States of Matter: Videos & Practice Problems

Under varying conditions of pressure and temperature, substances can exist in three primary states of matter: solids, liquids, and gases. Each state significantly influences the physical properties of the substance, which pertain to its physical appearance and state. Two important concepts to understand in this context are compressibility and viscosity.

Compressibility refers to the ability of a substance to decrease in volume when subjected to increased pressure. Gases are typically highly compressible because their molecules are spread out and can be pushed closer together when pressure is applied. This characteristic allows gases to occupy less space under higher pressure conditions.

On the other hand, viscosity is the measure of a fluid's resistance to flow or change in shape. A substance with high viscosity, such as honey, flows slowly due to its significant resistance to movement. In contrast, water has low viscosity, allowing it to flow easily. Therefore, the relationship between viscosity and flow rate is direct: the higher the viscosity, the greater the resistance to flow, resulting in slower movement of the substance.

Understanding the three states of matter—gases, liquids, and solids—reveals distinct characteristics regarding their shape, volume, compressibility, and viscosity. Gases are unique in that they can adapt to both the volume and shape of their containers. This adaptability is due to their high compressibility, which allows gas molecules to be pushed closer together when pressure is applied. For instance, if a gas is placed in a container and pressure is exerted, the molecules can compress significantly, demonstrating their ability to fill the available space.

In contrast, liquids take the shape of their containers but do not necessarily fill the entire volume. For example, if you have a 100 ml beaker but only 10 ml of liquid, the liquid will occupy the bottom of the beaker without filling it completely. Liquids exhibit moderate compressibility; while their molecules are not as tightly packed as those in solids, they can still be compressed to a limited extent.

Solids, on the other hand, maintain both their shape and volume. The molecules in solids are closely packed and locked in place, resulting in low compressibility. This means that applying pressure to a solid does not significantly change its volume.

Viscosity is another important property to consider. It refers to a substance's resistance to flow. Gases have low viscosity, allowing them to move freely and quickly within a container. Liquids, such as water, have moderate viscosity; they flow more easily than solids but can vary widely in their flow characteristics. For example, honey has a much higher viscosity than water. Solids possess high viscosity, as they resist movement and require an external force to change their position.

In summary, when examining the three phases of matter, it is essential to consider their shape and volume in relation to their containers, as well as their compressibility and viscosity. These properties help define how each state behaves under different conditions.

When considering the physical state of an unknown substance with a volume of 12.1 liters that remains unchanged despite a quadrupling of pressure, we can analyze the properties of different states of matter. The options include solid, liquid, and gas, while neutron is not a recognized physical state of matter and can be disregarded.

Gases are known for their high compressibility, meaning that a significant increase in pressure typically results in a noticeable decrease in volume. Therefore, if the volume remains constant despite a fourfold increase in pressure, the substance cannot be a gas. Liquids, while less compressible than gases, still exhibit some degree of volume change under pressure. A quadrupling of pressure would likely cause a slight adjustment in the volume of a liquid, ruling it out as well.

In contrast, solids are characterized by their incompressibility; they maintain a consistent volume even when subjected to high pressure. Given that the volume of the unknown substance does not change with the increase in pressure, it is reasonable to conclude that the substance is a solid. Thus, the correct answer is that the unknown substance is in a solid state.