chapter 15 heat & states of matter. at room temperature most elements are solids. the gases are...

Chapter 15

Heat & States of Matter

• At room temperature most elements are solids.

• The gases are hydrogen, nitrogen, oxygen, fluorine, chlorine and the noble gases.

• There are two liquids: bromine and mercury.

The state of matter is determined by two factors.

1. Attractive forces between the particles of the material.

LiquidSolid Gas

2. Temperature (Average Kinetic Energy)

At room temperature which factor determines the state of an element?

Transitions between the states of matter

• We can change the state of matter that a substance exhibits by adding/removing heat.

Heat

• Heat is thermal energy that flows from something warmer to something cooler.

Transitions between the states of matter

How many states of matter exist?

5

Plasma: The fourth state of matter

Transitions between the states of matter

• If we heat a gas to a high enough temperature it becomes a plasma.

Plasma

• A plasma is a super heated ionized gas.– Normally requires extremely high

temperatures to form.– It consists of electrons and positively charged

gas particles.

Plasma• Plasmas are the most common state of matter in the

universe. • It is estimated that 99% of the visible universe is plasma.

Plasma• Plasmas do not occur as frequently on earth.

“Cold” Plasmas

“Cold” Plasmas• Plasmas can exist at much lower temperatures than

normal in a vacuum.

The Fifth State of Matter

Bose – Einstein Condensate (BEC)

Bose – Einstein Condensate

• In the 1920s, Satyendra Bose and Albert Einstein, predicted this new state of matter. However they didn't have the equipment and facilities to make it.

Bose – Einstein Condensate• In 1995, three scientists, Karl Weiman, Wolfgang

Ketterle and Eric Cornell finally created this new state of matter.

• They were awarded the Nobel Prize in 2001.

Bose – Einstein Condensate

• If plasmas are super hot and super excited atoms, the atoms in a Bose-Einstein condensate (BEC) are total opposites. They are super-unexcited and super-cold atoms.

The Fifth State of Matter

• The BEC happens at super low temperatures.

• At zero Kelvin all molecular motion stops.

• At only a few billionths of a degree above absolute zero, you can create a BEC with a few special elements.

• Cornell and Weiman did it with Rubidium.

Time for a Chemistry Joke

Bose – Einstein Condensate• As temperatures get to within a few billionths of a degree of

absolute zero atoms begin to “clump”. • The result of this clumping is the BEC.• A group of atoms takes up the same place, creating a "super

atom."

• There are no longer thousands of separate atoms. They all take on the same qualities (quantum state) and for our purposes become one “superatom”.

What does a Bose Einstein Condensate Look Like?

• It looks like a dense little lump in the bottom of the magnetic trap/bowl.

• Picture a drop of water condensing out of damp air.

• When it first forms, though, the condensate is still surrounded by the normal gas atoms, so it looks a bit like a pit inside a cherry.

• When matter gets cold enough a dense blob forms in the center.

• You can see this in the pictures of Cornell and Wieman’s actual data as they cool the atoms from 400 billionths of a degree above absolute zero down to 50 billionths.

Bose-Einstein Condensation at 400, 200, and 50 nano-Kelvins