Difference Between Specific Heat And Molar Specific Heat

Edited by Diffzy | Updated on: September 05, 2022

       

Difference Between Specific Heat And Molar Specific Heat Difference Between Specific Heat And Molar Specific Heat

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Introduction

Heat capacity is a substance's ratio of heat absorbed to temperature change. Calories per degree are commonly used to express the actual amount of material being considered, which is typically a mole (the molecular weight in grams). Specific heat is the heat capacity expressed in calories per gram. One calorie per degree Celsius is the unit of measurement for the calorie, which is based on the specific heat of the water. Most elements' heat capacity per atom tends to be the same at sufficiently high temperatures. This estimate is already accurate for heavier metals at room temperature, giving birth to the Dulong and Petit law.

For other materials, variations in the energy levels of the atoms determine heat capacity and its temperature change (available quantum states). When the third law of thermodynamics was developed, it became necessary to measure heat capacities to determine the entropies of different materials. Heat capacities are measured using a variety of calorimeters. The most popular materials for sensitive thermometers are those with low specific heat. Materials having a high specific heat are used to create heat storage compounds. Heat exchange processes also lead to natural phenomena like the sea and land wind. Both molar-specific heat and specific heat have a wide range of uses.

Specific Heat Vs. Molar Specific Heat

The primary distinction between specific heat and molar-specific heat is that. In contrast, the former refers to a substance's heat capacity at a given mass, the latter relates to a substance's heat capacity at a certain molecular weight. Additionally, although molar-specific heat is independent of the substance's phase in the system, specific heat relies on it. Because it is the heat capacity of a material of unit mass that is independent of the substance's mass, specific heat is considered to be an intense attribute. For example, sand and metals often have low specific heats, which causes them to heat up fast. Contrarily, water has a very high specific heat, which makes it take a long time for temperatures to rise even slightly.

Because it is the heat capacity of a material with a mass of one mole, molar-specific heat is regarded as a broad attribute. Once more, there are two different forms of molar-specific heat. Gasses have a two-molar specific heat capacity. It is often expressed in cm and has the metric unit J•kg-1•mol-1. Take equal parts of water and oil, and heat them to a temperature of around 30 °C. Heat each one until it reaches a temperature of 50 °C. We can see that the water temperature rises to 50°C more slowly than oil. It suggests that raising the temperature of water takes more heat energy than oil does.

According to observations, the quantity of energy needed to raise the temperature of a particular body is known as specific heat capacity. A material's specific heat capacity is the amount of heat energy required to raise the temperature of one mole of that material. In other terms, the quantity of heat needed to increase the temperature of a single gram of a substance by one degree Celsius is known as the molar-specific heat capacity.

Difference Between Specific Heat And Molar Specific Heat in Tabular Form

Table: Specific Heat Vs. Molar Specific Heat
Parameters Of Comparison
Specific Heat
Molar Specific Heat
Description
The amount of heat energy needed by a material of a given mass to raise its temperature by one degree Celsius is known as specific heat (or 1K).
It is the heat energy needed for one mole of the material to raise its temperature by one degree Celsius (or 1K).
S.I. Unit
J•kg-1•K-1.
The molar-specific heat is written as J•K-1•mol-1 in S.I. units.
Method
Q = MCT is the equation for specific heat.
Molar-specific heat is calculated using the formula cM = q/nT.
indicated by
The symbol for it is c.
The symbol for it is cm.
Factors that affect it
Three things determine a substance's specific heat:
  • Temperature variation
  • The system's substance's nature
  • The substance's state within the body.
The following three variables affect a substance's molar-specific heat:
  • The substance's temperature
  • Description of the material
  • circumstances for applying heat.

What Is Specific Heat?

The heat needed to increase a substance's temperature by one degree Celsius in one gram is known as specific heat. Typically, calories or joules per gram per degree Celsius are used as the units of specific heat. The Scottish scientist Joseph Black developed the notion of specific heat in the 18th century because of his discovery that equal weights of various substances required varying quantities of heat to elevate them through the same temperature range. Early 19th-century French scientists Pierre-Louis Dulong and Alexis-Thérèse Petit proved that calculating a substance's atomic weight is possible by measuring its specific heat.

Specific Heat Capacity

The specific heat capacity of a substance is the amount of heat energy required to raise the temperature of 1 kilogramme of that substance by 1 Kelvin, or 1 °C.

We are aware of-

ΔQ = mSΔT

Thus, the following is how specific heat capacity is expressed:

S = ΔQ/ mΔT

Where,

The Specific Heat Capacity is abbreviated as S.

Q is the quantity of heat energy, and m is the substance's mass.

T stands for temperature change.

Both the heat capacity and the specific heat capacity are positive constants. J kg K1 is the S.I. unit for Specific Heat Capacity. J/kg°C and J/g°C are the S.I. units that express specific heat capacity in degrees Celsius.

Three characteristics of a material affect its specific heat capacity.

  • The substance's weight
  • The substance's temperature changing
  • Nature of the Substance's Material

The Significance of Specific Heat Capacity

Knowing how long a specific material will take to heat up or cool down is crucial. The specific heat capacity may be used to study the material's energy required, duration, expenses, and temperature change. The object's temperature with a lower specific heat capacity will rise quicker when two objects of the same mass are heated at the same rates.

The temperature of the object with a smaller Specific Heat capacity will decrease more quickly when two objects of the same mass are cooled at the same pace.

