Chapter 5 Flashcards
What are the key physical properties of liquids?
Definite volume, no fixed shape, less compressible than gases, moderate intermolecular forces.
What is vapor pressure and what affects it?
Pressure exerted by vapor in equilibrium with liquid. Increases with temperature; stronger intermolecular forces = lower vapor pressure.
Why does evaporation cause cooling?
High-energy molecules escape first, lowering the average kinetic energy of the remaining liquid.
What is the difference between evaporation and boiling?
Evaporation is surface-level and can occur below boiling point. Boiling occurs throughout liquid when vapor pressure = atmospheric pressure.
How does atmospheric pressure affect boiling point?
Higher pressure = higher boiling point. Lower pressure = lower boiling point.
What is the effect of intermolecular forces on boiling point?
Stronger forces = higher boiling point (more energy needed to separate molecules).
What is viscosity and how is it affected by temperature?
Viscosity is resistance to flow. Increases with stronger intermolecular forces and decreases with higher temperature.
What is surface tension and what causes it?
The force per unit length acting along a surface (N/m), caused by cohesive forces between molecules at the surface.
How is heat of fusion related to glaciers and ice caps?
Determines the energy needed to melt ice. Crucial for understanding glacier melting and sea level rise.
What are the two main types of solids?
Crystalline (ordered structure) and amorphous (disordered structure).
What is the difference between crystalline and amorphous solids in terms of melting point?
Crystalline have sharp melting points; amorphous do not melt sharply.
What are cleavage planes in crystals?
Flat surfaces along which a crystal can break, reflecting internal symmetry.
What does the term ‘habit of a crystal’ refer to?
The typical external shape or appearance of a crystal (e.g., cubic, needle-like).
What are liquid crystals and where are they used?
Substances that flow like liquids but have some order like solids. Used in LCDs, watches, screens.
Why doesn’t vapor pressure depend on surface area, while evaporation does?
Vapor pressure is a dynamic equilibrium property; surface area affects rate, not equilibrium.
What is the anomalous behavior of water?
Water is densest at 4°C; expands on freezing due to hydrogen bonding.
Why do water, alcohol, and glycol have different vapor pressures at 0°C?
Due to differences in intermolecular forces like hydrogen bonding.
What is vacuum distillation and where is it used?
Distillation under reduced pressure. Used for heat-sensitive liquids.
