November 18th, 2013
Starting to cover energy...
Section 9.1: Skim it
Section 9.2: Skim it.
Section 9.3: Now it starts getting ugly...
Chemical and physical changes "nearly always" come with changes
in energy.
Energy:
"The capacity to do work."
and Work = "Force acting through a distance".
and Force = "An influence tending to change the motion of a body
or produce motion or stress in a stationary body"
or
"All forms of energy are generated by changes in matter, and one
definition of energy is that which can produce a change in matter. "
Total energy = potential energy + kinetic energy
and potential energy = energy from an object's position or composition
and kinetic energy = energy of motion
thermal energy = the kinetic energy of atoms and molecules
System = what you are studying
Surroundings = EVERYthing else
First Law of Thermodynamics
Energy is neither created nor destroyed. It is only ever transferred.
Energy "used" is energy transferred: it is never destroyed, only
moved around.
Section 9.4: The ugly just keeps coming...
Entropy: disorder
Energy spreads out: heat part of something and what happens?
Nothing is 100% efficient: nothing.
So, can't make energy from nothing, and can't make something happen
without putting in energy, because you always lose some energy to the
surroundings.
Section 9.5: Units of Energy
Skip it: there are units - things like calories, Joules, kilowatt-hours - but
the details don't matter that much for us in this course.
Section 9.1: Skim it
Section 9.2: Skim it.
Section 9.3: Now it starts getting ugly...
Chemical and physical changes "nearly always" come with changes
in energy.
Energy:
"The capacity to do work."
and Work = "Force acting through a distance".
and Force = "An influence tending to change the motion of a body
or produce motion or stress in a stationary body"
or
"All forms of energy are generated by changes in matter, and one
definition of energy is that which can produce a change in matter. "
Total energy = potential energy + kinetic energy
and potential energy = energy from an object's position or composition
and kinetic energy = energy of motion
thermal energy = the kinetic energy of atoms and molecules
System = what you are studying
Surroundings = EVERYthing else
First Law of Thermodynamics
Energy is neither created nor destroyed. It is only ever transferred.
Energy "used" is energy transferred: it is never destroyed, only
moved around.
Section 9.4: The ugly just keeps coming...
Entropy: disorder
Energy spreads out: heat part of something and what happens?
Nothing is 100% efficient: nothing.
So, can't make energy from nothing, and can't make something happen
without putting in energy, because you always lose some energy to the
surroundings.
Section 9.5: Units of Energy
Skip it: there are units - things like calories, Joules, kilowatt-hours - but
the details don't matter that much for us in this course.