Glossary
Amorphous Solids
Solids that lack a long-range, ordered structure, meaning their particles are arranged randomly.
Example:
Glass is a common example of an amorphous solid; unlike a crystal, its atoms are not arranged in a repeating pattern.
Amplitude
The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position.
Example:
A brighter light has a larger amplitude than a dimmer light of the same color.
Beer-Lambert Law
A law that relates the absorbance of light by a solution to its concentration, path length, and molar absorptivity (A = εbc).
Example:
Chemists use the Beer-Lambert Law to determine the unknown concentration of a colored solution by measuring how much light it absorbs.
Capillary Action
The spontaneous rising of a liquid in a narrow tube or porous material, caused by the interplay of cohesive and adhesive forces.
Example:
Plants draw water from their roots to their leaves through capillary action in their vascular tissues.
Chromatography
A separation technique that separates components of a mixture based on their differential partitioning between a stationary phase and a mobile phase.
Example:
Forensic scientists use chromatography to separate and identify components in ink samples, helping to analyze documents.
Combined Gas Law
A gas law that combines Boyle's Law, Charles's Law, and Gay-Lussac's Law, relating the pressure, volume, and temperature of a fixed amount of gas.
Example:
If a gas's pressure, volume, and temperature all change, the Combined Gas Law can be used to find the new state.
Compressibility
The ability of a substance to decrease in volume when subjected to pressure.
Example:
Gases are highly compressible, which is why you can squeeze a large amount of air into a small scuba tank.
Covalent Network Solids
Solids in which atoms are held together by a continuous network of covalent bonds throughout the entire structure.
Example:
Diamond is an incredibly hard covalent network solid because each carbon atom is covalently bonded to four other carbon atoms in a strong, extended lattice.
Crystal Lattice
The highly ordered, repeating three-dimensional arrangement of atoms, ions, or molecules in a crystalline solid.
Example:
The precise cubic shape of a salt crystal reflects the underlying crystal lattice structure of sodium and chloride ions.
Crystalline Solids
Solids with a highly ordered, repeating three-dimensional arrangement of atoms, ions, or molecules.
Example:
Diamonds and snowflakes are perfect examples of crystalline solids, showcasing precise, repeating structures.
Dalton's Law of Partial Pressures
States that the total pressure of a mixture of non-reacting gases is equal to the sum of the partial pressures of each individual gas.
Example:
If you have a tank containing both oxygen and nitrogen, the total pressure inside is the sum of the partial pressures exerted by the oxygen and nitrogen separately.
Delocalized
Refers to electrons that are not confined to a single atom or bond but are spread out over multiple atoms or across an entire structure.
Example:
The excellent electrical conductivity of metals is due to their delocalized valence electrons, which can move freely throughout the material.
Density
A physical property defined as the mass of a substance per unit volume.
Example:
An ice cube floats in water because ice has a lower density than liquid water.
Diffusion
The process by which gas particles spread out and mix uniformly throughout a space due to their random motion.
Example:
When you open a bottle of perfume, the scent quickly spreads across the room through diffusion.
Dilution
The process of reducing the concentration of a solution by adding more solvent.
Example:
When preparing a less concentrated acid from a stock solution, chemists perform a dilution by adding water.
Dipole-Dipole Interactions
Attractive forces between the permanent dipoles of polar molecules, where the positive end of one molecule attracts the negative end of another.
Example:
Acetone, a common nail polish remover, has a higher boiling point than propane because of its stronger dipole-dipole interactions.
Distillation
A separation technique used to separate components of a liquid mixture based on differences in their boiling points.
Example:
Crude oil is separated into different products like gasoline and kerosene through fractional distillation.
Effusion
The process by which gas particles escape through a tiny hole into a vacuum.
Example:
Helium balloons deflate faster than air balloons because helium atoms, being lighter, effuse more quickly through the balloon's pores.
Electrolytes
Substances that produce ions when dissolved in a solvent, allowing the resulting solution to conduct electricity.
Example:
Sports drinks contain electrolytes like sodium and potassium ions to help replenish those lost during exercise, aiding nerve and muscle function.
Electromagnetic Spectrum
The entire range of electromagnetic radiation, ordered by wavelength or frequency, from radio waves to gamma rays.
Example:
Visible light, which we can see, is only a tiny portion of the vast electromagnetic spectrum.
Evaporation
A separation technique where a liquid solvent is vaporized, leaving behind the solid solute.
