The Formula for Energy Requirements

Oct 13, 2025 by wbrum.org 68 views

Introduction

In thermodynamics, the process of changing the state of a substance from solid to liquid or vice versa is known as phase change. This process requires energy, which can be either absorbed or released by the substance. In this article, we will explore the energy requirements for changing 150.0 grams of ice at -22.00°C to water at 95.15°C.

The Formula for Energy Requirements

The energy required for phase change can be calculated using the formula:

Q = m \cdot h_f

where:

$Q$ is the energy required for phase change (in joules, J)
$m$ is the mass of the substance (in kilograms, kg)
$h_f$ is the latent heat of fusion (in joules per kilogram, J/kg)

Latent Heat of Fusion

The latent heat of fusion is the energy required to change a unit mass of a substance from solid to liquid at its melting point. For water, the latent heat of fusion is approximately 334 J/g.

Calculating the Energy Requirements

To calculate the energy required to change 150.0 grams of ice at -22.00°C to water at 95.15°C, we need to use the formula:

Q = m \cdot h_f

where:

$m$ is the mass of the substance (150.0 g)
$h_f$ is the latent heat of fusion (334 J/g)

Plugging in the values, we get:

Q = 150.0 \, \text{g} \cdot 334 \, \text{J/g} = 50100 \, \text{J}

Energy Required for Temperature Change

In addition to the energy required for phase change, we also need to consider the energy required to change the temperature of the water from -22.00°C to 95.15°C. This can be calculated using the formula:

Q = m \cdot c \cdot \Delta T

where:

$Q$ is the energy required for temperature change (in joules, J)
$m$ is the mass of the substance (in kilograms, kg)
$c$ is the specific heat capacity of water (in joules per kilogram per degree Celsius, J/kg°C)
$\Delta T$ is the change in temperature (in degrees Celsius, °C)

The specific heat capacity of water is approximately 4.184 J/g°C. Plugging in the values, we get:

Q = 150.0 \, \text{g} \cdot 4.184 \, \text{J/g°C} \cdot (95.15°C - (-22.00°C)) = 104111.2 \, \text{J}

Total Energy Required

The total energy required to change 150.0 grams of ice at -22.00°C to water at 95.15°C is the sum of the energy required for phase change and the energy required for temperature change:

Q_{\text{total}} = Q_{\text{phase change}} + Q_{\text{temperature change}}

Q_{\text{total}} = 50100 \, \text{J} + 104111.2 \, \text{J} = 200211.2 \, \text{J}

Conclusion

In conclusion, the energy required to change 150.0 grams of ice at -22.00°C to water at 95.15°C is approximately 200211.2 joules. This calculation takes into account both the energy required for phase change and the energy required for temperature change. The results of this calculation can be useful in a variety of applications, such as designing heating systems or understanding the thermodynamic properties of water.

References

CRC Handbook of Chemistry and Physics, 97th ed. (2016)
International Union of Pure and Applied Chemistry, "Latent Heat of Fusion"
National Institute of Standards and Technology, "Specific Heat Capacity of Water"
Q&A: Understanding the Energy Requirements for Phase Change ===========================================================

Introduction

In our previous article, we explored the energy requirements for changing 150.0 grams of ice at -22.00°C to water at 95.15°C. In this article, we will answer some frequently asked questions related to this topic.

Q: What is the difference between latent heat of fusion and specific heat capacity?

A: The latent heat of fusion is the energy required to change a unit mass of a substance from solid to liquid at its melting point. The specific heat capacity, on the other hand, is the energy required to change the temperature of a unit mass of a substance by one degree Celsius.

Q: Why is the latent heat of fusion important?

A: The latent heat of fusion is important because it determines the energy required to change a substance from solid to liquid. This is a critical consideration in many industrial processes, such as melting ice or freezing water.

Q: Can you explain the concept of specific heat capacity?

A: The specific heat capacity is a measure of the energy required to change the temperature of a substance by one degree Celsius. It is an important property of a substance that determines how much energy is required to heat or cool it.

Q: How does the specific heat capacity of water compare to other substances?

A: The specific heat capacity of water is approximately 4.184 J/g°C, which is relatively high compared to other substances. This means that water requires a lot of energy to change its temperature, making it a good insulator.

Q: What is the significance of the temperature change in the energy calculation?

A: The temperature change is an important factor in the energy calculation because it determines how much energy is required to change the temperature of the substance. In the case of water, the temperature change from -22.00°C to 95.15°C requires a significant amount of energy.

Q: Can you explain the concept of phase change?

A: Phase change is the process of changing the state of a substance from solid to liquid or vice versa. This process requires energy, which can be either absorbed or released by the substance.

Q: How does the energy required for phase change compare to the energy required for temperature change?

A: The energy required for phase change is typically much larger than the energy required for temperature change. This is because the latent heat of fusion is a large energy value that determines the energy required to change a substance from solid to liquid.

Q: What are some real-world applications of the energy requirements for phase change?

A: The energy requirements for phase change have many real-world applications, such as designing heating systems, understanding the thermodynamic properties of water, and optimizing industrial processes.

Q: Can you provide some examples of substances with high and low latent heat of fusion?

A: Some substances with high latent heat of fusion include water (334 J/g), ice (334 J/g), and mercury (11.4 J/g). Some substances with low latent heat of fusion include helium (5.19 J/g) and hydrogen (28.8 J/g).

Conclusion

In conclusion, the energy requirements for phase change are an important consideration in many industrial processes and everyday applications. By understanding the concepts of latent heat of fusion, specific heat capacity, and phase change, we can better design and optimize systems that involve the transfer of energy.

References

CRC Handbook of Chemistry and Physics, 97th ed. (2016)
International Union of Pure and Applied Chemistry, "Latent Heat of Fusion"
National Institute of Standards and Technology, "Specific Heat Capacity of Water"