Module 5.1 Flashcards
Absolute Temperature
A temperature value relative to absolute zero.
Absolute Zero
The lowest possible temperature of a system, where no heat
remains and the particles in the system have no kinetic energy
Avogadro Constant
The number of particles that make up one mole of any gas
Boltzmann Constant
A constant relating the average kinetic energy of the
particles in a gas, to the gas’ temperature
Boyle’s Law
The pressure of an ideal gas is inversely proportional to its volume
when held at constant temperature.
Brownian Motion
The random motion of particles.
Change of Phase
The transitions between solids, liquids and gases. During a
change of phase, there is a change of internal energy but not temperature
Equation of State of an Ideal Gas
An equation linking pressure, volume, number
of moles, temperature and the ideal gas constant.
Gas
A phase of matter in which the particles are high energy and free to move.
Gases will fill the space they are placed in.
Internal Energy
The sum of the randomly distributed kinetic and potential
energies of the particles in a given system
Kelvin
The unit of absolute temperature
Liquid
A phase of matter in which the particles can slide over each other, but still
have forces of attraction between each other
Solid
A phase of matter in which the particles can only vibrate about fixed
positions, due to strong intermolecular forces
Specific Heat Capacity
The amount of energy required to increase the
temperature of 1kg of a substance by 1 Kelvin
Specific Latent Heat
The amount of energy required to change the state of 1kg
of a substance without a change of temperature.
Thermal Equilibrium
A stable state in which there is no thermal heat transfer
between two regions.
Thermodynamic scale of tempurature
uses the triple point of pure water, 273.16K and absolute 0
as its fixed points, and it is measured in kelvin
absolute 0 in Celsius
-273
The assumptions of kinetic theory
- Molecules of a gas behave as identical (or all have the same mass)
- Molecules of gas are hard, perfectly elastic spheres
- The molecules are in continuous random motion
- There are no forces of attraction or repulsion between the molecules
- External forces (e.g. gravity) are ignored
- Newton’s laws apply
- The volume of the molecules is negligible compared to the volume of the container
- The molecules collide perfectly elastically with the walls of the container exerting a pressure upon them
- The time of a collision is negligible compared to the time between collisions
- There are a very large number of molecules
How can you observe Brownian motion
Look at smoke particles in the air using a microscope
Internal energy
the sum of the randomly distributed kinetic and
potential energies associated with the atoms or molecules which make up the substance
The number of moles
mass of the substance / Molar mass
The number of particles
Avogadro’s constant X number of moles
How to find pressure using kinetic theory of gas
- Assume the collisions between atoms and the wall of the container are perfectly elastic.
- Therefore the atoms rebound from the wall at the same speed they travel in v
- Change in momentum, p = m(v-u)
= 2mv because u = v - Since change in momentum is equal to the force * time, F = (2mv) / t
- Using Newtons 3rd law, the total pressure on the wall is equal to the sum of the force of each collision between the atoms in the gas and the wall and the area of the wall
P = F/A
Charles’s law
for a fixed mass of gas at a constant pressure,
the volume is directly proportional to temperature
How to investigate Boyle’s law
a sealed syringe can be
filled with gas and connected to a pressure gauge.
-The syringe can be used to vary the volume
of the container, and the values for volume and pressure recorded.
-When a graph of pressure
against 1/volume is plotted, a straight line should be produced, showing a constant relationship.
-To increase accuracy in this experiment, the syringe should be lowered slowly so that no heat is
produced from friction.
How to estimate absolute zero using gas
To determine the value of absolute zero in °C, a sealed container of air, connected to a pressure
gauge, is placed in a water bath.
-The temperature of the water is varied, and the values of
temperature and pressure and recorded.
-When pressure is plotted against temperature, a linear
graph will be produced.
-At absolute zero, the gas molecules will have no kinetic energy, so
there will be no collisions with the container walls, resulting in there being no gas pressure.
-By
extrapolating the graph back the x intercept can be found, and this is equal to absolute 0.
Root mean square speed
determined by summing the square of all of the individual velocities of molecules, dividing by
the number of molecules, N, and then finding the square root of this value.
What kind of distribution is Maxwell-Boltzmann distribution and what is on the x and y axis
Normal distribution.
X-axis is molecular speed
y-axis is the number of molecules
What does the peak of the Maxwell-Boltzmann distribution mean. And what about slightly to the right and more to the right
From peak to slightly lower and more to the right
Most probable speed
Mean speed
Root mean squared speed
Use pV = NRT to get pV - nkT
pV = NRT
pV = nRT/Na (Na is Avogrado constant)
k = R/Na
pV = nkT
Internal energy of an idea gas
no potential energy due to no electrostatic forces between molecules in an ideal gas
Kinetic energy for gas molecules
3/2 kt = 1/2 mc^2
E = 3/2 kt
Thermal equlibrium
No net transfer of thermal energy between two objects at the same temperature.
What is needed for solids, liquid and gases
Kinetic model:
Solids: Strong electrostatic forces, vibrate around fixed positions.
Liquids: Weaker electrostatic forces, move around freely.
Gases: Negligible electrostatic forces, move freely and collide elastically.
Brownian motion:
Random motion of particles due to collisions with air molecules.
Specific heat capacity
Energy required per unit mass to increase temp by 1K.
Equation: E = mcΔθ (Jkg^-1K^-1)
Kinetic theory of gases
Amount of substance:
Measured in moles (6.02 x 10^23 particles).
Equation: n = m/M.
Assumptions of ideal gases:
Random, rapid motion.
Negligible volume of atoms.
Perfectly elastic collisions.
Negligible electrostatic forces (except during collisions).
Pressure and ideal gas laws:
Boyle’s Law: p ∝ 1/V (constant T).
Charles’ Law: V ∝ T (constant p).
Equation of state: pV = nRT.
Root mean square speed
Root Mean Square Speed (r.m.s.):
r.m.s. speed: √(sum of velocities^2 / N).
Equation: pV = (1/3)Nmς^2.
Maxwell-Boltzmann distribution:
Shows number of molecules vs. speed.
Higher temperature → peak shifts to higher speed.
Boltzmann constant (k):
k = R / NA (1.38 x 10^-23 JK^-1).
Equation: pV = NkT.
