All Flashcards
What is the effect of adding energy to a solid at its melting point?
The solid will begin to melt, transitioning to the liquid phase, without a change in temperature until all of the solid has melted.
What is the effect of increasing the temperature of a liquid at its boiling point?
The liquid will begin to vaporize, transitioning to the gas phase, without a change in temperature until all of the liquid has vaporized.
What is the effect of increasing pressure on a substance near its melting point?
For most substances, increasing pressure increases the melting point. However, water is an exception; increasing pressure decreases its melting point.
What is the effect of increasing temperature on the volume of a gas (at constant pressure)?
The volume of the gas increases (Charles's Law).
What is the effect of strong intermolecular forces on the heat of vaporization?
Stronger intermolecular forces lead to a higher heat of vaporization because more energy is required to overcome these forces and change the substance from a liquid to a gas.
Compare and contrast heating curves and cooling curves.
Heating curves: Endothermic, temperature increases with energy added, shows melting and vaporization. Cooling curves: Exothermic, temperature decreases with energy released, shows condensation and freezing. Both: Have slopes (temperature change) and plateaus (phase change).
Compare heat of fusion (H) and heat of vaporization (Hₜ).
H: Energy to change solid to liquid. Hₜ: Energy to change liquid to gas. Hₜ is almost always greater than H because all IMFs must be broken to vaporize.
Compare the processes occurring during the slopes versus the plateaus of a heating curve.
Slopes: Temperature changes, kinetic energy increases, q = mcΔT. Plateaus: Phase changes, potential energy increases (breaking IMFs), temperature remains constant, q = H(m) or Hₜ(m).
Differentiate between heat of vaporization and heat of condensation.
Heat of Vaporization: Energy absorbed when a liquid changes to a gas (endothermic). Heat of Condensation: Energy released when a gas changes to a liquid (exothermic); it's the negative of the heat of vaporization.
Differentiate between heat of fusion and heat of freezing.
Heat of Fusion: Energy absorbed when a solid changes to a liquid (endothermic). Heat of Freezing: Energy released when a liquid changes to a solid (exothermic); it's the negative of the heat of fusion.
On a typical heating curve, what do the slopes represent?
The slopes represent the change in temperature as heat is added within a single phase (solid, liquid, or gas).
On a typical heating curve, what do the plateaus represent?
The plateaus represent phase changes (melting/freezing, boiling/condensation) where the temperature remains constant as heat is added or removed.
On a phase diagram, what area represents the solid phase?
The solid phase is generally located in the high pressure and low temperature region of the phase diagram.
On a phase diagram, what area represents the liquid phase?
The liquid phase is generally located in the moderate pressure and moderate temperature region of the phase diagram.
On a phase diagram, what area represents the gas phase?
The gas phase is generally located in the low pressure and high temperature region of the phase diagram.