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Ch.11 - Liquids and Intermolecular Forces
All textbooksBrown 14th EditionCh.11 - Liquids and Intermolecular ForcesProblem 8b
Chapter 11, Problem 8b

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]

Verified step by step guidance
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Step 1: Understand the properties of liquid crystals. Liquid crystals are a state of matter that has properties between those of conventional liquids and those of solid crystals. For instance, a liquid crystal may flow like a liquid, but its molecules may be oriented in a crystal-like way.
Step 2: Know the different phases of liquid crystals. There are several different phases of liquid crystals, but the most common are the nematic, smectic, and cholesteric phases. In the nematic phase, the molecules are aligned along one direction, but not layered. In the smectic phase, the molecules are aligned along one direction and also layered. In the cholesteric phase, the molecules are aligned along one direction and layered, but also twisted.
Step 3: Identify the phase of the liquid crystal at each temperature. From the description given in the problem, identify which phase the liquid crystal is in at each temperature T1, T2, and T3.
Step 4: Understand the relationship between temperature and phase. As the temperature increases, the order of the liquid crystal decreases. This means that the liquid crystal goes from a more ordered phase (like smectic or cholesteric) to a less ordered phase (like nematic).
Step 5: Determine the highest temperature. Based on the phase of the liquid crystal at each temperature, determine which temperature is the highest. The highest temperature will be the one at which the liquid crystal is in the least ordered phase.

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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 substances that exhibit properties between those of liquids and solid crystals. They can flow like a liquid but have some degree of molecular order, which allows them to align in specific orientations under certain conditions, such as temperature changes. Understanding how temperature affects the alignment of molecules in liquid crystals is crucial for interpreting their behavior.
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The crystal field splitting pattern for octahedral complexes has the d orbitals on or along the axes as having the higher energy.

Temperature and Molecular Motion

Temperature is a measure of the average kinetic energy of molecules in a substance. As temperature increases, molecular motion becomes more vigorous, which can lead to changes in the state of matter. In the context of liquid crystals, higher temperatures typically result in a greater degree of disorder among the molecules, affecting their alignment and the overall properties of the material.
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Temperature vs Heat

Phase Transitions

Phase transitions refer to the changes in the state of matter that occur at specific temperatures, such as melting or boiling. In liquid crystals, these transitions can involve shifts between ordered and disordered phases, influenced by temperature. Identifying the highest temperature among T1, T2, and T3 involves understanding which temperature corresponds to the most disordered phase of the liquid crystal.
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Phase Changes in Diagrams
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:

(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?

Textbook Question

List the three states of matter in order of (a) increasing molecular disorder

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Textbook Question

List the three states of matter in order of (b) increasing intermolecular attraction.

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