Specific Heat Capacity – Class 11 | Chapter – 12 | Physics Short Notes Series PDF for NEET & JEE

Specific Heat Capacity: Specific heat is the amount of heat energy required to raise the temperature of a unit mass of a substance by one degree Celsius (or one Kelvin). It is typically expressed in units of joules per kilogram per degree Celsius (J/kg·°C) or calories per gram per degree Celsius (cal/g·°C). The SI unit of specific heat and specific heat capacity is J/Kg.

The specific heat capacity of a substance depends on its molecular structure, phase (solid, liquid, or gas), and temperature. Some substances have a higher specific heat capacity than others, meaning that they require more energy to raise their temperature by a certain amount. This property is important in many areas of science and engineering, such as thermodynamics, materials science, and environmental science.

Types of Specific Heat Capacity

There are two types of specific heat:

• 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 at constant volume.
• 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 at constant pressure.

Thermal Capacity

Thermal capacity is the amount of heat energy required to raise the temperature of an object by a certain amount. The formula for thermal capacity is:

Q = C × ΔT

where Q is the amount of heat energy required, C is the thermal capacity of the object, and ΔT is the change in temperature of the object.

The thermal capacity of an object depends on its mass and its specific heat capacity. The 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), as explained in the previous answer.

So, the formula for thermal capacity can also be written as:

C = Q / ΔT

where C is the thermal capacity, Q is the amount of heat energy required, and ΔT is the change in temperature.

Note that the units of thermal capacity depend on the units used for heat energy and temperature. In the SI system, the units for thermal capacity are joules per degree Celsius (J/°C) or joules per Kelvin (J/K).

Molar Heat Capacity

Molar heat capacity is the amount of heat energy required to raise the temperature of one mole of a substance by one degree Celsius (or one Kelvin). It is typically denoted by the symbol Cm and has units of joules per mole per degree Celsius (J/mol·°C) or calories per mole per degree Celsius (cal/mol·°C).

The molar heat capacity can be calculated by dividing the heat capacity of a substance (in joules or calories per degree Celsius) by the number of moles of the substance present. Therefore, the formula for molar heat capacity is:

Cm = C / n

where C is the heat capacity of the substance, n is the number of moles of the substance present.

The molar heat capacity of a substance depends on its specific heat capacity and molecular weight. It is useful in thermodynamics and in the study of chemical reactions, as it allows us to calculate the amount of heat energy required or released during a reaction based on the number of moles of reactants and products involved.

It is important to note that the molar heat capacity can vary with temperature and pressure, especially for gases, due to changes in the specific heat capacity and the behavior of the gas molecules.

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