C H. 13 H EAT & T EMPERATURE N OTES
V IDEO C LIP 20 & 21 uk/flv/
T EMPERATURE is a measure of the average kinetic energy of all particles within an object. indicates how warm or cold an object is with regards to the standard.
A thermometer is a device that measures temperature.
T EMPERATURE S CALES Fahrenheit is a temperature scale used mostly in the United States. Celsius is the temperature scale used mostly in other countries and in science. Based on 0 C being freezing point and 100 C being boiling point, the difference between those two points is divided up into 100 equal parts. Kelvin scale is the temperature scale used by scientists, where all of the numbers are positive. It is based off the idea of absolute zero.
W HAT IS THE C ELSIUS TO F AHRENHEIT CONVERSION ? F = (1.8 x C) Convert 25 C to F F = 77 (Did you get it right? Try this one!) Convert 0 C to F F = 32 (The freezing & melting point of water)
W HAT IS THE F AHRENHEIT TO C ELSIUS CONVERSION ? C = ( F ) 1.8 Convert your body temperature 98.6 F to C. C = 37 Convert a warm Spring day’s temperature of 78 F to C C = 26
W HAT IS THE C ELSIUS TO K ELVIN CONVERSION ? K = C Convert the temperature of a winter day at the North Pole ( C) to both degrees Fahrenheit and Kelvin.
T RY IT USING THE USUAL SET UP Unknown & Known: Equations:Substitute & solve: U: F = ? K = ? K: C = 40.0 F = (1.8 x C) K = C F = (1.8 x 40.0 C) F = 40.0 F K = 40.0 C K = 233 K
A BSOLUTE ZERO is the lowest possible temperature. An object’s energy is zero. There is no possible transfer of energy.
D EALING WITH TEMPERATURE WHEN DOES AN ENERGY TRANSFER OCCUR ? The feeling associated with temperature difference results from energy transfer. Energy is transferred from a hotter object to a cooler object.
Example –Holding a piece of ice. The ice is at a lower temperature than your hand, so the molecules of ice move very slowly. Your hand’s molecules are moving much faster than the ice because it is at a higher temperature. As a result, the molecules of your hand collide with the ice molecules and energy is transferred so the ice molecules start to move faster causing the ice to melt.
W HEN IS THERE NO TRANSFER OF ENERGY IN REGARDS TO TEMPERATURE ? If both objects are the same temperature there is no transfer of energy AND when the temperature is at absolute zero.
H EAT is the transfer of energy from the particles of one object due to a temperature difference between the two objects.
Draw a picture to show what happens to the molecules as thermal energy (heat) is added to the particles More Thermal Energy Draw a picture to show what happens to the molecules as thermal energy (heat) is taken away from the particles Less Thermal Energy ing_ice ing_ice
Molecules begin to move faster as thermal energy is added. More Thermal Energy Molecules begin to move slower as thermal energy is taken away. Less Thermal Energy
S ECT E NERGY T RANSFER N OTES
T HREE METHODS OF ENERGY TRANSFER … 1. Conduction 2. Convection 3. Radiation
W HAT IS CONDUCTION ? It is the transfer of energy as heat between particles as they collide within a substance or between two objects in contact. co.uk/flv/ co.uk/flv/ (24)
T WO FACTORS INVOLVED IN CONDUCTION 1. Has the direct contact of objects or atoms. 2. Usually is an energy transfer between solids Example: Leaving a metal spoon in a pot of soup cooking on the stove.
W HEN YOU HEAT A METAL STRIP AT ONE END, THE HEAT TRAVELS TO THE OTHER END.
W HAT IS CONVECTION ? It is the transfer of energy by the movement of fluids with different temperature. co.uk/flv/ co.uk/flv/ (27)
H OW DOES CONVECTION MOVE ? It is a result from the movement of hotter fluids to colder fluids.
T WO T YPES OF F LUIDS Gases and liquids.
C ONVECTION CURRENT. is the flow of a fluid due to the heated expansion followed by cooling and contraction Examples: Glowing embers caught in the warmed air above a campfire, or the movement inside the earth for the plate tectonic movement.
W ATER MOVEMENT Hot water rises Cooler water sinks Convection current Cools at the surface
W HAT IS RADIATION ? Radiation is the transfer of energy by electromagnetic waves. Examples: When you stand by fire, your skin absorbs the energy radiated by the fire. k/flv/ (29) k/flv/
How does heat energy get from the Sun to the Earth? There are no particles between the Sun and the Earth so it CANNOT travel by conduction or by convection. ? RADIATION
H OW DOES RADIATION DIFFER FROM CONDUCTION AND CONVECTION ? It does not involve or the movement of matter (or physical contact between objects). So it can travel through a vacuum like space.
H OW IS RADIATION LIKE CONVECTION ? Radiation is like convection in that it can travel through fluids.
C ONDUCTORS are materials through which energy can easily be transferred as heat. Examples - Some cooking pan, copper, and silver. In general metals are better than nonmetals.
I NSULATORS are materials that are poor energy conductors. Examples - Some insulators are wood, foam, rubber, and polystyrene