Unit 3 Solutions Chemistry IPC-Solutions-Borders

Can it be physically separated? Matter Flowchart MATTER yes no Can it be physically separated? MIXTURE PURE SUBSTANCE Is the composition uniform? no yes Can it be chemically decomposed? no yes Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element Colloids Suspensions IPC-Solutions-Borders

IPC-Solutions-Borders Pure Substances A pure substance has a definite composition. Pure substances can be elements or compounds IPC-Solutions-Borders

IPC-Solutions-Borders Mixtures Combination of 2 or more pure substances. Heterogeneous Not uniform throughout Homogeneous Uniform throughout IPC-Solutions-Borders

IPC-Solutions-Borders 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. IPC-Solutions-Borders

IPC-Solutions-Borders Concept Check 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? IPC-Solutions-Borders

IPC-Solutions-Borders Types of Solutions Gaseous solutions – air Liquid solutions – drinks Solid solutions – steel or other alloys IPC-Solutions-Borders

IPC-Solutions-Borders Miscible liquids can easily dissolve in one another. Immiscible liquids are not soluble in each other. IPC-Solutions-Borders

Miscible and Immiscible Liquids IPC-Solutions-Borders

Heterogeneous Mixtures Suspensions-contain large particles that “settle out” unless constantly stirred or agitated Colloids-contain intermediate particles between those in solutions and suspensions IPC-Solutions-Borders

IPC-Solutions-Borders Suspensions Heterogeneous Mixture in which the particles in the solvent are so large that they settle out unless the mixture is constantly stirred. IPC-Solutions-Borders

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IPC-Solutions-Borders How does a solid dissolve into a liquid? IPC-Solutions-Borders

How Does a Solution Form? Solvent molecules are attracted to surface ions. Each ion is surrounded by solvent molecules. Ionic solid dissolving in water IPC-Solutions-Borders

Dissolution vs reaction dry Ni(s) + HCl(aq) NiCl2(aq) + H2(g) NiCl2(s) Dissolution is a physical change—you can get back the original solute by evaporating the solvent. If you can’t, the substance didn’t dissolve, it reacted. IPC-Solutions-Borders

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. IPC-Solutions-Borders

IPC-Solutions-Borders Chemistry-Borders IPC-Solutions-Borders

IPC-Solutions-Borders Rate of Dissolution There are several factors that affect the rate or “how quickly” dissolving occurs. Heating Agitating Increasing Surface Area IPC-Solutions-Borders

IPC-Solutions-Borders Saturation IPC-Solutions-Borders

IPC-Solutions-Borders Saturation Types saturated solution containing undissolved solute in equilibrium with the solution unsaturated solution containing less than the maximum amount of solute supersaturated solution containing more solute than is normally allowed IPC-Solutions-Borders

IPC-Solutions-Borders 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. IPC-Solutions-Borders

IPC-Solutions-Borders 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. IPC-Solutions-Borders

IPC-Solutions-Borders Saturated Solution IPC-Solutions-Borders

IPC-Solutions-Borders Degree of saturation Supersaturated Solution Solvent holds more solute than is normally possible at that temperature. These solutions are unstable; crystallization can often be caused by adding a “seed crystal” or scratching the side of the flask. IPC-Solutions-Borders

IPC-Solutions-Borders A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature. An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature. A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature. Sodium acetate crystals rapidly form when a seed crystal is added to a supersaturated solution of sodium acetate. IPC-Solutions-Borders

IPC-Solutions-Borders Solubility IPC-Solutions-Borders

IPC-Solutions-Borders 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

IPC-Solutions-Borders 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

IPC-Solutions-Borders Temperature Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature. Chemistry-Borders IPC-Solutions-Borders

IPC-Solutions-Borders 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 O2 dissolved in them than cool lakes. IPC-Solutions-Borders

IPC-Solutions-Borders Temperature and Solubility Solid solubility and temperature solubility increases with increasing temperature solubility decreases with increasing temperature IPC-Solutions-Borders

IPC-Solutions-Borders Temperature and Solubility Gas solubility and temperature solubility usually decreases with increasing temperature IPC-Solutions-Borders

IPC-Solutions-Borders Electrolytes IPC-Solutions-Borders

IPC-Solutions-Borders 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