5. Newtonian World & Astrophysics Flashcards
How do you convert from Celsius to kelvin
Add 273
Why is the absolute scale used
It doesn’t depend on the properties of a given substance
0K means the particles have the minimum internal energy
Describe the arrangement and energy of particles in a solid, liquid and a gas
Solid -regular arrangement, vibrate around fixed positions
Liquid - close together, constantly moving past eachother
Gas- spaced far apart, free to move in all directions
How does Brownian motion give evidence for the particle model of matter?
Smoke particles suspended in air can be seen to move randomly in all directions. This must be the result of random collisions with particles making up the air
What is internal energy?
The sum of the potential and kinetic energies of a system
True or false - at a given temperature, all particles in a material have the same KE
False - the kinetic energies will be randomly distributed around a central ‘most likely’ amount
How can you increase the thermal energy of a system
Heating it up or doing work on the object
Explain the energy changes that occur during a change of state
During change of state the potential energy of the particles change but the kinetic energies don’t change
What equation can be used to determine the energy required to change the temperature of a substance
E=mc(change in temperature)
What is the specific heat capacity of a substance
The energy required to raise the temperature of 1kg of a substance by 1 K
Give the equation to work out the energy for change of state
E=mass * specific latent heat
What is the specific latent heat of a substance
The energy required to change the state per unit mass of a substance, while keeping the temperature constant
In an experiment to find ‘c’ for water, lots of energy input escapes to the surroundings. Will this lead to an over or underestimate of specific heat capacity
An overestimate
The change in temperature will be lower than it should be due to the escaped energy
What is Avogadros constant in words
The number of atoms there are in one mole of a substance
What are the key assumptions in the kinetic theory of gases
- there are a large number of molecules in random, rapid motion
- particles are negligibly small compared to the total volume of the gas
- all collisions are perfectly elastic
- the time taken for a collision is negligibly small compared with the time between collisions
- between collisions there are no forces between particles
Why do gases exert a pressure on the container they are in
- gas particles collide with the surface of the container
- the container exerts a force on the particles to change their direction. The particles exert an equal and opposite force on the container
- the pressure is force applied (in total, by all particles) per unit area
What is an ideal gas?
A gas where
- the gas molecules don’t interact with eachother
- the molecules are thought to be perfectly sphere
What is the ideal gas equation?
PV=nRT
What is Boyle’s law
Pressure is inversely proportional to volume, providing temperature is constant
Assuming constant volume, how are the pressure and temperature of a gas related?
They are directly proportional
Using the kinetic theory of gases to explain why a temperature increase leads to an increase in pressure
- a temperature increase means the particles have more kinetic energy
-more kinetic energy means a greater change in momentum during collisions with the container. And more frequent collisions - change in momentum is proportional to force applied and therefore to pressure as well
What equation links N, V, p, m and c
pV=1/3 N m c^2
P= pressure V = volume, N=number of particles, m= mass of a particle, c= mean square speed
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 does the area under a Maxwell-Boltzmann curve represent?
The total number of particles
How does the Maxwell-Boltzmann curve change if the temperature of a gas is increased?
The average particle speed, and maximum particle speed both increase (curve shifts right)
The curve becomes lower and more spaced out
The average kinetic energy of a particle in an ideal gas is equal to what
1.5kT
True or False - the internal energy of an ideal gas is proportional to absolute temperature
True
In an ideal gas there is no ‘potential energy’ component in the internal energy. This means the internal energy is proportional to the kinetic energy
Define absolute magnitude
