1. CHAPTER 2
SOLIDS, LIQUIDS, & GASES

2. I. States of Matter -
matter can exist in the universe in 4 states or phases - solid, liquid, gas, plasma
A. Solids - have definite volume & definite shape

3. 1. Particles in a solid
- are packed tightly together
- stay in fixed positions - shape
- are hard to separate

4. In a solid, the molecules are tightly bound together -
which holds a shape.
They vibrate in place
(Molecular Motion)

5. 2. Types of Solids
a. Crystalline solids - particles form regular repeating patterns
Iron pyrite

6. - ex.s sugar, salt, sand, snow
Melting point - the distinct temp. at which a crystalline solid melts.
The crystal structure of snow

7. The molecular structure of salt & a
microphotograph of salt crystals.

8. b. Amorphous Solids Particles are not arranged in regular patterns.
Do not have distinct melting point temperatures (just get softer & softer)
behave like slow moving, super-cooled liquids

9. - Can lose their shape under certain conditions
Ex.s - plastics, rubber, glass, wax, tar

10. Wax - an
amorphous
solid

11. B. Liquids
(Molecular Motion)
No definite shape but a definite volume - takes on the shape of its container.
Particles not held as closely together - free to move - flow.

12. - 100 mL of water = 100 mL in any
shaped container. (Definite volume)

13. Liquids do not easily compress or expand.
Viscosity - (a property of liquids) is the resistance of a liquid to flow
- honey has a high viscosity compared to water

14. Is lava liquid? Is it viscous?

15. C. Gases Have no definite shape or volume - volume can change.
Will fill any available space - a small amount of gas can fill a large volume.
Will expand without limit.

16. -Gases can be
compressed.
A larger
amount forced
into a smaller
space. (A change of volume)

17. The tanks worn by this diver contain
several hours of air. How does this work?

18. Molecules of a gas are free to move. They move very rapidly and are
(Molecular Motion)
Molecules of
a gas are free
to move. They
move very
rapidly and are
in constant
motion.

19. This is the Eagle Nebula. Its gas &
dust are expanding in space.

20. What would happen if this balloon had
a hole in it? What “limits” the gas?

21. D. Plasma 1. Plasma is - a super-heated, electrically charged gas.
Plasma is rare on earth.
Plasma is extremely energetic & dangerous.

22. Examples of plasma - the sun

23. Light bulbs & Neon lights

24. Lightning

25. Remember - particles of matter always move. (Molecular Motion)
Solids - particles vibrate in place, tightly bound together
Liquids - particles are freer, move faster - flow
Gases - particles even more free, rapid movement
Plasma - very rapid movement, lots of energy

26. Temperature affects particle movement. Heat - move faster
Temperature affects particle movement. Heat - move faster. Cold - move slower.
Absolute zero-
the temp. at which all molecular motion ceases.
- 273o C
0o Kelvin
- 459o F

27. This is dry ice (CO2).
What happens to it as the temperature rises?
What are its molecules doing?

28. This is water ice (H2O).
What happens to it as the temperature rises?
What are its molecules doing?

29. II. Gas Behavior A. Measuring Gases
1. - volume can change - gas will fill any available space so will be the same volume as its container
2. - temperature is the average energy of motion of the particles of a substance

30. (3. Temperature)
- The faster the particles are moving,
the greater their energy and the
higher the temperature
- A thermometer - a speedometer for
molecules!
- Gas molecules at 20o C - travel at
500 meters per second (typically)

31. 4. Pressure
Gas particles - constantly move & collide with each other & the walls of their containers.

32. (4. Pressure)
This results in an outward push by the gas.
This outward force is called pressure.
Pressure = Force/Area
Measured in units of kilopascals(kPa)

33. Objects like a soccer ball or
balloon, have gas under pressure
inside that keeps them inflated .
This is a pressurized space suit.
- What happens if any of these get a hole in them?

34. 4. Relating Pressure & Volume
Gases behave in predicable ways.
Robert Boyle - English scientist in the 1600’s
- found that when the pressure of a gas is increased at a constant temperature, the volume of the gas decreases. When the pressure decreases, the volume increases.

35. BOYLE’S LAW

36. Boyle’s Law also applies to situations where volume of a gas changes.
Then the pressure also changes.
What would happen
to the pressure & the
volume if you
squeezed one
of these balloons in
your hands?

