Question

In a sample of a gaseous substance, more than 99% of the overall volume of the sample is empty space. How is this fact reflected in the properties of a gaseous substance compared with the properties of a liquid or solid substance?

Short answer

The large proportion of empty space in a gaseous substance entails that gas particles are widely spaced, resulting in low density and high compressibility. Gaseous substances also exhibit weaker intermolecular forces, allowing them to change shape freely, and have higher diffusion and effusion rates compared to solids and liquids.

Step-by-step solution

1. Understand the three states of matter

In order to compare the properties of gaseous substances with those of liquids and solids, we should first remember the main differences between these three states of matter. Solids have a fixed shape and volume, liquids have a fixed volume but can change their shape, and gases can change both their volume and shape.

2. Gaseous substances have low density

The large proportion of empty space in a gaseous substance implies that the gas particles are widely spaced. This causes gases to have a lower density compared to solids and liquids. Due to their low density, gases can be easily compressed.

3. Gaseous substances have high compressibility

The large proportion of empty space in a gaseous substance means that there is a significant distance between particles. When pressure is applied to a gas, these particles can be forced closer together, resulting in a decrease in the volume of the gas. This high compressibility is a key property unique to gaseous substances.

4. Gaseous substances have weaker intermolecular forces

Compared to solids and liquids, gaseous substances have weaker intermolecular forces, due to the larger distance between their respective particles. This weaker force allows the particles in a gas to move freely and spread out, filling any available space and freely changing their shape.

5. Gaseous substances have high diffusion and effusion rates

Due to the large proportion of empty space and the weaker intermolecular forces in gaseous substances, gas particles can move and mix easily with other gases. As a result, gases have higher diffusion and effusion rates than solids and liquids. In conclusion, the fact that more than 99% of the overall volume of a gaseous sample is empty space is reflected in the properties of gaseous substances through their low density, high compressibility, weaker intermolecular forces, and high diffusion and effusion rates when compared to solid and liquid substances.

Key concepts

Properties of Gases

Gases are unique in their behavior and properties when compared to solids and liquids. One of the standout features of gases is their ability to fill the container they are in, regardless of its shape or size. This is primarily because more than 99% of the volume of a gaseous substance is empty space. Within this empty space, gas molecules move independently and freely.

This characteristic also contributes to other properties such as:

• Low Density: Gases are much less dense than solids and liquids because of the significant amount of empty space between molecules.
• Shape Flexibility: Gases do not have a fixed shape or volume; they will take the shape and volume of their container.
• High Mobility: Gas molecules have high kinetic energy, which allows them to move rapidly in all directions.

Understanding these properties helps us predict how gases will behave under different conditions.

Compressibility

One of the most striking properties of gases is their compressibility. This feature is rooted in the fact that gas molecules are widely spaced, making it easier to push them closer together under pressure.

In contrast to solids and liquids, which have tightly packed molecules, gases can be compressed significantly because there is ample space between their molecules. When pressure is applied to a gaseous substance:

• The molecules are squeezed closer to one another.
• The overall volume of the gas decreases.
• It becomes easier to store gases in compressed forms, which is why we often find gases in cylinders under high pressure.

This compressibility not only makes gases easy to store but also useful in various applications, like airbags, where rapid compression is needed for safety.

Intermolecular Forces

Gaseous substances exhibit weaker intermolecular forces compared to liquids and solids. This is because gas molecules are far apart, reducing the influence they have on each other.

In solids and liquids, molecules are tightly packed, leading to stronger intermolecular forces such as hydrogen bonding, Van der Waals forces, or ionic bonding. However, in gases, these forces are negligible, which results in:

• Free Movement: Gas molecules can move freely, leading to diffusion and effusion.
• High Rates of Diffusion: Since molecules are not held together strongly, gases can quickly mix or spread out in a space.
• Filling Spaces: This weak force allows gases to fill any container, regardless of its size.

The weak intermolecular forces in gases are pivotal in processes like respiration, where oxygen moves effortlessly through airways to reach cells.