Solutions Solution Solute Solvent Homogeneous mixture of two or more substances in a single physical state Solute Substance that is dissolved or broken down Generally of lesser quantity than solvent Solvent Substance that does the dissolving

Dissolving of solid sodium chloride.

Polar water molecules interacting with positive and negative ions of a salt.

Particle Models for Gold and Gold Alloy Section 1 Types of Mixtures Chapter 12 Particle Models for Gold and Gold Alloy

Types of Solutions Solid solutions Gaseous Liquid Aqueous See Table 1 pg. 402

Heterogeneous Aqueous Systems 15.3 Gelatin is a heterogeneous mixture called a colloid.

Suspensions 15.3 Suspensions are heterogenous because at least two substances can be clearly identified. A suspension is a mixture from which particles settle out upon standing. A suspension differs from a solution because the particles of a suspension are much larger and do not stay suspended indefinitely. A suspension is a heterogeneous mixture. Suspended particles can be removed by filtration. Comparing and Contrasting How does the filtration of a suspension compare with the filtration of a solution?

15.3 Colloids A colloid is a heterogeneous mixture containing particles that range in size from 1 nm to 1000 nm. The particles in a colloid are spread throughout the dispersion medium. Colloids have particles smaller than those in suspensions and larger than those in solutions. See Table 2, pg. 404

15.3 Colloids

Solutions, Colloids & Suspensions 15.3 Solutions, Colloids & Suspensions

Colloids The Tyndall Effect 15.3 The scattering of visible light by colloidal particles is called the Tyndall effect. The path of light is visible only when the light is scattered by particles. a) Fog or mist is a colloid and thus exhibits the Tyndall effect. b) Particles in colloids and suspensions reflect or scatter light in all directions. Solutions do not scatter light.

15.3 Colloids Particles in colloids and suspensions reflect or scatter light in all directions. Solutions do not scatter light. The path of light is visible only when the light is scattered by particles. a) Fog or mist is a colloid and thus exhibits the Tyndall effect. b) Particles in colloids and suspensions reflect or scatter light in all directions. Solutions do not scatter light.

Colloids Brownian Motion 15.3 The chaotic movement of colloidal particles, which was first observed by the Scottish botanist Robert Brown (1773–1858), is called Brownian motion. Brownian motion is caused by collisions of the molecules of the dispersion medium with the small, dispersed colloidal particles.

15.3 Colloids Coagulation A colloidal system can be destroyed, or coagulated, by the addition of ions having a charge opposite to that of the colloidal particles. The added ions neutralize the charged colloidal particles. The particles can clump together to form heavier aggregates and precipitate from the dispersion.

15.3 Colloids Emulsions An emulsion is a colloidal dispersion of a liquid in a liquid. An emulsifying agent (e.g. soap) is essential for the formation of an emulsion Mayonnaise is heterogeneous mixture of oil and vinegar. Such a mixture would quickly separate without the presence of egg yolk, which is the emulsifying agent. The addition of an egg yolk to a mixture of oil and vinegar produces mayonnaise, a stable emulsion.

Electrolytes and Nonelectrolytes 15.2 Electrolytes and Nonelectrolytes An electrolyte is a compound that conducts an electric current when it is in an aqueous solution or in the molten state. All ionic compounds are electrolytes because they dissociate into ions.

Electrolytes and Nonelectrolytes 15.2 Electrolytes and Nonelectrolytes The bright glow shows that sodium chloride is a strong electrolyte because nearly all the dissolved sodium chloride exists as separate Na+ and Cl– ions. A solution conducts electricity if it contains ions. a) Sodium chloride, a strong electrolyte, is nearly 100% dissociated into ions in water. b) Mercury(II) chloride, a weak electrolyte, is only partially dissociated in water. c) Glucose, a nonelectrolyte, does not dissociate in water.

Factors Affecting Rate of Dissolving Surface Area Stirring Temperature Pressure (only for gases)

How Solutions Form Solvation Interaction between solute and solvent Called hydration when solvent is water Can be exothermic or endothermic Solution may not form

16.1 Solubility A saturated solution contains the maximum amount of solute for a given quantity of solvent at a given temperature and pressure. An unsaturated solution contains less solute than a saturated solution at a given temperature and pressure. A supersaturated solution contains more dissolved solute than a saturated solution contains under the same conditions

16.1 Solubility In a saturated solution, the rate of dissolving equals the rate of crystallization, so the total amount of dissolved solute remains constant. In a saturated solution, a state of dynamic equilibrium exists between the solution and the excess solute. The rate of solvation (dissolving) equals the rate of crystallization, so the total amount of dissolved solute remains constant. Inferring What would happen if you added more solute?

Polar water molecules interacting with positive and negative ions of a salt. For Ionic Compounds, this process is known as hydration

16.1 Solubility The solubility of a substance is the amount of solute that dissolves in a given quantity of a solvent at a specified temperature and pressure to produce a saturated solution. Solubility is often expressed in grams of solute per 100 g of solvent.

Factors Affecting Solubility 16.1 Factors Affecting Solubility Changing the temperature usually affects the solubility of a substance. INTERPRETING GRAPHS a. Describe What happens to the solubility of KNO3 as the temperature increases? b. Identify Which substance shows a decrease in solubility as temperature increases? Which substance exhibits the least change in solubility? c. Apply Concepts Suppose you added some solid sodium chloride (NaCl) to a saturated solution of sodium chloride at 20°C and warmed the mixture to 40°C. What would happen to the added sodium chloride?

Factors Affecting Solubility 16.1 Factors Affecting Solubility

Solubility Rules Solute Polar Solvent H2O Nonpolar Solvent CCl4, C6H5CH3 polar soluble insoluble nonpolar ionic

An oil layer floating on water. Immiscible Water—polar Oil—non-polar

Factors Affecting Solubility 16.1 Factors Affecting Solubility Henry’s law states that at a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P) of the gas above the liquid. Pressure is a factor in the solubility of a gas. a) In a sealed bottle, both the pressure of CO2 above the liquid and the concentration of CO2 in the liquid are high and equal. b) When the cap is removed, the equilibrium is disturbed; the pressure of CO2 gas above the liquid decreases and carbon dioxide bubbles out of the liquid. example

Enthalpy of Solution The net amount of energy absorbed as heat by the solution when a specific amount of solute dissolves in solvent is the enthalpy of solution See page 416

Enthalpy of Solution The formation of a solution is accompanied by an energy change. If you dissolve some potassium iodide, KI, in water, you will find that the outside of the container feels cold to the touch. But if you dissolve some sodium hydroxide, NaOH, in the same way, the outside of the container feels hot. The formation of a solid-liquid solution can either absorb energy (KI in water) or release energy as heat (NaOH in water)

Steps involved in the preparation of a standard aqueous solution.

Key Equations Molarity (M) = moles of solute liters of solution Molality (m) = moles of solute kg’s of solvent Mole Fraction = moles of component total moles of solution

16.2 Making Dilutions The total number of moles of solute remains unchanged upon dilution, so you can write this equation. M1 and V1 are the molarity and volume of the initial solution, and M2 and V2 are the molarity and volume of the diluted solution.

16.2 Percent Solutions The concentration of a solution in percent can be expressed in two ways: as the ratio of the volume of the solute to the volume of the solution or as the ratio of the mass of the solute to the mass of the solution.