Temperature not a Measure of the Amount of Heat Present. If two similar basins containing unequal quantities of water are placed in
the sunshine on a summer day, the smaller quantity of water will become quite warm in a short period of time, while the larger quantity will become only lukewarm. Both vessels receive the same amount of heat from the sun, but in one case the heat is utilized in heating to a high temperature a small quantity of water, while in the second case the heat is utilized in warming to a lower degree a larger quantity of water. Equal amounts of heat do
not necessarily produce equivalent temperatures, and equal temperatures do not necessarily indicate equal amounts of heat. It takes more heat to raise a gallon of water to the boiling point than it does to raise a pint of water to the boiling point, but a thermometer would register the same temperature in the two cases. The temperature of boiling water is 100° C. whether there is a pint of it or a gallon. Temperature is independent of the quantity of matter present; but the amount of heat contained in a substance at any temperature is not independent of quantity, being greater in the larger quantity. The Unit of Heat. It is necessary to have a unit of heat just as we
have a unit of length, or a unit of mass, or a unit of time. One unit of heat is called a calorie, and is the amount of heat which will change the temperature of 1 gram of water 1° C.It is the amount of heat given out by 1 gram of water when its temperature falls 1° C., or the amount of heat absorbed by 1 gram of water when its temperature rises 1° C. If 400 grams of water are heated from 0° to 5° C., the amount of heat which has entered the water is equivalent to 5 × 400 or 2000 calories; if 200 grams of water cool from 25° to 20° C., the heat given out by the water is equivalent to 5 × 200 or 1000 calories. Some Substances Heat more readily than Others. If two equal quantities of water at the same temperature are exposed to the sun for the same length of time, their final temperatures will be the same. If, however, equal quantities of different substances are exposed, the temperatures resulting from the heating will not necessarily be the same. If a basin containing 1 lb. of mercury is put on the fire, side by side with a basin containing an equal quantity of water, the temperatures of the two substances will vary greatly at the end of a short time. The mercury will have a far higher temperature than the water, in spite of the fact that the amount of mercury is as great as the amount of water and that the heat received from the fire has been the same in each case. Mercury is not so difficult to heat as water; less heat being required to
raise its temperature 1° than is required to raise the temperature of an equal quantity of water 1°. In fact, mercury is 30 times as easy to heat as water, and it requires only one thirtieth as much fire to heat a given quantity of mercury 1° as to heat the same quantity of water 1°.
the sunshine on a summer day, the smaller quantity of water will become quite warm in a short period of time, while the larger quantity will become only lukewarm. Both vessels receive the same amount of heat from the sun, but in one case the heat is utilized in heating to a high temperature a small quantity of water, while in the second case the heat is utilized in warming to a lower degree a larger quantity of water. Equal amounts of heat do
not necessarily produce equivalent temperatures, and equal temperatures do not necessarily indicate equal amounts of heat. It takes more heat to raise a gallon of water to the boiling point than it does to raise a pint of water to the boiling point, but a thermometer would register the same temperature in the two cases. The temperature of boiling water is 100° C. whether there is a pint of it or a gallon. Temperature is independent of the quantity of matter present; but the amount of heat contained in a substance at any temperature is not independent of quantity, being greater in the larger quantity. The Unit of Heat. It is necessary to have a unit of heat just as we
have a unit of length, or a unit of mass, or a unit of time. One unit of heat is called a calorie, and is the amount of heat which will change the temperature of 1 gram of water 1° C.It is the amount of heat given out by 1 gram of water when its temperature falls 1° C., or the amount of heat absorbed by 1 gram of water when its temperature rises 1° C. If 400 grams of water are heated from 0° to 5° C., the amount of heat which has entered the water is equivalent to 5 × 400 or 2000 calories; if 200 grams of water cool from 25° to 20° C., the heat given out by the water is equivalent to 5 × 200 or 1000 calories. Some Substances Heat more readily than Others. If two equal quantities of water at the same temperature are exposed to the sun for the same length of time, their final temperatures will be the same. If, however, equal quantities of different substances are exposed, the temperatures resulting from the heating will not necessarily be the same. If a basin containing 1 lb. of mercury is put on the fire, side by side with a basin containing an equal quantity of water, the temperatures of the two substances will vary greatly at the end of a short time. The mercury will have a far higher temperature than the water, in spite of the fact that the amount of mercury is as great as the amount of water and that the heat received from the fire has been the same in each case. Mercury is not so difficult to heat as water; less heat being required to
raise its temperature 1° than is required to raise the temperature of an equal quantity of water 1°. In fact, mercury is 30 times as easy to heat as water, and it requires only one thirtieth as much fire to heat a given quantity of mercury 1° as to heat the same quantity of water 1°.
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