U9 Notes-1 Ch 14 States of Matter notes HChem

STATES OF MATTER

• States of Matter: Refers primarily to solids, liquids, and gases; characteristics vary by temperature and pressure adjustments.

• General Characteristics:

  • Gas: Total disorder, large empty spaces, particles move freely and are far apart.

  • Liquid: Disorder present, particles or clusters can move relative to each other, but are close together.

  • Crystalline Solid: Ordered particle arrangement, essentially fixed positions, and closely packed.

COMPARISON OF STATES OF MATTER

Properties

• Gas:

  • Assumes shape and volume of its container.

  • Compressible, flows quickly, and diffuses rapidly within its space.

• Liquid:

  • Takes shape of part of the container, does not expand to fill the entire volume, and is not easily compressible.

  • Flows readily, but diffusion occurs slowly.

• Solid:

  • Retains shape and volume, virtually incompressible, and does not flow.

  • Diffusion occurs extremely slowly.

KINETIC THEORY OF GASES

• Kinetic Energy (KE): The energy associated with the motion of particles.

• Kinetic Theory of Matter:

  • Matter consists of tiny, constantly moving particles.

  • Gases are characterized by:

    • Small hard spheres with negligible volume but are far apart.

    • Absence of attractive/repulsive forces between particles.

    • Rapid, constant, and random motion until collisions occur.

    • Elastic collisions resulting in no net energy loss of particles.

GAS CHARACTERISTICS

• Compressibility: Gases occupy less volume under pressure and can fill any shape uniformly.

• Density: Gases are far less dense than solids or liquids (e.g., solid/liquid = 1 g/mL, gas = 1 g/L).

• Pressure: Gases exert uniform pressure; pressure is generated from billions of collision of particles with surfaces.

BAROMETER AND ATMOSPHERIC PRESSURE

• Barometer: Device to measure atmospheric pressure; at sea level, it supports a 760 mm column of mercury due to atmospheric pressure.

• Atmospheric Pressure: Pressure exerted by Earth's atmosphere; decreases with altitude (e.g., mountain climbing).

KINETIC ENERGY AND TEMPERATURE RELATIONSHIP

• Heating Particles: When heated, particles absorb energy leading to increased KE and temperature, while some energy becomes potential energy.

• Kelvin Scale: Absolute zero (0K) is the temperature at which particle motion ceases.

• Phase Relationships: At constant temperature, all substances have the same KE; near absolute zero temperatures have been recorded.

LIQUID CHARACTERISTICS AND INTERMOLECULAR FORCES

• Nature of Liquids:

  • Exist within narrow temperature and pressure ranges; have definite volume and can flow.

  • More dense than gases and cannot be compressed.

  • Controlled by intermolecular forces (IMF) which are stronger than in gases but weaker than chemical bonds.

KEY TERMS

• Intermolecular Forces (IMF): Attractions between particles, strongest in solids, weakest in gases.

• Equilibrium: Dynamic state with opposing changes occurring simultaneously.

• Closed/Open Systems: A closed system allows energy but not matter to transfer; an open system allows both.

VAPORIZATION AND EVAPORATION

• Vaporization: Conversion of a liquid into gas (vapor).

• Evaporation: Surface process of liquid transforming into gas, depending on temperature; results in cooling effect as higher energy particles escape.

EQUILIBRIUM VAPOR PRESSURE

• Vapor Pressure (VP): Pressure in a closed container above the liquid; dynamic equilibrium achieved when rates of evaporation and condensation equalize.

VAPOR PRESSURE TRENDS

• VP increases with temperature due to higher KE and an increase in evaporation rate.

• Volatility: Liquids with high VP (weak IMF) evaporate easily, e.g., acetone; low VP (strong IMF) are harder to evaporate, e.g., water.

BOILING POINT

• Boiling: Both surface and within-liquid conversion from liquid to vapor.

• Normal boiling point: Temperature at which VP equals external pressure (water: 100°C at 1 atm).

• BP can vary under different atmospheric pressures affecting cooking and other processes.

VISCOSITY AND SURFACE TENSION

• Viscosity: Resistance of a liquid to flow related to molecular movement and strength of IMF.

• Surface Tension: Measure of the inward force on surface particles, resulting in a minimized surface area (e.g., spherical raindrops).

CRYSTALLINE AND AMORPHOUS SOLIDS

• Crystalline Solids: Have a fixed orderly arrangement of particles and high melting points due to strong intermolecular attractions.

• Amorphous Solids: Lack defined geometric shape, lower melting points, examples include glass and rubber.

PHASE CHANGES AND DIAGRAMS

• Phase changes require energy (absorption or release) to overcome particle attractions.

• Phase Diagrams: Graphs showing the relationship between temperature and pressure that dictate phase existence.

• Triple Point: Temperature and pressure conditions where all three phases coexist (e.g., for water).

CRITICAL POINT

• Critical Temperature and Pressure: Above which a substance cannot exist as a liquid regardless of pressure applied; for water, critical temperature is 374°C.