© Fall 2005, Pflugerville ISD, 8th Grade What is Temperature? What happens when you use a thermometer to measure temperature? What Do You Think?

© Fall 2005, Pflugerville ISD, 8th Grade

What is Temperature?

What happens when you use a thermometer to measure temperature?

What Do You Think?


Temperature Depends on Kinetic Energy

•Kinetic Energy is the energy of motion

•The faster the particles of matter move, the more kinetic energy they have



Measuring Temperature•Temperature is a measure of the Average Kinetic Energy of a substance

•When you measure temperature, you are measuring the average motion of the atoms


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

Thermometersare used to measure temperature



Temperature is expressed by one of 3 scales:



Thermal Expansion- As temperature rises, volume (size) increases



Thermal Expansion

•When the metal rails in this picture heated up, they increased in length and volume

•Thermal Expansion caused the rails to buckle and bend



Thermal Expansion

•The asphalt in the road expands when heated and contracts when cooled

•This results in cracks and potholes due to Thermal Expansion


THERMAL EXPANSION

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


THERMAL EXPANSION.

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.

Thermal expansion is why running a tight jar lid under warm water loosens the lid. *pg 154


What is Heat?

Which is warmer, the tile or the rug on a bathroom floor?

What Do You Think?


What is Heat?

Heat- A Transfer of Energy

•Heat is the transfer of energy between objects or particles that are at different temperatures


Another word for heat is THERMAL ENERGY.

Hot objects contain more thermal energy than cold objects

.


What is Heat?

Heat- A Transfer of Energy•Energy moves from the warmer object to the cooler object until both are the same temperature

•This is known as Thermal Equilibrium


THERMAL EQUILIBRIUM

The point at which two objects reach the same temperature.


What is Heat?

Reaching Thermal Equilibrium


THERMAL EQUILIBRIUMNo energy transfer occurs


What is Heat?

Energy is Transferred by 3 Methods:


What is Heat?

•Conduction is the transfer of thermal energy through direct contact

•Hold a metal wire in a flame and energy travels from atom to atom until it burns your hand


CONDUCTIONTransfer of heat from one substance to another by direct contact.Happens within and between objects that touch each otherExamples: 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 conductorsMetal 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?


What is Heat?

Convection

•Convection is the transfer of thermal energy by the movement of a liquid or a gas

•Convection is seen as hot material rises and cool material sinks


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.


What is Heat?

Radiation •Radiation is the transfer of energy through matter or space through light energy, such as visible light and infrared waves

•Radiation is the only type of energy transfer where the objects don’t have to touch


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.

© Fall 2005, Pflugerville ISD, 8th Grade Unit A : Chapter 1 : Section 1

Harcourt Science: States of MatterBBC: ScienceBrainPop: States of Matter

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© Fall 2005, Pflugerville ISD, 8th Grade What is Temperature? What happens when you use a thermometer to measure temperature? What Do You Think?