Thermodynamics Flashcards
The total energy of all the atoms and molecules in an object.
Thermal Energy
Temperature
A measure of the average kinetic energy of the particles of a substance.
a temperature scale based on the freezing point of water at 32 degrees and boiling at 212 degrees.
Fahrenheit
“Whenever heat flows into or out of a system, the gain or loss of thermal energy equals the amount of heat transferred.”
The First Law of Thermodynamics.
(By the way, the first law of thermodynamics is just a restatement of the law of conservation of energy)
The Third Law of Thermodyamics
“No system can reach absolute zero.”
(Believe me, they have tried)
(The problem is that you have to find somewhere for the last little bit of energy to go, and it will only go to someplace that is colder)
(You pretty much can’t ever find that place that is colder….)
Heat
Thermal Energy on the move.
(It has to be moving from one place to another to be considered “heat.”)
Joule
A unit used to measure energy. This is the SI unit.
Calorie
A unit used for measuring energy. This is the old unit of the English system and is still used in the United States.
Happens when the molecules of an object speed up and spread apart.
Thermal Expansion
The sum of the kinetic and potential energy of all the molecules in an object.
Thermal energy
(think kinetic and potential)
a temperature scale based on the freezing point of water at 0 degrees and boiling at 100 degrees.
Celsius
Absolute zero
The lowest possible temperature. The temperature at which the particles of an object have stopped moving completely. (You can’t go slower than stopped, so you can’t get any colder)
The second law of thermodynamics
Heat never spontaneously flows from a cold substance to a hot substance.
(In this context spontaneously means “by itself” or “without being forced” )
What is the definition of the word “heat?”
The thermal energy that is transferred from one object to another.
(Also known as “thermal energy on the move”)
Specific Heat Capacity
The quantity of thermal energy required to raise the temperature of a gram of some substance by 1 degree Celsius.
(It kind of tells you how hard or easy it is to heat something up)
(Water has an amazingly high heat capacity)
(That is why it takes a big lake until the late summer to heat up)
Thermal Energy
The total energy (kinetic plus potential) of the atoms and molecules that make up a substance.
(We typically just visualize the kinetic energy of the jiggling atoms and molecules, but it also includes some energy held in the bonds between atoms and molecules)
Thermal Expansion
When an object gets bigger (expands) because it gets hotter.
(When the particles jiggle more, they take up more space)
The bubbles you see forming in a pot of boiling water are made up of what?
A) Air
B) Water
C) Oxygen
D) Nitrogen
B
(If the bubbles were air, we would have to figure out where this air were coming from.
Are there little holes in the pot or something????)
(If the bubbles are made of water, we can explain that,
because the liquid water just turned into gaseous water, or steam)
Conduction
The transfer of heat energy by collisions between the particles in a substance.
(This is the primary mode of heat transfer in solids)
Melting
When a substance changes from the solid phase to the liquid phase
Is evaporation a heating process or a cooling process?
Cooling
(That is why your body sweats on a hot day)
When ice melts, does it absorb heat or give heat off?
It absorbs heat.
(You put ice in a cooler so that it can absorb the heat from your cans of soda pop. The ice absorbs the heat from the soda pop while the ice melts.)
Forced convection
When convection is made to occur with a fan or a pump.
(You probably have a “forced air” convection heating system in your home. Listen for the fan)
Natural convection
When convection happens because of differential heating of a fluid.
(In this context, “differential” means different parts of the fluid are at different temperatures)
(The heated air becomes less dense, then it rises. This causes all of the air to move, thus…convection)
In the thermal energy equation below, what does the “Q” stand for?
_Q_uantity of thermal energy
In the equation below, what does the “m” stand for.
The mass of the substance
In the thermal energy equation below, what does the “delta” stand for?
“Change in”
In this case, it works together with the “T” so that
delta T
means “change in temperature.”
In the thermal energy equation below, what does the “T” stand for?
“temperature”
Deposition
The change in phase directly from a gas to a solid.
the transfer of thermal energy in a liquid or a gas
(the particles containing the thermal energy actually move from one place to another.)
convection
the transfer of heat energy through direct contact
(the particles bump into each other and pass the energy from one to the next)
conduction
the transfer of energy by electromagnetic waves.
(this can transfer energy through empty space)
radiation
The three ways thermal energy can move from one place to another.
Conduction
Convection
Radiation
What do the “contrails” streaming behind this jet have to do with what we are studying in science?
Contrail is short for “Condensation Trail.”
The hot air coming out of the jets is filled with moisture. When the hot moist air hits the cold air outside, the water condenses into little droplets that look like a cloud.
What is being shown here?
A convection current in water.
What do you add to matter to change its physical state?
You add thermal energy.
Below is a heat/temperature curve for a substance. What is the melting point of the substance?
- 50 degrees Celsius.
The horizontal parts of the graphs are phase changes.
Below is a heat/temperature curve for a substance. What is the freezing point of the substance?
- 50 degrees Celsius.
(Melting and freezing both happen at the same temperature. )
What happens to the density of a gas when it is heated?
The density decreases.
What happens to the volume of a gas when it is heated?
It increases.
What happens to the volume of a solid when it is heated
The volume increases.
What happens to the density of a solid when it is heated?
Its density decreases. (It becomes LESS dense)
What happens to the density of a liquid when it is heated and absorbs thermal energy?
It decreases. The liquid becomes LESS dense
What happens to the volume of a liquid when it absorbs thermal energy and gets hotter?
Its volume increases. (It takes up more space)
