Temperature
An object can feel cold or hot when we touch it. It's
just cold when its temperature is less than the temperature
of our hand's skeen; and hot in the other case.
The temperature of an object is then relative. But,
in some circumtances, what is the temperature of an object?
Some definitions
1. Once we have boiled water from room temperature,
that is 200 Celsius to 1000 Celsius, we had added energy (electrical)to water.
Changing temperature requires adding or removing energy
2. The definition of temperature refers to how are the atoms (gas monatomic) or
molecules moving in an object: the faster, the warmer (or hotter) and the slower, the
cooler (or colder). Temperature is proportional to the kinetic energy of particles
in the substance.
The related motions could be:
- Translational ( atoms or molecules)
- Vibrational or rotational for molecules (molecules only)
The microscopic energy corresponding to those
random motions is called internal energy.
3. The final temperature of a blend of two or more substances lies
between their initial temperatures. blending coffee of three
separate cups; the first at 500 Celsius , the second at 700 Celsius, and the
third at 100 Celsius gives a blend of temperature between 100 and 700 Celsius.
4. Thermal equilibrium is obtained when two are more bodies,
with different initial temperature, in physical contact, have identical
temperature. This temperature stays the same as long as the conditions
for the system remains unchanged.
5. The thermal expansion stands for an increasing of the temperature,
then the increasing of the related volume. This effect is true for gases and liquids,
but not for solids( ice has a volume larger than its liquid making it floating).
6.The measure of temperature is not just the result inferred from our
sensation ( our sense of touch). Obviously, this quantitative indicator is
not releveant. The measurement of the temperature with precision requires
a standard definition and a device called thermometer and it's set in
the thermal equilibrium.
The thermometer device uses the properties of the thermal equilibrium and
the thermal expansion. Its contact with another substance allows its column
(of gas or liguid commenly mercury)to shrink or expand responding to the
change of the temperature. The final position of the liquid in the device
gives the value of the substance's temperature.
7. The temperature unit is the Degree Celsius. We use also the
Fahrenheit. Te relashionship between them is:
TC = (5/9)(TF - 32)
TC is the temperature is Celsius degrees (C), and
TF its correspondent if Fahrenheit degrees (F).
00 Celsius is called the ice point, that is the
point at which water freezes; and
1000 Celsius is called the steam point. the point at
which water starts to give vapor.
We use also the scale Kelvin (or absolute) degree (K) as follows:
TK = T = TC + 273.15
The second term in this equation (273.15) comes from the fact that if
an ideal gas is compressed until its volume becomes zero, then its
temperature is - 273.15 0 Celsius; that is 00 K; often called absolute zero.
