Specific Heat of Constant Pressure

What is Specific Heat Capacity?

The Universe is made of matter and electricity. The matter is made up of atoms and molecules (groupings of atoms) and energy causes atoms and molecules to always be in motion-either to bump into each other or to vibrate back and forth. The motion of atoms and molecules produces a source of energy called heat or thermal energy that is present in all matter. Even in the coldest space voids, the matter still has a very small but still measurable amount of heat energy.

Energy can take several forms and can change from one form to another. There are several different forms of energy that can be converted to heat energy. Light, electrical, mechanical, chemical, nuclear, sound, and thermal energy itself may cause a material to heat up by increasing the speed of its molecules. So, put the energy in the system, and it's heated, take the energy away, and it's cool. For example, when we're cold, we can jump up and down to get warmer.

With the help of examples, let's understand the definition of unique heat power. Take the same amount, say 1 liter, of three liquids. Wind, Mustard Oil, Mercury. The definition of real heat is related to the thermal properties of the body. Let's heat these three liquids using the same stove, maintaining the same conditions in all three experiments. Liquids are at room temperatures of 20oC and need to be taken to 60oC. Will the three samples take the same amount of time?

The chances are close to none of them. During the experiment, you will notice that in order to undergo the same temperature rise, under the same conditions, all three liquids take different times. Mercury is heated the fastest, followed by Mustard Oil, followed by Water. This property is measured by the capacity of the heat. The heat power represents a change in the temperature of the sample for a given amount of heat. The maximum heat in the SI Units is joule per kelvin (J kg-1). Specific Heat Capacity, which is different from the Heat Capacity, represents the amount of heat needed to increase the temperature of the unit mass of the substance by 1oC. The specific thermal formula is -

 S ( HeatCapacity)  = Q / ΔT     s = S / m=1/ m . Q / ΔT

The specific thermal capacity differs from the heat capacity only because the specific thermal capacity is the mass of the body and is, therefore, more specific and accurate than the thermal capacity. The SI unit of special heat is Joule per kelvin per kg (J kg-1 K-1). It is important to note that the specific thermal capacity of the water is 4,186 joule / gram oC, which is higher than any other common substance. As a result, water plays an enormous role in temperature control and, as a result, in weather conditions. If from the point of view of moles, the specific thermal capacity is considered, and not the mass, it becomes the molar specific thermal capacity of the substance. The molar specific thermal formula is -

 C =Sμ =1μ Q / ΔT

Here, the m represents the number of moles of the substance and the SI unit of the molar specific thermal capacity is J mol-1 K-1. One thing we need to know here is that none of the relationships discussed above apply in the event of a change in phase because the heat added or removed during a change in phase does not change the temperature. There is a great need to be precise. The molar's specific heat capacity is not accurate enough. One of the factors we did not consider while heating the sample was whether to leave the top open for evaporation or to keep it under constant pressure. Doing one of them will definitely change the results of the experiment. To counter this, scientists have subdivided basic heat efficiency into two classes. 


Molar Specific Heat Capacity at Constant Pressure: If the heat transfer to the sample is carried out when it is held at constant pressure, the specific heat obtained using this method is called the Molar Specific Heat Capacity at Constant Pressure. 


Molar Specific Heat Capacity at Constant Volume: If the heat transfer to the sample is achieved while the volume of the sample is kept constant, the actual heat obtained using this process is called the Molar Specific Heat Capacity at Constant Volume.

FAQ (Frequently Asked Questions)

Q1: Why Specific Heat of a Gas at Constant Pressure is always Greater than the Specific Heat of a Gas at Constant Volume?

CP is higher than CV because when the gas is heated at constant volume, no external work is done and the heat supplied is consumed only by increasing the internal energy of the gas. Yet if the gas is heated at constant pressure, the gas will expand against the external pressure, and some additional work will be performed. In this case, the heat is used to increase the internal energy of the gas and to perform some external work.

Since the internal energy depends only on the temperature, the internal energy of the gas mass will increase by the same amount, whether the pressure or volume remains constant, at the same temperature increase. But since external work is additionally done at constant pressure than at constant volume to produce the same increase in gas temperature.

Q2. What is the Specific Heat at Constant Volume?

Ans: Specific heat is the amount of energy required to increase the temperature of the object by one degree K per unit mass. It's not that simple, though. How much energy is needed depends on the conditions. In particular, is the volume of the object kept constant while heating, or is the pressure on the object kept constant? The specific heat of the object will be different in either case. The former is called the specific heat at constant volume, Cv, whereas the latter is called the specific heat at constant pressure, Cp. The distinction occurs because, at constant pressure, the object does not work on the surroundings when being heated, while for Cp, the object does work on the surroundings.