Chapter 19 - Thermal physics Flashcards
Energy transfer takes place between 2 objects when…?
- One object exerts a force on the other object and makes it move. In other words, one object does work on another.
- Temperature difference between 2 objects
What is the internal energy?
Internal energy of an object is the sum of the random distribution of the kinetic and potential energies of its molecules.
What is the first law of thermodynamics? (relates to internal energy)
Change of internal energy of the object = total energy transfer due to work done and heating
Why do substances change state when temperature is increased?
- Higher the temperature, more the molecules vibrate if they vibrate so much they break free this is changing state.
During a change of state, which type of energy is changing?
Potential, not kinetic
If an object gets hotter does it have more or less internal energy?
More
How do you convert from celcius to Kelvin?
Celcius + 273K
What is absolute zero?
Lowest possible temperature (0K). An object at absolute zero has minimum internal energy.
What is the specific heat capacity (C) of a substance?
Energy required to raise the temperature of the substance by 1K without change of state.
unit: JKg^-1K^-1
What’s the equation for energy required to raise substance from T1 to T2?
Q = mc(T2-T1) energy = mass x SHC x change in T
What is specific latent heat of fusion?
Energy needed to change state of 1Kg of substance from solid to liquid without temperature change.
What is specific latent heat of vaporisation?
Energy needed to change state of 1Kg of the substance from liquid to gas without temperature change
What is the equation for energy needed for substance to change state?
Q=ml
energy = mass x Specific latent heat
Draw a temperature - time graph of a substance changing state?
Look a paper flashcards.
Temp increases linear until melting and then increases again until boiling and then increases again.
