Thermal Physics

Question 1

Definition of internal energy of a substance

Answer 1

Sum of randomly distributed kinetic and potential energies of the molecules in a substance

Question 2

Definition of the potential energy of a molecule

Answer 2

The energies that particles have due to the electrostatic attraction that exists with other particles (in a non-ideal gas)

Question 3

Why is potential energy of a molecule always negative?

Answer 3

Energy must be supplied to break the atomic/molecular bonds

Question 4

What is potential energy defined to be in a gas?

Answer 4

0

Question 5

Why is potential energy 0 in a gas?

Answer 5

There are negligible electrostatic forces between the atoms

Question 6

Describe potential energy in a liquid

Answer 6

Has a negative value due to the electrostatic forces that need energy to be broken.

Question 7

Describe potential energy in a solid

Answer 7

The electrostatic forces between atoms are very large, giving the potential energy a large negative value

Question 8

What is specific latent hear

Answer 8

The energy needed to change the state of 1kg of a substance

Question 9

What is the triple point?

Answer 9

the specific temperature and pressure where all 3 phases of matter can exist in thermal equilibrium at the same time

Question 10

What is the triple point for water?

Answer 10

0.01C & 0.6 kPa (less than 1% of normal atmospheric pressure

Question 11

How to work out Kelvin?

Answer 11

C + 273.15

Question 12

Give the main properties of solids, including the molecular form and intermolecular forces:
How are atoms packed?
What arrangement?
What structure?
What is between atoms?
What do atoms vibrate around?
Therefore having what?

Answer 12

Close together
Regular arrangement
Crystalline structure.
Strong electrostatic forces of attraction
A fixed spot
KE

Question 13

Give the main properties of liquids, including the molecular form and intermolecular forces:
How many atoms?
Packed?
Arrangement? (2)
What don’t atoms have?
but they can..?
KE in relation to other states?

Answer 13

Many
Closely together
Not as regular as solids, can vary through time
Much space to move
Slide over each other, changing position.
More KE than atoms in a solid.

Question 14

Give the main properties of gasses, including the molecular form and intermolecular forces:
Arrangement of molecules?
Space between atoms compared to solids & liquids?
More or less KE?
what are atoms free to do?
what are the electrostatic forces between atoms?

Answer 14

No arrangement
Larger
More KE
Move past each other
Negligable

Question 15

What is the definition of temperature?

Answer 15

a measure of how hot or cold something is

Question 16

In what state is electrostatic PE the highest?

Answer 16

gases

Question 17

What number can the PE of a substance never be?

Answer 17

0

Question 18

What is absolute temperature?

Answer 18

temperature measured using the Kelvin scale where absolute 0 is 0 kelvin

Question 19

Define specific heat capacity

Answer 19

the amount of heat energy needed to raise the temperature of 1kg of a substance by 1 C / 1K

Question 20

What are the units for specific heat capacity?

Answer 20

Jkg^(-1)K^(-1)

Question 21

Equations that relates energy, mass, specific heat capacity, and change in temperature

Answer 21

E = mc∆c

Question 22

What is thermal equilibrium?

Answer 22

When two objects have 0 resultant energy transfer between them.

Question 23

When does thermal equilibrium occur?

Answer 23

only when the temperatures between two objects are equal

Question 24

In which direction does temperature transfer occur?

Answer 24

transfers from high to low

Question 25

What is the relationship between changes in hot temperatures and changes in cold temperatures?

Answer 25

∆E hot - ∆E cold

Question 26

Which equation can be used to show the relationship between changes of energies and temperatures?

Answer 26

mc(hot)∆T(hot-final) = mc(cold)∆T(final-cold)

Question 27

In an investigation for the SHC of a liquid such as water, what equipment would be required?

Answer 27

thermometer, cotton wool (insulator), solid block, immerstion heater

Question 28

In an investigation for the SHC of a liquid, which measurements need to be taken?

Answer 28

t = time the heater is on for, T = temperature at specific intervals, V = voltage, I = current, m = mass of block

Question 29

In an investigation for the SHC of a liquid, how would you minimise the uncertainty?

Answer 29

use electrical equipment instead of a thermometer

Question 30

use t, T, V, I, and m to find c

Answer 30

E = Pt = ItV E = mc∆T ItV = mc∆T c = ItV/m∆T

Question 31

Which quantities remain the same as a substance undergoes a change of state?

Answer 31

KE and temperature

Question 32

What are the units for pv/T?

Answer 32

Jmol^(-1)K^(-1)

Question 33

Which type of energy is responsible for a change in temp of a material?

Answer 33

Kinetic

Question 34

Which type of energy is responsible for a change of state in a material?

Answer 34

potential