April 8, 2011
DRILL
Answer the following in your notebook:
1. What is a more scientifically correct way of saying “the
ice cubes made my water cold”?
2.
The water transfers it’s energy to the ice. The water
loses heat and the ice gains heat.
Identify the methods of heat transfer expressed in the
pictures/diagrams below:
Radiation
Conduction
Convection
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Heat Transfer
• Energy needed to change the temperature
of a material depends on
– The mass of the material
– The type of material
• Conductors take less energy to heat than
insulators
– How much we increase the temperature
Test Review
Heat Transfer
• E = M * C * DT
– E – Energy – measured in calories
– M – is the mass of the substance measured in
grams
– C – is the heat capacity measured in
calories/gram(Celsius)
-DT is change in temperature
– Water has a heat capacity of 1 calorie/(g*C)
Test Review
Food
• 1 food calorie = 1,000 calories
• 1 pound of fat = 3,500 food calories
Test Review
Heat Transfer
• How much energy is required to raise
the temperature of 10 gram of water
20o C.
Step 1: Write down information
E=??
M = 10 g
C = 1 cal/(g *Celsius)
DT = 20 C
Step 2: Write equation
E = M *C *DT
Step 3: Substitute and Solve
E = 10g*1cal/(g*Celsius)*20 Celsius
E = 200 calories
Test Review
Is it Conduction, Convection, or Radiation?
1. Warm water rises in a lake. Cold water
descends. Convection
2. The sun transfers its heat to our planet through
space. Radiation
3. A thermometer under your tongue shows that
you have a high fever. Conduction
4. On cloudless nights, heat escapes from our
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planet and goes into space. Radiation
5. You place a spoon into a cup of cocoa and it gets
hot over time. Conduction
6. A thermos bottle has a shiny interior. What type of
heat transfer does it prevent? Radiation
7. Heat in the room moves with the warm currents
from warmer areas to cooler areas. Convection
8. Brownies bake in a glass pan using these 2
methods.
Convection(from oven) and
Conduction (through pan)
9. You feel the heat of a wood stove when you stand
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next to it. Radiation and Convection
1. Work with one partner and complete the Thermal
Technology Test Review sheet.
2. What you don’t finish in class, you must finish for
homework.
3. Quiz will be next Tuesday
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Test Review Solutions
3. What is the purpose of using infrared photography
if hot objects are often red to our eyes?
The more powerful radiation heat is in the form
of infrared light, which we cannot see with our
natural eyes. Therefore, infrared photography
allows us to “see” the heat given off by objects
even if the material is not hot enough for there
to be a color change.
Test Review
Test Review Solutions
1. Define the following
– Thermal Technology – the technology of producing,
storing, controlling, transmitting and getting work
from heat energy.
– Thermodynamics - the science dealing with internal
energy, heat, and work
– Photon – a particle of light
– Conduction – the transfer of heat through a
substance by collision of molecules.
– Convection – is the transfer of heat by movement of
a fluid.
– Radiation – the transfer of energy by
electromagnetic waves.
Test Review
Test Review Solutions
2. List 3 example of Thermal Technologies and
identify why they are considered a thermal
technology.
Example applications:
•Furnace,
•Hot water heater,
•Toaster,
•Insulation,
•Heat exchanger,
•Refrigerator,
•Hot air balloon,
•Fan,
•Engine cooling system,
•Oven,
•Blow-dryer,
•Thermos,
•Heat shrink,
•Styrofoam,
•Radiator,
•Blanket,
•Winter jacket,
•Wool socks…
Test Review
Test Review Solutions
4. What are the two types of convection? Explain
each.
• Natural Convection
– Fluid surrounding a heat source receives heat
and rises (due to lower density)
– Surrounding cooler fluid moves in to replace it.
– Cooler fluid is heated, rises, and cycle continues.
• Forced Convection
– Fans or other means are used to propel a fluid.
– An convection current is induced.
– Car engine and A/C are examples
Test Review
Test Review Solutions
5. Number the following from 1-5, 1 being coolest and
5 being hottest.
3 Yellow
1 Red
5 White
4 Blue
2 Orange
Test Review
Test Review Solutions
6. (Solid / Liquid / No Medium) is the medium for
conduction.
7. (Solid / Liquid / No Medium) is the medium for
convection.
8. (Solid / Liquid / No Medium) is the medium for radiation.
9. Thermal energy always travels from a region of
Higher
__________________
temperature to a region of
__________________
temperature.
Lower
10. The driving force for heat transfer is
______________________________________________
Temperature Difference (Difference of Temperature)
11. The more accurate way of saying an object is “cold” is
Lacks
saying that it ____________
heat.
12. The three methods of heat transfer are
____________________________________________.
Convection, Conduction, Radiation
13. The sun’s heat reaching us through space is an example
Radiation
of the method of _____________________.
Test Review
Test Review Solutions
14. A car engine cooling system is an example of the method
of _____________________.
Convection
15. Heat from a house in winter travels through the walls by
the method of _____________________.
Conduction
16. Give an example of a technology that combines
chemicals to produce heat: ___________________.
Heat Pads
17. Give an example of a technology that converts
mechanical energy to heat: ___________________.
Car Engine / Basketball
18. Give an example of a technology that converts electrical
energy to heat: ___________________.
Electric Stove
19. Give an example of a technology that converts light
energy to heat: ___________________.
Incandescent Light Bulb
20. Sketch an example of Conduction, Convection, and
Radiation:
Test Review