The concept of temperature in everyday life At the term temperature we often attribute experiences of everyday life. Precisely because of our innate idea of ​​cold and heat, we can feel one object warmer or colder than another, even though both have the exact same temperature . This is because one material can conduct heat more easily in our fingers than another: this phenomenon is known as thermal conductivity .
The qualitative concept of temperature is therefore associated, in our daily lives, with the sensation of heat and cold, implicitly allowing us to build our own "rudimentary scale" of temperature . Sometimes the temperature measurement is based on changes in the physical properties of materials: for example, the volume of a liquid tends to increase with temperature , a metal rod to elongate and the pressure of a gas present in a system limited to grow.

What is the temperature?The temperature is a fundamental macroscopic magnitude of the International System and can be considered as the measure of ' average kinetic energy of atoms and molecules that constitute a body or a substance. It is defined as an intensive physical property of a body, that is, a property that does not depend on the size of the object under examination and which allows us to measure how hot or cold a body can be.   

The thermometer: the instrument for measuring temperature The instrument that allows us to have indications on the temperature is the thermometer : it is based on the ability of some substances (liquid, gas or solid) to expand with increasing temperature . There are various types of thermometers: the mercury thermometer , the Galileo thermometer , etc. Each thermometer must be precisely calibrated : two reference temperatures , one maximum and one minimum, are chosen , and the interval between the two is divided equally.   

The three main thermometric scales The temperature measurement depends on the thermometric scale used. The main thermometric scales are three: 

Scala Celsius or centigrade

Kelvin scale (used in SI)

Fahrenheit scale

The Celsius scale The Celsius or centigrade scale is the scale for measuring the temperature most used in our daily lives, for commercial use and often in scientific research. The creator of the Celsius scale, Anders Celsius , initially set 100 ° C as the freezing point of the water and 0 ° C as the boiling point : these assumptions were subsequently corrected and the melting ice was considered as reference temperatures , corresponding to 0 ° C, and that of boiling water , corresponding to 100 ° C, at atmospheric pressure . The interval between the two temperatures was divided into 100 equal parts, each part corresponded to a degree Celsius or Centigrade , conventionally indicated by the symbol ° C .  

The Fahrenheit scale The Fahrenheit scale is used instead, especially in the United States , Jamaica and up to 70-80 years in Anglo-Saxon countries and then be replaced by the Celsius scale . L ' unit of measure of this scale is the degree Fahrenheit , indicated with the letter ° F . The Fahrenheit scale uses as reference temperatures 32 ° F and 212 ° F to indicate, respectively, the freezing and boiling point of water at sea level, at atmospheric pressure .  
The Fahrenheit scale was originally defined by setting 0 ° F as the lowest temperature point where a mixture of water, salt and ice melted, while as the maximum temperature 96 ° F, corresponding to the blood temperature of the horses .
The use of equine blood in the evaluations of the thermometric scale was however very complicated and generated many uncertainties on the accuracy of this scale , both because of the difficulty of transporting the horses in the laboratories and because the various specimens could have different blood temperatures . Based on these considerations, it was decided to set the temperatures as reference pointsfreezing and boiling of the water, thus avoiding any errors. The decision to use only water temperatures , in the range between 212 ° F and 32 ° F, allowed the division of the scale into 180 degrees Fahrenheit.  

How to convert degrees Fahrenheit to degrees Celsius To understand the value of the temperature considered, expressed in degrees Fahrenheit, it is often customary to convert it to degrees Celsius, the unit of measurement most used in our country, applying a simple mathematical formula :
t ( ° C) = (t (° F) - 32) / 1.8