Chem Exam 3 Study Set

Boyle's Law

Boyle's Law states that gas volume and pressure move in opposite directions at a constant temperature. When pressure goes up, volume goes down.

Charles's Law

Charles's Law states that a gas volume is directly proportional to its Kelvin temperature at constant pressure. This means gases expand when they get hotter.

Avogadro's Law

Avogadro's Law states that equal volumes of different gases at the same temperature and pressure contain the exact same number of molecules. This directly links gas volume to the number of moles.

Ideal Gas Law

Expressed as PV = nRT, this equation combines all the basic gas rules into one formula. It helps predict how ideal gases behave under standard conditions.
P (Pressure)
V (Volume)
n (Amount of substance)
R (Universal gas constant)
T (Absolute temperature, in Kelvin)

Dalton's Law of Partial Pressures

Daltons Law states that the total pressure of a gas mixture equals the sum of all the individual pressures combined. Each gas acts as if it is the only one present in the container.

Graham's Law of Effusion

Graham's Law states that lighter gas molecules move and escape through tiny openings much faster than heavier ones. The rate of effusion depends directly on the inverse square root of its molar mass.

Kinetic Molecular Theory

This theory describes gas particles as tiny objects in constant random motion with perfectly elastic collisions. It explains macroscopic properties like temperature and pressure based on particle movement.

Real Gases

Real gases deviate from ideal rules because their molecules actually take up physical space and pull on each other. These deviations get worse at very high pressures and very low temperatures.

Van der Waals Equation

This equation fixes the ideal gas law by adding factors for molecular volume and attractive forces. It helps calculate gas behavior accurately under extreme conditions.

Vapor Pressure

Vapor pressure is the pressure created by gas molecules sitting right above their liquid or solid phase in a closed container. A liquid boils when this pressure equals the outside atmospheric pressure.

Boiling Point

The boiling point is the exact temperature where a liquid's vapor pressure matches the outside air pressure. At this point, the liquid turns rapidly into a gas.

Melting Point

The melting point is the temperature where solid and liquid phases exist together in balance. Extra heat goes entirely into breaking the solid crystal structure instead of raising the temperature.

Sublimation

Sublimation is the phase change where a solid turns straight into a gas without melting into a liquid first. Dry ice is a common example of this process.

Deposition

Deposition is the phase change where a gas turns straight into a solid without becoming a liquid. The formation of frost on cold grass is a good example.

Phase Diagram

A phase diagram is a graph of pressure versus temperature that shows which state of matter is stable. It lets you predict when a substance will melt, freeze, or boil.

Triple Point

The triple point is the specific temperature and pressure on a phase diagram where solid, liquid, and gas all exist at the same time. Any small change will cause one phase to disappear.

Critical Point

The critical point is the end of the liquid-gas boundary line on a phase diagram. Beyond this point, the substance turns into a supercritical fluid with properties of both states.

Intermolecular Forces

These are the attractive forces that pull separate molecules toward each other. They are weaker than true chemical bonds, but they control physical traits like boiling points.

London Dispersion Forces

These are the weakest intermolecular forces and happen in all molecules due to temporary shifts in electrons. Larger molecules have stronger dispersion forces because they have more electrons.

Dipole-Dipole Interactions

These attractive forces happen between permanent positive and negative ends of polar molecules. They are stronger than dispersion forces because the electrical charges do not vanish.

Hydrogen Bonding

This is an extra strong dipole attraction that happens when hydrogen is bonded to nitrogen, oxygen, or fluorine. It is why water has an unusually high boiling point.

Ion-Dipole Forces

These forces happen when a fully charged ion pulls on a neutral polar molecule. They are the main reason why table salt dissolves easily in water.

Surface Tension

Surface tension is the tendency of a liquid surface to shrink into the smallest possible area. It happens because surface molecules are pulled inward by strong cohesive forces.

