Heterogeneous Mixtures matter pure substances mixtures matter pure elements substances compounds mixtures iron gold lead uranium sodium chloride glucose calcium carbonate water matter pure substances elements compounds iron gold lead uranium sodium chloride glucose calcium carbonate water mixtures homogeneous mixtures heterogeneous mixtures mixtures air gasoline 14 karat gold seawater granite soil blood chocolate cake matter pure substances elements iron gold lead uranium compounds mixtures homogeneous mixtures sodium chloride air glucose gasoline calcium carbonate 14 karat gold water seawater heterogeneous mixtures granite soil blood chocolate cake Mixtures • All matter is either a pure substance or a mixture. • Most of the “stuff” in this world is in the form of a mixture. Properties of Mixtures 1. Particles are physically combined, not chemically combined; so they can be separated by physical means. 2. A mixture can be made in any proportion. 3. The parts of a mixture keep their own properties. Six Phases of Mixtures 1. 2. 3. 4. 5. 6. Gel Sol Emulsion Foam Aerosol Heterogeneous Alloy Classifying Mixtures by Phase • A homogeneous mixture has one phase. Another word for this is solution. Classifying Mixtures by Phase • A heterogeneous mixture has distinct phases. If only the word mixture is used, it is understood to be heterogeneous. What is a solution? 1. 2. 3. 4. Homogeneous mixture Heterogeneous mixture Compound Pure Substance Question Classifying Mixtures by Phase • Continuous phase—an unbroken phase in which the other phases are mixed Ex: the sand in a sand-androcks mixture Classifying Mixtures by Phase • Dispersed phase—scattered throughout the continuous phase Ex: the rocks in a sand-androcks mixture Classification by Phase • Gel—a solid dispersed in a liquid that has some rigidity Ex: dessert gelatin Classification by Phase • Sol—a solid-in-liquid mixture that is more “liquidy” Ex: paints and inks Classification by Phase • Emulsions—contain two or more phases in the liquid state The liquids will not mix (immiscible). Sometimes a liquid is made of such small particles that it is not visible as a separate substance. Classification by Phase Over time the liquids will separate. Homogenization, a thorough mixing process, can slow the separation. Ex: cream cheese, milk, mayonnaise, and butter Classification by Phase • Foam—gas dispersed in a liquid Ex: whipped cream, shaving foams • Aerosols—solid or liquid dispersed in a gas Ex: dust in air, water in air Classification by Phase • Heterogeneous alloys—solidsolid mixture; usually metal Ex: fuel plate in nuclear reactors Ink is an example of a(n) ______. 1. 2. 3. 4. gel sol emulsion dispersed phase Question Classifying Mixtures by Particle Size 1. Colloidal Dispersion 2. Suspension Colloidal Dispersions • Colloidal dispersions consist of particles too small to see. • Therefore the dispersion can look like a homogeneous mixture. • The dispersed particles are called colloids. Colloidal Dispersions • The colloidal particles are too small to settle out. • The thermal vibrations of the continuous phase particles keep the dispersed phase mixed. • Many gels, sols, emulsions, foams, and aerosols are colloidal dispersions. Suspensions • Suspension particles are larger than colloids and will eventually settle out. Solutions • Solutions have the tiniest particles. Classifying Mixtures by Particle Size • The particles in a colloidal dispersion or suspension are large enough to scatter light. This scattering is called the Tyndall effect. • The particles dissolved in a solution are too small and do not scatter the light. suspensions/ dispersions solutions Which of the following contains particles that settle out? 1. 2. 3. 4. solution colloidal dispersion suspension homogeneous mixture Question Homogeneous Mixtures Homogeneous Mixtures • Homogeneous mixtures (solutions) are uniform mixtures with a single phase, but two substances are involved. • The solute is the substance being dissolved. • The solvent is the substance doing the dissolving. Homogeneous Mixtures • There is always less solute than solvent in the mixture. • Although the solute is completely mixed in the solvent, there is no chemical combination. • No new substance is formed. Types of Solutions by Solvent • Liquid solutions most common solute: solids, liquids, and/or gases Ex: salt + water, sugar + water, carbon dioxide + water Types of Solutions by Solvent • Solid solutions solute: solids, liquids, and/or gases • gas-in-solid: H2 into platinum • liquid-in-solid: mercury into gold (called an amalgam) • solid-in-solid: alloys (metals mixed in a liquid state and then cooled) Types of Solutions by Solvent • Gas solutions solute: only gases Ex: air (nitrogen + oxygen) Water • Water is the most common solvent in liquid solutions. • It is such a good solvent that it is nearly impossible to find 100% pure water. Water • Its structure (bent) makes it an effective solvent. • Since water is polar, it attracts ionic and polar covalent substances. The Solution Process • For an ionic solid such as salt to dissolve, the bonds between the sodium and chloride ions must be broken. • This process generally is called dissociation. • The specific term for dissociation of polar covalent or ionic solids is ionization. The Solution Process • Then other water molecules attach to the separated ions in a process called hydration. • If the solvent is not water, the second process is called solvation. The Solubility Rule Like dissolves like. This means that polar solvents dissolve polar and ionic solutes, and nonpolar solvents dissolve nonpolar solutes. “Like dissolves like” means: 1. 