Chapter 14 & 15 - Thermal Physics and Ideal Gases Flashcards
What is the KE model for solid
They have strong forces of attraction.
They have the most negative electrostatic potential energy (because external energy is added to separate the molecules)
They have KE and they move around in fixed positions.
What is the KE model for liquid
They have a greater separation than solids.
They have more KE to move around more.
They have less negative electrostatic potential energy than solids
What is the KE model for gas
They have the most KE to move
They collide elastically with each other
They have even less Electrostatic forces of attraction.
They have the maximum Electrostatic potential - 0J
What is Brownian Motion
Molecules of a gas that can travel in random motion and directions with random velocity.
This was first seen using pollen grains in water
What is Internal Energy
Sum of potential and Kinetic energy
When a substance is heated, but still in the same state, how does this affect the kinetic energy?
It increases
When a substance is heated, but still in the same state, how does this affect the potential energy?
Stays the same
When a substance is heated and changes state, how does this affect the kinetic energy?
Stays the same
When a substance is heated and changes state, how does this affect the potential energy?
Increases
Main assumptions about ideal gases
RAVED
Random - and rapid movement.
Attraction - there are no electrostatic forces between atoms (unless they are colliding)
Volume - the volume of gas atoms is negligible in comparison to the total volume of the gas
Elastic - all collisions are elastic
Duration - the time it takes for atoms to collide is negligible to the time in between collisions.
What is the thermodynamic scale?
Uses the triple point of pure water and absolute 0 as its fixed points
What is thermal equilibrium
A point at which 2 objects of different temperatures have the same temperature. Here, there is no net transfer of energy.
What is Absolute zero
When molecules completely stop moving
Minimal internal energy- there is no kinetic energy
How can you use the kinetic theory to show how particles can exert pressure on a wall
As a particle moves, it has momentum. When it collides with a wall, it has a change of momentum of 2mv. This way, the force becomes 2mv/time. Then use the formula p=fa.
This works because of Newton’s 3rd rule; that each object exerts a equal (in magnitude) but opposite (in direction) force on each other.
What are the 2 laws that are used to create pV=nRT
Boyles law and Charles Law
(B: Pressure is inversely proportional to the volume, of a fixed mass and constant temperature) (C: pressure is proportional to the temperature for a fixed mass and volume)
What is SHC
The amount of energy required to increase the temperature of 1kg substance by 1K.
What is the electrostatic potential energy
The electromagnetic forces acting amongst the atoms of an individual molecule and also between 2 molecules.
What is Boltzmann Constant
(k)
1.38 x 10 ^-23
R/ Avogadro’s number
Mean KE and temperature
pV=NkT and pV= 1/3 Nmc^2
KE = 3/2 kT
On a Maxwell-Boltzmann Distribution, what do the levels of peaks mean
Most probable speed (very peak)
Mean speed
Room mean speed.
How to calculate the RMS speed
Sum al the square of the individual speeds, then divide by the number of molecules.
giving:
pV= 1/3 Nmc^2
(calculated using the box- derivative)
How can you determine SHC (normal way)
Set up: - insulator - heater - thermometer (if a liquid- ensure to stir)
Then: E=VIt E=mcT VIt = mcT So, c= ItV/mT
How can you determine SHC using a mixture
Mixture of liquids
Using known masses, but different temperatures
Reach thermal equilibrium
Then use the SHC of one to calculate the other.
Determining the SLH of fusion
Use ice and a thermometer.
Energy transferred increases internal energy.
Take note of the duration that the temperature stays constant at.
Use a known power
E=mL
Determining the SLH of vaporisation
Using the weird flask thing.
Equation for SLH
IVt/ m
