8 Thermal effects Flashcards
Solid
- fixed shape
- fixed volume
- molecules are close together
- strong attraction force
- vibrate at fixed point
Liquid
- not fixed shape
- fixed volume
- molecules are near to each other
- very weak attraction force
- move / slide over each other
Gas
- not fixed shape
- not fixed volume
- molecules are far apart
- no force of attraction
- move randomly at high speed
Brownian motion
moved in zig-zag direction
more randomly
: smoke particles collided randomly with air molecules
Internal energy
KE + PE
: internal energy depends on KE
Temperature
Average KE per molecules
Object stationary
1) KE of mass = 0
2) KE of particles of mass /= 0 –> particles vibrate
Thermal expansion of solid
- heated
- KE increases
- Vibrate more
- Need more space
- Expand
Application of thermal expansion in solid
’ 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
Thermal expansion of liquid
- heat
- KE increases
- Vibrate + move more
- Need more space
- Expand
Application of thermal expansion in liquid
’ liquid thermometer ‘
: used to measure temperature
Thermal expansion in gas
- heat
- KE increases
- Moves faster
- Collide with wall stronger + more often
- Greater force on wall
- Greater pressure –> expand
Absolute zero ‘Kelvin’
- 273ºC
1 Kelvin = -273ºC
Pressure and Volume equation
P1V1 = P2V2
Conduction
- heated
- KE increases
- Vibrate faster
- Collide with neighboring particles
- NP vibrate faster
- Transfer of energy
Convection
- heated
- KE increases
hot fluid = less dense
cold fluid = more dense
hot fluid –> rises up
cold fluid –> replace hot fluid
Radiation
black = good absorb, good emit
silver / white = good reflector
Boiling point
Temperature at which liquid turns into gas
Boiling
Rapid form of evaporation
Evaporation
liquid molecules that have high enough KE at the surface will break bonds and become gas
Evaporation and Boiling
E B
occurs at SF. occurs anywhere
any temp. at boiling point
no bubbles. bubbles
temp of liquid dec. stays the same
Rate of evaporation
inc temp –> inc KE
inc SA –> increase chance for molecules to escape into the air
blow air + reduce humidity –> remove evaporated molecules gas
Specific heat capacity
energy required to raise the temperature of 1KG by 1ºC
E = mcΔT
Thermal capacity
E = mc
