Chapter 14 Thermal Physics Flashcards
What is temperature a measure of
A measure of “hotness” on a scale and thus kinetic energy , more = more hotter = higher temp
How does heat move when two bodies come in contact
what happens at thermal equilibrium
Heat in the form of a flow of ENERGY is transferred from the hotter object to the colder object until there is no more NET transfer of energy
When this point is resched , bodies are in THERMAL EQUILIBRIUM , and thus SAME TEMPERATURE
Again what is thermal equilibrium (2)
The point at which there is NO net transfer of energy between two objects
Therefore two objects are at the SAME TEMPERATURE
Example if you step into cold? What’s happening.
As you are hotter than surroundings , there will be a net transfer of energy to atmosphere, heating it up and cooling you down until no more net transfer of energy and at thermal equilibrium, thus at same temp
Why when we measure anything with a thermometer is the tempertaure recorded INACCURATE
However why is this not the case with our bodies?
This is because there is energy transfer to the thermometer when it touches, and only gives the thermal equilibrium temperature, thus lower what it should be
2) not the case with our bodies due to body internal heating system, NEGATIVE FEEDBACK SYSTEM MEANS that energy kept on pumped out so we at constant temperature for enzyme function, so even if thermometer lowers temp, body makes temp go up again so thermostat ends up recording right temp
However if you are in a room and touch heater why does it feel cold? Surely it should be same temp and thermal equilibrium?
Yes it is thermal equilibrium as everything else calm
However when you touch hester even tho itd same temp, it’s a GOOD CONDUCTOR, thus takes heat energy from your finger, which brain registers as FEELS COLD
The greater the rate of energy transfer from hand to metal, so the better the conductor, the more COLDER IT WILL FEEL!!!
What is the ZEROWTH law of thermodynamics (don’t need to know but may be useful)
Basically if two objects are both thermal equilibrium with a third, then all three are thermal equilibrium with each other !
Makes sense if A and C thermal equilibrium , and B and C too , that means they must all be the SAME temp, and thus A AND B ARE THERMAL EQUILIBRIUM TOO
What’s the Kelvin scale based on
To avoid any discrepancies like Celsius as that’s based on boiling point which can change with atmospheric pressure
Kelvin based on absolute 0 and triple point which are fixed
The increments same as Celsius’s, so 0K = -273 degrees and 0 degrees 273k
3 kinetic models of states
- arrangement
- forces of attraction
- motion
Solids
- atoms are arranged in regular fashion in a 3d structure
- string firces of attraction between particles
- vibrates in fixed positions
Liquids
- atoms are free to move over each other and take the shape of any container, however still close to each other
- weaker firces of attraction
- move over each other
Gases
- random arrangement as motion in all directions
- NGELIGIBLE forces of attraction between gases
Why are ice less dense than water when normally solid versions are more dense
Solid are more dense as same mass in less volume
However for ice, as the water freezes past 4° due to hydrogen bonds it’s held in FIXED positions in an open lattice structure, such that on average particles are further away from each other as a solid then when liquid
As same mass but MORE VOLUME, less density, makes it float and freeze from top down
What is definition for internal energy
Sum of randomly disrurbuted kinetic and potential energies of atoms in a substance
So sum of potential energy and kinetic
What is potential energy
So why do gases have most potential energy
This is due to electrostatic forces of attraction, when particles join in chem bond making they RELEASE ENERGY, so when they aren’t joined, they have POTENTIAL ENERGY (electrostatic potential energy that’s it )
So to think of it , potential energy is the POTNETIAL TO MAKE BONDS, so gases have the most potential energy
Why do gases have highest potential energy and what’s this value
What happens when potential energy decreases
Potential energy is potential to make bonds, so gasses have the highest value and this is at 0
So everything else has negative value
Basically this value provided to make it a gas again
THUS WHEN POTENTIAL ENERGY DECREASES, IT RELEASES ENERGY CONVERTED TO KINETIC SO TEMPERATURE ACTUALLY INCREASES
Again what happens when potential energy decreases
And thus what happens when water as gas condenses on window, and what happens to temperature
When potential energy decreases, it means bonds are being MADE
- therefore energy is being RELEASED
- this could be converted into KE, and transferred to something else’s
Therefore when water condenses on window, water potential energy decreases as it becomes liquid, so releases energy to the window and the WINDOW HEATS UP (not the water)
What is BROWNIAN MOTION
What is it a proof for ?
Brownian motion is a proof for the kinetic model, the fact that matter is made up of particles with kinetic energy
Brownian motion is the HAPHAZARD movement of particles as a result of collisions with surrounding gaseous particles which also move haphazardly
3) observed using a smoke cell, where smoke particles scatter light and the jittery movement of the light represents the smoke particles moving about in random velocities and directions due to collisions with air molecules
This shows matter made from molecules and has Ke, and thus Brownian motion proves the kinetic model
