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Grade 7 Science. Unit 2: Heat Chapter 6: “Heat is transferred from one place to another by three different processes.”. Heat Transfer. Heat transfers from a hot object to a cold object. Three types of Heat Transfer. Conduction Convection Radiation. 3 Types of Heat Transfer.

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Grade 7 Science

Unit 2: Heat

Chapter 6: “Heat is transferred from one place to another by three different processes.”


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Heat Transfer

Heat transfers from a hot object to a cold object.


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Three types of Heat Transfer...

  • Conduction

  • Convection

  • Radiation



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1. Conduction

  • Occurs when the particles in an object vibrate in place but collide with neighbouring particles passing kinetic energy to them.


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Stainless Steel Sides

Copper Bottom



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2. Convection

  • Occurs when warm fluids move from one place to another.

  • Occurs in liquids and gases.


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When air warms, the particles gain energy, spread out, become less dense and rise. As it cools, the particles lose energy, get closer together, become more dense and sink.

Convection Currents


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3. Radiation become less dense and rise. As it cools, the particles lose energy, get closer together, become more dense and sink.

  • Occurs when electromagnetic waves carry energy from a source to another object. The object absorbs the energy of the electromagnetic wave.


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  • There are become less dense and rise. As it cools, the particles lose energy, get closer together, become more dense and sink.no particles involved.

  • The waves can travel in a vacuum.


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Types of Electromagnetic Waves become less dense and rise. As it cools, the particles lose energy, get closer together, become more dense and sink.


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Radiant energy can be... become less dense and rise. As it cools, the particles lose energy, get closer together, become more dense and sink.

1. Reflected

Shiny, smooth,

light-colored

surfaces.


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2. Absorbed become less dense and rise. As it cools, the particles lose energy, get closer together, become more dense and sink.

Dull, rough,

dark-colored

surfaces.

Object will become

warmer.


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3. Transmission become less dense and rise. As it cools, the particles lose energy, get closer together, become more dense and sink.

The radiant

energy passes through.

Ex. Plastic, glass, paper,

etc.


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Absorption become less dense and rise. As it cools, the particles lose energy, get closer together, become more dense and sink.

Reflection

The Microwave

Transmission


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The three types of heat transfer, conduction, convection and radiation, can occur at the same time. For Example...


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Activity 6-1 C radiation, can occur at the same time. For Example...Page 182

Energy Transfers and Home Heating Systems


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Core Lab Activity radiation, can occur at the same time. For Example...

Activity 6-1D

“Absorb That Energy”

Page 184


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Home heating technologies... radiation, can occur at the same time. For Example...

1. Open Fireplace

  • Radiant heat from the fire and convection currents in the air spread the heat.


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2. Wood Stove radiation, can occur at the same time. For Example...

  • Efficient radiators due to the black color.


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2. Electric Heaters radiation, can occur at the same time. For Example...


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3. Oil Furnace radiation, can occur at the same time. For Example...

  • Air is drawn into the furnace and heated and fans would blow the warm air through the ducts into the rooms.

  • Water carried in a system of pipes can be used instead of air. (Hot water radiation)


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Forced-air furnace radiation, can occur at the same time. For Example...


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Hot Water Radiation radiation, can occur at the same time. For Example...


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4. Air to Air Heat Pump radiation, can occur at the same time. For Example...

  • Can be used to cool the home in the summer and heat the home in the winter.

Heat is exchanged with the outside air.


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5. Geothermal radiation, can occur at the same time. For Example...

  • Heat is exchanged with the ground.

  • In the summer, heat is pumped into the ground and in winter it is pumped up from the ground.


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Geothermal radiation, can occur at the same time. For Example...


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6. Solar radiation, can occur at the same time. For Example...

  • Converts light energy to electrical energy.


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Solar Panels radiation, can occur at the same time. For Example...


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Core radiation, can occur at the same time. For Example...stse

“Heat Pumps: An Alternative Way to Heat Homes”


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Conductors vs. Insulators radiation, can occur at the same time. For Example...

Conductors

  • Allow heat transfer

  • Ex. Metal (some metal are better than others)

Insulators

  • “Prevents” heat transfer

  • Ex. Wood, plastic


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Uses of Conductors radiation, can occur at the same time. For Example...

Cookware

Car Radiator


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Use of insulators radiation, can occur at the same time. For Example...

Animal Fur

Sod


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Fibreglass radiation, can occur at the same time. For Example...

Thermos


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The vacuum layer has radiation, can occur at the same time. For Example...no particles which prevents heat transfer.

Note: It is impossible to create a perfect vacuum.

Thermos


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Heat vs. Temperature radiation, can occur at the same time. For Example...

Heat is the energy which is transferred from hotter substances to colder substances.

It is the sum total of the energies of the particles in a substance. (Thermal energy)


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1+2+3+3+2+4+2+5+2+2 radiation, can occur at the same time. For Example...

= 26J

26 ÷10 = 2.6 ˚C

Heat

Temperature

3

2

2

4

2

3

1

2

5

2


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Specific heat capacity radiation, can occur at the same time. For Example...

The amount of heat needed to raise the temperature of 1.00 g of the substance by 1.00˚C.

Used to measure the amount of heat transfer.


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Different materials have different capacities for storing heat. This depends on:

  • Molecular structure

  • Phase

  • Molecular mass

  • Shape

  • Surface area


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Specific Heat Capacities heat. This depends on:


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Specific Heat Capacity An Example... heat. This depends on:


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Temperature Heat & technology heat. This depends on:

With a partner, list as many technologies that deal with the idea of temperature and heat.


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