Mixtures and Solutions Notes

Encounter the Phenomenon

  • Encounter the Phenomenon Question: How is it possible for a liquid to hold this shape?
  • What I Know:
    • Liquids take the shape of their container.
    • The molecular structure of liquids allows them to flow and change shapes while maintaining volume.
    • Surface tension plays a role in the shape of liquids.
  • What I Want to Find Out:
    • What forces are at play that allow liquids to maintain their shape temporarily?
    • How does the molecular interaction within the liquid contribute to its ability to hold a shape?
  • What I Learned: (To be filled in post-module)

Types of Mixtures

  • Definitions:

    • Solute: A substance dissolved in a solution.
    • Suspension: A mixture containing particles that settle out if left undisturbed.
    • Colloid: A mixture containing particles with diameters between 1 nm and 1000 nm.
    • Brownian Motion: Random movement of colloid particles due to collisions with dispersion medium particles.
    • Tyndall Effect: Scattering of light by colloidal particles.
    • Miscible: Two liquids that are soluble in each other in any proportion.
    • Immiscible: Two liquids that do not dissolve in each other.

  • Comparison of Soluble and Insoluble Substances:

    • Soluble: Substances that can dissolve in a solvent.
    • Insoluble: Substances that do not dissolve in a solvent.

Properties of Suspensions

  • Properties:
    1. Particles are larger than colloidal particles.
    2. Particles settle out over time.
    3. Can be separated by filtering.
  • Examples of Suspensions:
    1. Muddy water.
    2. Paint.
    3. Orange juice with pulp.

Properties of Colloids

  • Properties:
    1. Particles do not settle out.
    2. Cannot be filtered out easily.
    3. Display Brownian motion.
    4. Exhibit the Tyndall effect.

Differences Between Suspensions and Colloids

  • Suspension:
    • Particles settle out.
    • Can be studied directly.
  • Colloid:
    • Particles do not settle.
    • Can only be studied indirectly.

Solution Concentration

  • Definitions:

    • Solvent: The substance that dissolves a solute.
    • Concentration: Measure of solute in a specific amount of solvent.
    • Molarity (M): Moles of solute per liter of solution.
    • Molality (m): Moles of solute per kilogram of solvent.
    • Mole Fraction (X): Ratio of moles of one component to total moles in a solution.

  • Important Equation:

    • Percent by mass = (mass of solute / mass of solution) × 100.

  • Example Calculation:

    • 3.6 g NaCl in 100.0 g H2O:
    • Mass of solution = 3.6 g + 100.0 g = 103.6 g.
    • Percent by mass = (3.6 g / 103.6 g) × 100 = 3.48%.

Colligative Properties

  • Definitions:

    • Colligative Properties: Properties affected by the number of solute particles but not their identity.
    • Vapor Pressure Lowering: Decrease in vapor pressure when solute is added.
    • Boiling Point Elevation: Increase in boiling point of a solution compared to pure solvent.
    • Freezing Point Depression: Lowering of freezing point of a solution compared to pure solvent.
    • Osmosis: Movement of solvent across a semipermeable membrane from high to low solvent concentration.
    • Osmotic Pressure: Pressure required to prevent osmotic movement.

  • Electrolytes vs. Nonelectrolytes:

    • Electrolytes: Substances that ionize in water and conduct electricity.
    • Nonelectrolytes: Substances that do not ionize and do not conduct electricity.

  • Importance of Colligative Properties:

    • Properties depend on the number of solute particles and affect physical behaviors like freezing and boiling points.

Factors Affecting Solvation

  • Key Factors:

    1. Agitation of the mixture increases collision frequency.
    2. Decreasing particle size increases surface area for solvation.
    3. Increasing temperature enhances kinetic energy, leading to faster dissolving.

  • Temperature Influence:

    • Most substances: solubility increases with temperature but gases decrease.
    • Henry’s Law: Solubility of a gas is directly proportional to its pressure above the liquid.

Summary of Colligative Properties

  • Main Concepts:
    • Colligative properties arise from the number of solute particles in a solution, affecting various measurable outcomes such as vapor pressure, boiling point, and freezing point.
    • Understanding these properties is essential for predicting the behavior of solutions in different contexts.