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Bellringer

Learn about significant digits and how to solve problems involving them, as well as the nature of solutions and different separation techniques. Explore solubility and understand the concept of "like dissolves like".

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Bellringer

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  1. Bellringer • How many significant digits are in the following numbers • a. 5043 b. 0.005 000 • c. 5.28 X 105 d. 7 000 000 • Solve the following and round the answers to the correct number of significant digits • a. 150 + 0.05 b. 143.0 – 0.007 •  c. (2.956)(30) d. 1.800 X 1016/6.02 X 1023

  2. Ch. 13 – Liquids & Solids II. The Nature of Solutions

  3. MIXTURE PURE SUBSTANCE yes no yes no Is the composition uniform? Can it be chemically decomposed? Colloids Suspensions A. Solutions MATTER yes no Can it be physically separated? Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element

  4. Separating Mixtures: • Evaporation • Filtration • Decanting- a process for the separation of mixtures, by removing a layer of liquid, generally one from which a precipitate has settled. • Centrifuge – spins rapidly and separates liquids with different densities • Chromatography – (color) separates dyes in ink • Distillation - separates liquids with different boiling points using vaporization & condensation

  5. Tyndall Effect A. Solutions • Solution • Homogeneous mixture • very small particles • no Tyndall effect • particles don’t settle • EX: salt water, hydrogen peroxide, 3 M (molar) HCl

  6. A. Definitions • Solution: Solute - substance being dissolved Solvent - present in greater amount-does the dissolving

  7. A. Definitions • Types of solutions: • Solid Solutions: gold jewelry (gold + copper, 18k (karot) is 18/24=75% gold); alloy- brass (copper + zinc) • Gas Solutions: air (78% nitrogen, 21% oxygen, <1% argon and neon) • Liquid Solutions: oxygen dissolved in lakes; soda pop-CO2 in water

  8. A. Definitions • Aqueous Solutions: water is the solvent (universal solvent) • Salt + water • Sugar + water • 3% Hydrogen Peroxide • NaOH (aq)

  9. B. Solvation • Solvation • the process of dissolving • Increase rate by 3 things: stirring, increase temp. of solvent, smaller particle size. solute particles are surrounded by solvent particles First... solute particles are separated and pulled into solution Then...

  10. B. Solvation • 1. Dissociation • separation of an ionic solid into aqueous ions NaCl(s)  Na+(aq) + Cl–(aq) MgCl2 (s) Mg+2 (aq) + 2Cl- (aq)

  11. B. Solvation • 2. Ionization • breaking apart of some polar molecules into aqueous ions HNO3(aq) + H2O(l) H3O+(aq) + NO3–(aq) (nitric acid)

  12. B. Solvation • 3. Molecular Solvation • Molecules • Covalently bonded • stay intact C6H12O6(s)  C6H12O6(aq) (glucose, sugar)

  13. Polar Substances Water Salt (ionic solids) ammonia Vinegar (acetic acid) Rubbing alcohol (isopropyl) acetone Nonpolar substance Vegetable oil Waxes Petroleum oil Gasoline Carbon tetrachloride Hexane C. Solubility

  14. NONPOLAR + NONPOLAR POLAR + POLAR B. Solvation “Like Dissolves Like” • Detergents • polar “head” with long nonpolar “tail” • can dissolve nonpolar grease in polar water

  15. C. Solubility

  16. C. Solubility • Solubility • maximum grams of solute that will dissolve in 100 g of solvent at a given temperature and pressure • varies with temp. and pressure • based on a saturated solution - (maximum of solute has been dissolved)

  17. UNSATURATED SOLUTION more solute dissolves SATURATED SOLUTION no more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form C. Solubility concentration

  18. C. Solubility • Solubility Curve • shows the dependence of solubility on temperature

  19. C. Solubility • Solids are more soluble at... • high temperatures. • Gases are more soluble at... • low temperatures. • high pressures • EX: nitrogen narcosis, the “bends,” soda

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