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Comparison of the thermal properties of water with those of methane.
Comparison of the thermal properties of water with those of methane.
Answer
Water and methane exhibit significantly different thermal properties due to their molecular structures and the types of intermolecular forces present. Here’s a comparative analysis of their thermal properties:
Key Thermal Properties Comparison
| Property | Water (H₂O) | Methane (CH₄) |
|---|---|---|
| Polarity | Polar, capable of hydrogen bonding | Nonpolar, only weak dispersion forces |
| Boiling Point | 100°C (212°F) | -162°C (-260°F) |
| Melting Point | 0°C (32°F) | -183°C (-297°F) |
| Specific Heat Capacity | 4.18 J/g·K | ~2.2 J/g·K |
| Heat of Vaporization | 2260 J/g | ~510 J/g |
| Heat of Fusion | 334 J/g | ~- (not applicable, typically gas at room temperature) |
Analysis of Differences
Polarity and Intermolecular Forces
- Water is a polar molecule due to the significant electronegativity difference between oxygen and hydrogen, allowing it to form strong hydrogen bonds. These bonds require substantial energy to break, which contributes to water’s high boiling point, melting point, specific heat capacity, and heat of vaporization.
- Methane, on the other hand, is nonpolar and primarily experiences weak van der Waals (dispersion) forces. This results in much lower boiling and melting points compared to water because less energy is needed to overcome these weak interactions.
Boiling and Melting Points
- Water has a boiling point of 100°C, while methane boils at -162°C. This stark contrast is primarily due to the strong hydrogen bonds in water that require more energy to break compared to the weak dispersion forces in methane.
Specific Heat Capacity
- Water has a high specific heat capacity (4.18 J/g·K), meaning it can absorb a lot of heat before its temperature rises significantly. This property is crucial for regulating temperatures in natural environments and biological systems. Methane’s specific heat capacity is lower (~2.2 J/g·K), indicating it heats up more quickly than water when exposed to the same amount of heat.
Heat of Vaporization
- The heat of vaporization for water (2260 J/g) is much higher than that of methane (~510 J/g). This means that water requires significantly more energy to convert from liquid to gas, which is vital for processes like cooling through evaporation (e.g., sweating in humans).
Heat of Fusion
- Water also has a considerable heat of fusion (334 J/g), which is the energy required to change it from solid (ice) to liquid at 0°C. Methane does not have a defined heat of fusion under normal conditions since it remains gaseous at room temperature
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