Chapter 15 Kinetic Molecular Theory & Heat and States of Matter

Some Amazing Things

Kinetic Theory

All matter is composed of tiny particles.

Kinetic Theory All matter is composed of tiny particles –Atoms

Kinetic Theory All matter is composed of tiny particles –Atoms –Molecules

Kinetic Theory All matter is composed of tiny particles –Atoms –Molecules –Ions

Kinetic Theory These tiny particles are in constant motion. Liquid Solid Gas

Kinetic Theory Collisions between moving particles are perfectly elastic. –In an elastic collision there is no net change in kinetic energy.

Pressure Pressure depends on two factors 1.Force 2.Area Pressure = Force Area

Examples of Pressure

This demonstration requires that the demonstrator’s weight (force) be spread over as many nails as possible (area), resulting in reduced pressure. The most dangerous part occurs at the moment of lying down or getting up, when one's weight may briefly be supported on only a few nails. Some "beds" have rails mounted at the sides to help users lie down and get up safely.

Examples of Pressure The origin and age of snowshoes are not precisely known, although historians believe they were invented from 4,000 to 6,000 years ago.

Examples of Pressure It is illegal to wear high heels at Greek archaeological sites such as the Acropolis. Pointy heels pierce the delicate "skin" of these antiquities, officials determined in 2008 when they first sought the ban. Indeed, stilettos can transmit more pressure per square inch than an elephant, experts say.

Gas Pressure

Temperature How hot or cold Average kinetic energy

How do we lower temperature? We slow down the particles.

Absolute Zero K = °C °C = K - 273

Kinetic Energy KE = ½ mv 2 When considering kinetic energy we must consider two factors. 1.Mass 2.Velocity

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. Liquid Solid 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

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 At 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