Thermal Energy and Heat

1. Temperature
• Specifically – how fast the particles are
moving, average kinetic energy
• Matter is made of atoms that are always
moving, or they have kinetic energy
• The more kinetic energy, the higher the
temperature

2. • Measuring temperature measures the average
kinetic energy of an object
• Thermal expansion – increase in the size of a
substance in response to an increase in temp
(as temp increases, particles move faster,
spreading out)
• Because of thermal expansion, all materials can
expand and shrink when temperature changes

3. • Fahrenheit
– Boiling pt 212°F
– Freezing pt 32°F
• Celsius
– Boiling pt 100°C
– Freezing pt 0°C
• Kelvin
– Boiling pt 373K
– Freezing pt 273K
• Lowest temp on Kelvin scale is 0K or
absolute zero (-459°F), the temperature at
which all molecules stop moving

4. Heat -vs-Thermal Energy
• Heat is what moves between objects with
different temperatures
• Thermal Energy is the speed of the
objects particles, remember objects with
speed have energy
• Thermal energy is transferred from areas
warmer to areas that are cooler until both
are equal
• THEY ARE NOT THE SAME THING

5. Conductors and Insulators
• Materials that transfer heat are called
thermal conductors
• Materials that do not transfer heat are
called thermal insulators
• Examples:
– Insulators: feathers, blankets, plastics
(polymers)
– Conductors: metals
• Thermal conductivity is the rate at which
a material conducts heat

6. Conduction – the transfer of energy, as
heat, through a material (touching)

7. Radiation – the transfer of energy
as electromagnetic waves (sun)

8. • Radiant energy from the sun heats earth
• Examples:
– Fire
– Radiator
– Electric Oven
– Electric stove

9. Convection is the transfer of thermal energy
by the circulation or movement of a liquid or
a gas (solids do not convect)

10. • Energy transfer can not be measured
directly, instead it must be calculated
• Heat = joules (J)
• Summary:
• Conduction – transfer by direct contact
• Convection – movement of molecules
(rising and falling, only gas or liquid)
• Radiation – transfer by electromagnetic
waves

11. Review