Question

How does a gas compare with a liquid for each of the following properties: (a) density, (b) compressibility, (c) ability to mix with other substances of the same phase to form homogeneous mixtures, \((\mathrm{d})\) ability to conform to the shape of its container?

Short answer

(a) Liquids generally have higher density than gases due to closely packed particles in liquids and more spaced-out particles in gases. (b) Gases are highly compressible, while liquids are nearly incompressible because of particle spacing. (c) Both gases and liquids can mix with substances of the same phase, but gases mix relatively faster than liquids due to the large spaces between particles. (d) Both gases and liquids can conform to the shape of their containers, but gases completely fill the container they occupy, while liquids only take the shape of the portion they occupy with a flat surface level due to gravity.

Step-by-step solution

(a) Comparing Density

Density, defined as mass divided by volume, is generally higher in liquids compared to gases. Liquids have closely packed particles, leading to a higher mass per unit volume, while gas particles are more spaced out, causing lesser mass in the same volume.

(b) Comparing Compressibility

Gases are highly compressible compared to liquids because of the significant spaces between gas particles. Applying pressure can bring these particles closer together, increasing the density. Conversely, liquids are nearly incompressible since their particles are already tightly packed, leaving little room for further compression.

(c) Comparing Mixing Abilities

Both gases and liquids can mix with other substances of the same phase but with varying rates of diffusion. The mixing process in gases happens relatively faster compared to liquids due to the large spaces between gas particles, and they continue to move and spread until they fully mix with other gases. However, the mixing rate of liquids depends on the substances being mixed and external factors such as temperature and stirring.

(d) Comparing Conformity to Container Shape

Both gases and liquids can conform to the shape of their containers. The difference in their conformity is the tendency to fill the entire container. Gases, due to their random, high-speed particle movement, completely fill any container they occupy, whereas liquids only take the shape of the portion of the container they occupy, with their surface level staying flat under the influence of gravity.

Key concepts

Density

Density tells us how much mass is packed into a given volume. It's a key concept in understanding the states of matter. In the case of gases and liquids, the particles that make them up are arranged very differently.

Liquids have tightly packed particles. Think of a crowd of people standing closely together at a concert. This close arrangement leads to a higher density, because more mass fits into a smaller space.

Gases, on the other hand, have particles that are spread out, like people scattered across a large field. There's more space between these particles, which means less mass is packed into the same volume, resulting in a lower density.

Compressibility

Compressibility refers to how much a substance can decrease in volume under pressure. Let's break it down for gases and liquids.

**Gases:** Imagine squeezing a soft pillow; it easily compresses because there's a lot of air, which is very compressible. The particles in a gas have ample room between them. When we apply pressure, these particles can move closer together easily, making gases highly compressible.

**Liquids:** Now think of trying to compress a hard rubber ball; it hardly budges. Similarly, liquids are much less compressible. Their particles are already close together, much like the hard rubber, leaving little room to squeeze them tighter.

Diffusion

Diffusion is the process where particles spread out from areas of high concentration to low concentration. Both gases and liquids can undergo diffusion, but there's a twist!

**Gases:** Imagine spraying perfume in one corner of a room. The scent quickly spreads to fill the entire space. This is because gas particles move freely and rapidly due to the large gaps between them, promoting fast diffusion.

**Liquids:** Pour some food coloring into a glass of water. It might stay in place until stirred, spreading slowly on its own. Liquid particles are closer together, so they don't move as freely as gases, leading to a slower diffusion process. Factors like temperature or agitation can speed it up, much like someone stirring the water.

Container Shape

Understanding how substances take the shape of their container is fascinating. Both gases and liquids adapt to the shape, but they do so distinctively.

**Gases:** Think about blowing up a balloon. The gas inside expands to fill the entire balloon, conforming to its shape completely. This happens because gas particles move at high speeds in all directions, filling every available space within the container.

**Liquids:** Now, fill a glass up with water. The water takes the shape of the glass but only until it reaches a certain level, creating a flat surface. Liquids conform to the shape of their container at the bottom, under the influence of gravity, but unlike gases, they do not fill the entire space unless the container is filled up.