HEAT AND HEAT TRANSFER

What is the difference between temperature and heat? Temperature is a measure of the average kinetic energy of atoms. This means: the higher the temperature, the faster the atoms move the lower the temperature, the slower the atoms move Less Heat More Heat Thermometers are used to measure temperature

If energy is added to atoms, they move faster. The faster they move, the further apart they move. This spreading out of atoms happens in solids, liquids and gases. The term for this type of expansion is called THERMAL EXPANSION. Thermal expansion is why running a tight jar lid under water loosens the lid. Read pgs. In the textbook to see other examples of thermal expansion.

WHAT IS HEAT? The ancients used to think that heat was an invisible, weightless fluid that flowed from hot things to cold things. ACTUALLY Heat is transfer of energy between objects of different temperatures caused by atoms rubbing together

How cold is cold? There is no such thing as coldness. What we call cold is really absence of heat or slow atoms. Even when it is 15 degrees outside, that is 15 degrees of HEAT, NOT 15 degrees of COLD.

Another word for heat is THERMAL ENERGY. Heat (thermal energy) is transferred from warmer objects to cooler objects

YES, IT’S CALLED THERMAL EQUILIBRIUM No energy transfer occurs Can a balanced temperature ever be reached?

HEAT IS TRANSFERRED IN THREE WAYS BY CONDUCTION CONVECTION RADIATION

CONDUCTION  Transfer of heat from one substance to another by direct contact of molecules.  Happens in solids, liquids and gases  Best conduction happens in solids  Examples: Sauce pan on a stove top, metal spoon in a bowl of soup, ice melting in a warm hand, hot shower, walking on hot coals

Objects that heat up easily are called CONDUCTORS. Metals are the best conductors Metal objects feel cold because they conduct heat AWAY from your hand Objects that DO NOT heat up easily are called INSULATORS. Things like glass,wood, plastic and rubber are good insulators

Which parts of the pan are conductors and which are insulators?

CONVECTION  Transfer of heat in liquids and gases ONLY  Heat moves up and down in a motion called a CONVECTION CURRENT  Heated liquids and gases are less dense & rise carrying heat with them  Examples: movement of plate, ocean currents, home furnace heating & circulating air

Convection Currents in The house Convection Current

Convection currents cause the Earth’s tectonic plates to move about.

RADIATION  transfer of heat through empty space in form of infrared radiation waves (what we think of as heat waves)  When light strikes an opague object, it converts into heat  Examples: blacktop heats up on a sunny day, hot sand on a beach, electric heaters.

Explain how each of these uses radiant heat.

How does heat affect matter? Physically: heat changes the state in which matter exists i.e. melting, freezing, evaporating, condensing

Chemically: for chemical reactions to occur, chemical bonds must be broken and new compounds formed. Requires energy to be absorbed or released

Effects of Heat on the Earth Large bodies of water moderate the climate. The temperatures are not as extreme!! Ocean Currents- Caused by convection Currents.

Effects of Heat On the Earth Uneven heating in the atmosphere creates wind and storms.