Capillary Action

Capillary action is when a liquid climbs up a narrow tube against gravity. It happens when adhesive forces pulling the liquid to the glass are stronger than the liquid's internal cohesion.

Viscosity

Viscosity is a liquid's resistance to flowing. Liquids with very strong intermolecular forces have high viscosity and pour slowly.

Solution

A solution is a perfectly uniform mixture where solute particles are evenly spread through a solvent at the molecular level. Its physical state usually matches the solvent.

Solvent

The solvent is the main substance in a solution that does the dissolving. Water is the most common solvent because its molecules are polar.

Solute

A solute is the substance present in a smaller amount that gets dissolved by the solvent. The amount of solute determines how concentrated the mixture is.

Molarity

Molarity is the number of moles of solute dissolved in exactly one liter of solution. It changes with temperature because liquid volumes expand when heated.

Molality

Molality is the moles of solute divided by the kilograms of solvent. Because mass does not change with temperature, molality is great for precise calculations.

Mole Fraction

The mole fraction is the ratio of moles of one component compared to the total moles of everything in the mixture. The sum of all mole fractions in a mixture always equals one.

Mass Percent

Mass percent is the mass of the solute divided by the total mass of the solution, multiplied by 100. It is a concentration unit often used in chemistry and industry.

Parts Per Million

Parts per million is a unit used for very dilute solutions, equal to one milligram of solute per kilogram of solution. It is commonly used for testing water quality.

Volume Percent

Volume percent is the volume of a liquid solute divided by total solution volume, multiplied by 100. It is used when mixing two liquid solutions together.

Solubility

Solubility is the maximum amount of solute that can dissolve in a solvent at a specific temperature. It relies on the rule that like dissolves like.

Henry's Law

Henrys Law states that the solubility of a gas in a liquid goes up when the gas pressure above the liquid increases. This is why closed soda bottles keep their fizz until opened.

Saturated Solution

A saturated solution holds the absolute maximum amount of dissolved solute possible at that temperature. Any extra solute added will just sink to the bottom undissolved.

Unsaturated Solution

An unsaturated solution holds less solute than the maximum amount the solvent can handle. If you add more solute to this mixture, it will dissolve completely.

Supersaturated Solution

A supersaturated solution holds more dissolved solute than it theoretically should at that temperature. Dropping in a seed crystal causes the extra solute to rapidly crystallize out.

Miscible

Miscible liquids can mix together in any amount to form a single uniform solution. This happens when their intermolecular forces are very similar.

Immiscible

Immiscible liquids do not mix together and instead separate into distinct layers. Oil and water are immiscible because their internal forces are stronger than their attraction to each other.

Enthalpy of Solution

The enthalpy of solution is the total heat energy absorbed or released when a solute dissolves. It is exothermic if it releases heat and endothermic if it absorbs heat.

Colligative Properties

Colligative properties are physical traits of solutions that depend only on the number of dissolved particles, not what those particles actually are.

Vapor Pressure Lowering

Vapor pressure lowering happens when a nonvolatile solute blocks liquid molecules from escaping into the gas phase. This drops the overall vapor pressure of the solution.

Raoult's Law

Raoults Law states that a solution's vapor pressure equals the mole fraction of the solvent multiplied by the pure solvent's vapor pressure. It predicts how solutes reduce vapor pressure.

Boiling Point Elevation

Boiling point elevation means a solution boils at a higher temperature than a pure solvent. The added solute lowers vapor pressure, so you need more heat to make it boil.

Freezing Point Depression

Freezing point depression means a solution freezes at a lower temperature than a pure solvent. Solute particles get in the way and disrupt the solid crystal pattern.

Osmotic Pressure

Osmotic pressure is the external pressure needed to stop pure solvent from crossing a semipermeable membrane. It is driven by the tendency to dilute high concentrations.

Van't Hoff Factor

The Van't Hoff factor is the number of particles a substance breaks into when it dissolves. For sodium chloride, the theoretical factor is two because it splits into two ions.

