Difference Between Specific Heat and Thermal Conductivity

Edited by Diffzy | Updated on: April 30, 2023

       

Difference Between Specific Heat and Thermal Conductivity

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Whenever we are reading about science or other related subjects, we should be curious about the different topics that we come across. It’s very important to pay attention to the different specific details of the several topics. The more knowledge we gain, the broader our mindset becomes. And, this quality even enhances our personality as a person.

As we all very well know that Effective reading skills require us to be more focused and dedicated while we’re studying any topic. Without having enough concentration, it would be very difficult to understand things about the topic that we might be reading. Thus, whenever we read something, it becomes an obligation on us that we will be knowing everything about that particular topic. In order to maintain that expectation that our elders have from us, we should be very determined to learn and grow as a student and as a learner as well. This will make our teachers, mentors, professors, parents and everyone else happy and they’ll feel proud of us as well.

Thus, today we’ll be discussing about two topics, namely, the specific heat and the thermal conductivity. We’ll try to look for the differentiating points between the two and a lot more.

Specific Heat vs Thermal Energy

The phrase "specific heat" refers to the entire amount of heat energy required to raise the temperature of one unit of any substance by one degree Celsius. Thermal conductivity, on the other hand, refers to a material's ability to transfer or conduct heat energy.

Difference Between Specific Heat and Thermal Conductivity in Tabular Form

Parameters of Comparison Specific Heat  Thermal Conductivity
The Definition The total amount of heat energy required by one unit of any substance to raise its temperature by one degree Celsius is referred to as specific heat. Basically, the ability of a substance to move heat energy across it is referred to as thermal conductivity.
The abbreviations cp or s are common abbreviations for specific heat. K stands for thermal conductivity.
The Units Used Calories or joules per gram per degree Celsius or Kelvin (J/(kg K) or J/(kg °C)) are the most used units of measurement for specific heat. Thermal conductivity is measured in watts per meter kelvin (W/(mK)).
The Influencing Factors A substance's specific heat is determined by its nature and phase. The temperature and the direction of heat transport are the most important factors in thermal conductivity.
 The Applications Cookware such as kettles and frying pans are made of materials with low specific heat capacity. Low thermal conductivity materials are utilized as thermal insulators, while high thermal conductivity materials are employed as heat sinks (Difference Between Specific Heat and Thermal Conductivity (With Table), n.d.).

What is Specific Heat?

The amount of heat required to increase the temperature of one gram of a substance by one Celsius degree is known as specific heat. Calories or joules per gram per Celsius degree are commonly used as units of specific heat. Water, for example, has a specific heat of 1 calorie (or 4.186 joules) per gram per degree Celsius. In the 18th century, Scottish scientist Joseph Black noted that equivalent masses of different substances required varying quantities of heat to elevate them across the same temperature gap, and he developed the idea of specific heat from this finding.

The French scientists Pierre-Louis Dulong and Alexis-Thérèse Petit proved in the early nineteenth century that measuring the specific temperatures of substances allows for the computation of their atomic weights (specific heat, n.d.).

Heat energy is injected into a substance, which, in addition to rising its temperature, usually produces an increase in its volume and/or pressure, depending on how the sample is contained. Even for the identical starting pressure p and starting temperature T, the choice made about the latter has an impact on the measured specific heat capacity. There are two options that are frequently used:

  • When the pressure is kept constant (for example, at atmospheric pressure) and the sample is allowed to expand, the force from the pressure displaces the enclosure or the surrounding fluid, generating work. That work must be fuelled by the heat energy available. The specific heat capacity acquired in this way is said to be measured at constant pressure (or isobaric), and is typically denoted as cp.
  • If the expansion is prevented actually— for example, by a sufficiently rigid enclosure or by increasing the external pressure to counteract the internal one — no work is produced, and the heat energy that would have gone into it must instead contribute to the sample's internal energy, which may include raising its temperature by a significant amount. The specific heat capacity acquired in this manner is said to be measured at constant volume (or isochoric) and is represented by cv.
  • Usually, the value of cv is less than the value of cp. This disparity is especially noticeable in gases, where constant pressure values are typically 30% to 66.7 percent higher than constant volume values. As a result, the heat capacity ratio of gases is typically 1.3 to 1.67.

Applicability

For gases, liquids, and solids with a reasonably general composition and molecular structure, the specific heat capacity can be defined and measured. Gas mixtures, solutions, and alloys, as well as heterogeneous materials like milk, sand, granite, and concrete, can all be examined on a vast scale.

As long when the changes are reversible and gradual, the specific heat capacity can be established for materials that change state or composition as temperature and pressure vary. For example, the ideas can be defined for a gas or liquid that dissociates as the temperature rises, as long as the dissociation products recombine quickly and completely when the temperature falls.

If the substance, for example, suffers irreversible chemical changes or a phase transition, such as melting or boiling, at a sharp temperature within the measurement's range of temperatures, the specific heat capacity is meaningless.

Measurement

A substance's specific heat capacity is normally measured by measuring the heat capacity of a sample of the substance, for example, with a calorimeter, and then dividing it by the mass of the sample. The heat capacity of a substance can be estimated using a variety of methods, including fast differential scanning calorimetry.

By confining the sample in a hard container, the specific heat capacity of gases can be determined at a constant volume. For liquids and solids, however, determining the specific heat capacity at constant volume can be prohibitively difficult, as it sometimes necessitates unreasonable pressures to avoid the expansion produced by even slight temperature increases.

