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Ch.11 - Liquids and Intermolecular Forces
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Brown 14th EditionCh.11 - Liquids and Intermolecular Forces문제 41
11장, 문제 41

(a) What phase change is represented by the "heat of fusion" of a substance? (b) Is the heat of fusion endothermic or exothermic? (c) If you compare a substance’s heat of fusion to its heat of vaporization, which one is generally larger?

검증된 단계별 안내
1
Step 1: Understand the term 'heat of fusion'. The heat of fusion refers to the amount of energy required to change a substance from the solid phase to the liquid phase at its melting point, without changing its temperature.
Step 2: Determine whether the heat of fusion is endothermic or exothermic. Consider that during the melting process, energy is absorbed by the substance to overcome the forces holding the solid together, indicating an endothermic process.
Step 3: Compare the heat of fusion to the heat of vaporization. The heat of vaporization is the energy required to change a substance from the liquid phase to the gas phase at its boiling point. This process generally requires more energy than melting because it involves completely breaking the intermolecular forces.
Step 4: Conclude that the heat of vaporization is generally larger than the heat of fusion. This is because vaporization requires overcoming all intermolecular forces to transition to a gas, whereas fusion only requires enough energy to allow molecules to move past each other in the liquid state.
Step 5: Summarize the concepts: (a) Heat of fusion involves the solid to liquid phase change, (b) it is an endothermic process, and (c) the heat of vaporization is typically larger than the heat of fusion due to the greater energy needed to transition to a gaseous state.

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Heat of Fusion

The heat of fusion is the amount of energy required to change a substance from a solid to a liquid at its melting point. This phase change involves breaking the intermolecular forces that hold the solid structure together, allowing the molecules to move freely in the liquid state. It is a crucial concept in thermodynamics and is specific to each substance.
추천 영상:
가이드 코스
02:19
Heat Capacity

Endothermic vs. Exothermic Processes

Endothermic processes absorb heat from the surroundings, resulting in a temperature decrease in the environment, while exothermic processes release heat, causing a temperature increase. The heat of fusion is an endothermic process because energy is absorbed to overcome the forces holding the solid together, allowing it to transition into a liquid.
추천 영상:
가이드 코스
1:48
Endothermic & Exothermic Reactions Example 2

Heat of Vaporization

The heat of vaporization is the amount of energy required to convert a liquid into a gas at its boiling point. Generally, the heat of vaporization is larger than the heat of fusion for a given substance because it involves breaking all intermolecular forces to allow the molecules to escape into the gas phase, whereas fusion only requires overcoming some of these forces.
추천 영상:
가이드 코스
02:19
Heat Capacity
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Name the phase transition in each of the following situations and indicate whether it is exothermic or endothermic: (d) Molten lava from a volcano turns into solid rock.

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Name the phase transition in each of the following situations and indicate whether it is exothermic or endothermic: (c) Rubbing alcohol in an open container slowly disappears.

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교과서 질문

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교과서 질문

Ethyl chloride (C2H5Cl) boils at 12 °C. When liquid C2H5Cl under pressure is sprayed on a room-temperature (25 °C) surface in air, the surface is cooled considerably. (b) Assume that the heat lost by the surface is gained by ethyl chloride. What enthalpies must you consider if you were to calculate the final temperature of the surface?

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교과서 질문

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