Example:
To recover salt from saltwater, one can use evaporation to boil off the water, leaving the solid salt crystals behind.
Filtration
A separation technique used to separate insoluble solid particles from a liquid or gas by passing the mixture through a porous material.
Example:
Brewing coffee involves filtration, where hot water passes through coffee grounds, leaving the solid grounds behind.
Fluidity
The ability of a substance to flow, characteristic of liquids and gases.
Example:
Honey has lower fluidity than water because its stronger intermolecular forces make it more resistant to flow.
Frequency
The number of wave cycles that pass a given point per unit of time, typically denoted by the Greek letter nu (ν) or f.
Example:
High-energy X-rays have a very high frequency compared to low-energy radio waves.
Gases
A state of matter characterized by an indefinite shape and indefinite volume, with particles far apart and moving randomly.
Example:
The air in a balloon expands to fill the entire volume of the balloon, illustrating the properties of a gas.
Hydrogen Bonding
A particularly strong type of dipole-dipole interaction occurring when hydrogen is covalently bonded to a highly electronegative atom (F, O, or N) and attracted to another F, O, or N atom.
Example:
The unique properties of water, such as its ability to float as ice, are largely due to extensive hydrogen bonding between its molecules.
Ideal Gas Law
An equation of state, PV=nRT, that describes the relationship between the pressure (P), volume (V), moles (n), and temperature (T) of an ideal gas.
Example:
Using the Ideal Gas Law, you can calculate how many moles of gas are in a balloon given its volume, pressure, and temperature.
Intermolecular Forces (IMFs)
Attractive forces that exist between molecules, influencing a substance's physical properties like boiling point and viscosity.
Example:
The reason water has a relatively high boiling point compared to methane is due to its strong intermolecular forces.
Interstitial Alloy
An alloy where smaller atoms of one element fit into the empty spaces (interstices) within the crystal lattice of a larger element.
Example:
Steel is an interstitial alloy where small carbon atoms occupy the gaps between larger iron atoms, making the material stronger and harder.
Intramolecular forces
The strong attractive forces that hold atoms together within a molecule, such as covalent or ionic bonds.
Example:
The covalent bonds holding hydrogen and oxygen atoms together within a single water molecule are intramolecular forces.
Ion-Dipole Interactions
Attractive forces between an ion and a polar molecule, where the ion's charge is attracted to the partial charge of the polar molecule.
Example:
When table salt (NaCl) dissolves in water, the Na+ and Cl- ions are surrounded by water molecules through strong ion-dipole interactions.
Ion-Ion Attractions
The strong electrostatic attractive forces between oppositely charged ions in an ionic compound.
Example:
The high melting point of sodium chloride (NaCl) is a direct result of the powerful ion-ion attractions holding its crystal lattice together.
Ionic Solids
Crystalline solids formed by the electrostatic attraction between positively and negatively charged ions.
Example:
Table salt (NaCl) is a classic ionic solid, characterized by its high melting point and brittleness.
Kinetic Molecular Theory (KMT)
A model that explains the macroscopic properties of gases based on the behavior of their microscopic particles, assuming negligible volume and no intermolecular forces for ideal gases.
Example:
The observation that gases expand to fill their containers is explained by the Kinetic Molecular Theory's assumption of constant, random particle motion.
Liquids
A state of matter characterized by a fixed volume but an indefinite shape, with particles close together but able to move past each other.
Example:
Water poured into a glass will take the shape of the container but maintain its original volume, typical behavior of a liquid.
London Dispersion Forces (LDFs)
Weak, temporary attractive forces present in all molecules, arising from instantaneous dipoles caused by electron movement.
Example:
Even nonpolar molecules like oxygen (O2) can condense into a liquid at low temperatures because of London Dispersion Forces.
Maxwell-Boltzmann Distributions
Graphs that show the distribution of molecular speeds for a gas at a given temperature, indicating that not all particles move at the same speed.
Example:
At higher temperatures, the Maxwell-Boltzmann distribution curve broadens and shifts to higher speeds, indicating a greater range of velocities and a higher average kinetic energy.
Metallic Solids
Solids composed of metal atoms held together by a 'sea' of delocalized valence electrons, giving them properties like conductivity and malleability.
Example:
Copper wiring is effective because metallic solids like copper allow electrons to move freely, conducting electricity.
Molarity
A common unit of concentration defined as the number of moles of solute per liter of solution (mol/L).
