Chapter 21 Thermal Physics and 22 Ideal Gases

Question 1

Internal energy

Answer 1

Sum of the random distribution of kinetic and potential energies of its atoms or molecules

Question 2

Changing internal energy

Answer 2

Heating and compressing and passing a current through it, makes it bounce off faster and gain kinetic energy and temperature rises

Question 3

First Law of Thermodynamics

Answer 3

Increase in internal energy = energy supplied by heating + energy supplied by doing work

Question 4

First law of thermodynamics equation

Answer 4

U = q + w

Question 5

Thermal energy

Answer 5

Hotter to cooler

Question 6

Thermal equilibrium

Answer 6

Two objects of the same temp no transfer of energy

Question 7

Thermodynamic Kelvin Scale

Answer 7

Absolute zero- min internal energy

Triple point- ice, liquid, vapor of water

Question 8

Celsius to Kelvin

Answer 8

Theta+273.15

Question 9

Thermometers

Answer 9

Resistance
Voltage
Volume of a fixed mass at constant pressure
Color of heated wire

Question 10

Thermistor adv

Answer 10

Very robust
Fast response
Accurate
Sensitive at low temps

Question 11

Thermocouple

Answer 11

Faster response 
Wider range 
Small thermal capacity 
Physically small, readings taken at a point
Power supply not needed

Question 12

Thermistor dis

Answer 12

Narrower range 
Slower response time 
Larger thermal capacity 
Larger in size 
Not suitable to measure varying temp

Question 13

Thermocouple dis

Answer 13

For accurate reading, high resistance Voltmeter required

Question 14

Melting and boiling

Answer 14

No change in temp
Temp is Ke
All energy used to break bonds
No change in ke no change in temp

Question 15

Cooling effect of evaporation

Answer 15

Particles which escape are those with higher velocity so avg Ke of remaining decrease
Temp = avg Ke
Overall temp decreases

Question 16

Kinetic theory of a gas

Answer 16

Molecules hit and rebound off walls
Change in momentum gives rise to force
Many impulses averaged to give constant force and pressure
Brownian motion: random motion of smoke particles

Question 17

Ideal gas kinetic theory

Answer 17

Large number of particles
Negligible-
-intermolecular forces of attraction
-volume compared to container
Collisions perfectly elastic and no time spent
Avg Ke directly proportional to absolute zero

Question 18

Boyle’s law and Charles law

Answer 18

Boyle’s: 
P € 1/V ; pV = k 
Charles’s: 
V € T; V/T = k 
P1V1/T1 = P2V2/T2

Question 19

Ideal gas equation

Answer 19

PV = nRT

Question 20

Specific latent heat

Answer 20

Is the energy required per kilo of the substance to change its state without any change in temperature

Question 21

Specific latent heat equation

Answer 21

E = mL
L is slh
VIt = mL

Question 22

Specific heat capacity

Answer 22

Energy required per unit mass of the substance to raise the temperature by 1k or 1°C

Question 23

Pressure of molecules proof

Answer 23

Check book or revision guide

Question 24

Temperature and molecular kinetic energy proof

Answer 24

Check book

Question 25

Mean kinetic energy, mass and temperature

Answer 25

ke € T

ke € v^2