Question

Choose one of the following terms to match the definition or description given. a. alloy b. specific heat c. crystalline solid d. dipole-dipole attraction e. equilibrium vapor pressure f. intermolecular g. intramolecular h. ionic solids i. London dispersion forces j. molar heat of fusion k. molar heat of vaporization I. molecular solids m. normal boiling point n. semiconductor energy required to melt 1 mol of a substance

Short answer

The correct term that matches the given definition "energy required to melt 1 mol of a substance" is (j) molar heat of fusion.

Step-by-step solution

Identify the relevant terms related to heat and phase changes

If we look at the list of terms, we find a few that are related to heat or phase changes. These terms are: b. specific heat j. molar heat of fusion k. molar heat of vaporization

Eliminate irrelevant terms

Now, let's eliminate any irrelevant terms from the list above by examining each one closely: - Specific heat (b) refers to the amount of heat needed to raise the temperature of 1 gram of a substance by 1 degree Celsius, so this term is not related to the melting process. - Molar heat of vaporization (k) represents the amount of heat required to vaporize 1 mol of a substance, which refers to the phase change from liquid to gas, not from solid to liquid.

Find the term that matches the definition

The term that remains in our list is: j. molar heat of fusion This term represents the amount of heat required to melt 1 mol of a substance, which matches the given definition in the exercise. So, the correct answer is: (j) molar heat of fusion.

Key concepts

Molar Heat of Fusion

Understanding the molar heat of fusion is crucial when studying phase changes in chemistry. In essence, this term describes the energy required to convert one mole of a solid into its liquid form without changing its temperature. This happens when a substance reaches its melting point.

For instance, ice turning into water requires the addition of a certain amount of heat. The molar heat of fusion is substance-specific—each material has its unique value because of its unique molecular structure. Substances with stronger bonds will generally have higher values of molar heat of fusion, indicating that more energy is necessary to break the bonds holding the solid together.

As an educational hint, think of molar heat of fusion like the energy ticket a molecule must 'buy' to change from being part of a structured solid to a more liberated liquid.

Importance in Calculations

When performing calculations involving heat and phase changes, knowing the molar heat of fusion allows you to determine the amount of energy needed to melt a given mole of a substance—in a sense, it tells you the cost of the ticket in terms of energy.

Specific Heat

Specific heat, a concept often interwoven with any discussion of thermal energy in chemistry, is a measure of how much heat energy is needed to raise the temperature of a given amount of substance by a certain temperature interval—typically 1 degree Celsius or 1 Kelvin.

This property is intrinsic to the material and can be thought of as a reflection of how resistant a substance is to changing temperature. Water, for example, has a high specific heat, meaning it absorbs a lot of heat before it begins to get warmer. This characteristic of water is why it's great for cooling systems and why the ocean can store so much solar heat.

The concept of specific heat is crucial when calculating the energy required for heating or cooling a substance before it even reaches the point of a phase change.

Practical Applications

Understanding specific heat is not only important for solving chemistry problems, but it also has practical applications in areas such as meteorology, cooking, and even in the design of heating and cooling systems.

Molar Heat of Vaporization

While the molar heat of fusion is about the solid-liquid transition, the molar heat of vaporization focuses on the liquid-gas change. This is the amount of heat needed to turn one mole of a liquid into a gas at constant temperature and pressure—an essential part of understanding the energy involved in the phase change known as vaporization or boiling.

Like molar heat of fusion, this value varies from substance to substance. Liquids that are held together more tightly due to stronger intermolecular forces will generally have a higher molar heat of vaporization. For example, it takes a significant amount of energy to vaporize water due to the hydrogen bonds between the molecules.

Remembering molar heat of vaporization can be seen as a parallel to molar heat of fusion—it's like the 'entry fee' a liquid pays to become a gas.

Role in Phase Change Diagrams

The molar heat of vaporization is vital in constructing phase diagrams and also for understanding the distillation process, where a mixture is separated into its components based on different boiling points.