Thermal Physics Flashcards
Define Specific Heat Capapcity
The energy needed to raise the temperature of a unit mass of the substance by 1 Kelvin without a change of state
What is the internal energy of a body
Sum of all the kinetic and potential energies of all its particles
The energy of its molecules due to their positions and movements
What happens on a molecular level when energy is transferred to a solid
Molecules vibrating about fixed points gain kinetic energy so their temperature increases to their melting/boiling point.
Then they stop gaining K.E and gain potential energy and break/weaken the bonds between them
How to know if a substance is pure
It will melt at its melting point and boil at its boiling point
Compare the density of a substance in the three states of matter, explain why
Density of a gas is much less than for a liquid/solid
Dist. between molecules of gas is much larger
Why can’t solids flow
Atoms have strong enough bonds and not enough kinetic energy to break/weaken these strong bonds so they can flow
Define Latent Heat of Fusion
The energy required to change the state of 1kg of a substance from solid to liquid without a change of temperature
Explain on a molecular level how a substance melts
When a solid is heated at its melting point, it gains enough potential energy to weaken the bonds between molecules and become a liquid.
There is no temperature increase as all the energy is being transferred to the P.E store
Define Latent Heat of Vaporisation
The energy required to change the state of 1kg of a substance from a liquid to gas without a change of temperature
What is Brownian Motion
The random motion of larger particles in a fluid caused by collisions with surrounding particles
How may one see brownian motion
Looking at smoke particles under a microscope
Use M.K.T to explain Boyle’s Law
Increasing the volume of a gas allows molecules to move more freely with less frequent collisions
Use M.K.T to explain Charles’s Law
Increasing the temperature of a gas increases the Av. K.E of molecules
One must increase the volume in order to keep the frequency of the collisions the same since molecules are traveling faster
Use M.K.T to explain the Pressure Law
Increasing the temp. of a gas increases its average K.E
Since they are moving faster, but in the same confined space, they collide more frequently and faster.
Rate of change of momentum for collisions with walls increases
Hence Pressure will increase
Name the 5 assumptions of M.K.T
No intermolecular forces act on molecules
Duration of collisions is negligible in comparison to time between collisions
Motion of molecules is random and are perfectly elastic collisions
Motion of molecules follow Newton’s Laws
Molecules move in straight lines
