Textbook Question
The molecules
have the same molecular formula (C3H8O) but different chemical structures. (b) Which molecule do you expect to have a larger dipole moment? [Sections 11.2 and 11.5]
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Ch.11 - Liquids and Intermolecular Forces
Chapter 11, Problem 8a
At three different temperatures, T1, T2, and T3, the molecules in a liquid crystal align in these ways:
(a) At which temperature or temperatures is the substance in a liquid crystalline state? At those temperatures, which type of liquid crystalline phase is depicted?
Verified step by step guidance1
Step 1: Understand that liquid crystals are a state of matter that has properties between those of conventional liquids and those of solid crystals. They can flow like a liquid, but have the ordered structure of a crystal.
Step 2: Identify the temperature or temperatures at which the substance is in a liquid crystalline state. This is typically when the molecules are aligned in a specific pattern, but can still move around like a liquid. The exact temperatures will depend on the specific substance and its properties.
Step 3: Determine the type of liquid crystalline phase depicted at those temperatures. There are several types of liquid crystalline phases, including nematic, smectic, and cholesteric. The nematic phase is characterized by molecules that have no positional order but tend to point in the same direction. In the smectic phase, the molecules maintain a layered structure. In the cholesteric phase, the molecules form a helical structure.
Step 4: Compare the alignment of the molecules at each temperature to the characteristics of the different liquid crystalline phases. This will allow you to identify the type of phase at each temperature.
Step 5: Remember that the exact temperatures and phases will depend on the specific substance and its properties. Different substances will have different liquid crystalline phases at different temperatures.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Liquid Crystals
Liquid crystals are states of matter that exhibit properties between those of conventional liquids and solid crystals. They can flow like a liquid but have some degree of molecular order, which allows them to respond to electric or magnetic fields. Understanding the behavior of liquid crystals is essential for identifying their phases at different temperatures.
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03:04
The crystal field splitting pattern for octahedral complexes has the d orbitals on or along the axes as having the higher energy.
Phase Transitions
Phase transitions refer to the changes in the state of matter that occur when a substance is subjected to varying temperature or pressure. In the context of liquid crystals, these transitions can lead to different phases, such as nematic or smectic, which are characterized by distinct molecular arrangements. Recognizing these transitions is crucial for determining the liquid crystalline state at specific temperatures.
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Temperature Dependence of Molecular Alignment
The alignment of molecules in liquid crystals is highly temperature-dependent. As temperature changes, the kinetic energy of the molecules increases or decreases, affecting their arrangement and the phase they adopt. Identifying the temperatures at which the liquid crystal exhibits a specific phase is key to understanding its properties and applications.
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Related Practice
Textbook Question
The phase diagram of a hypothetical substance is
(b) What is the physical state of the substance under the following conditions? (i) T = 150 K, P = 0.2 atm; (ii) T = 100 K, P = 0.8 atm; (iii) T = 300K, P = 1.0atm. [Section 11.6]
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Textbook Question
At three different temperatures, T1, T2, and T3, the molecules in a liquid crystal align in these ways:
(b) Which is the highest of these three temperatures? [Section 11.7]
Textbook Question
List the three states of matter in order of (a) increasing molecular disorder
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