SPS7. Students will relate transformations
and flow of energy within a system.
a. Identify energy transformations within a
system (e.g. lighting of a match).
b. Investigate molecular motion as it relates
to thermal energy changes in terms of
conduction, convection,
c. Determine the heat capacity of a
substance using mass, specific heat, and
temperature.
What are the three
methods by which
thermal energy is moved
from place to place?
All matter is made up of constantly
moving particles. All moving
things possess kinetic energy.
Thermal energy is the total energy of the
particles in a material. This total
includes:
1. Kinetic energy – vibrations and
movement within and between particles
2. Potential energy – forces that act within
or between the particles (bonds)
Thermal energy depends on:
1. Mass – the greater the mass, the larger
the number of moving particles
2. Temperature – the higher the
temperature, the faster the particles are
moving
Example – Temperature as a factor
Example –Mass as a factor
Example –
http://www.youtube.com/watch?v=f1eAOyg
DP5s
Thermal energy travels as heat from a
material of higher temperature to a
material of lower temperature. Thermal
energy will flow from warmer objects to
cooler ones until the temperature
equalizes.
Bill Nye on Thermal energy
http://www.teachertube.com/viewVideo.php?video_id=186099
Method #1
Conduction – transfer of thermal energy
through matter by direct contact of particles
Transfer by
Collisions
Conduction
When you heat a metal strip at one end, the heat
travels to the other end.
As you heat the metal, the particles vibrate, these
vibrations make the adjacent particles vibrate, and so on
and so on, the vibrations are passed along the metal and
so is the heat. We call this? Conduction
Conduction can take place
in solids, liquids and
gases.
Matter must be present
for conduction to take
place!
Examples:
Heating a pan on a stove (pan heats up by
conduction) or place a spoon in a bowl of
soup (spoon heats up by conduction)
Method #2
Convection – transfer of thermal
energy by bulk movement of
matter
Convection can take place in
fluids (materials that flow).
Liquids and gases are fluids.
Currents carry less dense, warmer
material up while cooler, denser
material sinks.
Convection
What happens to the particles in a liquid or a
gas when you heat them?
The particles spread out and
become less dense.
What is a fluid?
A liquid or gas.
This effects fluid movement.
Fluid movement
Cooler, more d____,
ense fluids
sink through w_____,
armer less
dense fluids.
In effect, warmer liquids and
ise up.
gases r___
Cooler liquids and gases s___.
ink
Water movement
Cools at the
surface
Cooler
water sinks
Convection
current
Hot water
rises
Why is it windy at the seaside?
Cold air sinks
Where is the
freezer
compartment
put in a fridge?
It is put at the top,
because cool air
sinks, so it cools the
food on the way
down.
Freezer
compartment
It is warmer at
the bottom, so
this warmer air
rises and a
convection
current is set up.
Matter must be
present for
convection to take
place!
Examples:
Ocean currents, wind, boiling water
Convection questions
Why does hot air rise and cold air sink?
Cool air is more dense than warm air, so
the cool air ‘falls through’ the warm air.
Why are boilers placed beneath hot
water tanks in people’s homes?
Hot water rises.
So when the boiler heats the water,
and the hot water rises, the water tank
is filled with hot water.
Temperature is a measure of
the average kinetic energy of
the particles in a sample of
matter.
As the particles in a sample
move faster and faster, the
kinetic energy becomes
greater and the temperature
of the object rises.
Temperature is measure with a
thermometer.
Common Temperature Scales
Pure
Pure
Water
Water
freezes boils
Scale
Based on
Fahrenheit
Celsius
Kelvin
Salt water
32
Pure water
0
Motion of an 273
atom
212
100
373
Absolute Zero – temperature at which
all atomic motion stops; ZERO on the
Kelvin Scale