Electrolyte

An electrolyte is a substance that breaks into charged ions when dissolved in water. The moving ions allow the liquid solution to conduct electricity.

Nonelectrolyte

A nonelectrolyte dissolves in water but stays as intact neutral molecules. Because it creates no free ions, the solution cannot conduct electricity.

Strong Electrolyte

A strong electrolyte breaks apart completely into ions in water, making the solution a great conductor of electricity. Soluble ionic salts are classic examples.

Weak Electrolyte

A weak electrolyte only partially breaks into ions in water, creating an equilibrium with mostly whole molecules. It conducts electricity poorly.

Colloid

A colloid is a mixture with particles bigger than normal molecules but too small to settle out by gravity. Milk and fog are stable examples of this mixture.

Tyndall Effect

The Tyndall effect is when a beam of light becomes visible as it shines through a colloid. True solutions do not show this because their particles are too small to scatter light.

Suspension

A suspension is a heterogeneous mixture with large particles that eventually settle to the bottom over time. You usually have to shake them before use.

Emulsion

An emulsion is a colloid made of two or more liquids that normally do not mix. A special stabilizing agent is needed to keep them from separating.

Aerosol

An aerosol is a colloid where tiny solid or liquid particles are suspended in a gas. Hair spray and clouds are common examples.

Foam

A foam is a colloid made by trapping a large amount of gas inside a liquid or solid. Shaving cream and whipped cream are good examples.

Gel

A gel is a semi-solid colloid where a liquid is trapped inside a network of solid fibers. It acts mostly like a solid while holding a lot of liquid.

Sol

A sol is a colloidal suspension of very fine solid particles dispersed inside a liquid. It keeps the ability to flow like a fluid.

Hydrophilic

Hydrophilic substances are polar or ionic materials that love water. They form hydrogen bonds and dissolve easily in aqueous environments.

Hydrophobic

Hydrophobic substances are nonpolar and avoid water completely. They group together to escape polar molecules, which is why oil droplets pool together in water.

Micelle

A micelle is a tiny spherical cluster formed by soap or surfactant molecules in water. The water-hating tails hide inside, while the water-loving heads face outward.

Surfactant

A surfactant is a compound that lowers surface tension between two liquids. Its dual nature lets substances like oil and water mix together safely.

Amorphous Solid

An amorphous solid lacks a repeating crystal structure. Because its bonds vary in strength, it softens gradually when heated instead of melting at a single high temperature.

Crystalline Solid

Crystalline solids have particles arranged in an orderly, repeating three-dimensional pattern. They melt at one exact, sharp temperature.

Unit Cell

The unit cell is the smallest repeating block of a crystal lattice. Repeating this pattern in all directions builds the entire crystal.

Simple Cubic

A simple cubic unit cell has atoms located only at the eight corners of a cube. It is a very loose packing arrangement with a lot of space.

Body-Centered Cubic

A body-centered cubic unit cell has atoms at the eight corners plus one extra atom right in the middle. It packs atoms more tightly than a simple cubic cell.

Face-Centered Cubic

A face-centered cubic unit cell has atoms at the eight corners and in the center of all six faces. It is one of the most efficient ways to pack spherical atoms.

Coordination Number

The coordination number is the count of immediate neighbor atoms surrounding any single atom in a crystal. A higher number means a more tightly packed structure.

Packing Efficiency

Packing efficiency is the percentage of a crystal unit cell volume actually filled by atoms. Face-centered cubic cells have the highest efficiency at about seventy-four percent.

Ionic Crystals

Ionic crystals are held together by strong electrostatic attractions between positive and negative ions. They are hard, brittle, and conduct electricity only when melted or dissolved.

Covalent Network Crystals

These are massive structures where every single atom is linked by strong covalent bonds. Diamond is a great example, featuring extreme hardness and high melting points.

