Download CHAPTER 10 NOTES FOR EIGHTH GRADE PHYSICAL SCIENCE

CHAPTER 10 NOTES FOR EIGHTH GRADE PHYSICAL
SCIENCE
TEMPERATURE IS A MEASURE OF THE AVERAGE KINETIC ENERGY OF
THE MOLECULES IN A SUBSTANCE.
HEAT IS THE TRANSFER OF THERMAL ENERGY BETWEEN OBJECTS THAT
ARE AT DIFFERENT TEMPERATURES.
A THERMOMETER IS AN INSTRUMENT FOR MEASURING TEMERATURE.
MERCURY AND ALCOHOL ARE USUALLY THE LIQUIDS USED IN A
THERMOMETER.
THE SCALE OF A THERMOMETER SHOWS THE TEMPERATURE IN DEGREES CELSIUS (C). THE
DEGREE CELSIUS IS THE METRIC UNIT MOST OFTEN USED TO MEASURE TEMPERATURE. WATER
FREEZES AT 0 DEGREES C. AND BOILS AT 100 DEGREES C.
ANOTHER METRIC TEMPERATURE SCALE OFTEN USED BY SCIENCTISTS IS THE KELVIN SCALE.
TO CONVERT CELSIUS DEGREES TO KELVIN, SIMPLY BY ADDING 273 DEGREES TO THE CELSIUS
TEMPERATURE.
THERE ARE 3 METHODS OF HEAT TRANSFER:
1. CONDUCTION
A. HEAT IS TRANSFERRED BY THE DIRECT CONTACT OF MOLECULES.
B. WHEN FAST-MOVING WARMER MOLECULES COLLIDE WITH SLOW-MOVING COOLER MOLECULES,
ENERGY IS TRANSFERRED FROM THE WARMER MOLECULES TO THE COOLER MOLECULES.
C. CONDUCTION CAN TAKE PLACE IN SOLIDS, LIQUIDS, AND GASES BECAUSE THESE 3 PHASES OF
MATTEER ARE MAD OF MOLECULES.
D. SUBSTANCES THAT CONDUCT HEAT MORE EFFECTIVELY THAN OTHERS ARE CALLED HEAT
CONDUCTORS.
1. COPPER
2. SILVER
E. SUBSTANCES THAT DO NOT CONDUCT HEAT EASILY ARE CALLED INSULATORS.
1. GLASS
2. WOOD
2. CONVECTION
A. HEAT IS TRANSFERRED IN LIQUIDS AND GASES AS MOLECULES MOVE IN CURRENTS
B. THE WARMER PART OF THE LIQUID OR GAS BECOMES LESS DENSE THAN THE COOLER PART.
C. BECAUSE IT IS LESS DENSE THAN THE SURROUNDING LIQUID OR GAS, THE HEATED PORTION
RISES, CREATING CURRENTS THAT CARRY HEAT.
D. AS WARM AIR NEAR THE SURFACE OF THE EARTH IS HEATED, IT BECOMES LESS DENSE AND
TENDS TO RISE.
E. THE AIR CURRENTS IN THE EARTH'S ATMOSPHERE, WHICH CONTRIBUTE TO OUR WEATHER, ARE
CAUSED BY CONVECTION CURRENTS
3. RADIATION
A. HEAT IS TRANSFERRED THROUGH SPACE
B. THE HEAT ENERGY IS THE FORM OF INVISIBLE LIGHT KNOWN AS INFRARED RAYS.