Properties of Solutions

Chemistry: The branch of science concerned with the substances of which matter is composed, their properties, and the changes they undergo.
Solutions: Homogeneous mixtures formed from two or more pure substances, where the solute is uniformly distributed throughout the solvent.

Solute: The substance dissolved in the solution, generally present in a lesser amount.
Solvent: The substance that solute dissolves in; generally the substance present in a greater amount.

Various types of intermolecular forces can influence the formation of solutions:
- Dispersion Forces: Weak attractions due to temporary dipoles in atoms.
- Dipole-Dipole Interactions: Attractions between polar molecules that exhibit permanent dipoles.
- Hydrogen Bonds: Strong interactions occurring between a hydrogen atom bonded to a highly electronegative atom and another electronegative atom.
- Ion-Dipole Forces: Attractions between an ion and a polar molecule, critical in solvation processes.

During solution formation, several energy changes occur:
- ΔH_solute: Energy required to break solute-solute attractions.
- ΔH_solvent: Energy required to break solvent-solvent attractions.
- ΔH_mix: Energy change during the mixing of solute and solvent.
Solutions can be exothermic ($ ext{ΔH}{ ext{soln}} < 0$) or endothermic ($ ext{ΔH}{ ext{soln}} > 0$).
Entropy: The degree of disorder in the system, tends to increase during solution formation, favoring spontaneity.

Opposing Processes: Solution-making and crystallization are opposing processes. When these processes reach equilibrium, a saturated solution is formed.
Saturated Solutions: Contain the maximum quantity of solute that can dissolve in the solvent at a specific temperature.
Unsaturated Solutions: Contain less solute than can be dissolved at a given temperature.
Supersaturated Solutions: Contain more solute than would normally dissolve at that temperature; unstable and can lead to crystallization when disturbed.

Solubility of a solute depends on:
- Solute-Solvent Interactions: Like dissolves like; polar solutes dissolve in polar solvents and nonpolar solutes in nonpolar solvents.
- Temperature: Generally, increasing temperature increases the solubility of solids but decreases the solubility of gases.
- Pressure: Has a minimal effect on solids and liquids but significantly affects the solubility of gases (see Henry's Law).

States that the solubility of a gas in a liquid is proportional to the partial pressure of that gas above the liquid: ext{S}g = k imes Pg
- Where Sg is the solubility, k is a constant specific to the gas and solvent, and Pg is the partial pressure.

Mass Percentage:
ext{Mass \%} = \left( \frac{\text{mass of solute}}{\text{total mass of solution}} \right) \times 100
Parts per Million (ppm):
\text{ppm} = \left( \frac{\text{mass of solute}}{\text{total mass of solution}} \right) \times 10^6
Parts per Billion (ppb):
\text{ppb} = \left( \frac{\text{mass of solute}}{\text{total mass of solution}} \right) \times 10^9
Mole Fraction (χ):
\chi = \frac{\text{moles of component}}{\text{total moles of all components}}
Molarity (M): Moles of solute per liter of solution:
M = \frac{\text{moles of solute}}{\text{liters of solution}}
Molality (m): Moles of solute per kilogram of solvent:
m = \frac{\text{moles of solute}}{\text{kilograms of solvent}}

Osmosis: The movement of solvent molecules through a semipermeable membrane from a region of lower solute concentration to higher solute concentration until equilibrium is established.
Types of Solutions in Osmosis:
- Isotonic Solutions: Solutions with equal osmotic pressure; solvent moves in and out at the same rate.
- Hypotonic Solutions: Solutions with lower osmotic pressure; solvent leaves faster than it enters, potentially leading to hemolysis in cells.
- Hypertonic Solutions: Solutions with higher osmotic pressure; solvent enters faster than it leaves, potentially leading to crenation in cells.

Colloids: Mixtures where one substance of microscopically dispersed insoluble particles is suspended throughout another substance.
Tyndall Effect: Colloidal mixtures can scatter light, unlike true solutions.
Stabilizing Colloids: Involve adsorption of ions to colloidal particles, preventing them from aggregating and settling.
Brownian Motion: The random motion of particles suspended in a fluid, resulting from collisions with the fast-moving molecules in the liquid.

Colloids play a vital role in biological systems by aiding in emulsification, which is crucial for the digestion of fats and oils.

Natural Tendency Toward Mixing: Solutions form spontaneously due to an increase in entropy.
Intermolecular Forces and Solubility: Specific combinations of intermolecular interactions determine whether substances will dissolve together.
Thermodynamics: Understand the energetic dynamics that occur during solution formation, including enthalpy and entropy considerations.
Colligative Properties: Recognize and understand the significance of colligative properties in solutions, including their applications and implications in real-world scenarios, such as biological processes.