What is the Difference Between Latent Heat and Specific Heat

Latent heat and specific heat are both important concepts in thermodynamics and heat transfer, but they refer to different phenomena.

What is the difference between latent heat and specific heat? Latent heat refers to the heat energy absorbed or released during a change of state of a substance, such as from solid to liquid or liquid to gas and vice versa. In contrast, specific heat refers to the amount of heat energy required to raise the temperature of one unit mass of a substance by one unit of temperature by keeping the pressure constant.

Key Areas Covered

1. What is Latent Heat
      – Definition, Features, Uses
2. What is Specific Heat
      – Definition, Features, Uses
3. Similarities Between Latent Heat and Specific Heat
      – Outline of Common Features
4. Difference Between Latent Heat and Specific Heat
      – Comparison of Key Differences
5. FAQ: Latent Heat and Specific Heat
      – Answers to Frequently Asked Questions

Key Terms

Latent Heat, Specific Heat

What is Latent Heat

Latent heat is the energy absorbed or released by a substance during a change of state, such as melting, boiling, freezing, or condensing, without any change in its temperature.  This is the energy taken to break or form bonds rather than increasing the motion of the molecules or atoms.

Even though heat is being added or removed, the temperature of the substance stays the same during the state change. This energy is used to rearrange the particles. There are two main types of latent heat. One is the latent heat of fusion, and the other is the latent heat of vapourization.

Latent heat of fusion is the energy absorbed during melting (turning from solid to liquid) or released during freezing (turning from liquid to solid). For example, ice melts into liquid water taking up heat (energy) without a temperature change. Similarly, liquid water turns into a solid state of ice by releasing heat (energy), which is the latent heat without changing the temperature.

Latent heat of vapourization is the energy absorbed when a substance changes its state from liquid to gas, (boiling water, converting liquid water into water vapour) or energy released when gas converts into liquid(condensation).

There are many instances where the latent heat could be observed in the environment. For example, oceans absorb and release latent heat during evaporation and condensation, influencing weather patterns.  Another example is that sweating uses the latent heat of vaporization. As sweat evaporates, it takes heat away from our skin, keeping us cool.

What is Specific Heat

Specific heat refers to the amount of heat energy required to raise the temperature of one unit mass of a substance by one unit of temperature by keeping the pressure constant.  In other words, specific heat tells you how readily a substance absorbs heat and translates that into a rise in temperature.

Different materials have different specific heat values. For example, water has a high specific heat, meaning it takes a lot of heat to raise its temperature. In contrast, metals generally have lower specific heat, so they heat up more easily with the same amount of heat input.

When considering the units of measurement of specific heat, it is typically measured in Joules per kilogram per Kelvin (J/kg⋅K) or Joules per gram per degree Celsius (J/g⋅°C).

The formula to calculate the specific heat is

Q = c × m × ΔT where,

Q= heat trasfer,

c= specific heat,

m = mass of the substance,

delta T = temperature change

There are many applications of specific heat. Specific heat is being used in cooking, building materials and in energy storage.

Similarities Between Latent Heat and Specific Heat

1. Both concepts involve the transfer of thermal energy (heat) to or from a substance.
2. Both latent heat and specific heat can be expressed in the same units.

Difference Between Latent Heat and Specific Heat

Definition

• Latent heat refers to the heat energy absorbed or released during a change of state of a substance, such as from solid to liquid or liquid to gas and vice versa. In contrast, specific heat refers to the amount of heat energy required to raise the temperature of one unit mass of a substance by one unit of temperature by keeping the pressure constant.

Change

• Latent heat deals with the phase change of a substance, while specific heat deals with temperature changes within a single state of matter.

Temperature

• In latent heat, temperature remains constant during the phase change. In specific heat, the temperature increases with the addition of heat.

Use

• Latent heat the energy is used to break or form bonds between the particles during the phase change. In specific heat, the energy increases the average kinetic energy of the particles.

Conclusion

Latent heat is the energy involved in phase changes, such as melting or boiling, without a temperature change. Specific heat is the amount of heat needed to raise the temperature of a unit mass by one degree. While both involve heat transfer, latent heat pertains to phase transitions, whereas specific heat pertains to temperature changes within a single state.

FAQ: Latent Heat and Specific Heat

1. How to calculate specific latent heat?

Specific latent heat is calculated by the equation, E=mL, where E is the energy absorbed or released (latent heat), m is the mass, and L is the specific latent heat.

2. Is latent heat directly proportional to specific latent heat?

Yes, latent heat is directly proportional to specific latent heat and the mass of the substance. This means that as the specific latent heat or the mass increases, the latent heat increases proportionally.

3. What are the two types of latent heat? 

The two types of latent heat are latent heat of fusion and latent heat of vapourization. The latent heat of fusion involves melting, whereas the latent heat of vapourization involves boiling.

4. Is latent heat exothermic or endothermic?

When the phase transition is from solid to liquid, the latent heat is endothermic. When the phase transition is from liquid to gas, it is endothermic. Conversely, the reverse processes are exothermic.

5. How to calculate specific heat?

You can calculate specific heat using its formula. The formula to calculate the specific heat is Q = c × m × ΔT where,

Q= heat transfer,

c= specific heat

m = mass of the substance

delta T = temperature change.

Reference:

1. “Latent Heat.” Encyclopedia Britannica.
2. “Specific Heat Capacity.” Science Direct.

Image Courtesy:

1. “Water temperature vs heat added” By Cmglee – Own work (CC BY-SA 4.0) via Commons Wikimedia