What is the Specific Latent Heat of Fusion in Chemistry?
Specific Latent Heat of Fusion is essential in chemistry and helps students understand various practical and theoretical applications related to this topic. From phase changes in water to industrial melting processes, its role is crucial in both daily life and scientific studies.
What is Specific Latent Heat of Fusion in Chemistry?
The specific latent heat of fusion refers to the amount of energy required to change 1 kg of a substance from solid to liquid at its melting point, without any temperature change. This concept appears in chapters related to phase transitions, thermal properties, and energy calculations, making it a foundational part of your chemistry syllabus.
Molecular Formula and Composition
The molecular formula is not used for the specific latent heat of fusion because it's a property, not a single compound. Instead, it is measured for substances like ice (H2O), metals (like Fe, Cu), and others. This property helps in studying how heat energy changes matter’s physical state.
Preparation and Synthesis Methods
To observe the specific latent heat of fusion, you prepare an experiment where you heat a known mass of a solid (like ice) until it fully melts, recording the energy supplied. No chemical synthesis is needed—just precise heating and temperature control at the melting point.
Physical Properties of Specific Latent Heat of Fusion
The specific latent heat of fusion is measured in units of joules per kilogram (J/kg) or kilojoules per kilogram (kJ/kg). Each substance has its own unique value. For example, ice has a specific latent heat of fusion of about 334,000 J/kg. The value does not change unless the substance or its conditions change.
Chemical Properties and Reactions
Specific latent heat of fusion does not involve a chemical reaction. It is a physical change—energy is absorbed to overcome the strong intermolecular forces in solids. There is no formation of new substances; the molecules remain the same but move more freely as the substance melts.
Frequent Related Errors
- Confusing specific latent heat of fusion with latent heat of vaporization.
- Using wrong units (for example, using just joules instead of J/kg).
- Assuming temperature rises during the melting process.
- Missing out on the mass variable in calculation (forgetting the 'm' in Q = mL).
Uses of Specific Latent Heat of Fusion in Real Life
The specific latent heat of fusion is widely used in ice storage systems, weather study (like glaciers and polar ice melting), food preservation, and the metal casting industry. It helps explain why ice keeps drinks cold and why snow melts slowly, absorbing heat from the environment.
Relation with Other Chemistry Concepts
Specific latent heat of fusion is closely related to Phase Changes. It also connects with the concepts of Specific Heat Capacity and Thermal Properties of Matter, helping students understand energy flow during state changes.
Step-by-Step Reaction Example
1. Take a beaker with 100 g of ice at 0°C.2. Supply heat gradually and measure the energy supplied using a calorimeter.
3. When all the ice melts into water (still at 0°C), note the total energy used.
4. Use the formula: Q = mL
Lab or Experimental Tips
Remember that temperature stays constant during melting. Only record heat supplied until the last bit of solid turns to liquid. Vedantu educators often demonstrate placing a thermometer in both melting ice and boiling water to show this temperature plateau clearly in live classes.
Try This Yourself
- Calculate the energy needed to melt 250 g of ice using the fusion value for ice.
- Explain why the specific latent heat of fusion is important for the survival of polar animals.
- List two daily scenarios where melting or freezing involves this concept.
Final Wrap-Up
We explored specific latent heat of fusion—its definition, formula, errors, uses, and real-life importance. For stepwise solutions and interactive doubt clearing, check Vedantu’s online resources where concepts are explained with fun activities and examples.
| Substance | Specific Latent Heat of Fusion (J/kg) |
|---|---|
| Ice (H₂O) | 334,000 |
| Lead (Pb) | 23,000 |
| Iron (Fe) | 276,000 |
FAQs on Specific Latent Heat of Fusion Explained
1. What is specific latent heat of fusion?
Specific latent heat of fusion is the amount of heat energy required to change 1 kilogram of a solid into liquid at its melting point without any temperature change.
- Measured in joules per kilogram (J/kg).
- Depends on the substance.
- Important for understanding phase changes.
2. What is the specific latent heat of fusion of ice?
The specific latent heat of fusion of ice is approximately 334 kJ/kg (334,000 J/kg).
- This means 334,000 joules of energy is needed to melt 1 kg of ice at 0°C without changing its temperature.
3. What is the formula to calculate the latent heat of fusion?
The formula for latent heat of fusion is:
Q = mL
- Q = Heat energy (Joules, J)
- m = Mass (kilograms, kg)
- L = Specific latent heat of fusion (J/kg)
4. What are the units of specific latent heat of fusion?
Specific latent heat of fusion is measured in Joules per kilogram (J/kg).
- Kilojoules per kilogram (kJ/kg) is also common for large values.
5. Does temperature change during the fusion process?
No, temperature remains constant during fusion.
- All heat energy supplied is used to break intermolecular bonds, not to increase temperature.
- Phase change from solid to liquid occurs at constant temperature (the melting point).
6. How do you calculate the energy required to melt a certain mass of a substance?
To calculate energy:
Q = mL
- Multiply the mass (m) of the substance by the specific latent heat of fusion (L).
- Example: To melt 2 kg of ice: Q = 2 kg × 334,000 J/kg = 668,000 J.
7. What is the difference between specific latent heat of fusion and specific latent heat of vaporization?
Specific latent heat of fusion is the energy needed to convert a solid to a liquid at its melting point, while specific latent heat of vaporization is the energy required to convert a liquid to a gas at its boiling point.
- Fusion: solid to liquid
- Vaporization: liquid to gas
- Each process involves different energy values for the same substance.
8. Why doesn’t temperature rise when a solid melts at its melting point?
During melting, added energy is used to break intermolecular forces, not to increase kinetic energy.
- This energy is the latent heat of fusion.
- Temperature stays constant until the entire solid has melted.
9. Is the specific latent heat of fusion the same for all substances?
No, each substance has its own unique specific latent heat of fusion, depending on its molecular structure and bonding.
- Example values: Ice - 334,000 J/kg; Lead - 24,500 J/kg; Iron - 247,000 J/kg.
10. What are some common applications of specific latent heat of fusion?
Specific latent heat of fusion is important in many real-life areas:
- Food industry: Ice-based refrigeration and freezing.
- Weather & Climate: Melting of snow and glaciers affects temperature regulation.
- Metallurgy: Used in metal casting and purification processes.
- Everyday life: Making ice packs or melting ice for drinks.
11. Can the specific latent heat of fusion be negative?
No, the specific latent heat of fusion is always a positive value because it represents energy absorbed to overcome intermolecular forces during melting.
12. How does pressure affect the specific latent heat of fusion?
Pressure can slightly alter the specific latent heat of fusion by changing the melting point and molecular arrangement of a substance.
- Higher pressure may increase or decrease the melting point, thus affecting the latent heat required.
