States of Matter: Properties, Classification, and Practice Questions

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):

$P_1V_1 = P_2V_2$

• Viscosity (general):

$\eta = \frac{F}{A \cdot v}$

where $\eta$ is viscosity, $F$ is force, $A$ is area, and $v$ is velocity.