Happy Thursday!!! 1-28-16
• Get ready for warm up #2
• Be prepared to continue your notes from
yesterday
Warm up #2
• Betty has a mass of 55.0 kg and took the stairs
up to the second floor, a total height of 3.73
m. It took Betty 11.4 seconds to get to the
second floor. Determine the power output of
Betty during this time.
Differences between heat and
temperature
• Heat
• Total thermal energy
• 2L of boiling water has
more energy than 1L of
boiling water
• Measured in Joules
• Energy that flows as the
result of a difference in
temperature
• Temperature
• Average kinetic energy
of molecules
• 2L of boiling water has
the same temperature
as 1L of boiling water
• Measured in Celsius,
Fahrenheit or Kelvin
• How we determine the
“hotness” of an object
Heat and Thermal Energy
• Imagine heating a cup of coffee
to a temperature of 100°C.
• Next think about heating up
1,000 cups of coffee to 100°C.
• The final temperature is the
same in both cases but the
amount of energy needed is
very different.
Thermal Energy
• “Thermal Energy” – the overall energy of
motion of the particles that make up an
object
Thermal Equilibrium
• Two bodies are in
thermal equilibrium
with each other when
they have the same
temperature.
• In nature, heat always
flows from hot to cold
until thermal
equilibrium is reached.
Methods of Heat Transfer
• Conduction – Kinetic energy is transferred through
collisions of electrons, atoms, & molecules
– i.e., through direct contact between objects
• Ex: Thermometer – particles in your body hit the
glass, transferring their KE to the mercury & raising its
KE
Convection
• Convection – Warm, less-dense fluid (gas
or liquid) rises and cool, more-dense fluid
sinks
– “Convection Current”
• Examples:
– Sea breeze & land breeze
– Heating & cooling vents in your home
Radiation
• Radiation
– Infra-red electromagnetic wave that can travel
through empty space
– Created by vibrating electrons
• Examples:
– Night vision goggles
– Infra-red satellite images
– “Heat-seeking” missiles
Temperature
• 3 commonly used temp scales:
–Fahrenheit (United States) (98.6 ° F = avg
body temp)
–Celsius (most of the rest of the world)
–Kelvin (scientific community – i.e., us!)
• Both C and K scales are “metric” scales
because FP and BP are 100 degrees apart
on each
Temperature
Temp. Scale
Freezing Point
Boiling Point
Fahrenheit
32° F
212 ° F
Celsius
0°C
100 ° C
Kelvin
273 K
373 K
Kelvin Temperature Scale
• K = °C + 273
• If a substance has a temperature, then the
substance’s particles have kinetic energy. Therefore,
the particles are moving.
• “Absolute Zero” = 0 K
• Absolute zero – 0 K – all motion of all
particles stops completely.
– 0 K is the lowest you can go! You can’t
stop motion more than 0.
• absolute zero
• absolute zero #2