What is the difference between
a hot cup of coffee and a cold cup of coffee?
Temperature is a measure the hotness of a given body
Measure of hotness can be done simply by touching the body.
But it is not a standard method as it is based on an individual's
perception and may vary from a person to person and can
be injurious if the body that we touch is very hot.
Measure of hotness should not
be confused with heat irself.
The difficulty in using the sensation as a measure of hotness
arises because of the fact that the terms hot and cold are
relative terms and cannot be used in the absolute measurement
of hotness.
Often the concepts of heat and
temperature are thought to be the same, but they are not.
Perhaps the reason the two incorrectly thought to be the
same is because our everyday experience suggests that when
one applies heat example : putting a pot of water on the
stove, then the temperature of water goes up. More heat,
more temperature - so they must be the same, right? this
is actually not true.
Heat is a measurement of the total energy in a substance.
That total energy is made up of not only of the kinetic
energies of the molecules of the substance, but is also
made up of their potential energies.
Temperature, when measured in
Kelvin degrees, is a number that is directly proportional
to the average kinetic energy of the molecules in a substance.
So, when the molecules of a substance have a small average
kinetic energy, then the temperature of the substance is
low. But the potential energy could be high leading to higher
heat. Leading to false notion of temperature.
Therefore, there is a need of some standard for the measurement
of the hotness of a body. The degree of hotness of a body
is called its temperature. It is measured by devices called
thermometer
How Does a thermometer work :
A common liquid in glass thermometer takes advantage of
the fact that liquids generally expand more than solids
as their temperatures increase. The glass envelope of the
thermometer contains a fine hollow capillary with a sealed
reservoir at its base that's filled with a liquid such as
alcohol or mercury. If both the liquid and glass expanded
equally as they became warmer, the thermometer would simply
change sizes slightly as its temperature increased. But
the liquid expands more than the glass and can't simply
remain in place. Some of it moves up the capillary. That's
why the level of liquid in the thermometer rises as the
thermometer's temperature rises.
In 1954 the triple point of water-that is, the point at
which the three phases of water (vapor, liquid, and ice)
are in equilibrium-was adopted by international agreement
as 273.16 K. The triple point can be determined with greater
precision than the freezing point and thus provides a more
satisfactory fixed point for the absolute thermodynamic
scale. In cryogenics, or low-temperature research, temperatures
as low as 0.003 K have been produced by the demagnetization
of paramagnetic materials. Momentary high temperatures estimated
to be greater than 100,000,000 K have been achieved by nuclear
explosions (see Nuclear Weapons).
Absolute zero is a theoretical temperature. It is that
temperature at which all substances have no heat energy.
It is defined as zero Kelvin (0 Kelvin). 0 Kelvin is equivalent
to -273.16 degrees Celsius, and -459.69 degrees Fahrenheit
In 1967, by international agreement, The Kelvin temperature
scale was decided to be a scale of units rather than degrees.
It is proper therefore to describe the temperature of the
boiling point of water at sea level as being 373.15 Kelvin
(not 373,15 degrees Kelvin), and the freezing point of water
as 273.15 Kelvin (or 273.15 K)
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