February 9th, 2010

Covalent Molecular Crystals
- The crystals structure of a covalent molecular substance consists of covalently bonded molecules held togethor by intermolecular forces.
- If the molecules are nonpolar, there are only weak London dispersion forces between molecules.
- Covalent moleculer crystals have low melting points, are easliy vaporized, and are good insulators

Amorphous Solids
- Amorphous means "without shape" in Greek
- Unlike atoms that form crystals, the atoms that make up amorphous solids aren't arranged in a regular pattern

Changes of State and Equilibrium
- a phase is any part of a system with uniform compisition and properties.
- Condensation is the process by which a gas changes to a liquid
- a gas in contact with its liquid or solid phase is called a vapor
- Equilibrium is a dynamic condition in which two opposing changes occur at equal rates in a closed system


-Eventually in a closed system, the rate of condensation equals the rate of evaporation and a state of equilibrium is established.

p.s. I am sincerely sorry to post this blog one day late and I hope you forgive me

Vapor molecules in equilibrium with a liquid in a closed system exert a pressure proportional to the concentration of molecules in the vaporphase.

The pressure exerted by a vapor in equilibrium with its corresponding liquid at a given temperature is called the EQUILIBRIUM VAPOR PRESSURE of the liquid.

The equilibrium vapor pressure increases with temperature

increasing the temperature of a liquid increases the average kinetic energy of the liquid's molecules

Because all liquids have characteristic forces of attraction between their particles, every liquid has a specific equilibrium vapor pressure at a given temperature

VOLATILE LIQUIDS are liquids that evaporate readily and have weak forces of attraction between particles

NONVOLATILE LIQUIDS have strong forces of attraction between their particles

BOILING is the conversion of liquid to vapor on the surface as well as within the liquid

BOILING POINT of a liquid is the temperature at which the equilibrium vapor pressure equals the atmospheric pressure

The lower atmospheric pressure is the lower boiling point is

At the boiling point all the energy absorbed is used to evaporate the liquid and temperature remains constant as long as atmospheric pressure does not change

Normal atmospheric pressure is boiling point of water

Energy must be added continuously to keep a liquid boiling. and the temperature will remain constant despite constant addition of energy

MOLAR ENTHALPY OF VAPORIZATION is the amount of energy as heat needed to vaporize one mole of liquid at the liquids boiling point at constant pressure

the stronger the attrction between particles the more energy needed to overcome it

liquid to solid is FREEZING

FREEZING POINT is the temperature at which the solid and liquid are at equilibrium at 1 atm pressure.. at freezing point particles of the liquid and solid have the same kinetic energy

melting is the reverse of freezing and occurrs at constant temperature

at equilibrium melting and freezing proceed at equal rates
at normal atmospheric pressure the temperature of a system containing ice and liquid water will remain at 0 degrees C as long as both ice and water are present (and you keep stirring)

at sufficiently low temperature and pressure liquid cannot exist so the substaance exits equilibrium as vapor instead of liquid

SUBLIMATION is the change of state from a solid directly to a gas

DEPOSITION is a change of state directly from a gas to a solid

whos the blogger

today we took notes and watched Dr. B's (cute grandson according to matt orians) play animal crossing. we talk about solids, liquids, and gases which can be found in Ch. 10 of your book

Friday

Law of Diffusion

Low Rate of Diffusion

• The rate of diffusion is millions of times slower in solids than in liquids

Crystalline Solids

• Crystalline solids exist either as single crystals of as groups of crystals fused together
• The total three-dimensional arrangement of particles in the crystal can be represented by a coordinate system called the lattice
• The smallest portion of a crystal lattice that shows the 3-D pattern of the entire lattice is called unit cell

Unit Cell Types

• simple cubic (4 atoms)
• body-centered (5 atoms)
• face-centered (14 atoms)

Crystalline Solids

• A crystal and its unit cells can have anyone of seven types of symmetry

Binding Forces in Crystals

• Crystal structures can also be described in terms of the types of particles in them and the types of chemical bonding between the particles

1. Ionic Crystals - The ionic crystals structure consists of positive and negative ions arranged in a regular pattern

• These crystals are hard and brittle, have high melting points, and are good insulators

2. Covalent network crystals - In covalent network crystals, each atom is covalently bonded its nearest neighboring atoms

• The covalent bonding extends throughout a network that includes a very large number of atoms
• The network solids are very hard and brittle, have high melting points, and are usually nonconductors or semiconductors

3. Metallic Crystals - The metallic crystal structure consists of metal cations surrounded by a sea of delocalized valence electrons

• The electron come from the metal atoms and belong to crystal as whole
• The freedom of these delocalized electron to more throughout the crystal explains the high electric conductivity of metal's

February 3, 2010

The Test
People who got less than a 75 on the last test will be able to retake the test sometime next week (either Monday, Wednesday, or Friday), using the book. Dr. B will put your score on this test on the website in addition your previous test, so that it averages out.