Important Considerations For Specific Heat Capacity

  • A substance's specific heat capacity is the amount of heat energy required to increase the temperature of 1 kilogramme of that substance by 1 Kelvin, or 1 °C.
  • Heat capacity is the term used to describe t
  • he change in temperature of a substance for a given amount of heat.
  • The molar-specific heat capacity
  •  is the amount of heat energy required to raise the temperature of one mole of a substance.
  • The specific heat produced by heating a solid substance at constant pressure is known as the molar-specific heat capacity. Cp indicates it.
  • The specific heat produced by heating a solid substance at constant volume is known as molar-specific heat capacity at Constant Volume. Cv indicates it.
  • The correlation between Molar Specific Heat
  • Cp - Cv = nR can be used to express the relationship between molten specific heat capacity at constant volume and molten specific heat capacity at constant pressure.

What Is Molar Specific Heat?

Increase the temperature of a material in a mole. The quantity of heat in joules needed to elevate one mole of a material by one Kelvin is known as the molar heat capacity in S.I. units (symbol: in).cn is equal to Q/T, where Q is heat and T is the temperature change. The majority of the time, heat capacity is listed as an intrinsic quality, which means it is a feature of a certain substance. A calorimeter is used to calculate heat capacity. The calculations are performed at constant volume in a bomb calorimeter. Coffee cup calorimeters are suitable for determining the heat capacity under constant pressure.

The Molar Specific Heat Capacity is denoted by:

C = S / μ

C = Q / (μ ΔT)

Q = µ C T.

Here,

What does C stand for when referring to a mol?

The amount of heat energy is Q.

ΔT stands for temperature change.

μ is moles of solid.

  • The amount of heat required to raise the temperature of 1 mole of a material by 1 Kelvin is known as its molar heat capacity.
  • Since the joule is the molar heat capacity's equivalent in the S.I., it is measured in units of J/molK.
  • Specific heat capacity per unit mass is known as molar heat capacity.

Molar Heat Capacity Units

The units used to indicate molar heat capacity are J/K/mol or J/molK, where J stands for joules, K for Kelvin, and m for the number of moles. The value is predicated on no phase shifts. Usually, you'll start with the molar mass value, which is expressed in kilograms per mole (kg/mol). The kilogram-Calorie (Cal) or its cgs equivalent, the gram-calorie, are less often used heat units (cal). Rankine or Fahrenheit temperatures can also be used to represent heat capacity in units of pound-mass.

Molar Specific Heat Capacity: Different Types

We do not define the phase shift when the substances are heated; instead, we merely take into account the quantity of energy that will be added or taken away because of the absence of a temperature shift during the phase change.

The two forms of molar-specific heat capacity are as follows:

  1. Molar-specific heat capacity at Constant Pressure: This term refers to the amount of specific heat that can be transferred when a solid material is heated at a constant pressure. Cp designates it.
  2. Molar-specific heat capacity at Constant Volume is the term used to describe the amount of specific heat that can be transferred when a solid is heated at a constant volume. Cv is the indicator.

Specific heat has an endless range of values because of diverse elements and circumstances. To produce a constant specific heat value, the gas must be supplied with a constant heat source. Therefore, volume, evaporation, and pressure conditions must be taken into account.

For a perfect gas:

nR = Cp - Cv

Where,

Molar-specific heat capacity at constant pressure is denoted by Cp.

Molar-specific heat capacity at constant volume is denoted by Cv.

n is the substance's quantity.

R = 8.3144598 is the molar gas constant.

Main Difference Between Specific Heat And Molar Specific Heat in Points

  • The amount of heat energy required by a material of a given mass to raise its temperature by one degree Celsius is known as specific heat (or 1K). However, molar-specific heat is the amount of heat energy required for one mole of material to raise its temperature by one degree Celsius (or 1K).
  • The symbol for specific heat is c. On the other hand, cm stands for molar-specific heat.
  • Q = MCT is the equation for specific heat. While cm = q/nT is the equation for molar-specific heat.
  • J•kg-1•K-1 is the S.I. unit for specific heat, whereas J•K-1•mol-1 is the S.I. unit for molar-specific heat.
  • A substance's specific heat is dependent on temperature variation, the type of material present in the system, and the phase the substance is in. On the other hand, a substance's molar-specific heat is influenced by its temperature, composition, and the circumstances in which heat is applied.
  • The related phrase specific heat capacity refers to the heat capacity per unit mass, whereas molar heat capacity refers to the heat capacity per mole. Specific heat is another name for specific heat capacity. Sometimes volumetric heat capacity is used in engineering calculations instead of specific heat based on mass.
  • The International Standards of measurement advice include a mass unit in the calculation for "specific heat." 75.32 J/mol K is the molar-specific heat capacity of water. The molar-specific heat capacity of copper is 24.78 J/mol K.
  • The heat capacity of a substance is defined as the amount of heat required to raise its temperature by 1 kg to 1 K. The molar heat capacity of a substance is defined as the amount of heat required to elevate 1 mole of that substance's temperature to 1 k.

Conclusion

By using calorimetry, which is the act of measuring heat exchange in various processes, one may determine the specific heat and molar-specific heat of substances. A calorimeter is employed to assess how much heat is being exchanged. Calvet-type calorimeters, reaction calorimeters, bomb calorimeters, adiabatic and droperidol calorimeters, etc., are only a few examples of the many calorimeters available. The calorimeter that is employed is typically well-insulated. The major purpose of this is to stop any heat transfer from the environment to the calorimeter. The calorimetric readings are recognized and approved all throughout the world.

References

  • https://www.thoughtco.com/definition-of-molar-heat-capacity-and-examples-605362#:~:text=Molar%20heat%20capacity%20or%20molar,of%20a%20substance%201%20Kelvin.

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