U3g – L3 Answer the following in your notebook: 1.What is a more scientifically correct way of saying “the ice cubes made my water cold”? 2.Identify the.

U3g – L3

Answer the following in your notebook:

1. What is a more scientifically correct way of saying “the ice cubes made my water cold”?

2. Identify the methods of heat transfer expressed in the pictures/diagrams below:

April 8, 2011

DRILL

Convection

Radiation Conduction

The water transfers it’s energy to the ice. The water loses heat and the ice gains heat.

Test Review

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

• 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

Heat Transfer

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

U3g – L3

Is it Conduction, Convection, or Radiation?

1. Warm water rises in a lake. Cold water descends.

2. The sun transfers its heat to our planet through space.

3. A thermometer under your tongue shows that you have a high fever.

4. On cloudless nights, heat escapes from our planet and goes into space.

Convection

Radiation

Conduction

Radiation

U3g – L3

5. You place a spoon into a cup of cocoa and it gets hot over time.

6. A thermos bottle has a shiny interior. What type of heat transfer does it prevent?

7. Heat in the room moves with the warm currents from warmer areas to cooler areas.

8. Brownies bake in a glass pan using these 2 methods.

9. You feel the heat of a wood stove when you stand next to it.

Conduction

Radiation

Convection

Convection(from oven) and Conduction (through pan)

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

U3g – L3

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.

Test Review

Test Review Solutions

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…

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.

Yellow

Red

White

Blue

Orange

Test Review

Test Review Solutions

1

2

3

5

4

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

__________________ temperature to a region of __________________ temperature.

10. The driving force for heat transfer is ______________________________________________

11. The more accurate way of saying an object is “cold” is saying that it ____________ heat.

12. The three methods of heat transfer are ____________________________________________.

13. The sun’s heat reaching us through space is an example of the method of _____________________. Test

Review

Test Review Solutions

HigherLower

Temperature Difference (Difference of Temperature)

Lacks

Convection, Conduction, Radiation

Radiation

14. A car engine cooling system is an example of the method of _____________________.

15. Heat from a house in winter travels through the walls by the method of _____________________.

16. Give an example of a technology that combines chemicals to produce heat: ___________________.

17. Give an example of a technology that converts mechanical energy to heat: ___________________.

18. Give an example of a technology that converts electrical energy to heat: ___________________.

19. Give an example of a technology that converts light energy to heat: ___________________.

20. Sketch an example of Conduction, Convection, and Radiation:

Test Review

Test Review Solutions

Convection

Conduction

Heat Pads

Car Engine / Basketball

Electric Stove

Incandescent Light Bulb