Thermal physics (incomplete) Flashcards
What are the conditions for energy transfer between two objects?
1) An object exerts a force on another object (work is done).
2) Energy transfer by heating due to a temperature difference between the two objects.
What is the definition of internal energy?
The sum of the random distribution of the kinetic and potential energies of its molecules.
What is the definition of thermal energy?
The internal energy of an object due to its temperature.
What are the factors effecting internal energy?
1) Energy transfer by heating/cooling.
2) Energy transfer by work done.
What are the conditions for internal energy to be constant?
1) No energy transfer/ work done.
2) Energy transfer by heating and work done balance each other out.
What is the first law of thermodynamics?
The change of internal energy of the object = the total energy transfer due to work done and heating.
What is temperature?
A measure of the degree of hotness.
What is thermal equilibria?
When there is no overall energy transfer between two or more objects. This occurs when the temperature of all objects is equal.
How do you convert from Celsius to kelvin?
Add 273.
What is the triple point of water?
273.16k, the temperature at which ice, water and water vapour co-exist in thermodynamic equilibrium.
What is absolute zero?
1) The point where an object has minimum internal energy.
2) 0k / -273C
What are the factors effecting temperature rise of an object when it is heated?
1) Mass of the object.
2) Amount of energy supplied to it.
3) Substance the object is made of.
What is the definition of specific heat capacity?
The energy required to raise the temperature of a unit mass of a substance by 1k without a change of state.
Why can liquids and gasses flow while solids can’t?
This is because the molecules in a solid are locked down by strong bonds, preventing them from breaking free.
In liquids and gasses, the molecules have too much kinetic energy and the bonds aren’t strong enough to keep the molecules fixed together.
What is the definition of the specific latent heat of fusion?
The amount of energy required to melt 1kg of a substance without changing its temperature.
What is the definition of the specific latent heat of vaporisation?
The amount of energy required to vaporise 1kg of a substance without changing its temperature.
What happens during fusion of a substance?
The atoms in a solid gain so much energy that they begin to vibrate so much that they break free from each other, becoming a liquid.
What happens during vaporisation of a substance?
Molecules gain enough energy to overcome bonds holding them close together
What is sublimation?
When a solid directly vaporises, skipping the liquid phase.
What unit is pressure measured in?
Pascals (Pa)
What unit is pascals equivalent to?
Nm^-2
What is Boyle’s law?
The pressure exerted by a gas (of fixed mass and temperature) is inversely proportional to the volume.
What is Charles’ law
The volume of a gas is directly proportional to temperature, assuming that the pressure is constant.
What is Gay-Lussac’s law (pressure law)?
Pressure is directly proportional to temperature, assuming that mass and volume of the gas are fixed.
What is Brownian motion?
The motion of large gas particles in a fluid where they seem to move unpredictably when observed under a microscope.
What is the definition of Avogadro’s constant?
The number of atoms in exactly 12g of carbon-12.
What is an ideal gas?
A gas that obeys Boyle’s law.
What are the kinetic theory assumptions?
1) The volume of each molecule is negligible compared to the volume of the gas.
2) The molecules move in continual random motion.
3) All collisions are elastic collisions.
4) Molecules don’t attract each other.
5) Each collision with the container surface is of much shorter duration than the time between impacts.
