food, in Plain Words about

Food, by Ellen H. Richards. ($1.00, postage 10c

Sanitary and Applied Chemistry, by Bailey, Chapter on The Atmosphere, Fuels. ($1.40 postage 12c.)

Topics: The Formation of Coal - See any good encyclopedia and geologies. Fire Worship - See "Popular Science Monthly," Volume X, page 17, also "Public Opinion, Volume XIV, page 251.