Transcript Heat • Heat – Thermal Energy moving from a warm object to a cooler object • Heat can transfer or move in 3 ways –

Heat
• Heat
– Thermal Energy moving from a warm object
to a cooler object
• Heat can transfer or move in 3 ways
– Conduction
– Convection
– Radiation
Conduction
Heat transferred from one molecule to
another without the object moving itself
Always from Warmer to Cooler
Usually Requires Contact
Convection
• Heat is transferred by the mass movement of
molecules from one place to another
• Occurs within a Liquid or Gas
Warm, less dense water
at bottom rises and is
replaced with cooler, more
dense water from above
A circulation gets established called
Convection Currents
Radiation
• Conduction and Convection require a medium,
like metal and water, to transfer heat from a hot
region to a cold region
• Radiation transfers heat
through a gas or a vacuum:
– Heat from the Sun
– Heat from surface of a hot
object
Electromagnetic (EM) Waves
• Wave is transfer of Energy by vibration
• Radiation is the transfer of Energy by a special
type of wave called an Electromagnetic Wave
• There are many types of EM waves and many
applications:
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Infrared we sense as Heat
Visible light we sense as color
X-Rays
Radio & TV
Cell Phone
All Wireless devices
Conduction, Convection, and Radiation
often occur together
Thermal Expansion & Contraction
• As the thermal energy of a substance increases,
its molecules vibrate faster, spread out and the
substance expands
• As the thermal energy of a substance decreases,
its molecules vibrate slower, get closer and the
substance shrinks
• Matter expands when heated
• Matter contracts when cooled
Interesting Demos
on
Conduction
Convection
Radiation