In your everyday life and in your study
of Chemistry, you are likely to encounter three different temperature scales. When
you watch the weather report on the news, they will report the temperature on one scale,
yet you measure temperature in the laboratory on a different scale. Many Chemistry
equations must be done using yet another temperature scale. Clearly, you can see the
importance of the use of units when reporting temperature. You can also see the
need, for a student of Science, to be able to convert temperatures from one scale to
another. This page is designed to help you do just that.
The Fahrenheit Scale - The Fahrenheit scale is
the scale that is used when they report the weather on the news each night. It is probably
the temperature scale that you are most familiar with, if you live in the United States.
The thermometers that you have in your house, for uses such as; swimming pools,
cooking, bath tubs, or reading body temperature, are all likely to be in Fahrenheit.
In Canada and most other countries, the news will report the temperature on the
Celsius scale.
The Celsius Scale - The Celsius scale, is
commonly used for scientific work. The thermometers that we use in our laboratory
are marked with the Celsius scale. The Celsius scale is also called the Centigrade
scale because it was designed in such a way that there are 100 units or degrees between
the freezing point and boiling point of water. One of the limitations of the Celsius
scale is that negative temperatures are very common. Since we know that temperature
is a measure of the kinetic energy of molecules, this would almost suggest that it is
possible to have less than zero energy. This is why the Kelvin scale was
necessary.
The Kelvin Scale - The International System of
Measurements (SI) uses the Kelvin scale for measuring temperature. This scale makes
more sense in light of the way that temperature is defined. The Kelvin scale is
based on the concept of absolute zero, the theoretical temperature at
which molecules would have zero kinetic energy. Absolute zero, which is about
-273.15 oC, is set at zero on the Kelvin scale. This means that there is
no temperature lower than zero Kelvin, so there are no negative numbers on the Kelvin
scale. For certain calculations, like the gas laws, which you will be learning soon,
the Kelvin scale must be used.
There will be times when
you need to be able to convert a temperature from one scale to another. In real
life, you might be in a country where temperature is reported in Celsius and you will want
to convert that into Fahrenheit, in order to figure out if you need to wear a
sweater. In your laboratory work, you may need to change from Celsius to Kelvin in
order to calculate the volume that a gas might occupy at standard temperature and
pressure. The table below will show you the formulas that you can use to change from
one scale to another.
