Measurement of Thermodynamic Properties

Here we will see how the thermodynamic property is measured. There are usually three ways to measure a thermodynamic property- "First by measuring their volume, second by measuring their temperature and third by measuring their pressure". For this, first of all we should know what is volume, temperature and pressure and how they are used to measure thermodynamic properties. 

Let's Understand About Them
VOLUME
"The amount of three dimensional space occupied by an object is called the volume of that object". It is always measured in cubic meter or cubic centimetre. It sometimes measured in litres, gallons, barrels, etc. Unit of volume is a unit of measurement for measuring volume.
         Volume is an extensive property whereas specific volume (ratio of volume to the mass of an object) or molar volume (ratio of volume to the number of moles) is an intensive property.
Here,
       V- Volume of an object
       m - Mass of an object
       n - Number of moles
       v - Specific volume/Molar volume
➛Volume is defined only for three dimensional quantities. Therefore the volume of one dimensional and two dimensional quantities (or an object) is equal to zero.
➛The volume of a container is generally the capacity of the container that is, the amount of fluid (gas or liquid) that can be held in the container, not the amount of space that the container itself displaces.
➛Volume is a state function. 
➛Volume is interrelated with the temperature and pressure.

TEMPERATURE
What happens when you keep on hitting the nail with hammer?
Yes, you are right. It will become warm
What happens when you rub your hands together? 
Yes, you are right. Your hands will become warm.
But why such things happen?
This happens because when we hit the nail with a hammer or we rub our hands, the molecules start to move fast. This increases the kinetic energy of the molecules and because of this we feel our hand warmer when they are rubbed together. In general, the warmer body possesses more kinetic energy and the colder body possesses less kinetic energy.

We have seen in the above examples that, if kinetic energy is more, then the body is warm (or hot) and if kinetic energy is less, then the body will be cold. 
Thus,
"Temperature is nothing but a measure of the average kinetic energy of the molecules or atoms in any object (or within the system )".
Or
"Temperature is a physical quantity that describes how hot or cold an object is". 
This means that temperature is a measure of the hotness and coolness of a system. It is denoted by a symbol 'T'. 
The unit of measurement of temperature is "Degree Centigrade", "Degree Rankine", "Degree Fahrenheit" and (mostly probably used temperature unit) "Kelvin".

NOTE
☛ There are four different scales to measure the temperature of a system (or any object) and these are;
• Centigrade/Celcius scale (measure in "°C")
• Kelvin scale (measure in "K")
• Fahrenheit scale ( measure in "°F")
• Rankine scale (measure in "°R")
☛ Everything is made up of atoms and molecules. Systems are also made up of these same molecules and atoms. These molecules or atoms are always swinging and bouncing within the system. Due to which they have their own kinetic energy and the average of the kinetic energy of these individual atoms or molecules is called Average kinetic energy. 
☛ THERMOMETER
It is an instrument by which the temperature of any object is measured. It actually measures the average kinetic energy of the molecules and atoms present inside the object (or within system).
Other temperature measuring instruments are;
Liquid in glass thermometer, Constant volume gas thermometer, Constant pressure gas thermometer, Thermocouple, Silicon diode, Thermistors, Bulb and capillary sensors, Pyrometers, Resistance temperature detector (RTD), etc.
☛ Conversion between temperature units;
☛ "Temperature is proportional to the average kinetic energy of individual atoms or molecules in the system". Higher the average kinetic energy of the molecules, higher will be the temperature of the system. 
☛ Temperature is a state function and an intensive property.
☛ Freezing point of water at "Celcius scale" is zero (0°C) while the boiling point/steam point of water at "Celcius scale" is 100°C. While in Fahrenheit scale, freezing point of water is 32°F and the steam/boiling point of water is 212°F.
☛ The temperature on the Celsius scale is 273.15 degrees lower than on the Kelvin scale. While the temperature on the Fahrenheit scale is 459.67 degrees lower than on the Rankine scale.