Example:
A 1.0 Molarity (M) solution of HCl means there is 1.0 mole of HCl dissolved in every liter of the solution.
Mole Fraction
The ratio of the number of moles of one component to the total number of moles of all components in a mixture.
Example:
In a gas mixture, the mole fraction of oxygen tells you the proportion of oxygen moles relative to the total moles of gas.
Molecular Solids
Solids in which discrete molecules are held together by relatively weak intermolecular forces.
Example:
Ice (solid H2O) is a molecular solid with a low melting point because only the weak hydrogen bonds between water molecules need to be overcome, not the covalent bonds within them.
Photoelectric Effect
The phenomenon where electrons are ejected from a metal surface when light of a sufficiently high frequency shines on it.
Example:
Solar panels convert sunlight into electricity using the photoelectric effect, where photons knock electrons loose from semiconductor materials.
Photon
A discrete packet or quantum of electromagnetic energy, considered to be the fundamental particle of light.
Example:
When a light-emitting diode (LED) glows, it is releasing individual photons of light.
Planck's Constant
A fundamental physical constant (h) that relates the energy of a photon to its frequency (E = hν).
Example:
The energy of a single photon of blue light can be calculated using its frequency and Planck's Constant.
Polarizability
A measure of how easily the electron cloud of an atom or molecule can be distorted by an external electric field, leading to temporary dipoles.
Example:
Larger atoms like iodine are more polarizable than smaller atoms like fluorine, leading to stronger London Dispersion Forces in I2 compared to F2.
Saturated Solution
A solution that contains the maximum amount of solute that can be dissolved at a given temperature, with any additional solute remaining undissolved.
Example:
If you add sugar to water until no more dissolves, you have created a saturated solution.
Solids
A state of matter characterized by a fixed shape and fixed volume, with particles tightly packed and vibrating in fixed positions.
Example:
A block of ice maintains its shape and volume, demonstrating the properties of a solid.
Solubility
The maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature.
Example:
The solubility of sugar in hot tea is much higher than in iced tea, allowing more sugar to dissolve.
Solute
The substance that is dissolved in a solvent to form a solution, typically present in a smaller amount.
Example:
In a sugar-water solution, sugar is the solute that gets dissolved.
Solution
A homogeneous mixture of two or more substances, meaning the components are uniformly distributed at a molecular level.
Example:
Saltwater is a solution because the salt is completely dissolved and evenly dispersed throughout the water.
Solvent
The substance in which a solute is dissolved to form a solution, typically present in a larger amount.
Example:
Water is often called the 'universal solvent' because it can dissolve many different substances.
Spectrophotometry
An analytical technique that measures the amount of light absorbed by a substance at different wavelengths, often used to determine concentration.
Example:
In a lab, spectrophotometry is commonly used to quantify the amount of protein in a biological sample.
Spectroscopy
The study of the interaction between matter and electromagnetic radiation, used to analyze the composition and structure of substances.
Example:
Astronomers use spectroscopy to determine the chemical composition of distant stars by analyzing the light they emit.
Substitutional Alloy
An alloy where atoms of one element replace atoms of another element in the crystal lattice, typically when the atoms are of similar size.
Example:
Brass, an alloy of copper and zinc, is a substitutional alloy where zinc atoms replace some copper atoms in the crystal structure.
Supersaturated Solution
A solution that contains more dissolved solute than a saturated solution at the same temperature, typically prepared by cooling a hot saturated solution carefully.
Example:
Rock candy is often grown from a supersaturated solution of sugar, where excess sugar crystallizes out over time.
Surface Tension
The cohesive forces between liquid molecules at the surface that cause the liquid to minimize its surface area, acting like a stretched elastic film.
Example:
A water strider can walk on water due to the high surface tension of water, which supports its weight.
Van der Waals equation
A modified ideal gas law that accounts for the finite volume of gas particles and the attractive forces between them, providing a more accurate description for real gases.
Example:
To accurately predict the behavior of a gas at high pressure, where particle volume becomes significant, the Van der Waals equation would be more appropriate than the ideal gas law.
Viscosity
A measure of a liquid's resistance to flow, primarily determined by the strength of its intermolecular forces and molecular size.
Example:
Maple syrup has a high viscosity because its large molecules and strong intermolecular forces make it flow slowly.
Wavelength
The distance between two consecutive crests or troughs of a wave, typically denoted by the Greek letter lambda (λ).
Example:
Red light has a longer wavelength than blue light, which is why they appear as different colors.