Profile
Settings
Refer your friends
Sign out
When it comes to heat, thermodynamics is concerned in its whole. Heating means energy in transit nowadays, according to the dictionary definition. The heat was once thought to be the measure of an invisible fluid, caloric, that could be found in any matter prior to the understanding of thermodynamic rules. The ability of a substance to retain this fluid was referred to as the heat capacity of that substance at the time of its discovery. As thermodynamics progressed and the relationship between heat transfer and temperature became more clear, the definition of heat shifted accordingly.
Modern thermodynamics defines heat as a measure of a system’s total internal energy, which is measured in degrees Celsius. For the purpose of quantifying both the thermal energy associated with matter and its dependency on temperature, two characteristics were established. Specific heat capacity and heat capacity of the system were the names given to these characteristics.
Formula for Heat Capacity
- Heat energy is a measure of a system’s total internal energy, which is measured in joules. This contains both the overall kinetic energy of the system as well as the potential energy of the individual molecules in the system.
- It has been demonstrated that the internal energy of a system can be modified either by delivering heat energy to it or by doing work on it, respectively.
- It has been discovered that the internal energy of a system increases as the temperature of the system rises. Internal energy increases as a function of temperature differences, the amount of matter present, and other factors.
- The amount of heat energy necessary to raise the temperature of a given quantity of matter by one degree Celsius is defined as the heat capacity of the stuff in question.
- The heat capacity of a given matter is dependent on the size or quantity of the matter, and as a result, it is an extensive attribute. The unit of heat capacity is the joule per Kelvin or the joule per degree Celsius, depending on the temperature.
Mathematically,
Q=CΔT
Where Q is the amount of heat energy required to cause a temperature change of t and C is the amount of heat capacity available in the system under consideration.
Specific Heat Capacity
Specific Heat Capacity is a measure of how much heat may be produced in a given amount of time.
For thermodynamic investigations, scientists need a quantity that was independent of the quantity or size of the matter under examination, which led them to develop the concept of specific heat capacity (SHC). It is referred to as an intense attribute since it is independent of the quantity or size of the stuff being studied or measured. When it comes to any substance or matter, the specific heat capacity can be described as the amount of heat energy required to raise the temperature of a unit mass of that substance or matter by one degree Fahrenheit. The following is how it is expressed mathematically:
Q= m c ΔT is the product of two variables.
Amount of heat energy necessary to change the temperature of a substance by one degree Celsius is denoted by Q, while specific heat capacity of the system is denoted by s.
Thermodynamics continues to play a significant role in our lives, whether directly or indirectly through the use of heat. In order to create novel processes for reactions that have high efficiency and product yield, scientists and engineers apply the rules of thermodynamics. The concepts of thermodynamics are applied by chemical and mechanical engineers in the design of heat engines that have high efficiency and provide higher output.
What is the difference between Heat Capacity C, Cp, and Cv?
Molar Heat Capacity
is defined as the amount of heat that a molecule can hold (C)
The molar heat capacity (C) of a substance is defined as the entire amount of energy in the form of heat required to raise the temperature of one mole of that substance by one unit. It also has a substantial impact on the nature, size, and content of a material in a system, among other factors.
q = n C ∆T
Where,
q is the amount of heat that must be supplied or required to cause a change in temperature (T) in one mole of any given substance.
n is the molecular weight of the substance,
The constant C is referred to as the molar heat capacity of the substance’s body, and it is defined as
Cp
At constant pressure and temperature, Cp is the quantity of heat energy emitted or absorbed by a unit mass of a substance in response to a change in temperature in a closed system. In other words, when under constant pressure, it is the transfer of heat energy between a system and its surroundings that is being measured. As a result, when the pressure is constant, Cp indicates the molar heat capacity, C. The change in temperature of a system will always result in a change in the enthalpy of the system being affected.
The amount of heat energy absorbed or released by a system is measured in enthalpy (H). Furthermore, enthalpy change occurs when a substance undergoes a phase transition or changes its state.
For example, when a solid turns into a liquid form (for example, when ice melts into water), the enthalpy change is referred to as the heat of fusion (or heat of fusion). Heat vaporisation is the term used to describe the enthalpy shift that occurs when a liquid transitions to its gaseous state (for example, the transformation of water into water vapour).
Cv
When a slight change in the temperature of a substance occurs, Cv is the quantity of heat energy absorbed or released per unit mass of the substance where the volume of the substance does not change. In other words, Cv is the heat energy transfer between a system and its surroundings that occurs without a change in the volume of the system being considered. When the volume is constant, the molar heat capacity C is represented by the symbol Cv. As long as the volume of a substance remains constant, the change in volume is equal to zero, and the change in volume is equal to zero.
Conclusion
We can explain the reason for the high specific heat of water by referring to the hydrogen bonds that exist between water molecules. The molecules must vibrate in order to raise the temperature of the water, which is due to the large number of hydrogen bonds that have been formed. A greater amount of energy is required to cause the water molecules to break apart by vibrating them as a result of the enormous number of hydrogen bonds present.
In a similar vein, it takes some time for hot water to cool down. Thermal radiation causes the temperature to drop and the vibrational activity of water molecules to slow down when heat is radiated away. The heat that is emitted counteracts the chilling effect of the heat loss from the liquid water by providing an equal amount of heat.
