## Specific Heat Capacity – Class 11 | Chapter – 13 | Physics Short Notes Series PDF for NEET & JEE

Specific Heat Capacity: Specific heat capacity is the amount of heat energy required to raise the temperature of a unit mass of a substance by one degree Celsius or Kelvin. It is a physical property of a material that reflects how much energy is required to change its temperature. The specific heat capacity is usually denoted by the symbol “c” and has units of J/(kg·K) in SI units.

The specific heat capacity of a material depends on several factors, such as its molecular structure, density, and temperature. Different materials have different specific heat capacities, and the value can vary depending on the conditions under which the material is measured. Some common examples of specific heat capacities for different materials are:

• Water: 4.18 J/(g·K)
• Copper: 0.385 J/(g·K)
• Iron: 0.449 J/(g·K)
• Aluminum: 0.902 J/(g·K)

## Types of Specific Heat Capacity

There are two types of specific heat capacity:

• Specific Heat Capacity at Constant Volume (Cv): This is the amount of heat energy required to raise the temperature of a unit mass of a substance by one degree Celsius or Kelvin while keeping its volume constant. At constant volume, the substance cannot do any external work, and all the heat energy supplied is used to increase the internal energy of the substance. The symbol for specific heat capacity at constant volume is “Cv”.
• Specific Heat Capacity at Constant Pressure (Cp): This is the amount of heat energy required to raise the temperature of a unit mass of a substance by one degree Celsius or Kelvin while keeping its pressure constant. At constant pressure, the substance can do external work, such as expanding against a piston, in addition to increasing its internal energy. The symbol for specific heat capacity at constant pressure is “Cp”.

The value of Cp is always greater than Cv because at constant pressure, some of the heat energy supplied is used to do external work. The difference between Cp and Cv is given by the gas constant “R”, which is a constant that depends on the molecular structure of the substance. For an ideal gas, the difference between Cp and Cv is equal to the gas constant “R”.

## Formula of Specific Heat Capacity

The formula for specific heat capacity (c) is:

c = Q / (m * ΔT)

where:

• Q is the amount of heat energy transferred to or from the substance
• m is the mass of the substance
• ΔT is the change in temperature of the substance

This formula shows that specific heat capacity is the ratio of the heat energy transferred to or from a substance to the change in temperature of the substance and the mass of the substance.

The SI unit of specific heat capacity is joules per kilogram per Kelvin (J/kg·K). However, the units of Celsius or Fahrenheit can also be used in place of Kelvin, as the temperature change is the same in all three scales.

It’s important to note that the specific heat capacity of a substance can vary depending on the conditions, such as temperature and pressure. In addition, the specific heat capacity at constant pressure (Cp) and the specific heat capacity at constant volume (Cv) are different for most substances, and this difference can be significant for gases.

## Heat Capacity

Heat capacity is a physical property of a substance that describes its ability to absorb or release thermal energy. It is defined as the amount of heat energy required to raise the temperature of a substance by one degree Celsius or Kelvin. Heat capacity is usually represented by the symbol C, and its SI unit is joules per Kelvin (J/K).

## Types of Heat Capacity

There are two types of heat capacity:

• Specific heat capacity: It is the amount of heat energy required to raise the temperature of a unit mass of a substance by one degree Celsius or Kelvin. Specific heat capacity is denoted by the symbol c, and its unit is J/(kg·K).
• Molar heat capacity: It is the amount of heat energy required to raise the temperature of one mole of a substance by one degree Celsius or Kelvin. Molar heat capacity is denoted by the symbol Cm, and its unit is J/(mol·K).

The relationship between specific heat capacity, mass, and molar heat capacity is given by the following formula:

C = m x c = n x Cm

where:

• C is the heat capacity of the substance
• m is the mass of the substance
• n is the number of moles of the substance

The heat capacity of a substance can be measured experimentally using a calorimeter, which is a device that measures the heat absorbed or released by a substance during a chemical reaction or a physical change.

Heat capacity is an important property of materials that is used in various applications, including the design of heating and cooling systems and the prediction of thermal behavior of materials.

## Formula of Heat Capacity

The formula for heat capacity (C) is:

C = Q / ΔT

where:

• Q is the amount of heat energy transferred to or from the substance
• ΔT is the change in temperature of the substance

This formula shows that heat capacity is the ratio of the heat energy transferred to or from a substance to the change in temperature of the substance.

The SI unit of heat capacity is joules per Kelvin (J/K). However, other units such as calories per degree Celsius (cal/°C) or British thermal units per degree Fahrenheit (BTU/°F) may also be used.

It is important to note that the heat capacity of a substance depends on its mass and specific heat capacity. Therefore, for a substance with a given mass, the heat capacity will increase as the specific heat capacity increases. Similarly, for a substance with a given specific heat capacity, the heat capacity will increase as the mass of the substance increases.

## Need of Specific Heat Capacity

The concept of specific heat capacity is important in thermodynamics and thermal physics because it allows us to quantify the thermal behavior of materials and to understand the transfer of heat energy between different substances.

Some of the key uses and applications of specific heat capacity are:

• Design of heating and cooling systems: Specific heat capacity is an important factor to consider when designing heating and cooling systems, such as air conditioning units or radiators. By knowing the specific heat capacity of the materials being used, engineers can determine the amount of energy required to heat or cool a room or building.
• Prediction of thermal behavior: The specific heat capacity of a material can provide information on how it will respond to changes in temperature. By measuring the specific heat capacity, researchers can predict how a material will behave when exposed to different temperatures and thermal stresses.
• Phase changes: Specific heat capacity is also important in understanding phase changes, such as the transition from solid to liquid or liquid to gas. During a phase change, the energy required to break the bonds between molecules is much greater than the energy required to raise the temperature of the substance. As a result, the specific heat capacity of a substance changes during a phase change.
• Chemical reactions: Specific heat capacity is also useful in understanding the energetics of chemical reactions. By measuring the heat released or absorbed during a reaction, researchers can calculate the specific heat capacity of the reactants and products.

In summary, the specific heat capacity of a material is an important property that allows us to understand and predict the thermal behavior of materials in a wide range of applications, from designing heating and cooling systems to studying chemical reactions and phase changes.

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### Specific Heat Capacity – Class 11 |...

Class 11 Physics Notes PDF