Warm Up 9 Some plants have a hard waxy coating on their leaves that helps prevent water loss. In which environment do these plants most likely grow? A Desert B Marine C Grassland D Rain forest

Thermal Energy

What is thermal energy? The total of the amount of kinetic energy of the moving particles, PLUS the potential energy that exists between the particles. In short, the total energy of the particles that make up an object.

Temperature Depends on the amount of thermal energy of an object. The amount of thermal energy of an object depends on the kinetic energy of the particles that make up the object. Temperature, therefore is a measurement of the average kinetic energy of the particles that make up an object.

Temperature When an object is heated, its particles move faster and its total kinetic energy rises. More kinetic energy  higher temperature Thermometers measure temperature.

Temperature Scales The Fahrenheit Scale proposed in 1714 by G. Daniel Fahrenheit. Referenced to the freezing and boiling point of water. 32 o F - freezing point. 212 o F - boiling point.

Temperature Scales The Celsius Scale was proposed by Anders Celsius in Referenced to the freezing and boiling point of water. 0 o C - freezing point. 100 o C - boiling point.

Temperature Scales The Kelvin Scale was developed by Lord Kelvin in Zero (0) on the Kelvin scale is "Absolute Zero" or the theoretical temperature at which all particle motion stops. This temperature is equal to -273  C. 273 K – freezing point 373 K – boiling point

The Kelvin Scale uses the same scale as Celsius –Difference between 1 degree is the same

Temperature Conversions Fahrenheit (T F ) to Celsius (T C ) scale: T C = 5/9 (T F - 32) subtract 32 first = (T F - 32) /(1.8) Celsius (T C ) to Fahrenheit (T F ) scale: T F = (9/5)(T C ) + 32 add 32 later = (1.8)(T C ) + 32

Temperature Conversions Celsius (T C ) to Kelvin (T K ) T K = T C Kelvin (T K ) to Celsius (T C ) T C = T K - 273

Practice The yearly temperature range in the Houston area is 22  F to 98  F. What is this range in degrees Celsius and in Kelvin? T C = 5/9 (T F - 32) = 5/9 ( ) = 5/9(-10) =  C T C = 5/9 (T F - 32) = 5/9 ( ) = 5/9(66) =  C T K = T C =  C = K T K = T C =  C = K

Heat The flow of thermal energy from an object of higher temperature to an object of lower temperature. Heat, is not thermal energy, but the movement of thermal energy from one object to another. Eg. When your hands feel cold, that is because thermal energy in your hands are moving out of your body.

Heat Transfer When two objects are at the same temperature, no heat flows between them. Thermal energy may be transferred as heat in 3 ways: Conduction, Convection and Radiation.

Heat Transfer Conduction occurs when two objects are in contact with each other.

Heat Transfer Convection occurs by transferring the masses of warm fluids. Fluids can be either liquid or gas. All convection occurs by movement of the heated substance. Since solids cannot move, only liquids and gases can transfer thermal energy by convection.

Heat Transfer Radiation is transfer of thermal energy in the form of electromagnetic waves. Radiation differs from conduction and convection as it does not involve the movement of matter, or collision of one form of matter with another.

Thinking question On a hot summer day, you went inside to open the fridge to get some beverages. You immediately feel the cold air from the fridge moving towards your direction. Do you agree to this statement? Why?

Slightly modified from G. Garcia