Lesson Objectives Describe the unique role of water In chemical systems In biological systems

1. Lesson Objectives • Describe the unique role of water • In chemical systems • In biological systems • Develop and use general rules regarding solubility through investigations with aqueous solutions • Water

2. Over 70% of Earth covered by water • Water constitutes over 50% of the human body • Water is the solvent in most body fluids • Water is a reactant in photosynthesis • Water Light + 6CO2 + 6H2OC6H12O6 + 6O2 By Rdsmith4 (Own work) [CC-BY-SA-2.5]

3. Exists as a solid, liquid, and gas in nature • Phases of Water

4. Water molecules are more tightly packed in the liquid phase than in the crystalline structure of the solid phase • Denser as a liquid than as a solid • Ice floats on water preserving aquatic life in cold climates • Density of Water

5. Polarity – the separation of electrical charge within a molecule, which causes partial positive and negative charges to form • “Like dissolves like” • Polar substances dissolve other polar substances Ex) Ammonia and water • Non-polar substances dissolve other non-polar substances Ex) Bromine and carbon tetrachloride • Polarity and Solubility

6. Polar and non-polar substances are not soluble and do not form solutions Ex) Oil and water • Polarity and Solubility By Victor Blacus (Victor Blacus) [GFDL]

7. Determine which products are soluble in water using a solubility table Ex) NaNO3 is soluble Ex) AgCl is insoluble Ex) Mg(OH)2 is insoluble • Solubility Rules

8. Remains in liquid form under most conditions on Earth • High boiling point compared to other small molecular compounds • High specific heat • Water is usually available as a solvent • Solvent– substance in a solution that is present in the greatest amount, in which the solute is dissolved • Solute– substance in a solution that is present in a lesser amount, which is dissolved in a solvent • Solution– homogeneous mixture of the solute and solvent • Aqueous solution – solution in which water is the solvent • Water as a Solvent

9. Water is the “universal solvent” • Water is a polar molecule • Water as a Solvent δ– O H H δ+ δ+

10. Polarity of water molecules make it a good solvent for most ionic compounds and other polar substances • Water as a Solvent

11. Solvation – process of solvent particles surrounding solute particles, pulling the solute apart and forming a solution • Attractive forces between the solute and solvent particles are stronger than the attractive forces binding the solute particles together • Solvation

12. Dissociation of Salt • Water as a Solvent

13. What happens to the liquids shortly after you stop shaking salad dressing? Oil is insoluble in vinegar; and thus oil and vinegar are said to be immiscible Two liquids that are soluble in each other are said to be miscible In order to form a solution, solute particles must separate from one another and the solute and solvent particles must mix. SOLUTIONS

14. Solubility – greatest quantity of solute that can be dissolved in a certain amount of solvent at a given pressure and temperature • Soluble substances can be dissolved by the solvent • Insoluble substances cannot be dissolved by the solvent • Solubility Insoluble Soluble By Dr.T (Own work) [CC-BY-SA-3.0]