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Particles move, which means they have what kind of energy?
Kinetic energy
Thermal energy (U)
(aka internal energy) the sum of KE and PE
What does NOT depend on the number of particles?
Temperature
What does depend on the number of particles?
Thermal energy
Why can two object of the same temperature can have different thermal energies?
The size of the object can vary. A big object would have more particles, and a small one would have less
Thermal conduction
The transfer of thermal energy that occur when particles collide
Thermal equilibrium
the states in which the rate of energy flow between 2 objects is equal
Temperature limits
Temperatures do not have an upper limit, but do have a lower limit
Heat (Q)(SI unit J) flows from….
hot to cold
Convection
heating caused by the motion of fluid in a liquid or gas due to temperature differences
Radiation
the transfer of energy by electromagnetic waves
Conductors
transfer energy easily
Insulators
does not transfer energy easily
Specific Heat (C) (SI unit J/KgK or J/KgC)
the amount of energy that must be added to the material to raise the temperature of a unit mass by one temperature unit
Hotter objects mean more…
kinetic energy
What happens to molecules at absolute zero?
They stop moving
Heat will flow until what is met?
equilibrium
Heat, energy, and work, are all measured in…
Joules
Positive Q means
object has absorbed thermal energy
Convection
Heating caused by the motion of fluid in a liquid or gas due to temperature difference
Why is temperature constant during transition of state?
All thermal energy goes to overcoming particle forces
Latent heat of fusion (Hf)
The amount of energy needed to melt 1kg of the substance
Latent heat of vaporization (Hv)
The amount of energy needed to vaporize 1kg of the substance
The first law of thermodynamics
The change in thermal energy (U) of an object is equal to the heat (Q) minus the work (W) done by the object
In the 1st law of thermodynamics, when is work positive and when is it negative?
Negative when work is done BY the system. Positive when work is done ON the system
What other law does the law of thermodynamics restate?
The law conservation of energy
Heat engine
Device that converts thermal energy to mechanical
QH
Input heat
QC
Waste heat, heat that has not been converted into work
Does the internal energy change if the engine is continuously working?
No
Do machines ever have 0 QC
No
Can you remove thermal energy from a colder energy and give it to a warmer object?
Yes but only if work is done
Efficiency
A measure of how well an engine operates, can be calculated as a ratio of work done by the engine to the added energy to the system as heat during one cycle
What happens to entropy (s) if work is done on a system, but the thermal energy does not change?
no change in entropy
Second law of thermodynamics
whenever there is an oppurtunity for energy dispersal, the energy always spreads out to achieve a uniform distribution
Thermal expansion, matter expands as temperature…
increases
Equation for head (Q, SI unit J)
Q=mC△T = mC(Tf - Ti)
Conservation of thermal energy equation
[mC(Tf - Ti)]A = -[mC(Tf - Ti)]B
First law of thermo dynamics equation when work is done ON the system
△U=Q+W
Efficiency (e) (no SI unit) equation
e=Wnet/Qh= Qh-Qc/Qh
