4: Module 4 - Gases and Liquids

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4.1: Kinetic Molecular Theory- A Model for Gases
The physical behavior of gases is explained by the kinetic theory of gases. An ideal gas adheres exactly to the kinetic theory of gases.
4.2: Pressure - The Result of Constant Molecular Collisions
Pressure is a force exerted over an area. Pressure has several common units that can be converted.
4.3: Boyle’s Law - Pressure and Volume
Boyle’s Law relates the pressure and volume of a gas at constant temperature and amount.
4.4: Charles’s Law- Volume and Temperature
Charles’s Law relates the volume and temperature of a gas at constant pressure and amount. In gas laws, temperatures must always be expressed in kelvins.
4.5: Gay-Lussac's Law- Temperature and Pressure
Gay-Lussac's Law states that the pressure of a given mass of gas varies directly with the absolute temperature of the gas, when the volume is kept constant. Gay-Lussac's Law is very similar to Charles's Law, with the only difference being the type of container. Whereas the container in a Charles's Law experiment is flexible, it is rigid in a Gay-Lussac's Law experiment.
4.6: Avogadro’s Law- Volume and Moles
The original statement of Avogadro’s law states that equal volumes of different gases at the same temperature and pressure contain the same number of particles of gas. Because the number of particles is related to the number of moles, Avogadro’s law essentially states that equal volumes of different gases at the same temperature and pressure contain the same amount (moles, particles) of gas.
4.7: The Ideal Gas Law- Pressure, Volume, Temperature, and Moles
The Ideal Gas Law relates the four independent physical properties of a gas at any time. The Ideal Gas Law can be used in stoichiometry problems with chemical reactions involving gases. Standard temperature and pressure (STP) are a useful set of benchmark conditions to compare other properties of gases. At STP, gases have a volume of 22.4 L per mole. The Ideal Gas Law can be used to determine densities of gases.
4.8: Mixtures of Gases - Why Deep-Sea Divers Breathe a Mixture of Helium and Oxygen
The pressure of a gas in a gas mixture is termed the partial pressure. Dalton’s Law of Partial Pressures states that the total pressure in a gas mixture is the sum of the individual partial pressures. Collecting gases over water requires that we take the vapor pressure of water into account. Mole fraction is another way to express the amounts of components in a mixture.
4.9: Interactions between Molecules
The melting point is the temperature at which a solid changes into a liquid. Intermolecular forces have a strong influence on melting point.
4.10: Properties of Liquids and Solids
All liquids evaporate. If volume is limited, evaporation eventually reaches a dynamic equilibrium, and a constant vapor pressure is maintained. All liquids experience surface tension, an imbalance of forces at the surface of the liquid. All liquids experience capillary action, demonstrating either capillary rise or capillary depression in the presence of other substances. Solids can be divided into amorphous solids and crystalline solids.
4.11: Intermolecular Forces in Action- Surface Tension and Viscosity
The surface tension of a liquid is a measure of the elastic force in the liquid's surface. Liquids with strong intermolecular forces have higher surface tensions than liquids with weaker forces.
4.12: Evaporation and Condensation
Evaporation is the conversion of a liquid to its vapor below the boiling temperature of the liquid. Condensation is the change of state from a gas to a liquid. As the temperature increases, the rate of evaporation increases.
4.13: Melting, Freezing, and Sublimation
Phase changes can occur between any two phases of matter. All phase changes occur with a simultaneous change in energy. All phase changes are isothermal.
4.14: Intermolecular Forces- Dispersion, Dipole–Dipole, Hydrogen Bonding, and Ion-Dipole
All substances experience dispersion forces between their particles. Substances that are polar experience dipole-dipole interactions. Substances with covalent bonds between an H atom and N, O, or F atoms experience hydrogen bonding. The preferred phase of a substance depends on the strength of the intermolecular force and the energy of the particles.
4.15: Water - A Remarkable Molecule
Water has several properties that make it a unique substance among substances. It is an excellent solvent; it dissolves many other substances and allows those substances to react when in solution. In fact, water is sometimes called the universal solvent because of this ability. Water has unusually high melting and boiling points. Unlike most substances, the solid form of water is less dense than its liquid form, which allows ice to float on water.