뒤로States of Matter: Properties, Classification, and Practice Questions
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States of Matter
Overview of States of Matter
Substances can exist in three primary states of matter: solid, liquid, and gas. The physical properties of these states are influenced by pressure and temperature, which affect their appearance and behavior.
Compressibility: The ability of a substance to flatten or reduce in size when pressure is applied.
Viscosity: The resistance of a substance to flow or to change in shape.
Comparison of States of Matter
State | Volume | Shape | Compressibility | Viscosity |
|---|---|---|---|---|
Gas | Assumes volume of container | Assumes shape of container | High | Low |
Liquid | Assumes volume of container | Retains own shape | Moderate | Moderate |
Solid | Maintains fixed volume | Maintains fixed shape | Low | High |
Types of Solids
Crystalline: Solids with a well-organized, repeating 3D structure.
Amorphous: Solids lacking organized patterns or shapes.
Example: Table salt (NaCl) is a crystalline solid, while glass is an amorphous solid.
Practice Questions and Explanations
Physical Properties and State Identification
Example: An unknown substance has a volume of 12.1 L and upon quadrupling the pressure, the volume remains unchanged. This indicates the substance is a solid, as solids are incompressible and retain their volume under pressure.
Viscosity Comparison
Practice: Which of the following choices will have the lowest observed viscosity?
Answer: Helium gas. Gases generally have much lower viscosity compared to liquids and solids.
State Determination by Temperature
Practice: Nitric acid, with a melting point of -42°C and a boiling point of 83°C, is at a temperature of 110°C. What is its physical state?
Answer: Liquid. Since 110°C is above the boiling point, nitric acid would be in the gas phase. Additional info: The answer marked is 'liquid', but the correct state at 110°C (above boiling point) should be gas.
Key Terms and Definitions
Compressibility: The measure of how much a substance's volume decreases under pressure.
Viscosity: The measure of a fluid's resistance to flow.
Crystalline Solid: A solid with a regular, repeating pattern of particles.
Amorphous Solid: A solid with no long-range order or pattern.
Important Equations
Boyle's Law (for gases):
Viscosity (general):
where is viscosity, is force, is area, and is velocity.
