What is Specific Heat?
Specific heat isthe quantity of heat required to raise the temperature of one gram of a substance by one Celsius degree. The units of specific heat are usually calories or joules per gram per Celsius degree. For example, the specific heat of water is 1 calorie (or 4.186 joules) per gram per Celsius degree.
Different materials require different amounts of energy to change temperature. The amount of energy needed depends on:
- the mass of the material
- the substance of the material (specific heat capacity)
- the desired temperature change
It takes less energy to raise the temperature of a block of aluminium by 1°C than it does to raise the same amount of water by 1°C. The amount of energy required to change the temperature of a material depends on the specific heat capacity of the material.
Specific Heat Capacity Formula:
Specific heat capacities provide a means of mathematically relating the amount of thermal energy gained (or lost) by a sample of any substance to the sample’s mass and its resulting temperature change. The relationship between these four quantities is often expressed by the following equation:
Q = C m ∆tWhere
- Q = quantity of heat absorbed by a body
- m = mass of the body
- ∆t = Rise in temperature
- C = Specific heat capacity of a substance depends on the nature of the material of the substance.
- S.I unit of specific heat isJ kg-1K-1.
What is Latent Heat?
Latent heat can be understood as energy in hidden form which is supplied or extracted to change the state of a substance without changing its temperature. It could either be from a gas to a liquid or liquid to solid and vice versa. Latent heat is related to a heat property called enthalpy.
Examples are latent heat of fusion and latent heat of vaporization involved in phase changes. The latent heat associated with melting a solid or freezing a liquid is called the heat of fusion; that associated with vaporizing a liquid or a solid or condensing a vapour is called the heat of vaporization. The latent heat is normally expressed as the amount of heat (in units of joules or calories) per mole or unit mass of the substance undergoing a change of state.
The term was introduced around 1762 by Scottish chemist Joseph Black. It is derived from the Latinlatere(to lie hidden). Black used the term in the context of calorimetry where a heat transfer caused a volume change in a body while its temperature was constant.
Specific Latent Heat
Specific latent heat is characterized as the measure of heat energy (heat, Q) that is consumed or discharged when a body experiences a steady temperature process.
The formula for specific latent heat is:
L = Q/m
Where:
L is the specific latent heat
Q is the heat retained or discharged
m is the mass of a substance
The values of latent heat are variable depending on the nature of the phase change taking place:
- The latent heat of fusion is the change from liquid to solid.
- The latent heat of vaporization is from liquid to gas.
- The latent heat of sublimation is the change from solid to gas.
Specific Heat vs Latent Heat: Key Differences
| Points of Comparison | Specific Heat | Latent Heat |
| Definition | Specific heat is the heat required for change of temperature by 1 degree for the quantity of 1gm in constant pressure. | The Latent heat is a measurement of the energy exchange which can be either absorbed or released during the process. |
| Time | It is the heat at the time of change in the temperature of the substance. | It is the heat at the time of change in the phase of the substance. |
| Temperature | In the process of specific heat temperature changes. | In the process of latent heat, no temperature change occurs. |
| Phase Change | Specific Heat is not considered in the case of phase change. | In the process of latent heat, a phase change occurs. |
| In relation to water | To change the water’s temperature by 1 degree Celsius, the amount of energy required is 4.186 J. | To change the phase of water from liquid to air, the required temperature is 100 degrees Celsius and energy respectively. |
Key Takeaways
- Specific heat is the energy required to change a unit mass of a material by 1°C. Its units is energy per unit mass per degree which is Joules per kilogram per Kelvin. The unit symbols is J/kg/K.
- Latent heat is equal to the energy required to change the state (gas, liquid, solid) of a unit mass of material. Its units which refers to energy per unit mass is Joules per kilogram. The unit symbol is J/kg.
- Latent heat is the internal energy concerning phase change and can’t be sensed. Latent heat is the energy absorbed or released by a system undergoing an isothermal process.
- Latent heat arises from the work required to overcome the forces that hold together atoms or molecules in a material.
- Specific heat associates the change in temperature of a substance with a given amount of energy input. Thus, when you dump energy into something, specific heat lets you figure out the resulting temperature rise.
- Specific heat is that form of energy which is utilized to increase/decrease temperature of a body keeping phase constant whereas in case of latent heat the heat is utilized to change the phase at constant temperature.
- Specific Heat is not considered in the case of phase change as the phase gets changed despite temperature change whereas In the process of latent heat, a phase change occurs, and according to that heat is measured and it is also determined whether it is released or absorbed.
- The specific heat of water is 4.186 joules per gram per Kelvin or 4.186 kJ/kg/K.