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

• 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

• 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

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

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

Energy Transfer

• Only 3 ways to transfer all energy• Convection – circular motion of a gas or

liquid• Conduction – by direct contact (touch)• Radiation – as electromagnetic waves

Conduction – the transfer of energy, as heat, through a material (touch)

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

• Radiant energy from the sun heats earth• Examples:

– Fire– Radiator– Electric Oven– Electric stove

Convection is the transfer of thermal energy by the circulation or movement of a liquid or

a gas (solids do not convect)

• Energy transfer can not be measured directly, instead it must be calculated

• Heat = joules (J)• Summary:• Conduction – transfer by direct contact

(touch)• Convection – movement of molecules

(rising and falling, only gas or liquid)• Radiation – transfer by electromagnetic

waves

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