Transferring Thermal Energy

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13.2
Transferring Thermal Energy

1. Transfer of Energy

1. Conduction-transfer of energy by direct contact.

1. Faster moving particles of one substance come
   into contact with slower moving molecules of
   another substance.

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1. Conduction can take place in solids, liquids,
   gases.

1. It is more likely to take place in solids

1. Metals are especially good conductors.

1. Convection-transfer of energy in a fluid by the
   movement of the heated particles.

1. Any material that can flow is considered a fluid.

2. Heated particles collide with each other and
transfer their energy.
3. As particles move faster, they tend to be
farther apart.
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Offshore convection currents
Convection currents form by fluids heating up,
rising, cooling off, falling.
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1. Radiation-the transfer of energy by
   electromagnetic waves.

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1. Insulators- materials that slows heat flow.

1. Metals are typically poor insulators.

2. Gases are very good insulators.
3. Some types of insulators use pockets of air
to help keep heat from flowing.
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1. Specific Heat

1. Specific Heat-the amount of heat that is needed
   to raise the temp. of 1kg of some material by 1C
   (or 1K).

1. Specific heat is measured in J/kgK OR J/gºC

Table 1 pg. 432

1. Water is a good coolant because it has a high
   specific heat.

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Specific Heat Problem 1
How much energy must be transferred as heat to
the 420 kg of water in a bathtub in order to
raise the waters temperature from 250C to 370C?
Symbol Meaning Unit
Q Energy Joules (J)
Dt change in temperature ºC
m mass Grams(g) OR kilograms(kg)
c specific heat J/kg.K OR J/g?ºC
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Specific Heat Problem 2
Identify an unknown substance with a mass of
0.455 kg that absorbs 6.33 x 103J, in which a
temperature change of 15.50C is observed?
Symbol Meaning Unit
Q Energy Joules (J)
Dt change in temperature ºC
m mass Grams(g) OR kilograms(kg)
c specific heat J/kg.K OR J/g.ºC
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Practice Pg. 434 Questions 1 6