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 guidance

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.

Key Concepts

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.

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.

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.