Chapter 3.3 Flashcards
What is the first law of thermodynamics? How does it describe energy? Are non-conservative forces accounted for in the first law of thermodynamics
- change in total internal energy of a system
- > is the amount of that transferred to the system- energy transferred in the form of work
- energy cannot be created or destroyed
- > it can only be changed from one form to another
- yes
- > non-conservative forces are accounted for in this equation
What is the second law of thermodynamics
- objects in thermal contact
- > not in thermal equilibrium
- will transfer heat energy from an object with a higher temperature to an object with lower temperature
- > until both subjects are at thermal equilibrium
-heat can never be transferred from a cooler object to a warmer one unless work is being done on the system
What are three ways that heat can transfer energy
-conduction, convection and radiation
What is conduction? Does physical contact need to exist? What are the best heat conductors? What are the poorest heat conductors
- it is the direct transfer of energy from molecule to molecule
- > physical contact needs to exist for this to occur
- metals are the best heat conductors
- > metallic bonds contains a density of atoms embedded in a sea of electrons
- > so rapid energy transfer
- gases are the worst heat conductors
- > they got a lot of space between individual molecules
- > so energy-transferring collisions occur infrequently
What is convection? Give an example
- it is the transfer of heat by physical motion of a fluid
- > over a material
- > if fluid has higher temperature then it will transfer energy to the material
-eg; running a cold water bath in a lab to cool a reaction
What is radiation? What is the one main difference between conduction/convection and radiation
-transfer of energy by electromagnetic waves
- radiation can transfer energy through a vacuum
- > conduction and convection cannot
-eg; radiant ovens
What is the specific heat defined as
- it is the amount of heat energy
- >to raise one gram of a substance by one degree Celcius or one unit Kelvin
Does a phase change mean change in temperature? When does temperature begin to change? Are changes in phase related to potential energy or kinetic energy?
- phase changes occur at a constant temperature
- > so no, temperature does not change during a phase change
- > therefore, the average kinetic energy is the same during this phase change
-the temperature begins to change once all of the substance has been converted from one phase to another
- it is related to changes in potential energy
- > not kinetic energy
Describe the change in potential energy as heat is added to water molecules
- in ice, water has low potential energy
- > stable due to relative closeness of one molecule to another and by hydrogen bonds
- add heat
- > heat causes water molecules to move away from one another
- > greater degree of freedom by water molecules= greater potential energy
-greater degree of freedom= greater number of microstates
What is the phase change from liquid to solid referred to as? What is the phase change from solid to liquid referred to as? At what point does this occur? What is the corresponding heat of transformation referred to as?
Liquid to solid
->freezing
Solid to liquid
->melting or fusion
- these processes occur at the melting point
- > heat of transformation= heat of fusion
What is the phase change from liquid to gas referred to as? What is the phase change from gas to liquid referred to as? At what point does this occur? What is the corresponding heat of transformation referred to as?
Liquid to gas
->boiling
Gas to liquid
->condensation
- these processes occur at the boiling point
- > heat of transformation=heat of vaporization
Describe the processes of : isothermal, adiabatic, isovolumetric and isobaric
Isothermal
- > constant temperature
- > no change in internal energy
Adiabatic
->no heat exchange
Isovolumetric
- > no change in volume
- > therefore, no work achieved
Isobaric
->constant pressure
What results in negative and positive values for:
- > change in internal energy
- > heat
- > work
Positive for change in internal energy
->increasing temperature(decreasing temperature is negative)
Positive for heat
->heat flows into system(heat flows out of system is negative)
Positive for work
- > work is done by the system(expansion)
- > negative for work is word done on the system(compression)
