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Introduction to Solutions
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Matter Flowchart MATTER Can it be physically separated? Homogeneous Mixture (solution) Heterogeneous MixtureCompoundElement MIXTUREPURE SUBSTANCE yesno Can it be chemically decomposed? noyes Is the composition uniform? noyes ColloidsSuspensions
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Pure Substances A pure substance has a definite composition. Pure substances can be elements or compounds
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Mixtures A mixture can be either homogeneous or heterogeneous. A homogeneous mixture is one in which all of the components are UNIFORMILY distributed. –Ex: chocolate milk A heterogeneous mixture is one in which the components are NOT UNIFORMILY distributed. –Ex: pizza HOMOGENEOUS HETEROGENEOUS
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Solutions Solutions, in chemistry, are homogeneous mixtures of two or more substances. The substance present in largest quantity usually is called the solvent. The solvent can be either a liquid or a solid. The substance that is present in smallest quantity is said to be dissolved and is called the solute. The solute can be either a gas, a liquid, or a solid.
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Coke lists as its ingredients as: “carbonated water, high fructose corn syrup and/or sucrose, caramel color, phosphoric acid, natural flavors, caffeine”. What is the solvent? What are the solutes? What can we classify CO 2 as in carbonated beverages? Concept Check
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Miscible liquids can easily dissolve in one another. Immiscible liquids are not soluble in each other. IPC-Solutions-Borders
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Heterogeneous Mixtures Suspensions-a heterogeneous mixture that contains large particles that “settle out” unless constantly stirred or agitated Ex: freshly squeezed OJ, salad dressing Colloids-a heterogeneous mixture in which the components are microscopic and will not separate when left standing. Ex: mayonnaise, milk, stick deodorant
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How does a solid dissolve into a liquid? Solvent molecules are attracted to surface ions. Each ion is surrounded by solvent molecules. Ionic solid dissolving in water
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Dissolution vs. Reaction Dissolution is a physical change—you can get back the original solute by evaporating the solvent. If you cant, the substance didn’t dissolve, it reacted. Ni(s) + HCl(aq)NiCl 2 (aq) + H 2 (g)NiCl 2 (s) dry
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Factors Affecting Solubility Chemists use the saying “like dissolves like:” Polar substances tend to dissolve in polar solvents. Nonpolar substances tend to dissolve in nonpolar solvents. Oil is nonpolar while water is polar. They are immiscible.
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Saturation Types Saturated Unsaturated
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Degree of saturation Unsaturated Solution Less than the maximum amount of solute for that temperature is dissolved in the solvent. No solid remains in flask.
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Degree of saturation Saturated solution Solvent holds as much solute as is possible at that temperature. Undissolved solid remains in flask. Dissolved solute is in dynamic equilibrium with solid solute particles.
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Saturated Solution IPC-Solutions-Borders
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Degree of saturation Supersaturated Solution Solvent holds more solute than is normally possible at that temperature. These solutions are unstable
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Chemistry-Borders Temperature and Solubility Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature.
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Solubility What amount of CaCl 2 can be dissolved in 100 g H 2 O at 20° C? ANSWER: 75 g CaCl 2
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Let’s play a quick game of…. Chemistry-BordersIPC-Solutions-Borders
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Saturated or Unsaturated? a solution that contains 70g of NaNO 3 at 30°C Chemistry-BordersIPC-Solutions-Borders
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UNSATURATED! Chemistry-BordersIPC-Solutions-Borders
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Saturated or Unsaturated? a solution that contains 50g of NH 4 Cl at 50°C Chemistry-BordersIPC-Solutions-Borders
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SATURATED! Chemistry-BordersIPC-Solutions-Borders
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Saturated or Unsaturated? a solution that contains 20g of KClO 3 at 50°C Chemistry-BordersIPC-Solutions-Borders
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SATURATED! Chemistry-BordersIPC-Solutions-Borders
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Saturated or Unsaturated? a solution that contains 70g of KI at 0°C Chemistry-BordersIPC-Solutions-Borders
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UNSATURATED! Chemistry-BordersIPC-Solutions-Borders
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Saturated or Unsaturated? A mass of 100 g of NaNO 3 is dissolved in 100 g of water at 80ºC Chemistry-BordersIPC-Solutions-Borders
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UNSATURATED! Chemistry-BordersIPC-Solutions-Borders
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THE END Chemistry-BordersIPC-Solutions-Borders
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Solubility of Gases In general, the solubility of gases in water increases with increasing mass. Why? Larger molecules have stronger dispersion forces. IPC-Solutions-Borders
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Gases in Solution The solubility of liquids and solids does not change appreciably with pressure. But, the solubility of a gas in a liquid is directly proportional to its pressure. Increasing pressure above solution forces more gas to dissolve. IPC-Solutions-Borders
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Temperature The opposite is true of gases. Higher temperature drives gases out of solution. Carbonated soft drinks are more “bubbly” if stored in the refrigerator. Warm lakes have less O 2 dissolved in them than cool lakes. IPC-Solutions-Borders
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Temperature and Solubility Solid solubility and temperature solubility increases with increasing temperature solubility decreases with increasing temperature IPC-Solutions-Borders
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Temperature and Solubility Gas solubility and temperature solubility usually decreases with increasing temperature IPC-Solutions-Borders
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Electrolytes IPC-Solutions-Borders
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Electrolyte Electrolyte: a substance that dissolves in water to give a solution that conducts electric current Any soluble ionic compound is an electrolyte Strong acids are electrolytes IPC-Solutions-Borders
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