Metallic Crystals

Metallic crystals feature positive metal ions surrounded by a moving sea of shared electrons. This electron cloud makes metals flexible and great at carrying electrical current.

Molecular Crystals

Molecular crystals are made of neutral molecules held together by weak intermolecular forces. They are usually soft and melt at low temperatures.

Allotrope

Allotropes are different physical forms of the same chemical element in the same state. Diamond and graphite are both pure carbon allotropes with different structures.

X-ray Crystallography

X-ray crystallography is a laboratory method used to map out the exact atomic layout of a solid crystal. It uses the diffraction patterns of X-ray beams.

Bragg's Law

Braggs Law is an equation that relates X-ray wavelength and diffraction angles to the distance between crystal planes. It is used to calculate internal lattice dimensions.

Lattice Energy

Lattice energy is the massive amount of energy released when gaseous ions bind to form a solid ionic crystal. Smaller ions with higher charges produce higher lattice energy.

Born-Haber Cycle

The Born-Haber cycle is a thermochemical model used to calculate lattice energy indirectly. It breaks the crystal formation down into easier steps like sublimation and ionization.

Heat of Fusion

The heat of fusion is the energy needed to turn a solid into a liquid at its melting point. Temperature stays constant while this phase change happens.

Heat of Vaporization

The heat of vaporization is the energy needed to turn a liquid into a gas at its boiling point. It takes a lot of energy because every intermolecular bond must be broken.

Heating Curve

A heating curve is a graph showing how temperature rises as heat is added over time. The flat horizontal plateaus show where phase changes happen at constant temperature.

Cooling Curve

A cooling curve charts how temperature drops as a substance loses heat over time. Flat plateaus on the graph represent exothermic phase changes like freezing.

Specific Heat Capacity

Specific heat capacity is the energy needed to raise the temperature of one gram of a substance by one degree Celsius. Water has a high specific heat, helping stabilize temperatures.

Clausius-Clapeyron Equation

This equation connects a liquid's vapor pressure at different temperatures to its heat of vaporization. It helps calculate vapor pressure changes across varying temperatures.

Dynamic Equilibrium

Dynamic equilibrium happens in a closed system when forward and reverse processes occur at the exact same rate. Microscopic changes keep happening while macroscopic properties stay steady.

Evaporation

Evaporation is a surface phase change where liquid molecules gain enough energy to escape into the gas phase. It happens below the boiling point and cools the remaining liquid.

Condensation

Condensation is the exothermic phase change where a gas loses heat and turns back into a liquid. It happens when gas molecules hit a colder surface.

Volatile

A volatile liquid evaporates very easily at room temperature because it has weak intermolecular forces and high vapor pressure.

Nonvolatile

A nonvolatile substance does not evaporate easily and has a very low vapor pressure. Adding it to a solvent lowers the overall vapor pressure of the mixture.

Ideal Solution

An ideal solution is a liquid mixture that follows Raoult's law perfectly across all concentrations. The forces between mixed molecules match the forces in the pure liquids.

Non-ideal Solution

A non-ideal solution breaks Raoult's law because the forces between mixed molecules differ from the pure liquids. This causes volume and heat changes during mixing.

Positive Deviation

A positive deviation from Raoult's law happens when mixed molecules attract each other less than they did in their pure states. This makes them escape into gas easier, raising vapor pressure.

Negative Deviation

A negative deviation happens when mixed molecules attract each other more strongly than in their pure states. This holds them in the liquid phase, lowering total vapor pressure.

Fractional Distillation

Fractional distillation separates miscible liquids with different boiling points. It uses a tall column to run multiple cycles of evaporation and condensation.

Azeotrope

An azeotrope is a liquid mixture that boils at a constant temperature while keeping its exact composition. Because the vapor matches the liquid ratio, it cannot be separated by simple distillation.

Reverse Osmosis

Reverse osmosis uses high pressure to push water through a semipermeable membrane against normal osmotic flow. It is widely used to desalinate seawater into clean drinking water.