The Lab
For the lab tomorrow, you have to do the normal prelab stuff: title, purpose, materials, procedure, data tables, and prelab questions.
You must also draw a grid with all the anions and cations. The cations will occupy the header of the grid, while the anions will occupy the left side of the grid.
You will first drop a cation into each well in the column, followed by the correct anion. After you drop the anion, you will need to make the following observations:
- Color change
- Gas release
- Precipitate
- No reaction

Notes

Definite Melting Point
- Melting is the physical change of a solid to a liquid by the addition of energy as heat
- The temperature at which a solid becomes a liquid is its melting point
- At this temperature, the kinetic energies of the particles within the solid overcome the attractive forces holding them together
- Amorphous solids are sometimes classified as supercooled liquids which are substances that retain certain liquid properties even at temperatures at which they appear to be solid
- These properties exist because the particles in amorphous solids are arranged randomly
High Density and Incompressability
- In general, substances are most dense in the solid state
- The higher density results from the fact that the particles of a solid are more closely packed than those of a liquid or a gas
- For practical purposes, solids can be considered incompressable

Reagents for the Lab
- Sodium phosphate – sodium is soluble, phosphate is an anion
- Potassium hydroxide – potassium is soluble, hydroxide is an anion
- Sodium oxalate – sodium is soluble, oxalate is an anion
- Cobalt chloride – chloride is soluble, cobalt is a cation
- Strontium chloride – chloride is soluble, strontium is a cation
- Potassium iron hexacyanate – potassium is soluble, iron hexacyanate is an anion
- Sodium carbonate – sodium is soluble, carbonate is anion
- Silver nitrate – nitrate is soluble, silver is a cation
- Copper (II) sulfate – sulfate is soluble, copper (II) is a cation
- Nickel (II) chloride – chloride is soluble, nickel (II) is a cation
- Potassium iodide – potassium is soluble, iodide is an anion
- Lead (II) nitrate – nitrate is soluble, lead (II) is a cation
- Iron (III) nitrate – nitrate is soluble, iron (III) is a cation

section 2 & 3

Properties of Liquids and the kinetic- molecular theory cont.

• the particles in a liquid are not bound together in fixed positions, instead they move about constantly
• a fluid is a substance that can flow and therefore take the shape of it container

relitively high density

• at normal atmospheric pressurre, most substances are hundreds of times denser in a liquid state than in a gaseos state

relative incompressiblity

• liquids are much less compressible than gasses because liquid particles are more closely packed together

ability to diffuse

• any liquid gradually diffuses throughout any other liquid in which in can dissolve
• the constant, random motion of particles causes diffusion in liquids

diffusion is much slower in liquids than in gasses

• liquid particles are closer together
• the attractive forces between the particles of a liquid slow their movement
• as the temperature of liquid is increased diffusion occurs more rapidly

surface tension

• a property common to all liquids is surface tension, a force that tends to pull adjacent parts of a liquid's surface together, thereby decreasing surface area to the smallest possible size
• the higher the force of attraction between the particles of a liquid, the higher the surface tension
• the molecules at the surface of the water can form hydrogen bonds with the water, but not with the molecules in the air above them
• capillary action is the attraction of the surface of a liquid to the surface of a solid
• this attraction tends to pull the liquid molecules upward along the surface and against the pull of gravity
• the same process is responsible for the concave liquid surface, called a meniscus, that forms in a test tube or graded cylinder

evaporation and boiling

• the process by which a liquid or solid changes to a gas is vaporization
• evaporation is the process by which particles escape from the surface of a non-boiling liquid and enter a gas state
• boiling is the change of a liquid to bubbles of vapor that appear throughout the liquid
• evaporation occurs because the particles of a liquid have different kinetic energies

formation of solids

• when a liquid is cooled, the average energy of its particles decrease
• the physical changes of a liquid to a solid by removal energy as heat is called freezing or solidification

