Flashcards in General Chemistry-Thermochemistry Deck (190)
What happens each time the liquid loses a high-energy particle?
The temperature of the remaining liquid decreases.
Evaporation is what type of process?
Endothermic process for which the heat source is the liquid water.
What is boiling?
A specific type of vaporization that occurs only under certain conditions.
Boiling is the rapid bubbling of the entire liquid with rapid release of the liquid as gas particles.
What is the difference between normal evaporation and boiling?
Evaporation can happen in all liquids at all temperatures,
Boiling can only occur above the boiling point of a liquid and involves vaporization through the entire volume of the liquid.
What is condensation?
In a covered or closed container, the escaping molecules are trapped above the solution. These molecules exert a countering pressure, which forces some of the gas back into the liquid phase.
When is condensation facilitated?
By lower temperature or higher pressure
What is vapor pressure?
The pressure the gas exerts over the liquid at equilibrium
When does vapor pressure increase? Why?
As temperature increase because more moleucles have sufficient kinetic energy to escape into the gas phase.
What is boilig point?
The temperature at which the vapor pressure of the liquid equals the ambient (also known as external, applied, or incident) pressure.
Will solids have molecule movement?
Each atom or molecule can undergo motions about some equilibrium position
When do the vibrational motions of molecules in a solid state increase?
When heat is applied
What happens to molecules when temperature is increased?
The molecules have greater freedom of movement and energy disperses
What is the transition from the solid state to the liquid state called?
Fusion or Melting
What is the transition from the liquid state to the solid state called?
Solidification, Crystallization or Freezing
What is the temperature of a solid liquid change or a liquid solid change called?
Melting point or freezing point
What has distinct melting points and what has ranges of melting points?
Pure crystalline solids have distinct, very precise melting points, amorphous solids such as glass, plastic, chocolate and candle wax tend to melt or solidify over a larger range of temperatures, due to their less-ordered molecular structure
What is sublimation?
When a solid goes directly into the gas phase
What is an example of a substance that sublimates?
Dry ice (solid CO2) sublimates at room temperature and atmospheric pressure
What is deposition?
Transition from the gaseous state to the solid state
What is a cold finger device in organic chemistry?
A device that may be used to purify a product that is heated under reduced pressure causing it to sublime. The desired produt is usually more volatile than the impurities, so the gas is purer than the original product and the impurities are left in the solid state. The gas then deposits onto the cold finger, which has a cold water flowing through it, yeilding a purified soid product than can be collected.
What are phase diagrams again?
Graphs that show the temperature and pressure at which a substance will be thermodynamically stable in a particular phase. They also show the temperatures and pressures at which phases will be in equilibrium.
What are the lines on a phase diagram called? What do they indicate?
The lines of equilibrium or the phase boundaries
They indicate the temperature and pressure values for the euilibria between phases. The lines of equilibirum divide the diagram into three regions corresponding to the three phases and they themselves represent the phase transformations.
In general, where is the gas phase found?
At high temperatures and low pressures.
In general, where is the solid phase found?
At low temperatures and high pressures.
In general, where is the liquid phase found?
At moderate temperatures and pressures.
What is the triple point?
The point at which the three phase boundaries meet. This is the temperature and pressure at which the three phases exist in equilibrium.
In a phase diagram, the phase boundary seperating the solid and liquid does what?
Extends indefinitely from the triple point
What is the critical point in a phase diagram?
The phase boundary between the liquid and gas phases, terminates at this point. This is the temperature and pressure above which there is no distinction between the phases.
All temperatures and pressures above the critical point are what?