TEAS Version 7 Science: Chemistry - Properties of Solutions

Water: A Remarkable Molecule

• Structure and Polarity
  • Water molecule: Oxygen (highly electronegative) attracts more electrons than hydrogen.
  • Oxygen and hydrogen form covalent bonds.
  • Oxygen has 8 protons/electrons; needs 2 more electrons to complete the octet rule.
  • Polarity results in hydrogen bonding: slightly negative oxygen bonds with slightly positive hydrogen.
• Special Properties
  • Solvent abilities, surface tension, high boiling point.
  • Adhesion: Water attracts to other materials, defies gravity.
  • Cohesion: Water molecules attract each other, creating surface tension.

Solutions: Solute, Solvent, and Solutions

• Experiment with Water
  • Salt, sugar dissolve in water forming homogeneous mixtures.
  • Pebbles do not dissolve, resulting in heterogeneous mixtures.
• Definitions
  • Solution: Homogeneous mixture with no visible separation.
  • Solute: Substance dissolved in smaller amounts (e.g., salt, sugar).
  • Solvent: Substance in larger amounts (e.g., water).

Examples of Solutions

• Cold drinks, fog, clouds, and alcohol in water.
• Water as the universal solvent, dissolves polar substances well.
• Hydrophilic vs Hydrophobic
  • Hydrophilic: Water-loving, dissolves well (e.g., salts, polar molecules).
  • Hydrophobic: Water-fearing, does not dissolve well (e.g., oils, fats).

Molarity and Dilution

• Concentration
  • Moles of solute per liter of solution (M = moles/L).
  • Can be changed via dilution (adding solvent reduces concentration).
• Example Calculations
  • Calculate molarity using the formula M = moles/volume.
  • Example problem solutions provided.

Osmosis

• Process
  • Movement of water through a semi-permeable membrane.
  • Water moves from areas of high to low concentration (or low solute to high solute concentration).
• Key Terms
  • Hypertonic: Higher solute concentration (compared to another solution).
  • Hypotonic: Lower solute concentration.
  • Isotonic: Equal solute concentrations.

Practical Applications of Osmosis

• Importance of using isotonic IV solutions to prevent cell damage.
• Risk of pure water IV causing cells to swell and burst.

Diffusion

• Process
  • Movement of molecules from high to low concentration (passive transport).
  • Not limited to liquids, includes gases like air fresheners.
• Facilitated Diffusion
  • Uses protein channels for larger molecules, still passive transport.

Factors Influencing Diffusion

• Distance, temperature, solvent characteristics, traveling characteristics, barrier characteristics.

Active Transport

• Process
  • Movement of molecules against concentration gradient (requires energy).
  • Involves ATP and protein channels (pumps).
• Importance
  • Essential for nutrient uptake, waste removal, ion balance.
  • Relevant in physiology (e.g., nutrient absorption in intestines, ion reabsorption in kidneys).

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