Heterogeneous Mixtures

Heterogeneous Mixtures

matter puresubstances mixtures

matter puresubstances elements compounds mixtures iron gold lead uranium sodium chloride glucose calcium carbonate water

matter puresubstances mixtures elements compounds iron gold lead uranium sodium chloride glucose calcium carbonate water

homogeneousmixtures heterogeneousmixtures mixtures air gasoline 14 karat gold seawater granite soil blood chocolate cake

matter puresubstances mixtures elements compounds homogeneousmixtures heterogeneousmixtures iron gold lead uranium sodium chloride glucose calcium carbonate water air gasoline 14 karat gold seawater 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 • Particles are physically combined, not chemically combined; so they can be separated by physical means. • A mixture can be made in any proportion. • The parts of a mixture keep their own properties.

Six Phases of Mixtures • 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? • Homogeneous mixture • Heterogeneous mixture • Compound • Pure Substance

Classifying Mixtures by Phase • Continuous phase—an unbroken phase in which the other phases are mixed • Ex: the sand in a sand-and-rocks mixture

Classifying Mixtures by Phase • Dispersed phase—scattered throughout the continuous phase • Ex: the rocks in a sand-and-rocks 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—solid-solid mixture; usually metal • Ex: fuel plate in nuclear reactors

Ink is an example of a(n) ______. • gel • sol • emulsion • dispersed phase

Classifying Mixtures by Particle Size • Colloidal Dispersion • 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? • solution • colloidal dispersion • suspension • homogeneous mixture

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: • what you like dissolves • polar dissolves polar • polar dissolves nonpolar • a substance eats whatever it likes

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: • Temperature • 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.

Heterogeneous Mixtures