4.4 Matter Very Simple Flashcards
Which temperature scale starts at absolute zero?
The Kelvin scale.
What happens at absolute zero?
All particles have minimum possible kinetic energy.
What is 0K in degrees Celsius?
-273.15ºC
Which temperature scale is used in thermal physics equations?
The Kelvin scale.
What is Boyle’s law?
At a constant temperature, the pressure and volume of a has are inversely proportional. pV = constant.
What is Charle’s law?
At a constant pressure, the volume of a gas is directly proportional to its absolute temperate. V/T = constant.
What is the Pressure law?
At a constant volume, the pressure of a gas is directly proportional to its absolute temperature. p/T = constant.
What equation do you get from combining the three gas laws?
pV/t = constant
What is the value of the molar has constant?
8.31 J mol^-1 K^-1
What is the ideal gas equation?
pV = nRT
What does n represent in the ideal gas equation?
The number of moles of gas present.
What is Avogadro’s constant, NA?
The mole of gas particles in one mole.
What is the value of Avogadro’s constant?
6.02 x 10^23
What is the Boltzmann’s constant equivalent to?
R / NA
What is the meaning of the Boltzmann’s constant?
The gas constant for one particle of gas.
What is the value of Boltzmann’s constant?
1.38 x 10^-23
What is the equation of state of an ideal gas?
pV = NkT
Using a cubic box analogy, explain why particle velocity is proportional to pressure.
The faster a particle is travelling, the more momentum is exchanged with the walls more frequently. This means a larger force on the wall and therefore a higher pressure.
Using a cubic box analogy, explain why the number of particles is proportional to pressure.
Each particle exerts a force on the wall as it hits it so total force is proportional to number of particles. This results in a higher pressure since P = F / A.
Using a cubic box analogy, explain why the volume of the box is proportional to the pressure.
Describing the size of the box increases the rate of collisions and reduces the area of the walls. Hence a higher pressure.
Why is mean square speed used?
To take into account the difference in particle velocities.
Why is the mean square speed multiplied by one third?
Because there are 3 dimensions, it can be assumed that a third of all particles are moving in one dimension at a time.
Give the third equation involving pV.
pV = 1/3 Nm(ć^2)
What is r.m.s. speed?
Root mean square speed, the typical speed of a particle.
Give four assumptions used in kinetic theory.
The gas contains a large number of particles. The particles move rapidly and randomly. The motion of the particles follows Newton’s Laws. Collisions between particles themselves and the container are perfectly elastic.
What is a random walk of a particle?
A model of the movement of particles.
What does a random walk involve?
Moving a step in a random direction repeatedly.
What is the relationship between average distance moved after N steps and number of steps moved?
Distance is proportional to √N.
What is the zeroth law of thermodynamics?
If body A and body B are both in thermal equilibrium with body C, body A and body B must be in thermal equilibrium with each other.
Where does thermal energy flow to and from?
Regions of high temperature to low temperature.
What is the definition of specific thermal capacity, c?
The amount of energy needed to raise the temperature of 1kg of a substance by 1K.
Give the word equation for specific heat capacity.
energy change = mass x specific thermal capacity x change in temperature
Give the symbol equation for specific heat capacity.
∆E = m c ∆θ
What are the units of c, specific heat capacity?
J kg^-1 K^-1
Describe the shape of the graph comparing proportion of particles with a given speed and particle speed.
A Maxwell-Boltzmann distribution curve.
What happens to particle speeds as the temperature of a gas increases?
The average particle speed increase and the maximum particle speed increases. The means the speed distribution curve will be more spread out.
What happens when gas particles collide?
Energy is transferred between the particles.
When gas particles collide, some may particles may gain speed whilst others…
Slow down.
Describe the speed of gas particles between collisions.
Constant.
Give three assumptions used in kinetic theory.
There are no attractive forces between particles. Any forces that act during collisions are instantaneous. Particles have a negligible volume compared with the volume of the container.
Despite the change in energy of individual particles as a result of collisions, the total energy of the system…
Is unchanged.
The total energy of the system is constant so the average speed of the particles in the system will stay the same provided…
Temperature of the gas is constant.
What the internal energy of a gas?
The sum of kinetic and potential energy of the particles within a system.
What is average kinetic every of an individual particle proportional to?
Absolute temperature.
Give the equation for average kinetic energy of an individual particle, 1/2 m ć^2
1/2 m ć^2 = 3/2 (n R T)/N
Give the two equations used to derive the equation for average kinetic energy of an individual particle.
pV = 1/3 Nm(ć^2) and pV = nRT
