14. Thermal Physics Flashcards
Module 14
Define thermal equilibrium
Thermal equilibrium is when there is no net flow of thermal energy between two objects. This means any object in thermal equilibrium must be at the same temperature.
what does absolute temp scale use as their fixed position?
The absolute temperature scale use the triple point of pure water and absolute zero as its fixed points.
What is the SI unit for temp on absolute scale?
The SI base unit of temperature on the absolute scale is called the Kelvin.
How do you go from temp in theta to temp in kelvin?
T(K) = theta (degree C) + 273
What is the kinetic model?
describes how all substances are made up of atoms or molecules.
Can you describe solids in terms of spacing, ordering, and motion of atoms or molecules?
SOLIDS:
- atoms or molecules are regularly arranged and packed closely together
- strong electrostatic forces of attraction hold them in position
- they vibrate and therefore have Ke
Can you describe liquids in terms of spacing, ordering, and motion of atoms or molecules?
LIQUIDS:
- atoms or molecules still very close but have more kinetic energy than solids
- they can change position and flow past each other
Can you describe gases in terms of spacing, ordering, and motion of atoms or molecules?
GAS:
- Most Ke
- free to move past each other as there are negligible electrostatic forces between then
- move with diff speeds in diff directions
What is Brownian motion?
The idea that substances were made of particles (atoms or molecules)
Explain Brownian motion in terms of collisions
Collisions between pollen grains and millions of tiny molecules were elastic and resulted in a transfer of momentum from the water molecules to the pollen grains, causing the grains to move in haphazard ways.
Define internal energy
The sum of the randomly distributed kinetic and potential energies of atoms and molecules within the substance.
Define Absolute zero
Absolute zero: the lowest temperature possible, 0K
What is the internal energy at absolute zero?
internal energy is min but not zero cuz substance still has electrostatic P.E. Even at 0K, P.E can’t be reduced to 0.
Two ways to increase Internal Energy:
- Increase in temp can cuz Ke rises
- A change of state/phase of a substance can increase P.E
How does P.E vary depending on the state (solid, liquid and gas)?
- SOLID: electrostatic force is large so P.E is a negative value
- LIQUID: electrostatic force gives negative P.E which means that energy must be supplied to break the stomic or molecular bonds
- GAS: P.E is zero as there are negligible electric forces between atoms or molecules
