8 Thermal effects

Question 1

Solid

Answer 1

• fixed shape
• fixed volume
• molecules are close together
• strong attraction force
• vibrate at fixed point

Question 2

Liquid

Answer 2

• not fixed shape
• fixed volume
• molecules are near to each other
• very weak attraction force
• move / slide over each other

Question 3

Gas

Answer 3

• not fixed shape
• not fixed volume
• molecules are far apart
• no force of attraction
• move randomly at high speed

Question 4

Brownian motion

Answer 4

moved in zig-zag direction
more randomly
: smoke particles collided randomly with air molecules

Question 5

Internal energy

Answer 5

KE + PE
: internal energy depends on KE

Question 6

Temperature

Answer 6

Average KE per molecules

Question 7

Object stationary

Answer 7

1) KE of mass = 0
2) KE of particles of mass /= 0 –> particles vibrate

Question 8

Thermal expansion of solid

Answer 8

• heated
• KE increases
• Vibrate more
• Need more space
• Expand

Question 9

Application of thermal expansion in solid

Answer 9

’ thermostat ‘
: used to switch on / off by temperature
- temp increases –> 2 metal expand and expansion of 2 metals are different so they bend
eg. temp inc –> thermostat bend and lost contact so heater stop working

Question 10

Thermal expansion of liquid

Answer 10

• heat
• KE increases
• Vibrate + move more
• Need more space
• Expand

Question 11

Application of thermal expansion in liquid

Answer 11

’ liquid thermometer ‘
: used to measure temperature

Question 12

Thermal expansion in gas

Answer 12

• heat
• KE increases
• Moves faster
• Collide with wall stronger + more often
• Greater force on wall
• Greater pressure –> expand

Question 13

Absolute zero ‘Kelvin’

Answer 13

• 273ºC
  1 Kelvin = -273ºC

Question 14

Pressure and Volume equation

Answer 14

P1V1 = P2V2

Question 15

Conduction

Answer 15

• heated
• KE increases
• Vibrate faster
• Collide with neighboring particles
• NP vibrate faster
• Transfer of energy

Question 16

Convection

Answer 16

• heated
• KE increases
  hot fluid = less dense
  cold fluid = more dense
  hot fluid –> rises up
  cold fluid –> replace hot fluid

Question 17

Radiation

Answer 17

black = good absorb, good emit
silver / white = good reflector

Question 18

Boiling point

Answer 18

Temperature at which liquid turns into gas

Question 19

Boiling

Answer 19

Rapid form of evaporation

Question 20

Evaporation

Answer 20

liquid molecules that have high enough KE at the surface will break bonds and become gas

Question 21

Evaporation and Boiling

Answer 21

E B
occurs at SF. occurs anywhere
any temp. at boiling point
no bubbles. bubbles
temp of liquid dec. stays the same

Question 22

Rate of evaporation

Answer 22

inc temp –> inc KE
inc SA –> increase chance for molecules to escape into the air
blow air + reduce humidity –> remove evaporated molecules gas

Question 23

Specific heat capacity

Answer 23

energy required to raise the temperature of 1KG by 1ºC
E = mcΔT

Question 24

Thermal capacity

Answer 24

E = mc