States of Matter: Solids, Liquids, and Gases

States of Matter

• Chemistry involves understanding matter, its behavior, and explaining/predicting said behavior.
• Matter includes all substances and materials in the physical universe.
• Matter can be categorized into three states: solids, liquids, and gases.
• The kinetic particle theory helps explain matter's behavior, including the differences in properties between the three states and how these properties relate to the strength of bonds between particles.

Solids, Liquids, and Gases

• Solids have a definite volume and shape at a given temperature.
  • Heating a solid causes expansion (increase in size), while cooling causes contraction (decrease in size).
• Liquids have a fixed volume but take the shape of their container at a given temperature.
  • A liquid's volume is slightly affected by temperature changes, similar to solids.
• Gases have neither a definite shape nor a definite volume at a given temperature.
  • Gases take the shape of their container and spread evenly within it.
  • The volumes of gases are greatly affected by temperature changes, unlike solids and liquids.
• Liquids and gases are compressible, meaning their volume can be reduced by applying pressure.
  • Gases are more compressible than liquids.

Kinetic Particle Theory

• Main points:
  • All matter consists of tiny, moving particles (atoms, molecules, or ions) that are invisible to the naked eye.
  • Different substances have different types of particles with varying sizes.
  • Particles are always in motion and move faster at higher temperatures.
  • Heavier particles move more slowly than lighter ones at the same temperature.
• The kinetic particle theory is a scientific model that explains how the arrangement of particles relates to the properties of the three states of matter.

Explaining States of Matter

• In solids, particles attract each other and are held close together by attractive forces.
  • Particles in solids have limited movement, generally only vibrating around a fixed position.
  • The regular arrangement of particles in solids explains why many solids form crystals.
  • Crystals can be modeled using spheres to represent particles.
• In liquids, particles are still close but move randomly and collide with each other.
  • The forces of attraction between particles in liquids are weaker than in solids.
  • Particles in the liquid state possess more energy than in the solid state of the same substance.
• In gases, particles are relatively far apart and move freely within the container.
  • Gas particles move randomly at high speeds, colliding with each other and the container walls.
  • They exert virtually no forces of attraction on each other due to their distance.
  • The existence of solids and liquids relies on the presence of significant attractive forces; without these, only gases would exist.

Changes of State

• Kinetic particle theory explains state changes:
  • Heating a solid increases particle vibration, causing them to push neighboring particles away, leading to expansion.
  • Eventually, heat energy weakens attractive forces, causing the solid to melt.
  • Melting point is the temperature at which a solid melts, and the temperature remains constant during melting.
• Solids with high melting points have stronger interparticle attraction forces than solids with low melting points.
• Heating a liquid increases particle energy and speed, leading to evaporation as surface particles escape to form a gas.
  • At the boiling point, gas bubbles form within the liquid and the pressure of the gas above the liquid equals atmospheric pressure.
  • Liquids with high boiling points have stronger interparticle forces than liquids with low boiling points.
• Cooling a gas decreases particle energy, causing them to move closer together. Attractive forces lead to condensation into a liquid. Cooling a liquid leads to freezing into a solid.
• Energy is released during condensation and freezing.
• Changes of state are physical changes.
  • Temperature remains constant during a physical change and no new substance is formed.

Heating and Cooling Curves

• Graphs plotting temperature against time illustrate changes of state.
• A flat portion of the curve indicates a change of state and that the temperature remains constant.

Effects of Temperature and Pressure on Gas Volume

• Pressure inside a balloon is caused by gas particles striking the inside surface:
  • Higher temperatures increase particle energy and speed, leading to more frequent collisions and higher pressure.
  • Balloons stretch due to increased pressure.
  • Increase in gas volume with temperature is a property of all gases.
• JA Charles concluded that gas temperature increases also increase volume (at fixed pressure).
• Increasing the pressure on a fixed gas volume increases its temperature:
  • Increased pressure forces molecules closer, increasing collision frequency.
  • Frictional forces increase temperature.
  • Intermolecular bonds form, further increasing temperature.
  • Faster-moving molecules cause more collisions.

Diffusion

• Diffusion is the process of gas particles spreading through the air in a haphazard, random manner.
• All gases diffuse to fill available space.
• Diffusion can be explained by kinetic particle theory, stating that all matter is composed of constantly moving small particles.
  • In gases, particles move randomly and collide with each other.
• Gases diffuse at different rates.
  • Lighter particles diffuse faster (e.g. ammonia) than heavier particles (e.g. hydrogen chloride).
• Diffusion also occurs in liquids, but it is slower than in gases due to the slower movement of liquid molecules.
• Diffusion can occur between a liquid and a gas, due to random collisions between particles and sufficient space.