chapter 11 Flashcards
when is work positive?
when energy is transferred into a system
when is work negative
when energy is transferred out of a system
what is efficiency
it describes the amount that we get divided by the amount that you pay
a larger efficiency means you spent less energy to get it
what is the efficiency of a human?
25%
what is thermal energy
thermal energy is the total sum of all the kinetic and elastic potential energies of moving atoms in a gas/ object
what is the temperature defintion in an ideal gas
it is a measure of the average kinetic energy of the atoms that make of the gas
how is temperature related to kinetic energy
it is proportional to the average kinetic energy
if you have a higher kinetic energy, you will have a higher temperature
what is heat?
it is the energy transferred between two objects with a temperature difference
what is Q?
what does it mean when Q is positive? what does it mean when it is negative?
Q is the heat transfer. If it is positive, it means that energy is flowing into the system
if it is negative, it means that energy is flowing out of the system
if we put a flame under a pan with cool water, what is the heat? what happens to the thermal energy and temperature?
the heat is the energy from the hotter pan transferred to the colder water
the thermal energy and temperature increase
what is thermal equilibrium
it is when two systems in thermal contact will transfer thermal energy from hot to cold until their final temperatures are the same
what is the first law of thermodynamics
it says that, in systems where only thermal energy changes, the change in thermal energy is equal to the energy transferred into or out of system as work, heat, or both
∆Ethermal = Q +W
when is work positve in a system? when is it negative?
when work is done on the system it is positive
when work is done by the system it is negative
when is heat positive in a system? when is it negative
when heat is added to the system, it is positive
when heat is taken from the system, it is negative
what is an energy reservoir
it is a body so large that the temperature does not change when heat is transferred between the system and the reservoir
what is a heat engine
it is a system that takes energy as it is transferred from a hot reservoir to a cold reservoir and uses it to do work
is energy conserved in a heat engine
yes, the amount of energy that makes it into the cold reservoir is equal to the amount of energy from the hot reservoir minus the amount we used to do work
what is a heat pump
it transfers heat energy from a cold reservoir to a hot reservoir but it requires an input of energy
the spontaneous transfer of heat from hot to cold is
an irreversible process that occurs in one direction
what is entropy
entropy describes the randomness and thermal spread of energy
what does the second law of thermal dynamics say
it says that the entropy of an isolated system will never decrease and it will only increase until it is at equilibrium and it will stay at equilibrium
what happens to entropy if we add heat
the thermal energy increases so entropy increases
what happens to entropy if we remove heat
the thermal energy decreases so entropy decreases
