TEMPERATURE 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 GRADIENT? Interphase between two different temperatures or kinetic energies. Interphase between two different temperatures or kinetic energies. What happened to the common temperature as compared to the “FAST” atoms? What happened to the common temperature as compared to the “FAST” atoms? What happened compared to the “SLOW” atoms? What happened compared to the “SLOW” atoms?

In which direction would you expect the energy to flow? From HIGH energy to LOW ENERGY From HIGH energy to LOW ENERGY When the barrier is removed, the fast (“hot'') atoms collide with the slow (“cold'') ones. When the barrier is removed, the fast (“hot'') atoms collide with the slow (“cold'') ones. In such collisions, the FASTER atoms LOSE some speed and the SLOWER ones GAIN speed; thus, the fast ones transfer some of their kinetic energy to the slow ones. In such collisions, the FASTER atoms LOSE some speed and the SLOWER ones GAIN speed; thus, the fast ones transfer some of their kinetic energy to the slow ones. The slower the speed, the lower the temperature The slower the speed, the lower the temperature This transfer of kinetic energy from the hot to the cold side is called a flow of heat through conduction. This transfer of kinetic energy from the hot to the cold side is called a flow of heat through conduction.

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

Here is how it works: Heat Energy is what makes the coffee hot. Heat Energy is what makes the coffee hot. Heat Energy Heat Energy Since the inside of refrigerator has a lower temperature than the coffee, heat energy TRAVELS FROM the COFFEE to the FRIDGE, following the temperature gradient. Since the inside of refrigerator has a lower temperature than the coffee, heat energy TRAVELS FROM the COFFEE to the FRIDGE, following the temperature gradient. The temperature gradient is kind of like the slope of a hill --- the steeper the hill, the faster a ball will roll down it…. The temperature gradient is kind of like the slope of a hill --- the steeper the hill, the faster a ball will roll down it…. In a similar way, heat will leave the coffee faster in the beginning and at a slower and slower rate as the coffee cools. In a similar way, heat will leave the coffee faster in the beginning and at a slower and slower rate as the coffee cools.

Heat Transfer Heat always moves from a warmer place to a cooler place. Heat always moves from a warmer place to a cooler place. Hot objects in a cooler room will cool to room temperature by GIVING AWAY its energy Hot objects in a cooler room will cool to room temperature by GIVING AWAY its energy Cold objects in a warmer room will heat up to room temperature by GAINING ENERGY Cold objects in a warmer room will heat up to room temperature by GAINING ENERGY

Question If a cup of coffee and a red pop-sickle were left on the table in this room what would happen to them? Why? If a cup of coffee and a red pop-sickle were left on the table in this room what would happen to them? Why? The cup of coffee will cool until it reaches room temperature. The pop-sickle will melt and then the liquid will warm to room temperature. The cup of coffee will cool until it reaches room temperature. The pop-sickle will melt and then the liquid will warm to room temperature.

Conduction 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 work? The liquid is most often colored alcohol but can also be a metallic liquid called mercury. The liquid is most often colored alcohol but can also be a metallic liquid called mercury. WHAT HAPPENS TO THE VOLUME OF SUBSTANCES AS THEY ARE HEATED? WHAT HAPPENS TO THE VOLUME OF SUBSTANCES AS THEY ARE HEATED? Gets larger (expands) Gets larger (expands) Why? Why? The particles move faster and farther apart. The particles move faster and farther apart.

Both mercury and alcohol grow bigger when heated and smaller when cooled. Both mercury and alcohol grow bigger when heated and smaller when cooled. Inside the glass tube of a thermometer, the liquid has no place to go but up when the temperature is hot and down when the temperature is cold. Inside the glass tube of a thermometer, the liquid has no place to go but up when the temperature is hot and down when the temperature is cold.

CELSIUS Thermometer