States of Matter: Videos & Practice Problems

Substances exist in three states of matter: solids, liquids, and gases, each with distinct physical properties. Gases are highly compressible and assume both the volume and shape of their containers. Liquids have moderate compressibility, taking the shape but not the volume of their containers. Solids maintain both shape and volume, exhibiting low compressibility. Viscosity, the resistance to flow, varies: gases have low viscosity, liquids have moderate viscosity, and solids have high viscosity, indicating their movement characteristics under different conditions.

States of Matter Concept 1

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 a 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 flows slowly due to its greater resistance to movement. For example, water has a low viscosity, allowing it to flow easily, while honey, which has a high viscosity, flows much more slowly. Thus, 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.

States of Matter Concept 2

The three states of matter—gases, liquids, and solids—exhibit distinct characteristics in terms of shape, volume, compressibility, and viscosity. Gases are unique in that they can take both the shape and volume of their containers. This means that if a gas is placed in a container, it will expand to fill the entire space available. One of the key properties of gases is their high compressibility; the molecules are spaced far apart, allowing them to be pushed closer together when pressure is applied.

In contrast, liquids can assume the shape of their container but do not have a fixed 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 have moderate compressibility; while their molecules are not as tightly packed as in solids, they can still be slightly compressed under pressure.

Solids maintain both their shape and volume, with molecules locked in place, resulting in low compressibility. This means that solids cannot be easily compressed, as their atoms are already closely packed together.

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 not as freely as gases. Solids, on the other hand, exhibit high viscosity, meaning they resist movement and require an external force to change their position.

In summary, understanding the differences in shape, volume, compressibility, and viscosity among gases, liquids, and solids is crucial for grasping the fundamental properties of matter.

States of Matter Example 1

When considering the physical state of an unknown substance with a volume of 12.1 liters that remains unchanged upon quadrupling the pressure, we can analyze the properties of solids, liquids, and gases. 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 does not change despite the increase in pressure, the substance cannot be a gas.

Liquids, while less compressible than gases, still experience some volume change under increased pressure. Thus, if the volume remains constant when pressure is quadrupled, the substance cannot be classified as a liquid either. This leaves us with solids, which are characterized by their incompressibility. When pressure is applied to a solid, its volume remains relatively constant, making it the most likely candidate in this scenario.

In conclusion, the unknown substance is most likely a solid, as it exhibits the property of maintaining its volume despite significant changes in pressure.

Which of the following choices will have the lowest observed viscosity?  

• A. Water
• B. Helium gas
• C. Molasses
• D. Tar

Answer: (B)

Nitric acid, which is used in the production of fertilizers, plastics and dyes, has a melting point of – 42ºC and a boiling point of 83ºC. Determine its physical state at a temperature of 110ºC.

• A. Solid
• B. Liquid
• C. Gas
• D. Plasma

Answer: (C)

Here’s what students ask on this topic:

What are the three states of matter and their characteristics?

The three states of matter are solids, liquids, and gases. Solids maintain both their shape and volume, exhibiting low compressibility and high viscosity, meaning they resist flow. Liquids take the shape but not the volume of their containers, have moderate compressibility, and moderate viscosity, allowing them to flow more easily than solids. Gases assume both the volume and shape of their containers, are highly compressible, and have low viscosity, meaning they flow and spread out easily.

How does compressibility differ among solids, liquids, and gases?

Compressibility refers to the ability of a substance to decrease in volume under pressure. Gases are highly compressible because their molecules are far apart and can be pushed closer together. Liquids have moderate compressibility; their molecules are closer than in gases but still have some space to be compressed. Solids have low compressibility because their molecules are tightly packed and cannot be easily compressed further.

What is viscosity and how does it vary among the states of matter?

Viscosity is the resistance of a substance to flow. Gases have low viscosity, meaning they flow easily. Liquids have moderate viscosity; for example, water flows easily, but honey flows more slowly. Solids have high viscosity, meaning they resist flow and do not move unless a force is applied. The higher the viscosity, the slower the substance moves.

How do gases, liquids, and solids behave in containers?

Gases assume both the volume and shape of their containers, spreading out to fill the entire space. Liquids take the shape of their containers but do not fill the entire volume unless there is enough liquid to do so. Solids maintain their own shape and volume regardless of the container, meaning they do not change shape to fit the container.

What is the relationship between temperature, pressure, and the states of matter?

Temperature and pressure significantly affect the states of matter. Increasing temperature generally causes substances to move from solid to liquid to gas (melting and boiling). Increasing pressure can compress gases into liquids or solids. For example, water vapor (gas) can condense into liquid water under high pressure. Conversely, reducing pressure can cause liquids to evaporate into gases. These changes are due to the energy and spacing of molecules in different states.