TEMPERATURETEMPERATURE  Definition: of temperature is a

measure of the average kinetic energy

Measurement of HOTNESS or COLDNESS

Related to the SPEED of the particles

“AVERAGE”….NOT all particles of a substance are going the same speed.

What is a TEMPERATURE What is a TEMPERATURE GRADIENT?GRADIENT?

Interphase between Interphase between two different two different temperatures or temperatures or kinetic energies.kinetic energies.

What happened to the What happened to the common temperature common temperature as compared to the as compared to the “FAST” atoms?“FAST” atoms?

What happened What happened compared to the compared to the “SLOW” atoms?“SLOW” atoms?

In which direction would you In which direction would you expect the energy to flow?expect the energy to flow?

From HIGH energy to From HIGH energy to LOW ENERGYLOW ENERGY

When the barrier is When the barrier is removed, the fast (“hot'') removed, the fast (“hot'') atoms collide with the slow atoms collide with the slow (“cold'') ones.(“cold'') ones.

In such collisions, the In such collisions, the FASTERFASTER atoms atoms LOSELOSE some some speed and the speed and the SLOWERSLOWER ones ones GAINGAIN speed; thus, the speed; thus, the fast ones transfer some of fast ones transfer some of their kinetic energy to the their kinetic energy to the slow ones. slow ones.

The slower the speed, the The slower the speed, the lower the temperaturelower the temperature

This transfer of kinetic This transfer of kinetic energy from the hot to the energy from the hot to the cold side is called a flow of cold side is called a flow of heat through conduction. heat through conduction.

If you put a hot cup of coffee into a refrigerator, If you put a hot cup of coffee into a refrigerator, would “cold” transfer from the fridge to the coffee, would “cold” transfer from the fridge to the coffee,

or would “hot” transfer from the coffee to the or would “hot” transfer from the coffee to the fridge?fridge?

Hmmmm….Hmmmm….

Here is how it works:Here is how it works: Heat Energy is what makes the coffee hot.is what makes the coffee hot. Since the inside of refrigerator has a lower Since the inside of refrigerator has a lower

temperature than the coffee, heat energy temperature than the coffee, heat energy TRAVELS FROM the COFFEE to the FRIDGE, TRAVELS FROM the COFFEE to the FRIDGE, following the following the temperature gradienttemperature gradient..

The temperature gradient is kind of like The temperature gradient is kind of like the slope of a hill --- the steeper the hill, the slope of a hill --- the steeper the hill, the faster a ball will roll down it….the faster a ball will roll down it….

In a similar way, heat will leave the coffee In a similar way, heat will leave the coffee faster in the beginning and at a slower and faster in the beginning and at a slower and slower rate as the coffee cools.slower rate as the coffee cools.

Heat TransferHeat Transfer Heat always moves from a warmer Heat always moves from a warmer

place to a cooler place.place to a cooler place. Hot objects in a cooler room will cool Hot objects in a cooler room will cool

to room temperature by GIVING to room temperature by GIVING AWAY its energyAWAY its energy

Cold objects in a warmer room will Cold objects in a warmer room will heat up to room temperature by heat up to room temperature by GAINING ENERGYGAINING ENERGY

QuestionQuestion

If a cup of coffee and a red pop-sickle If a cup of coffee and a red pop-sickle were left on the table in this room were left on the table in this room what would happen to them? Why?what would happen to them? Why?

The cup of coffee will cool until it The cup of coffee will cool until it reaches room temperature. The pop-reaches room temperature. The pop-sickle will melt and then the liquid sickle will melt and then the liquid will warm to room temperature.will warm to room temperature.

ConductionConduction

When you heat a metal strip at one end, the heat travels to the other end.

As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat. We call this? Conduction

How does a thermometer How does a thermometer work?work?

The liquid is most often The liquid is most often colored alcohol but can colored alcohol but can also be a metallic also be a metallic liquid called mercury. liquid called mercury.

WHAT HAPPENS TO WHAT HAPPENS TO THE VOLUME OF THE VOLUME OF SUBSTANCES AS THEY SUBSTANCES AS THEY ARE HEATED?ARE HEATED?

Gets larger (expands)Gets larger (expands) Why? Why? The particles move The particles move

faster and farther faster and farther apart.apart.

Both mercury and Both mercury and alcohol grow bigger alcohol grow bigger when heated and when heated and smaller when smaller when cooled. cooled.

Inside the glass Inside the glass tube of a tube of a thermometer, the thermometer, the liquid has no place liquid has no place to go but up when to go but up when the temperature is the temperature is hot and down when hot and down when the temperature is the temperature is cold. cold.

CELSIUS ThermometerCELSIUS Thermometer