Book: UTC: 12 Flashcards
How does the interplay between kinetic and potential energy underlie the properties of the three states of matter and their phase changes?
Potential energy shows up in the form of intermolecular forces, and kinetic energy is reflected by the temperature of the substance, in that higher temperatures lead to faster motion. In gases, KE > PE. With liquids, particles are stuck together but can move around; so PE is not sufficient to fix them. With solids, PE dominates and particles are essentially fixed in place.
Explain the processes involved, both within a phase and during a phase change, when heat is added or removed from a pure substance.
During phase changes, heat added breaks the particles from the intermolecular forces fixing them. Between phase changes, heat added goes directly into kinetic energy increases within the substance.
The meaning of vapor pressure and how phase changes are dynamic equilibrium processes.
In a closed system of liquid gas, there are two things happening: some molecules at the surface of the liquid have enough E_k to vaporize, but also, some molecules in the vapor collide with the surface and slower ones are attracted strongly enough to condense, so there’s an equilibrium between these two processes which is reached as dynamic equilibrium when the rate of condensation equals the rate of vaporization. Both are still happening, but they occur at the same rate.
How do temperature and intermolecular forces influence vapor pressure?
Temperature means more molecules have enough E_k to escape the surface of the liquid and vaporize to increase the vapor pressure. Intermolecular forces hold the molecules together better in the liquid, keeping them from vaporizing, so it decreases the vapor pressure.
Explain the relationship between vapor pressure and boiling point.
The boiling point is the temperature at which the vapor pressure inside bubbles in the liquid equals the external pressure (usually the atmosphere).
How do phase diagrams show the phases of a substance at differing conditions of pressure and temperature?
Phase diagrams plot pressure against temperature and curves are drawn through the diagram to cut the graph into the phases of the substance: solid, liquid, gas, and also showing the triple point, critical point, and the lines between the regions: vapor curves, condensation curves, and boiling curves.
What is the difference between bonding and intermolecular forces on the basis of Coulomb’s law and the meaning of the van der Waals radius of an atom?
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Explain the types and relative strengths of intermolecular forces acting in a substance, the impact of H bonding on physical properties, and the meaning of polarizability.
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What are the meanings of surface tension, capillarity, and viscosity and how do intermolecular forces influence their magnitudes?
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How do the important macroscopic properties of water arise from its atomic and molecular properties?
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Explain the structure of a crystal lattice and the characteristics of the three types of cubic unit cells.
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How does the packing of spheres give rise to the hexagonal and cubic unit cells?
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Explain the types of crystalline solids and how their intermolecular forces give rise to their properties.
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