This video explores the process of evaporation and the meaning of temperature. It deserve to be provided as a supplement to one investigation, or may stand top top its own to present a lesson or prolong student learning.

You are watching: The average kinetic energy of all the particles in a material


Ah, the humble thermometer. Whether we want to understand if our vacation turkey is cooking or if we need concrete proof the we’re also sick to to visit school, a thermometer is the precise scientific device we need. Yet what, exactly, walk a thermometer measure? In various other words, what is temperature, really?


Whether the solid, liquid, or gas, all matter is comprised of atoms and also molecules. These particles room constantly in motion. They collide with each other and also with the wall surfaces of anything castle are included in. We quantify the activities of the particles by your kinetic energies.

In chemistry, we define the temperature that a substance as the median kinetic power of every the atoms or molecules of that substance.

Not all of the corpuscle of a substance have actually the very same kinetic energy. At any given time, the kinetic power of the particles deserve to be represented by a distribution. Some atoms or molecules have actually a many kinetic energy and move an extremely fast. Various other atoms or molecules have a tiny kinetic energy and also move an extremely slowly. That is the mean kinetic power of the particles the thermometers measure and also we document as the temperature.

One procedure that illustrates differing kinetic energies particularly well is evaporation. As you most likely know, evaporation is a phase readjust where particles of a substance relocate from the fluid phase into the gas phase.

But have you ever wondered exactly how a pond of water have the right to evaporate at room temperature? save that in mind—we’ll come back to that question in a bit.


When us think about a phase adjust from liquid to gas, we regularly think about adding thermal power to a liquid by heating it up. When we do, the molecule of the liquid move faster and also spread slightly farther apart, until they acquire enough power to overcome the attractions they have actually for various other molecules of the liquid and also enter the gas phase.

Think around this: If someone asked friend to revolve a beaker full of water into water vapor, what would certainly you do?

Being the excellent young scientist that you are, you might put it on a warm plate and also crank up the heat. Now you can kick back and relax until the hot plate transfers enough power to obtain all the water molecule to shift from the liquid phase come the gas phase. In less science-y terms, you would certainly boil the water.

Boiling is a special instance of a liquid-to-gas phase adjust that wake up at a certain temperature dubbed the boiling point, whereby the vapor press of the problem is same to one environment pressure. Boil is usually carried out using a consistent input of energy from an external source (like a hot plate) to store the temperature constant.

The apparent conclusion is this: If girlfriend continuously add thermal power from a warm plate girlfriend can reason a phase change from fluid to gas.

But how have the right to a pond of water evaporate in ~ room temperature?

When water evaporates in ~ room temperature, part fast-moving, very energetic molecules have actually enough energy to get rid of the attractions the individual molecules have actually for one another and also enter the gas phase. Together these high-energy molecules leave the liquid phase, the average energy of the remaining liquid molecules is lowered, and their temperature decreases. This liquid is at a lower power than the surroundings, so that absorbs energy from those surroundings. The cycle proceeds as the puddle gradually disappears.

Boiling is a faster procedure because the next site (the warm plate) warm the fluid to a greater temperature where more molecules have actually high energy, for this reason vaporization is faster. The hot plate is hotter than the liquid, for this reason thermal power transfer is fast enough to store the fluid temperature continuous at the boiling temperature.

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Evaporation have the right to take location at any temperature due to the fact that some that the molecules in a liquid—the ones in ~ the higher end of the distribution—will constantly have enough power to enter the gas phase. Chris

To amount up, temperature to represent the average kinetic energy of the corpuscle of substance. Yet it’s the spread of kinetic energies amongst the individual particles that describes why puddles dried up.