Post on 22-Feb-2016
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Radiation and Thermal Energy
Our Model of the Atom Evolves
• In a chemical reaction, what is happening to the system when there is a change in temperature?
• What changes occur in a system when radiating is the transfer mechanism?
Observations?
Incandescent light bulb
• Watch carefully as the power delivered to the light bulb is increased.
• Write down your observations.
Incandescent light bulb
• Now view the light bulb through a spectrometer as the power delivered to the bulb is increased.
• Write down your observations
Compact fluorescent light bulb
• Watch carefully as the power delivered to the light bulb is increased.
• Write down your observations.
Compact fluorescent light bulb
• Now view the light bulb through a spectrometer.
• Write down your observations
What is the difference?
• A hot solid gives a continuous spectrum while a heated gas gives only a piece of the spectrum.
• An input of energy is required to make the atoms of an atomic gas emit radiation.
• The radiation emitted by each element is unique.
• A change in temperature results in a change in structure.
• A change in structure results in the emission of light.
• In a compound a change in structure can be explained by a rearrangement of the atoms.
• How about in atomic gases?
• In atomic gases the change in structure has to be at the atomic level.
Our current model of the atom….
• Does not account for these differences in structure, therefore we need a model of the atom with some more internal structure that can account for the radiation emitted by atoms.