Section 3

• The particles of a solid are more closely packed than those of a liquid or gas
• All interparticle attractions exert stronger affects in solids than in the corresponding liquid or gasses
• attractive forces tend to hold the particles of a solid in relatively fixed positions
• solids are more ordered than liquids and much more ordered than gases
• there are 2 types of solids, crystalline and amorphous solids
• most solids are crystalline solids - they consists of crystals
• a crystal is a substance in which the particles are arranged in an orderly, geometric, repeating pattern
• an amorphous solid is one in which the particles are arranged randomly

Definite shape and volume

• solids can maintain a definite shape without a container
• crystalline solids are geometrically regular
• the volume of a solid changes only slightly with a change in temperature or pressure
• solids have definite volume because their particles are packed closely together

Monday, February 1, 2010

Chapter 10 Section 1

The Kinetic-Molecular Theory of Matter

• The Kinetic-Molecular Theory is based on the idea that particles of matter are always in motion
• The theory can be used to explain the properties of solids, liquids, and gases in terms of particles and the forces that act between them

The Kinetic-Molecular Theory of Gas

• An ideal gas is a hypothetical gas that perfectly fits all the assumptions of the kinetic-molecular theory
• The kinetic-molecular theory of gases is based on the following five assumptions:

1. Gases consists of large number's of tiny particles that are far apart relative to their size

• Most of the volume occupied by a gas is empty space

2. Collisions between gas particles and between particles and conatiner walls are elastic collisions

• An elastic collision is one inwhich there is no net loss of total kinetic energy

3. Gas particles are in continuous, rapid, random motion. They therefore possess kinetic energy which is energy of motion

4. There are no forces of attraction between gas particles

5. The temperature of a gas depends on the average kinetic energy of the particles of the gas

• The kinetic energy of any moving object is given by this equation: KE= (1/2)(m)(v)^2
• V- velocity M-kilograms K-Kinetic Energy Answer is in Joules(J)

The Kinetic Molecular Theory of Gas(continued)

• All gases at the same temperature have the same average kinetic energy
• At the same temperature, lighter gas particles, have higher average speeds than do heavier gas particles
• Hydrogen molecules will have a higher speed than oxygen molecules

The Kinetic-Molecular Theory and the Nature of Gases

• The Kinetic-Molecular Theory applies only to ideal gases
• Many gases behave nearly ideally if pressure isn't very high and temperature isn't very low

Expansion

• Gases don't have a definite shape or a definite volume
• The completely fill any container in which they are encolsed
• Gas particles move rapidly in all directions (assumption 3) without significant attractino between them (asumption 4)

Fluidity

• Because the attraction forces betwen gas particles are insignificant (assumption 4) gas particles glide easily past one another
• Because liquids and gases flow, theyre both referred to as fluids

Low Density

• THe density of a gaseous substance at atmosphere pressure is about 1/1000 the density of the same substance in the liquid or solid state
• The reason is that the particles are so much farther apart in the gaseous state (assumption 1)

Compressibility

• During compression, the gas particles, which are initially very far apart (assumption 1) are crowded close together

Diffusion and Effusion

• Gases spread out and mix with one another, even without being stirred
• The random and continuous motion of the gas molecules (assumption 3) carries them throughout the available space
• Such spontaneous mixing of the particles of two substances by their motion is called diffusion
• Effusion is a process by which gas particles pass through a tiny opening
• The rates of effusion of different gases are directly proportionally to the velocities of their particles
• Molecules of low mass effuse faster than molecules of high mass

Deviations of Real Gases from Ideal Behavior

• Because particles of gases occupy space and next attractive forces on each other, all real gases deviate to some degree from ideal gas behavior
• A real gas is a gas that doesn't behave completely according to the assumptions of the kinetic-molecular theory
• At very high pressures and low tempreratures a gas is most likely to behave like a non-ideal gas
• The more polar the molecules if a gas are, the more the gas will deviate from ideal gas behavior

Chapter 10 Section 2

Liquids

Properties of Liquids Kinetic-Molecular Theory

• A liquid can be descried as a form of matter that has a definite volume and takes the shape of its container
• The atractive forces between particels in a liquid are more efective than those between particles in a gas
• This attraction between liquid particles is caused by the intermolecular forces
• Dipole-Dipole forces
• London dispersion forces
• Hydrogen Bonding