What is HEAT What Are Its Properties?

Heat Draw a teakettle of water heating on a burner. Draw an arrow pointing to the area where the water is the hottest. Draw an arrow pointing to the area where the water is the coolest. Predict the direction in which the hottest water is moving. Predict the direction in which the coolest water is moving.

HEAT - Definition  Heat is the MOVEMENT of thermal energy  Heat ALWAYS moves from Warmest to Coldest  Why?  It is always HIGHER Energy – to – LOWER Energy  There is no scientific definition of ‘Coldness’  Cold is a relative term

TYPES of HEAT  RADIATION – movement of energy through electromagnetic energy (light)  Like the sun shining on your skin  CONDUCTION – Heat moving through an object, passed from atom-to-atom and molecule to molecule  Like a hot metal spoon in boiling water  CONVECTION – Heat being carried through rising and falling currents of a liquid or gas  Like wind currents or steam rising

TYPES of HEAT  RADIATION – How do you stop it?  Good - Shade  Best (mirrors)  CONDUCTION – How do you stop it?  Good - Use an insulating material (one that doesn’t conduct)  Best – remove all material (vacuum)  CONVECTION – How do you stop it?  Good – put a lid on it  Better – internal barriers  Best –fill it to the top

Heat

CONDUCTORS  A Substance that passes HEAT easily  Hard  Shiny  Metallic  Dense  Examples:  Metals  Glass  Some plastics

INSULATORS  A Substance that DOES NOT pass Heat easily. Properties:  Not dense  Not-Metallic  Soft  Examples:  Cotton  Air  Fiberglass  Cloth  Plastics  Vacuum

Heat

Convection Radiation Conduction is the transfer of Thermal energy by