PRESSURE
In a simple way, "Pressure is defined as a force that acts on a unit area of an object". While in thermodynamics, pressure is defined as- "The pressure exerted by a fluid on a surface is equal to the normal force acting on the unit area of that surface". It is an Intensive property as well as a state function. It is denoted by a upper case letter "P". 
Pressure is usually measured in "Pascal" while other units of measurement of pressure are "N/m²", "standard atmosphere (or atm)", "kgf-m²", "mmHg", "psi", etc. 
Here,
     A is the cross-sectional area
     F is the force acting on the surface
☛ There are three types of pressure: gauge pressure, atmospheric pressure and absolute pressure. In thermodynamic calculations, absolute pressure is widely used. 
☛ Absolute pressure is equal to the sum of gauge pressure and atmospheric pressure.

Ideal Gas Law 
These three are simultaneously used in an equation know as ideal equation. This equation shows the ideal behaviour of a gas. This equation is given as,
                 ➩ [ PV ＝ nRT ]
Here, 
     P,V,T are pressure, volume & temperature
      n is the number of moles
     R is the universal gas constant or 
         proportionality constant


Hope you have found this article helpful!!
Let me know what you think about MEASUREMENT OF THERMODYNAMICS PROPERTY. Feel free to comment if you have any queries.!!

Comments

Post a Comment

Most Viewed Posts

Zeroth Law Of Thermodynamic: The Thermal Equilibrium Law

Image
In thermodynamics, we will see two types of walls. One is the Diathermic wall and the other is the adiabatic wall. Let us now go through them one by one.  • So the first is the Diathermic wall- " A Diathermic wall is a wall that allows the easy exchange of heat between two bodies (or between two systems or between system and surrounding) but does not allow the exchange of mass between them ". This means that it is a good conductor of heat. It is sometimes called as metallic wall because it is made of metal. • While the other is the adiabatic wall- " An Adiabatic wall is that wall which neither allows exchange of heat nor mass between two systems (or between system and surrounding) ". Since there is no exchange of heat and mass between the system and its surroundings, the system remains insulated from its surroundings. ➛ That's why whenever we separate the two systems by an adiabatic wall, then there is no concept of equilibrium between them. But whenever we sep...
Read more

Characteristics Of Entropy

Image
Entropy is an intrinsic property of a substance and is not affected by the external position of a system or its motion relative to other systems. It is a measure of the randomness of the system. Thus, the higher the randomness of the system, the higher the entropy of the system and the lower the randomness of the system, the lower the entropy of that system. Entropy   " Entropy is defined as a measure of the system's thermal energy that is incapable of doing work ". It is a state function.  For Example Heat is a form of energy that is incapable of doing work. Therefore, the more heat added to the system (or tranfer from the system), the higher (or the lower) will be its entropy.  The formula for change in entropy is given by the equation;                      ➩ ∆S = ∆Q/T For a reversible process, the change in entropy is given as; The Total Change In Entropy Entropy change is zero at equilibrium condition or whenev...
Read more

Reversed Carnot Cycle

Image
We have already discussed the concept of “ Carnot Cycle ”   & “ Its Efficiency ” and we have also seen the concept of “ Carnot Theorem And Its Explanation ” in our previous post. As we have already discussed that the Carnot Cycle is a reversible cycle and every process in the Carnot cycle is a reversible process. Therefore, every process of the Carnot cycle can be reversed. And the cycle can be operated in the opposite direction as well. In this article, we're interested in learning more about the reversed Carnot cycle, also known as the reversed Carnot heat engine cycle. Reversed Carnot Heat Engine It is important to note that if a reversible process is reversed, all related energy types—such as heat energy or work energy—will have the same magnitude but the direction of their interaction with matter will be changed. Let us first look at the Reverse Carnot Heat Engine  cycle here; The reversed Carnot heat engine cycle is depicted in the following figure. According to the...
Read more