Chapter 14 & 15 - Thermal Physics and Ideal Gases

Question 1

What is the KE model for solid

Answer 1

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.

Question 2

What is the KE model for liquid

Answer 2

They have a greater separation than solids.
They have more KE to move around more.
They have less negative electrostatic potential energy than solids

Question 3

What is the KE model for gas

Answer 3

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

Question 4

What is Brownian Motion

Answer 4

Molecules of a gas that can travel in random motion and directions with random velocity.
This was first seen using pollen grains in water

Question 5

What is Internal Energy

Answer 5

Sum of potential and Kinetic energy

Question 6

When a substance is heated, but still in the same state, how does this affect the kinetic energy?

Answer 6

It increases

Question 7

When a substance is heated, but still in the same state, how does this affect the potential energy?

Answer 7

Stays the same

Question 8

When a substance is heated and changes state, how does this affect the kinetic energy?

Answer 8

Stays the same

Question 9

When a substance is heated and changes state, how does this affect the potential energy?

Answer 9

Increases

Question 10

Main assumptions about ideal gases

Answer 10

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.

Question 11

What is the thermodynamic scale?

Answer 11

Uses the triple point of pure water and absolute 0 as its fixed points

Question 12

What is thermal equilibrium

Answer 12

A point at which 2 objects of different temperatures have the same temperature. Here, there is no net transfer of energy.

Question 13

What is Absolute zero

Answer 13

When molecules completely stop moving

Minimal internal energy- there is no kinetic energy

Question 14

How can you use the kinetic theory to show how particles can exert pressure on a wall

Answer 14

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.

Question 15

What are the 2 laws that are used to create pV=nRT

Answer 15

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)

Question 16

What is SHC

Answer 16

The amount of energy required to increase the temperature of 1kg substance by 1K.

Question 17

What is the electrostatic potential energy

Answer 17

The electromagnetic forces acting amongst the atoms of an individual molecule and also between 2 molecules.

Question 18

What is Boltzmann Constant

Answer 18

(k)
1.38 x 10 ^-23
R/ Avogadro’s number

Question 19

Mean KE and temperature

Answer 19

pV=NkT and pV= 1/3 Nmc^2

KE = 3/2 kT

Question 20

On a Maxwell-Boltzmann Distribution, what do the levels of peaks mean

Answer 20

Most probable speed (very peak)
Mean speed
Room mean speed.

Question 21

How to calculate the RMS speed

Answer 21

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)

Question 22

How can you determine SHC (normal way)

Answer 22

Set up:
- insulator 
- heater 
- thermometer
(if a liquid- ensure to stir)

Then: 
E=VIt 
E=mcT
VIt = mcT
So, c= ItV/mT

Question 23

How can you determine SHC using a mixture

Answer 23

Mixture of liquids
Using known masses, but different temperatures
Reach thermal equilibrium
Then use the SHC of one to calculate the other.

Question 24

Determining the SLH of fusion

Answer 24

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

Question 25

Determining the SLH of vaporisation

Answer 25

Using the weird flask thing.

Question 26

Equation for SLH

Answer 26

IVt/ m