2. 3. 4. what you like dissolves polar dissolves polar polar dissolves nonpolar a substance eats whatever it likes Question Solubility • A few liquid solutes are infinitely soluble in some liquid solvents. • This means that they can freely mix in any proportion. • The term for this property is miscible. Solubility • Ex: alcohol and water Solubility • The opposite of miscible is immiscible. • Liquid solutes that cannot mix with liquid solvents are immiscible. Solubility • Most solvents have a limit as to how much solute they can dissolve. • That limit is called solubility. • Solubility is stated in grams of solute that can be dissolved into 100 mL of water. Factors Affecting Solubility • There are two factors that affect solubility: 1. Temperature 2. Pressure Solubility and Temperature • When dissolving liquids or solids, an increase in temperature equals an increase in solubility. • When dissolving gases, an increase in temperature equals a decrease in solubility. Solubility and Pressure • When dissolving liquids or solids, pressure has no noticeable effect on solubility. • When dissolving gases, an increase in pressure equals an increase in solubility. Henry’s Law Solubility of gases increases with the partial pressure of the gas above the solution. Saturation • When a solute is at the solubility limit, the solution is said to be saturated. • If less than the maximum amount of solute is dissolved, the solution is unsaturated. Saturation • If a saturated solution is cooled, it can become supersaturated. • Supersaturated means it has more than the usual maximum amount of solute dissolved. • If the supersaturated solution is disturbed, the excess solute will quickly fall out of the solution (precipitate). When the solubility limit is exceeded, a ______ results. 1. 2. 3. 4. solution precipitate solvent solute Question If you are trying to dissolve a solid into a liquid and increase the temperature, the solid will 1. not dissolve. 2. fully dissolve. 3. dissolve less. 4. dissolve more. Question If you are trying to dissolve a gas into a liquid and increase the temperature, the gas will 1. not dissolve. 2. fully dissolve. 3. dissolve less. 4. dissolve more. Question The harder you push a gas into solution, 1. 2. 3. 4. the more it will dissolve. the less it will dissolve. the hotter it will become. the colder it will become. Question Rate of Solution • The rate of solution is affected by two factors: 1. inherent solubility 2. the number of effective solute-solvent collisions Number of Collisions • The number of collisions can be changed by: • changing the temperature • stirring • changing the surface area Solution Concentration Concentration • Concentration is the amount of solute that is dissolved. • Dilute and concentrated are too vague. Percentage by Mass g solute × 100 g solution This is comparing different concentrations of the same solution. Sample Problem If 5.81 g of salt is dissolved in water to make 56.3 g of solution, what is the percent by mass? 5.81 g solute × 100 = 10.3% 56.3 g solution If 10 g of sugar is added to 90 g of water, what is the percent by mass? 1. 2. 3. 4. 10% 11% 5% 20% 10 g sugar = 10% 100 g total Question When 25 g of salt is dissolved to make a 125 g solution, what is the percent by mass? 1. 2. 3. 4. 10% 25 g salt 20% = 20% 16.7% 125 g total 25% Question Molarity • Molarity is a measure of the number of solute particles dissolved rather than the mass of dissolved particles. • Since the size of the particles is so small, the number is tremendously large. Molarity • The unit used to measure the number of particles is the mole. • A mole of solute has 6.022 × 1023 particles. moles of solute molarity = L of solution Colligative Properties Colligative properties depend only on the number of solute particles dissolved in the solution. Colligative Properties • Colligative properties affect boiling point freezing point osmotic pressure Boiling Point • An increase in solute raises the boiling point. • Solute interferes with boiling, so the temperature must be increased in order to reach the boiling point. Freezing Point • An increase in solute lowers the freezing point. • Solute interferes with freezing, so the temperature must be lowered in order to reach the freezing point. Osmosis • Osmosis is the movement of solvent (often water) from a high concentration to a low concentration through a semipermeable membrane. • Water moves from a region of high concentration to a region of low concentration of water. Osmosis • Osmosis can also be described as water going from a diluted solution to a concentrated solution. Semi-permeable membrane Water Sugar Water Osmotic Pressure Osmotic pressure is the amount of pressure required to stop osmosis. Reverse Osmosis • Reverse osmosis also requires a semi-permeable membrane, which can be used to separate seawater from freshwater in order to make it drinkable. • The process of removing salt from seawater is called desalination.