Instead, it's more common to measure the specific heat capacity at constant pressure (allowing the material to expand and contract as it pleases), determine the material's coefficient of thermal expansion and compressibility separately, and then compute the specific heat capacity at constant volume using these data and thermodynamic laws (Specific heat capacity, n.d.).

What is Thermal Conductivity?

Thermal conduction is the transfer of energy across a temperature gradient due to random molecule motion. It differs from energy transport by convection and molecular work in that it does not include macroscopic flows or internal tensions that do work.

Thermal conduction energy flow is classed as heat, and the heat flux at position and time t is quantified by the vector q(r,t). Heat moves from a high to a low temperature, according to the second rule of thermodynamics. As a result, it's plausible to assume that is proportional to the temperature field's gradient.

Working in terms of values that are derivatives of thermal conductivity and implicitly take into account design-specific factors such as component dimensions is typical in engineering practise. Basically, the inverse of thermal conductivity is actually thermal resistance. Because thermal resistances are cumulative when occurring in sequence, it is a suitable parameter to utilise in multicomponent design. The heat transfer coefficient is actually a measurement of the amount of heat that transfers per unit time across a unit area of a plate of a given thickness when the temperature difference between its opposite faces is one kelvin.

In the sense that the material admits heat to flow, the heat transfer coefficient is also known as thermal admittance. Thermal transmittance is a word that describes a structure's thermal conductivity as well as heat transmission via convection and radiation. It is sometimes referred to as composite thermal conductance because it is measured in the same units as thermal conductance.

Measurement

There are various methods in order to determine thermal conductivity, each of which is appropriate for a specific set of materials. In general, measurement techniques are actually divided into two categories: steady-state and transient. the Transient procedures act on the instantaneous state of a system on the approach to steady-state, whereas steady-state techniques infer the thermal conductivity from data on the state of material once a steady-state temperature profile has been established.

Because steady-state approaches do not have an obvious time component, they do not necessitate complex signal analysis (steady-state implies constant signals). The downside is that a well-engineered experimental apparatus is normally necessary, and the time it takes to reach steady-state prevents quick measurements.

Fluid thermal properties are more difficult to investigate experimentally than solid thermal properties. This is because, in addition to thermal conduction, convective and radiative energy movement are also common unless precautions are made to prevent them. The creation of an insulating boundary layer can also cause a visible decrease in heat conductivity.

Basically, the thermal conductivities of typical materials range from four to eight orders of magnitude. Pure metals actually have a high thermal conductivity, whereas the gases have a low thermal conductivity. Copper, for example, has a heat conductivity of 10000 times that of air under typical conditions.

Main Differences Between Specific Heat and Thermal Conductivity (In Points)

Now let’s see the main points of differences between specific heat and thermal conductivity.

  • Basically, the electrons are responsible for electric and thermal conductivity, on the other hand, ion oscillations are responsible for the majority of specific heat (phonons).
  • Aluminium will be able to store more thermal energy than Iron (Are specific heat and thermal conductivity related?, n.d.).
  • Thermal conductivity is actually a measurement of how well a substance conducts heat from one end to the other via conduction. The higher the thermal conductivity value, the easier it is to transport heat.
  • The specific heat capacity of a substance is actually the measurement of how much heat it absorbs as its temperature rises gradually. Hence, the higher the specific heat, the more heat is absorbed by the substance.
  • Heat will travel faster and in greater proportion through a medium with higher thermal conductivity and lower specific heat. This is usually the case with good heat conductors, such as metals.
  • In reality, Heat will travel slower and in smaller proportion through a medium with a lower thermal conductivity and a greater specific heat. This is actually the case that happens frequently with poor heat conductors such as insulators, particularly ceramic-type insulators.

Conclusion

Thus, to conclude, it can be said that both specific heat and thermal conductivity, have their own pros and cons. Each is important and has its own applications and usability. The conceptual understanding of each topic becomes very necessary for gaining more knowledge and becoming intellectual and smart. It’s important to read thoroughly about their definitions, their measurement, the abbreviations that are used, the units that are used, their influencing factors, and so on. Moreover, it’s very vital to understand the key differentiating points between specific heat and thermal conductivity. Actually, it requires extra time to read and learn about such topics in detail. And, it becomes our duty to take out that extra time from our busy schedules. Then only, does the true sense of knowledge and understanding will get imbibed into our brains. This will not only enhance our brain’s capacity to grasp more things easily, but also, it’ll show that we take studies and knowledge seriously for our growth and professional success. Therefore, keep reading scientific topics, and keep learning more and more.

References

  • Are specific heat and thermal conductivity related? (n.d.). Retrieved from PHYSICS: https://physics.stackexchange.com/questions/16255/are-specific-heat-and-thermal-conductivity-related#:~:text=However%20specific%20heat%20is%20not%20directly%20related.%20This,contribute%20almost%20nothing%20for%20specific%20heat%20in%20metals.
  • specific heat. (n.d.). Retrieved from Britannica : https://www.britannica.com/science/specific-heat
  • Specific heat capacity. (n.d.). Retrieved from WIKIPEDIA: https://en.wikipedia.org/wiki/Specific_heat_capacity

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"Difference Between Specific Heat and Thermal Conductivity." Diffzy.com, 2024. Mon. 17 Jun. 2024. <https://www.diffzy.com/article/difference-between-specific-heat-and-thermal-conductivity-475>.



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