Solutions

1. Solutions

2. Solutions • Type of homogenous mixture • Has the same composition, color and density throughout • Composed of: • Solute – substance that is being dissolved • Solvent- substance that is doing the dissolving • Most common solution – solid in liquid • Solutions can also occur between: • solid- solid • gas - liquid

3. Solid in Liquid solutions • Solute- solid • Solvent – liquid • usually water- universal solvent • Examples: fruit drinks • sports drinks • Dissolution occurs are the surface of the solid • 1) water molecules (polar) surround the solid molecules with their • negative ends attracted to the positive ends of the solid • 2) water molecules then pull the solid into solution • 3) solid molecule and water molecules mix evenly

4. Other Solutions • Gas-Gas Solutions • ex: air • Liquid – liquid Solutions • Ex: lemonade; mango juice • liquids are more freely moving and thus can mix together • Solid-Solid Solutions (alloys) • Ex: Bronze ( Copper and tin) • Sterling Silver • Brass • Solids must first be melted and then mixed together because of the crystalline shape of solids

5. Rate of Dissolving • Techniques to speed up the rate of dissolution • Stirring – this brings more fresh solvent into contact with solute • polarity of both solute and solvent makes solute dissolve faster • 2) Crystal size- make large crystals smaller • this makes the surface area larger—because dissolution occurs at surface area of the solid increasing surface area allows more solvent to come into contact with solute • 3) Temperature- increasing temperature increases molecular movement of solvent • Controlling the Process- Combination of two of the above techniques increases dissolution even more

6. Solubility • Maximum amount of a solute that can be dissolved in a given amount of solvent at a given temperature • Concentrated solutions- large amount of solute is dissolved in the solvent • Diluted solutions - small amount of solute is dissolved in the solvent • Solubility of common substance in 100 g of water at 20°C: • salt 35.9 • baking soda 9.6 • sugar 203.9 • hydrogen 0.00017 • carbon dioxide 0.16

7. Types of Solutions • Saturated Solutions: • Solution that contains all the solute a solvent can hold at a given temperature • Unsaturated Solutions: • Solution that dissolve more solute at a given temperature • Supersaturated Solutions: • Solution that contains more solute than a saturated solution • This solution is very unstable---- energy is given off

8. Solubility Curve Rule of Thumb for reading the solubility curve: Unsaturated – below the curve Saturated - is the curve Supersaturated – above the curve

9. Solubility of Gases • Increasing Solubility: • 1) Pressure - Increasing pressure increases the amount of gas • dissolved in liquids • reason why soda fizzes when popped • 2) Temperature - cooling the solvent increases the amount of gas • that dissolves • reason why soda gets warm when top is popped- more CO2 • has escaped

10. Particles in Solution • Electrolytes – compounds that produce solutions of ions that conduct • electricity • Ex: NaCl – stong electrolyte • conducts strong current • exist completely as ions in solutions • Acetic Acid – weak electrolyte • conducts weak current • exist as molecules in solutions • Nonelectrolytes – compounds that do not produce solutions of ions • Ex: sucrose and ethyl alcohol

11. Particles in Solution • Two Ways to produce ionic compounds • Ionization – production of charged particles (ions) • ex: HCl • Dissociation – separation of positive and negative particles from ionic • crystals • ex: NaCl • -- NaCl crystals will break apart under the influence of water • -- Na and Cl pull apart (dissociate) and move freely in solution • -- Na and Cl ions can now produce an electric current

12. Solute Effect on Solvent • Lowers the freezing point of the solvent • - solute interferes with the formation of particle arrangement • ex: antifreeze • Raises the boiling point of the solvent • - solute interferes with the evaporation of solvent particles • - more energy is needed for solvent particles to change phase from • liquid to gas • ex: car radiators

13. Nonpolar Solutes • Many solutes do not dissolve in water • - there is no distinct dissociation of ions • Ex: Vinegar and Oil • Polar and Nonpolar Solutes • - polar end dissolves polar molecules; nonpolar end dissolves nonpolar molecules • Ex: Ethanol • - dissolves iodine (nonpolar0 • - dissolves water (polar) • Useful Nonpolar Molecules: Disadvantages of Nonpolar Molecules: • Mineral Oil 1) flammable • turpentine 2) toxic • dry cleaner solutions

14. Soaps • Salts of fatty acids • Hydrocarbons with carboxyl end (-COOH) • Contain both polar and nonpolar properties • The making of soaps: • H of the acid group is removed leaving a negative charge • K or Na ion left with positive charge • The ionic nature of the acid dissolves in water • The hydrocarbon end dissolves in oils

15. Vitamins • Vitamin A – nonpolar molecule that dissolves in fats • Vitamin B – polar molecule that dissolves in water • Vitamin C – polar molecule that dissolves in water • Nonpolar molecules can accumulate in the body and become toxic • Polar molecules do not accumulate in the body—excess is removed in urine