Unit 3 Solutions Chemistry IPCSolutionsBorders Matter Flowchart MATTER

Unit 3 Solutions Chemistry IPC-Solutions-Borders

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

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

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

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

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

Types of Solutions Gaseous solutions – air Liquid solutions – drinks Solid solutions – steel or other alloys 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 v. Suspensions-contain large particles that “settle out” unless constantly stirred or agitated v. Colloids-contain intermediate particles between those in solutions and suspensions 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

Solutions IPC-Solutions-Borders

Solutions 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 Ni(s) + HCl(aq) Ni. Cl 2(aq) + H 2(g) dry Ni. Cl 2(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”: Ø Polar substances tend to dissolve in polar solvents. Ø Nonpolar substances tend to dissolve in nonpolar solvents. Oil is nonpolar while water is polar. They are immiscible. 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

Saturation 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

Degree of saturation • Unsaturated Solution Ø Less than the maximum amount of solute for that temperature is dissolved in the solvent. Ø No solid remains in flask. IPC-Solutions-Borders

Degree of saturation • Saturated solution Ø Solvent holds as much solute as is possible at that temperature. Ø Undissolved solid remains in flask. Ø Dissolved solute is in dynamic equilibrium with solid solute particles. IPC-Solutions-Borders

Saturated Solution IPC-Solutions-Borders

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

Solubility 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

Gases in Solution Increasing pressure above solution forces more gas to dissolve. • 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. IPC-Solutions-Borders

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

Temperature • The opposite is true of gases. Higher temperature drives gases out of solution. Ø Carbonated soft drinks are more “bubbly” if stored in the refrigerator. Ø Warm lakes have less O 2 dissolved in them than cool lakes. IPC-Solutions-Borders

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

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

Electrolytes IPC-Solutions-Borders

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