CHAPTER II

TEMPERATURE AND HEAT


14. 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.

15. 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.,