Thermal Physics Flashcards
What is Boyle’s Law?
Pressure is INVERSELY PROPORTIONAL to Volume
What is Charles’ Law?
Temperature is DIRECTLY PROPORTIONAL to Volume
What is the Pressure Law?
Pressure is DIRECTLY PROPORTIONAL to Temperature
What does NOT change while a substance is changing from a liquid to a solid?
The Temperature
What is the theoretical point at which all molecular motion ceases?
Absolute Zero
What type of energy means the sum of the potential and kinetic energies?
Internal Energy
What type of quantity is temperature?
Scalar
What is a gas that obeys the gas laws at all temperatures and pressures called?
An Ideal Gas
What is the type of latent heat energy involved in the process of changing from solid to liquid?
Latent Heat of Fusion
What type of energy do we assume is zero for an ideal gas?
Potential Energy
If there is no net heat energy flow between two bodies they are said to be in what?
Thermal Equilibrium
What type of latent heat is involved in changing a liquid to a gas?
Latent heat of Vaporisation
Using pV = 1/3 Nmc² it can be shown that: p = 1/3 ρc² , how can this equation be proved?
Using the definition of density and the fact that the gas’ total mass will N x m
What is the equation of state for n moles of an ideal gas?
pV = nRT
State three assumptions that are made in the derivation pV=1/3Nmc² (Molecular Kinetic Theory)
● All particles are identical
● Collisions of gas molecules are elastic
● Intermolecular forces are negligible (except during collisions)
What is Internal Energy?
The sum of the potential and kinetic energies of a system
How can you increase the thermal energy of a system?
By heating it up or doing work on the object
Explain the energy changes that occur during a change of state
Potential energies of the particles change but the kinetic energy does not
What equation can be used to determine the energy required to change the temperature of a substance?
Q =mcΔT
What is the equation to work out the energy for change of state?
Q =ml
What is the Ideal Gas equation?
pV = nRT
What is the first law of thermodynamics?
ΔU = Q - W
What is the Specific Heat Capacity of a substance?
The energy required to raise the temperature of 1kg by 1K
What is the Specific Latent Heat of a substance?
The energy required to change the state of 1kg, whilst keeping the temperature constant
What is an Ideal Gas?
A gas where: the molecules don’t interact with each other, and the molecules are thought to be perfect spheres
What is the internal energy of an Ideal Gas equal to?
The sum of the kinetic energy of all its particles
In an Ideal Gas, how would increasing the volume change the temperature of the gas, whilst the pressure remains constant?
As volume increases, so does the temperature
Explain how increasing the temperature of a balloon, whist keeping the volume the same, will increase the pressure
● Average KE increases
● Particles travel faster
● More frequent collisions
● Particles exert greater force
● Increases rate of change of momentum
What is Absolute Zero?
At -273°C, where objects have no KE
What is Avogadro’s Constant? (In words)
The number of atoms there are in one mole of a substance
True or False: “All collisions between particles and between particles and the wall are elastic” is an assumption of an Ideal Gas?
True
State an assumption of an Ideal Gas related to time
The time for each collision is negligible in comparison to the time between collisions
What is meant by the root mean square speed?
The square root of the mean of the squares of the speeds of the molecules
What is Brownian Motion?
Very small objects have random motion in a liquid or gas due to random bombardment by molecules in the substance
What is the mnemonic to remember the assumptions of the kinetic theory of gases?
RAVED
In the mnemonic for remembering the assumptions of the kinetic theory of gases, what does R stand for?
Random motion
In the mnemonic for remembering the assumptions of the kinetic theory of gases, what does A stand for?
Attraction - there is none between particles
In the mnemonic for remembering the assumptions of the kinetic theory of gases, what does V stand for?
Volume - molecules/particles have negligible volume compared to that of the gas
In the mnemonic for remembering the assumptions of the kinetic theory of gases, what does E stand for?
Elastic collisions - Kinetic energy is conserved
In the mnemonic for remembering the assumptions of the kinetic theory of gases, what does D stand for?
Duration of collisions is very short compared to time between
What is the formula for the force exerted by a particle of an Ideal Gas on the wall of its container, according to the kinetic theory of gases?
F = -mv²/L
