Problem 9 - Chemistry: The Central Science in SI Units, Global Edition

Question

List the three states of matter in order of (a) increasing molecular disorder and \((\mathbf{b})\) increasing intermolecular attraction. (c) Which state of matter is most easily compressed?

Step-by-Step Solution

Answer

(a) The three states of matter, ordered by increasing molecular disorder, are solid, liquid, and gas. The molecules in a solid are ordered and packed closely together, but in a liquid, they are arranged in a more disorderly manner. In a gas, the molecules are highly disordered and move freely. (b) The states of matter, sorted by increasing intermolecular attraction, are gas, liquid, and solid. Gases have the least intermolecular attraction because the molecules are far apart; liquids have more intermolecular attraction since the molecules are closer together; solids have the most attraction as their molecules are tightly packed and strongly attracted to each other. (c) Gases are the most easily compressed state of matter. Despite liquids being somewhat compressible, gases are more so due to the vast spaces between their molecules, which allow them to be forced closer together under pressure.

Step 1: Understanding Molecular Disorder and Intermolecular Attraction

Molecular disorder refers to how randomly the molecules in a substance are arranged. In a substance with high molecular disorder, the molecules are disorganized and move about freely. Intermolecular attraction refers to the forces that hold molecules together. Higher attraction means the molecules are more tightly bound together.

Step 2: Listing States of Matter in Order of Increasing Molecular Disorder

The three states of matter are solid, liquid, and gas. We need to list them in order of increasing molecular disorder, which means we start with the state that has the lowest molecular disorder and move to the one with the highest: 1. Solid \( \rightarrow \) lowest molecular disorder as the molecules are tightly packed in a regular pattern 2. Liquid \( \rightarrow \) moderate molecular disorder as the molecules are more randomly arranged than in solids but still somewhat held together 3. Gas \( \rightarrow \) highest molecular disorder, as the molecules are very randomly arranged and move freely

Step 3: Listing States of Matter in Order of Increasing Intermolecular Attraction

Now we need to list the three states of matter in order of increasing intermolecular attraction, which means we start with the state that has the lowest intermolecular attraction and move to the state with the highest: 1. Gas \( \rightarrow \) lowest intermolecular attraction, as the molecules are far apart and experience weak forces 2. Liquid \( \rightarrow \) moderate intermolecular attraction, as the molecules are closer together than in gases, but not as close as in solids 3. Solid \( \rightarrow \) highest intermolecular attraction, as the molecules are tightly packed and strongly attracted to each other

Step 4: Determining the State of Matter that is Most Easily Compressed

(c) The compressibility of a substance depends on how easily its molecules can be brought closer together. In the case of solids, the molecules are already closely packed, making them difficult to compress. Liquids are slightly more compressible, as their molecules have more room to move closer. Gases are the most compressible state of matter, due to the large spaces between their molecules, which allows them to be forced closer together under pressure. Therefore, the gas state of matter is the most easily compressed.

Key Concepts

Understanding Molecular Disorder

Molecular disorder describes how the molecules in a substance are arranged and how freely they can move around. In the three states of matter, namely solid, liquid, and gas, the degree of molecular disorder varies significantly.
The arrangement of molecules can largely influence the behavior and properties of each state.

• In solids, the molecules are tightly packed in a well-organized pattern, resulting in very low molecular disorder. In this state, molecules have restricted movement and vibrate in fixed positions.
• In liquids, molecules are more loosely arranged. They are close together but not in a fixed pattern, which means they can slide past each other. This gives liquids moderate molecular disorder.
• Gases exhibit the highest level of molecular disorder. Here, molecules are spread far apart and move freely, leading to random motion in all directions.

Recognizing different levels of molecular disorder helps us understand the unique characteristics and behaviors of each state of matter.

Exploring Intermolecular Attraction

Intermolecular attraction refers to the forces acting between the molecules in a substance that draw them together. These attractions play a crucial role in defining the stability and properties of solids, liquids, and gases.

• In gases, the intermolecular attractions are weakest. The large distances between molecules result in minimal forces pulling them together, giving gases the ability to expand indefinitely.
• Liquids have moderate intermolecular attraction. Molecules in liquids are closer to each other than in gases, which means they can form transient bonds allowing liquids to flow while still maintaining a definite volume.
• Solids exhibit the highest degree of intermolecular attraction. Molecules are packed tightly, usually in a regular pattern. This results in strong forces holding them together, giving solids a fixed shape and volume.

Understanding these attractions helps explain why and how substances transition between different states of matter under varying conditions.

Compressibility of Different States of Matter

Compressibility is a material's capability to reduce its volume under pressure. This property is closely linked to the arrangement of molecules in the different states of matter.

• Solids are the least compressible state. Due to the densely packed and orderly arrangement of their molecules, squeezing them closer is quite challenging.
• Liquids, with their less rigid structure compared to solids, offer a bit of space for slight compressibility. However, this effect is minimal because the molecules are still fairly close together.
• Gases are the most easily compressed. The significant spaces between molecules allow them to be pushed closer together with ease under applied pressure.

Being aware of compressibility aids in the practical applications of materials, such as in storage and transport, and highlights the versatility of gases in adapting to varying pressures.