Module 5 - Thermal Physics (Solid, Liquid and Gas)

Question 1

What are the properties of solids in terms of spacing

Answer 1

• Tightly packed molecules
• Because there are strong electrostatic forces of attraction between molecules
• No spacing between molecules
• Meaning they are incompressible

Question 2

What are the properties of solids in terms of ordering

Answer 2

• Regular lattice structure

Question 3

What are the properties of solids in terms of motion

Answer 3

• They have kinetic energy which allows for vibrations about fixed positions

Question 4

What force is responsible for fixing the positions of particles in solids

Answer 4

Electrostatic Forces

Question 5

What are the properties of liquids in terms of spacing

Answer 5

• Small spacing between molecules
• Meaning they are incompressible
• Tightly packed molecules but less tight than solid
• Because although there is a strong electrostatic attraction it it less than in solids

Question 6

What are the properties of liquids in terms of ordering

Answer 6

• Irregular and random arrangement of particles

Question 7

What are the properties of liquids in terms of motion

Answer 7

• Particles have more kinetic energy than solid particles and so they can slide past each other

Question 8

What are the properties of gases in terms of spacing

Answer 8

• Large spaces between particles meaning they can be compressed

Question 9

What are the properties of gases in terms of ordering

Answer 9

• No ordering of the gasesW

Question 10

What are the properties of gases in terms of motion

Answer 10

• Particles in gases have the most KE meaning that they moves the most, randomly in all directions

Question 11

Describe Brownian motion in pollen grains

Answer 11

• Pollen grain on water, instead of staying still they were observed to jitter in a random path.
• This was found to be caused by water molecules that exerted forces on the pollen grains to move
• This was the only explanation that aligned with Newtons 1st Law

Question 12

State 2 conclusions about the molecules from the liquid from the motion of pollen grains

Answer 12

• The molecules are smaller than the pollen grains because they could not be seen in the microscope
• The molecules move in random directions

Question 13

What is meant by internal energy

Answer 13

The sum of the randomly distributed kinetic and potential energies of particle in a substance

Question 14

What is the equation for internal energy

Answer 14

U = KE + PE

Question 15

What is Temperature and what is its relation with KE

Answer 15

Temperature is the average KE of particles in a substance. Temperature is directly proportional to KE

Question 16

What is meant by potential energy at this scale

Answer 16

A measure of the electrostatic potential between molecules whose magnitude decreases as the distance between them increases

Question 17

Do gases have potential energy, why/why not

Answer 17

• No because there is not electrostatic attraction between particles

Question 18

What does potential energy represent

Answer 18

• The enrgy required to break the bonds between particles

Question 19

How is Potential energy modelled

Answer 19

It is modelled as negative and as it increases it approaches 0

Question 20

What causes pressure on walls of a container filled with gas

Answer 20

Collision of gas particles with the walls

Question 21

What is meant by temperature

Answer 21

The average kinetic energy of particles in a system.