LECTURE                     STATES AND PHASES OF MATTER

In this lecture you will learn:

CHARACTERISTICS AND PROPERTIES OF MATTER: STATES AND PHASES
States of matter on earth: summary

 1. Gas: high kinetic energy: no definite shape: volume varies radically with temperature and pressure
 2. Liquid: medium kinetic energy: take form of container: definite volume
 3. Solid: lowest kinetic energy: own shape: definite volume
GAS
-  this phase of matter is the most energetic. Energy makes molecules move. The more they move, the larger the area that they take up in bouncing around. In a room, nearly 99.5% of the room is empty. Only 0.5% of the room is actually occupied by matter.  So all the atoms of gas in the room would fill a basketball.  All the rest of the space between atoms is empty.
 
Gas cant be seen the way liquids and solids can.  However, bring the palm of your hand up close to your mouth and blow hard. What you FEEL is the molecules of gas hitting your hand. 

EXAMPLE: When a balloon is blown up, a whole bunch of the energetic molecules of air are forced into a smaller container.  The bouncing of the air molecules forces the walls of the balloon outward and keeps the balloon inflated. However, when a balloon is left out in very cold weather, the gas molecules lose kinetic energy in the form of heat. The less energetic molecules of gas can no longer bounce fast enough to keep the balloon fully inflated. As soon as the balloon is moved into a warm room the molecules start to pick up heat energy and the molecules more rapidly bounce off the walls and reinflates the balloon. Blowing up a balloon requires the addition of lots of atoms from the outside UNDER PRESSURE. 

In outer space, a typical balloon just bursts because there is no gravity holding air molecules in a thick envelope around the earth.  This thick envelop is AIR PRESSURE, the soup of gases that constitutes barometric pressure. 
- it is the LEAST DENSE state

LIQUIDS 

- this phase is less energetic than gas, but more energetic than solids. The atoms take the shape of the container.
MYTH: Look at very old glass window panes and you will see that the glass is thicker at the bottom of the window. It has slowly oozed down. Glass is a dense liquid.
REALITY: Glass is a solid, but old fashioned glass was not made evenly, it is variable in thickness all over.
- water is the major naturally occurring liquid.
- it has no permanent form of its own
- gas can be dissolved in water, as can small molecules of solids (called solutes) like NaCl

SOLIDS

- this phase is the least energetic. It has it's own shape, although it can be reshaped by making it a liquid and then molding it into another shape. The movement of molecules is limited in solids by their low kinetic energy.
- is the most dense state

http://www.chem.purdue.edu/gchelp/atoms/states.html 

characteristic  gas liquid solid
energy high medium low
shape none of container has own 
volume changes
readily
definite definite

 
WHY DO ATOMS MOVE?
Atoms have THERMAL OR KINETIC ENERGY due to the movement of electrons.  Gas has more energy per atom than liquids which have more than solids.  "Thermal Energy, or heat, is the internal energy in substances––the vibration and movement of the atoms and molecules within substances. "

- atoms move.  Randomly.  They are vibrating with kinetic energy. This is called DIFFUSION or BROWNIAN MOTION.Click HERE  for a fantastic java of Brownian Movement

Example: If you put one used sweat sock or 1 open bottle of perfume in the corner of the room, soon you will smell it as you walk in the door. The airborne smelly molecules diffuse across the room. If you have a good nose, you can follow the increase in concentration of the smelly molecules to the source. Put a spoonful of sugar into coffee or tea without stirring. At first, you cannot taste the sugar. Later, after the sugar has dissolved and diffused, the sugar will be evenly distributed throughout the liquid.

- Light weight molecules pick up more energy when they are bumped by other molecules and go further, faster.
- Heavy molecules, when they are bumped, have more mass to move and as a result move slowly. Think of ping-pong balls vs bowling balls. The weight of a bowling ball makes it possible to knock down 10 lighter weight pins. How many pins could you knock down with a ping-pong ball?

- The molecular weight of a compound affects how fast they move and how far they will diffuse in a certain time. At any given temperature, each element and compound has a specific kinetic energy. At any given temperature, some elements/compounds are gaseous, some are liquid and some are solids. But all have kinetic energy and move, even if it is limited, like in solids.


 
PHASE TRANSITIONS: SUMMARY
Phase transitions: summary
 gas --> liquid = condensation: lose energy
 gas <-- liquid = vaporization: requires energy
 liquid --> solid = freezing or solidification: lose energy
 liquid <-- solid = melting: requires energy
 sublimation = solid –> gas, like dry ice
What drives phase transitions?   Heat and pressure 

FOR EXAMPLE:  WATER
- When energy like heat is added to water, it makes a PHASE TRANSITION to gas. 
- When water vapor is cooled, it loses energy and phase transitions (condenses) first to a liquid (rain) and if cooled further, it freezes to snow flakes or ice crystals.
 