37. 5. Relating Pressure & Temperature
Thought Exercise:
Think of a sand storm.
Would pouring a handful of sand over your arm feel different than being in a strong storm?
HOW?

38. The greater the speed of the sand particles, the more energy they carry & transfer.
Gas particles also travel at great speeds.
Remember: pressure measures how much gas particles push outward on their container.
- the greater the speed of the gas particles, the greater the pressure.
- Temp. is the average speed of particles.

39. Charles’s Law - 1700’s French Scientist Jacques Charles
When the temperature of a gas at a constant volume is increased, the pressure of the gas increases.
When the temperature is decreased, the pressure of the gas decreases.

40. Charles’s Law

41. III. Graphing Gas Behavior
Graphs are diagrams that tell how 2 variables or factors are related.
- graphs can be used to make predictions

42. Collecting data - use a data table

43. Data from a data table can then be graphed.
This graph shows the linear relationship between temp. & volume which are directly proportional.

44. This graph
shows the relation-
ship between pressure & volume which varies inversely.

45. IV. Changes of State - physical change of matter from one state or phase to another. (ex. solid - liquid)
A. Energy & changes in state
1. A substance changes state when its thermal (heat) energy increases or decreases by a sufficient amount.
2. Thermal energy - the energy of a substances particles
- transferred from one substance to another

46. - always flows from a warmer substance to a cooler substance
Remember: the arrangement & motion of particles in a substance determine whether substances are solid, liquid, or gas.
- particles of solids have the least thermal energy, gas the most.

47. B. Changes of State or Phase
1. MELTING - solid to liquid
- melting point of a substance is determined by how strongly its particles are attracted.
- Thermal energy makes molecules vibrate faster. At a certain temperature (the melting point) they can break free.

48. Melting wax

49. Melting ice
- ice begins to melt at 0o C, the temperature
at which molecules are moving fast enough to flow as a liquid.

50. Molten silver - What
happens to the molecules
as the metal cools?

51. Do substances require the same amount of thermal (heat) energy to melt?
THINK of melting:
- water ice
- steel
- plastic
- rock

52. 2. Freezing - liquid to solid
Liquid loses energy as it cools.
Molecules slow down.
When water reaches 0oC, its molecules are moving so slowly that it starts to form into regular patterns - ice crystals
This is the same temperature at which ice melts!

53. So what does happen to molten silver molecules
as the metal cools?

54. 3. Vaporization - liquid to gas
Occurs when a liquid gains enough energy to become a gas.
Two main types:
- evaporation - molecules on the surface escape
- ex.s a drying puddle, sweating
- boiling -takes place inside a
liquid & on the surface

55. Note: Evaporation happens at the surface & boiling inside the liquid
Note: Evaporation happens at the surface & boiling inside the liquid. Boiling is actually water molecules turning into a bubble of gas inside the liquid & then bubbling out as densities change. Which requires more energy?

56. - a. boiling point - is the temperature a which a liquid boils
Boiling points of substances:
- water (at sea level) = 100oC
- salt = 1413o
- diamond = 4827oC
Boiling point is affected by air pressure. The lower the air pressure, the less energy is needed for molecules to escape. Water will boil at 95oC in Denver, Colorado.

57. 4. Condensation - gas to liquid
Occurs when gas particles lose enough energy to become a liquid.
- ex.s clouds, mist,breath on a mirror
Steam is NOT condensation (water vapor) but tiny drops of liquid water suspended in the air.

58. Water vapor condensing on a flower.
This happens when the water vapor touches a cooler surface & loses thermal energy.
Think of a cold glass on a humid day.

59. Fog - water vapor cooling & condensing in the rainforest.

60. 5. Sublimation - solid to gas
Occurs when the surface particles of a solid gain enough energy to become a gas.
- particles do NOT pass through a liquid state.
Ex.s - dry ice, naphthalene(moth balls,) iodine, water ice

61. Dry ice - CO2
Note that the
fog you see is
not CO2 gas, (you can’t see that) - it’s water vapor condensing in the cold surrounding the dry ice.

62. Dry ice - CO2
Sublimating - Iodine

63. Water ice & snow will also sublimate.
How could this happen?
Hint: It happens in very cold places like Antarctica.

64. C. Identifying Substances Through Changes of States/Phase
The properties of substances can help to identify them.
- boiling/melting points
If you were given 3 colorless liquids you could identify them by their boiling & melting points.

65. Freezing - Boiling
Water o o C
Ethanol o o
Chloroform o o