Temperature (sometimes called thermodynamic temperature) is a measure of the average kinetic energy of a systems particles. Temperature is the degree of "hotness" ( or "coldness"), a measure of the heat intensity.
When two objects of different temperature are in contact, the warmer object becomes colder while the colder object becomes warmer. It means that heat flows from the warmer object to the colder one.
Degree Celsius (oC) and Degree Fahrenheit (oF)
Thermometer helps us determine how cold or how hot a substance is. Temperatures in science (and in most of the world) are measured and reported in degrees Celsius (oC). In the US, it is common to report temperature in degrees Fahrenheit (oF). On both the Celsius and Fahrenheit scales the temperature at which ice melts (water freezes) and the temperature at which water boils, are used as reference points.
- On the Celsius scale, the freezing point of water is defined as 0 oC, and the boiling point of water is defined as 100 oC.
- On the Fahrenheit scale, the water freezes at 32 oF and the water boils at 212 oF.
Thus the following formulas can be used to convert temperature between the two scales:
tF = 1.8 tC + 32 = 9/5 tC + 32 (1)
tC = 0.56(tF -32) =5/9(tF - 32) (2)
where
tC = temperature in oC
tF = temperature in o
Example - A patient with SARS (Severe Acute Respiratory Syndrome) has a temperature of 106 oF. What does this read on a Celsius thermometer?tC = 5/9 (106-32)= 41.1 oC
Degree Kelvin - K
Another scale (common in science) is Kelvin, or the Absolute Temperature Scale. On the Kelvin scale the coldest temperature possible, -273 oC, has a value of 0 Kelvin (0 K) and is called the absolute zero. Units on the Kelvin scale are called Kelvins (K) and no degree symbol is used.
Because there are no lower temperatures the Kelvin scale do not have negative numbers.
A Kelvin equal in size to a Celsius unit: 1 K= 1 oC.
To calculate a Kelvin temperature, add 273 to the Celsius temperature:
tK = tC + 273.16 (3)
Example - What is normal body temperature of 37 oC on the Kelvin scale?
tK = tC + 273.16 = 37 + 273.16 = 310.16 K
Degree Rankine - R
In the English system the absolute temperature is in degrees Rankine (R), not in Fahrenheit:
tR = tF + 459.69 (4)