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 warm water loosens the lid. *pg 154

THERMAL EXPANSION The spreading of particles or increased volume when an object is heated is known as THERMAL EXPANSION

WHAT IS HEAT? Heat=transfer of energy between objects that are different temperatures (atoms rubbing together). pg. 155

Another word for heat is THERMAL ENERGY. Hot objects contain more thermal energy than cold objects Heat Transfer= Heat (thermal energy) is transferred from warmer objects to cooler objects.

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.

YES, IT’S CALLED THERMAL EQUILIBRIUM No energy transfer occurs Pg. 156 Can a balanced temperature ever be reached?

THERMAL EQUILIBRIUM The point at which two objects reach the same temperature.

HEAT IS TRANSFERRED IN THREE WAYS BY CONDUCTION CONVECTION RADIATION

CONDUCTION  Transfer of heat from one substance to another by direct contact.  Happens within and between objects that touch each other  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 circular motion called a CONVECTION CURRENT  Heated liquids and gases are less dense & rise carrying heat with them  Examples: hang gliders, soaring birds, home furnace heating & circulating air

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)  Examples: blacktop heats up on a sunny day, hot sand on a beach, electric heaters.

Explain how each of these uses radiant heat.

BELLRINGER 1. Describe how heat is created. 2. Give 2 examples of thermal expansion. 3. What is the difference between hot and cold? 4. How does heat move? 5. Describe all the heat transfers in the diagram.

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

HEAT ON EARTH WATER AND LAND Heat comes to the Earth from the Sun by radiation.  Light passes through the atmosphere  Land and water absorb the light and become warm  Land and water reflect infrared waves (also radiant energy) back into space BUT NOT ALL OF IT.  Water vapor, CO2 and other gases block these waves and the Earth gets hotter. Called the Greenhouse Effect

HEAT ON EARTH

THE ATMOSPHERE Because of the Earth’s curved shape, its surface and atmosphere are NOT heated evenly.  If Earth was flat, all surfaces would be heated evenly  Convection causes air to move between warm regions and cold ones.  This redistributes the sun’s energy all over the Earth.  Wind is caused from these convection patterns

HEAT ON EARTH THE ATMOSPHERE

HEAT ON EARTH THE ATMOSPHERE

HEAT ON EARTH THE OCEAN  One interesting property of water is that it can absorb large amounts of heat.  Since most of Earth’s surface is covered by water, it is able to store much more heat than land.  The climate of the entire Earth is much more moderate than it would be if the oceans did not exist.  The oceans act like vast heat storage tanks.

HEAT ON EARTH THE WEATHER The convection patterns in the atmosphere, the heat stored in the oceans and the evaporation caused by the sun’s rays striking the Earth all cause the WEATHER.

HEAT ON EARTH THE WEATHER KATRINA APPROACHES

HEAT ON EARTH UNDERGROUND  Interior heat left over from when the Earth was formed 4.5 billion years ago.  Convection currents carry heat to the crust but extremely slowly.  Rock is a poor conductor.  Evidence of interior heat: volcanoes, geysers, bubbling hot springs.

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BELLRINGER 1. Describe how heat is created. 2. Give 2 examples of thermal expansion. 3. What is the difference between hot and cold?