 
FOR WATER IT TAKES 1 calorie OF ENERGY TO HEAT 1 GRAM OF WATER 1 DEGREE CELSIUS.  ANOTHER "STANDARD" BASED ON WATER.  1 cal/g/1oC

"Plasma is a partially ionized gas, in which a certain proportion of electrons are free rather than being bound to an atom or molecule. The ability of the positive and negative charges to move somewhat independently makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma therefore has properties quite unlike those of solids, liquids or gases and is considered to be a distinct state of matter. see plasma lamp here" AIR: Air is made up of mostly nitrogen, oxygen and a pinch of argon. Air (including vaporized liquids) is actually pretty dense. The earth's gravity pulls on the molecules, and they press down on us and everything else. This is called barometric or atmospheric pressure. As you leave earth on your way out into space, the molecules of air thin out to nothing.  In Denver, which is 1 mile above sea level, there are fewer air molecules on top of everyone and everything and the pressure is less. As a result, water boils (vaporizes) at a lower temperature, and cooking must be adjusted to the lower pressure.
- Flying is only possible because of the density of air. 
- Travel in space is propulsion, not flying, no wings required!

 
AND ONE MORE THING
ACTUAL TRANSITIONS IN PHASE REQUIRE WAAAAAAY MORE HEAT than just 1 cal/g/1oC.  It is the reason that steam burns so much worse than boiling water.  Each gm of boiling water must aquaria an additional 539 calories of heat to make the transition from boiling to steam. 


 

79.7 (80 cal) extra to melt 1 gm of ice
100 cal to move 1 g of 0oC water to 100oC water
540 cal to turn 100oC water into steam.
 

"When a substance undergoes a phase change, evaporates, condenses, freezes, melts, etc ... the arrangement of its molecules changes."

with INCREASING TEMPS 
– If the new arrangement has a higher internal energy, the substance must absorb  some heat in order to make the phase transition. DURING the phase transition the energy is being absorbed but NO CHANGE in temp is seen.  This is the sign that a phase transition is "in the works".  The amount of heat absorbed  per unit mass during evaporation is called  the latent heat of vaporization

with DECREASING TEMPS
– If the new arrangement has a lower internal energy, the substance must release some heat in order to make the phase transition.   DURING the phase transition the energy is being released but NO CHANGE in temp is seen.  This is the sign that a phase transition is "in the works".
– The "excess" heat energy required is the energy needed to  overcome the molecular forces holding the material together in a certain configuration.

Sooooo
-- For water to vaporize into steam, 540 calories must be put into the water for every gram of H2O.
-- 1 gram of boiling water (100oC) loses 75 calories to come down to 25oC (room temperature)
-- 1 gram of steam must first lose 540 calories to condense back to water and then lose an additional 75 calories to reach 25oC
-- steam, therefore, can burn worse than boiling water (think of that next time you either take the lid off a boiling pot or loosen the radiator cap of a hot car!)
–OTOH, it takes 79 cal/gm for ice to MELT at 0 degrees C.

EXAMPLE:
- The change from solid to liquid --- melting.
- To melt 1 gram of ice requires 80 calories. (A calorie is defined as the amount of energy needed to raise one gram of water 1°C.)
- The change from liquid to water is called solidification. This process will release 80 calories per gram.
- The change from liquid to vapor is called evaporation. This process requires 600 calories.
- The opposite of evaporation is called condensation. The latent heat of condensation will release 600 calories per gram of liquid water.

EXAMPLE:
How many calories does it take to sublimate ice (0°C) to vapor (100°C)?
- From solid to liquid is 80. From 0° to 100° is 100. From liquid to vapor is 600. 80+100+600=780 calories.
- when material absorbs energy, it expands changing the DENSITY
- a concrete (inflexible material) road in summer, it gets over 100 and suddenly the road is buckling because it has expanded too much
- Ice is unusual in that the packing of molecules is odd due to the bond angle and hydrogen bonding, so between 4o and 0o, it EXPANDS instead of CONDENSING, gets LESS DENSE and floats on the water.
- as it freezes, therefore, it expands, which is what happens to cans or glasses of soda or any other kind of rigid container with water based liquid.



REVIEW QUESTIONS

Discuss everything you know about the differences between gases, liquids and solids.
What is Brownian motion?  Give an example.
Fill in the blanks

  
characteristic  gas liquid solid
energy      
shape      
volume      
density      
LABEL THE FOLLOWING

explain what is happening in the following picture

Why does it seem an ice cream seem to suddenly melt?

Why are steam burns worse than boiling water?

Why do atoms move?