Question

Describe the common properties of gases.

Short answer

The common properties of gases include compressibility, low density, expansion, diffusibility, and uniform distribution of pressure. Gases are highly compressible due to the large amount of empty space between molecules, allowing their volume to be reduced under pressure. They have a low density because molecules are spaced far apart, resulting in a lower mass per unit volume compared to solids and liquids. Gases also expand when heated as their kinetic energy increases. They have the ability to diffuse and mix rapidly with other gases due to the constant motion and large distances between molecules. Finally, gases exert uniform pressure on the walls of their containers, which is a result of the balanced momentum in all directions from the constant movement and collisions of gas molecules.

Step-by-step solution

1. Compressibility

Gases are highly compressible, meaning that their volume can be reduced significantly under pressure. This is because gas molecules are far apart from each other, with a large amount of empty space between them. When pressure is applied, the gas molecules are brought closer together, reducing the volume of the gas.

2. Low Density

Gases have a much lower density compared to solids and liquids. This stems from the fact that gas molecules are spaced far apart from one another. As a result, the mass of gas molecules per unit volume is significantly less than that of solids and liquids, leading to a lower density.

3. Expansion

When gases are heated, they expand. This occurs because as the temperature increases, the kinetic energy of the gas molecules also increases. With more kinetic energy, gas molecules move more rapidly and spread out further, causing the overall volume of the sample to increase.

4. Diffusibility

Gases have the ability to diffuse rapidly, meaning they spread out and mix with other gases. This property is a result of gas molecules being in constant motion and having relatively large distances between them. Gas molecules are able to move through the spaces between other gas molecules, leading to rapid mixing and diffusion.

5. Uniform Distribution of Pressure

Gases exert uniform pressure on the walls of their containers. This property is a result of the constant movement of gas molecules and the large distances between them. As gas molecules collide with the walls of their container and with each other, their momentum is balanced in all directions, which leads to a uniform distribution of pressure.

Key concepts

Compressibility

Gases are known for their remarkable compressibility. Imagine the spacious arrangement of gas molecules like an airy dance hall where each molecule enjoys its own space. However, when pressure is applied, this "dance floor" becomes more crowded as molecules move closer to each other. This is why gases can dramatically decrease in volume when squeezed. It's akin to compressing a sponge, but with a flexibility that solids do not inherently have.

One practical illustration of compressibility can be found in air compressors. These devices rely on the ability to compress air to fit more effectively in storage tanks. Such compressibility has various applications, including in vehicle safety systems like airbags, where the gas must reduce its volume swiftly during inflation.

Low Density

Another characteristic of gases that sets them apart from solids and liquids is their low density. Low density is a direct reflection of how sparsely gas molecules are distributed within a given volume. Unlike solids where atoms are tightly packed, gas molecules are akin to distant neighbours sharing an expansive plot of land.

This property explains why a helium balloon floats in air. Helium, being less dense than the surrounding atmospheric air, rises due to buoyancy. It appears light because the mass per volume, or density, is less compared to that of air. Therefore, this fundamental property of gases makes phenomena like balloons and blimps possible.

Thermal Expansion

When it comes to thermal expansion, gases are experts in growth whenever heated. As the temperature rises, so does the energy within the gas molecules. More energy translates to livelier movements, causing molecules to spread out further. In essence, heating a gas is like adding heat to a pot of popcorn, causing kernels (or molecules) to burst and occupy more space.

Car tires can exemplify thermal expansion. On hot days, the air inside a tire expands because of increased temperature, leading to a rise in pressure. This phenomenon is why drivers should check tire pressure regularly, especially during temperature fluctuations.

Diffusion

Diffusion is a fascinating feature allowing gases to mingle effortlessly. Picture gas molecules as social butterflies, incessantly moving and weaving through any space they occupy. This motion causes gases to spread out, or diffuse, until they form a uniform mixture with other constituents in the environment.

A real-world example of diffusion can be sensed when you spray air freshener in a room. Despite placing it in a single corner, the scent travels throughout the space, blending with existing air due to the ever-active movement of gas molecules. This diffusion ensures that gas compositions evenly balance over time, without any assistance.

Pressure Distribution

Gases take the crown for maintaining equal pressure across any container they fill. It's all about the action-packed world of gas molecules constantly crashing around. This movement combined with the vast distances they cover means that gases bombastically hit every wall of their container.

Such equal pressure distribution is why balloons maintain their round shape; the molecules inside push outwards uniformly in all directions, creating even pressure. This fundamental property plays a critical role in applications ranging from ordinary tire pressure to creating the uniform atmospheric pressure we experience at sea level.