Title: HEAT
1HEAT THERMAL ENERGY
2State indicator
- 17. Demonstrate that thermal energy can be
transferred by conduction, convection or
radiation (e.g., through materials by the
collision of particles, moving air masses or
across empty space by forms of electromagnetic
radiation).
3Heat flows spontaneously from hot objects to cold
objects
- Heat is also the transfer of thermal energy.
4What is Temperature?
5- Temperature is related to the average kinetic
energy of an objects particles due to their
random motion through space.
6Temperature
- The reference point on the Kelvin scale for temp
erature is absolute zero. - 0 -273o C
- Absolute zero a temperature of 0K. Â
- Room temp. would be 293o K
- The purpose for this is when we study gases,
which have very low freezing points.
7Thermal energy depends on mass, temperature and
phase of an object.
8Thermal expansion occurs because particles of
matter tend to move farther apart as temperature
increases.
9- Gas expands more than liquids and solids
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11Specific Heat
- The lower a materials specific heat is, the more
its temperature will rise when energy is applied. - Heat needed to raise the temp. of a 1g of an
object 1 Celcius.
12Specific Heat
- Unique to every material
- The lower an objects specific heat, the moreÂ
the temp. increases when heat is absorbed. - Water has a large specific heat.
- Needs a lot of heat to change its temp
13Heat
- Heat is measured in Joules or calories.
- One calorie is the energy the required to raise
the temp. of 1g of water by 1oC. - One calorie is equal to 1.184 J
- The unit for specific heat is J/g oC
14Q  m   c   ?TÂ
- Q heat
- M mass
- C specific heat (unique for the substance)
- ?T change in temperature
15- A calorimeter uses the principal that heat flows
from hotter to colder objects until they both
reach the same temperature.
16Heat and Thermodynamics
- Conduction in gases is slower than liquids
solids because the particles collide less often - Transfer of heat through direct contact is
CONDUCTION
17Thermal ConductorsÂ
- Material that conducts thermal energy well.
Examples copper aluminum pots pans wood
vs. tile flooring
18Thermal InsulatorsÂ
- Material that conducts thermal energy poorly.
- Examples air in a double pane window, wood, Â Â
fiberglass, fat
19Convection
- Transfer of heat through movingÂ
particles in fluids (liquids  gases). - Convection currents are important in many natural
cycles. - Convection Current occurs when a fluid circulates
in a loop as it heats and cools. Example oven
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21Radiation Â
- Examples Heat from the sun, heat lamps used inÂ
restaurants -  light colored object ?
- Â Reflect heatÂ
- Â dark colored object ?
- Â Absorb heat
22The first law of thermodynamics
23The 2nd Law of thermodynamics
- Heat can only flow from colder to hotter if work
is done on the system.
24The 3rd Law of Thermodynamics
- Absolute Zero cannot be reached
- People are trying!
- Current record is down to about 90 picokelvin!
Thats 9.0 x 10(-11)
25Temperature and Conductivity
- http//www.youtube.com/watch?vyXT012us9ng
262 types of engines
- Internal combustion
- External combustion
- A heat engine is any device that converts heat
into work. - Thermal energy that is not converted into workÂ
is called waste heat. - Waste heat is lost to the environment.Â
27Internal combustion engine
28External combustion engine
29Most heating systems are convection to distribute
thermal energy
30- Heat pumps must do work on a refrigerant in order
to reverse the flow of thermal energy
31Alternate home heating is part of our energy
future!