Thermal Physics Flashcards
What is the kinetic theory of matter?
All matter is made up of small particles which are moving.
Define temperature
The average kinetic energy of the particles in that material.
Define specific heat capacity
The heat energy required to change the temperature of 1kg of the material by 1K without a change in state.
What is the specific heat capacity of water?
4200J/kgK
How is the specific heat capacity of a material calculated?
c = Q/mΔT
What is Newton’s law of cooling?
A rate of energy loss per second from an object which is proportional to the temperature difference between the object and its surroundings.
Define latent heat of fusion.
The heat energy required to change 1kg of a material from a solid to a liquid without a change in temperature.
How is the energy needed to change a mass of a material from a solid to a liquid calculated?
Q=mL
Define latent heat of vapourisation.
The heat energy required to change 1kg of a material from a liquid to a gas with no change in temperature.
Describe the shape of a cooling curve
- The rate of temperature change is initially high.
- There is no temperature change as the material changes state.
- The rate of temperature change decreases as the temperature of the material nears the temperature of the surroundings.
Why is there no temperature change when changing state?
The rate of heat energy produced by bond formation is equal to the rate of heat energy lost due to cooling.
How is the specific heat capacity of a material found from a constant heating graph?
c = P/(m x gradient)
How is the latent heat of fusion of a material found from a constant heating graph?
L = Pt/m where t = time taken for the solid to melt
Define the atomic mass unit.
1/12 of the mass of a Carbon 12 atom
Describe and explain the nature of the radiation that may be emitted from an excited
nucleus of the moderator.
Gamma radiation since nucleus de-excites in discrete energy levels.
Outline what is meant by an ideal gas
The gas obeys the ideal gas law at all temperatures/pressures.
Explain what is meant by the Rayleigh criterion
Two sources will be resolved if the central maximum of the diffraction pattern of one coincides with the first minimum of the other.
How is the age of the universe found from Hubble’s constant?
Age = 1/H
kmS^-1Mpc^-1 –> ms^-1pc^-1 –> ms^-1m^-1
What is a binary system?
Two stars revolving about a common centre of mass.
State what is meant by the binding energy of a nucleus
the amount of energy required to separate a nucleus into its separate neutrons and protons/nucleons
State and explain the purpose of the concrete other than its structural function for a nuclear reactor core.
forms a shield to reduce the intensity of radiation
from neutron radiation
Explain what is meant by the Big Bang theory
- The universe has expanded from a single hot dense point - Evidence comes from the Hubble relationship and observations of the red shift of distant galaxies. - This shows that the galaxies are moving outwards from a single common point. - evidence comes from the cosmological microwave background radiation - This follows a black body radiation curve which corresponds to a temperature of 2.7 K - This can be interpreted as the left over “heat” of the big bang, Hydrogen and helium is present in the Universe in the ratio 3:1 - This supports the idea that a very brief period of fusion occurred when the Universe was very young, which is consistent with the Big Bang theory.
State what is meant by a standard candle.
an object whose absolute magnitude is known
Explain how measurements of a type 1a supernova can be used to determine how far
away it is from the Earth.
All type 1a supernovae have same peak absolute magnitude
Apparent magnitude can be measured (at this peak).
ref to m-M = 5 log (d/10)
Explain what is meant by a parsec.
1 pc is the distance at which 1AU subtends an angle of 1 arc second.
What is a decay constant?
probability of decay per unit time
Give two reasons why it is difficult to obtain a reliable age from carbon dating
- May use wood from long after tree was dead.
- Different levels of carbon 14
