Thermal Physics Flashcards
How is the speed of particles in a body distributed?
Randomly
How does the varying speed of particles in a body affect the kinetic energy?
Kinetic energy is distributed randomly
How is the average kinetic energy of the particles affected by the temperature?
Higher temperature leads to higher average kinetic energy
What is the internal energy of a body?
The sum of the randomly-distributed kinetic and potential energies of all its particles
What is a system?
A group of bodies considered as a whole
What is a closed system?
One that doesn’t allow any transfer of matter in or out
How does the internal energy of a system change if it’s not heated and no work is done?
Constant
How is energy constantly transferred between particles in a system?
Collisions between particles
How can the internal energy of a system be changed?
By heating it
By doing work (changing its shape)
Does the internal energy of a substance change when it undergoes a change in state?
Yes, it changes
Does the kinetic energy of a substance change when it undergoes a change in state?
No, it doesn’t change
Does the potential energy of a substance change when it undergoes a change in state?
Yes, it changes
When happens to the potential energy and temperature when a liquid changes to a gas?
The potential energy increases but the temperature stays the same
Define specific heat capacity
The amount of energy needed to raise the temperature of 1kg of the substance by 1K.
What apparatus can be used to find the specific heat capacity?
Continuous-Flow Calorimeter
Describe a Continuous-Flow Calorimeter
A steady rate of water flowing over a heating element, with two thermometers to measure temperature difference
Define specific latent heat (of fusion/vaporisation)
The amount of thermal energy required to change the state of 1kg of a substance
What is Boyle’s Law?
(At a constant temperature) the pressure and volume of a gas are inversely proportional
What is Charles’ Law?
(At a constant pressure) the volume of a gas is directly proportional to its temperature (K)
What is the Pressure Law?
(At a constant volume) the pressure of a gas is directly proportional to its temperature (K)
What is the molecular mass?
The mass of one molecule of that gas
What is molecular mass relative to?
The mass of a carbon-12 atom
What is the molar mass of a substance?
The mass that one mole of that substance would have
What is the Ideal Gas Equation?
(pV)/T = constant
What is the constant in the Ideal Gas Equation equal to?
number of moles × molar gas constant (nR)
what is the equation for work done in changing the volume of a gas at a constant pressure?
work done = pΔV
What is Newton’s Second Law?
Force equals the rate of change of momentum
How do you calculate the mean square speed of a particle?
The average of the [squared speeds] of all the particles
What is pressure equal to?
Force ÷ area
What are the Simplifying Assumptions used in Kinetic Theory?
Molecules move randomly Molecules follow Newton's Laws Molecules move in straight lines Collisions a perfectly elastic Collision forces act much shorter than the time between them
What do you call a gas that follows the Simplifying Assumptions in Kinetic Theory?
Ideal Gas
What temperature (C) is Absolute Zero?
-273
Are the Gas Laws empirical or theoretical?
Empirical
Is Kinetic Theory empirical or theoretical?
Theoretical
Describe Brownian motion
Particles suspended in a fluid move with a “zig-zag”, random motion, due to collisions with fast, randomly-moving particles
Give an example of Brownian motion
Smoke in air
What is the random motion of smoke in air evidence of?
That the air is made up of tiny particles (atoms or molecules) moving quickly
For which law is the pressure and volume of a gas inversely proportional?
Boyle’s Law
For which law is the volume of a gas directly proportional to its temperature (K)?
Charles’ Law
For which law is the pressure of a gas directly proportional to its temperature (K)?
Pressure Law
