Chpt. 13, Solids, Liquids, and Gases

Question 1

intermolecular forces

Answer 1

forces that occur between different molecules, rather than within a single molecule

Question 2

dipole-dipole forces

Answer 2

forces of attraction that occur between polar molecules

Question 3

hydrogen bonds

Answer 3

extremely strong dipole-dipole force that occur between molecules with H-O, H-F, and H-N bonds; because these molecules are extremely polar due to the high difference in electronegativity between these two molecules, and because the lone pairs on the O, F, or N atoms can get really close to the hydrogen atom on another molecule, these forces are way stronger than regular dipole-dipole forces

Question 4

London dispersion forces

Answer 4

attractions caused by temporarily induced dipoles in non-polar molecules; Van der Waals forces are almost the exact same thing as these, although there are some small differences; the process occurs as follows:

1. random movement of electrons in a molecule causes it to be temporarily polar
2. this polarity causes electrons to shift in an adjacent molecule (be driving them away from the negative spot), making it polar, too
3. the two molecules, temporarily polar, stick to each other in the manner of dipole-dipole forces
4. the electrons eventually go back to their original state, doing away with the temporary polarity

Question 5

similarity between liquids and solids

Answer 5

states of matter in which the attraction between molecules, ions, or atoms keep them from moving away from each other

Question 6

ionic solid characteristics

Answer 6

hard, brittle, high melting and boiling points, and conductive of electricity when melted or dissolved, generally less flammable than covalent compounds

Question 7

molecular solids

Answer 7

crystalline solids in which molecules are stuck to each other via intermolecular forces; the melting and boiling points of these compounds will depend largely on how strong these forces are, as well as how big the molecules are, though mp; they are also generally soft, electrical insulators, and have lower energy; examples include sugar and water ice

Question 8

covalent network solid characteristics

Answer 8

crystalline solids held together by multiple of covalent bonds; though there are exceptions, these solids have very high melting and boiling points, though lower than ionic compounds, more likely to burn than ionic compounds (C and H have more occurrence in them due to their identical electronegativities); examples include quartz, diamond, and silicon

Question 9

metallic solids

Answer 9

malleable, ductile, conducive of electricity, highly conductive of thermal energy, luster, insoluble in most solvents (electrons cannot easily go into solution)

Question 10

amorphous solids

Answer 10

unlike crystalline solids, there’s no long-range order in an amorphous solid; amorphous solids contain compounds as varied as glasses, rubbers, and plastics; they are the only type of solids that does not exhibit a crystal structure

Question 11

atomic solid

Answer 11

solids that occur when noble gases are cooled to very low temperatures and lock themselves in place using very weak London dispersion forces; these solids almost never occur naturally because they only occur when temperatures are extremely low

Question 12

other types of substances

Answer 12

alloys (interstitial or substitutional)

Question 13

flammability criteria

Answer 13

cannot be flammable unless it contains carbon and oxygen

Question 14

liquids

Answer 14

the state of matter in which particles are attracted to each other enough that they don’t fly apart (like a gas) or stick in place like a solid; liquids generally have lower densities than solids, but have much higher densities than gases; as a result, if a solid is melted, it will grow in volume

Question 15

properties of liquids

Answer 15

1. cannot be compressed– already very close to one another
2. they flow– they have enough attraction to keep them together, but not enough to prevent them from flowing apart due to gravitational and other forces
3. they have viscosity
4. they have surface tension– stronger the intermolecular forces of a liquid, the higher the surface tension
5. they experience capillary action

Question 16

capillary action

Answer 16

the process by which some liquids are pulled up a thin tube, this is caused by cohesion and adhesion; the liquid is pulled up until the gravitational downward force equals the upwards force of the cohesion and adhesion; the thinner the tube, the higher the liquid will be pulled

Question 17

viscosity

Answer 17

another term for “thickness”; what it really measures is the strength of the force between the particles of a liquid

Question 18

phase changes

Answer 18

melting (solid to liquid)
freezing (liquid to solid)
vaporization (liquid to gas)
condensation (gas to liquid)
sublimation (solid to gas)
deposition (gas to solid)

Question 19

melting

Answer 19

This is when you turn a solid into a liquid. This is done by adding enough energy to disrupt the forces between the particles in the solid, but not so much that the particles in the solid fly apart into a gas.

Question 20

freezing

Answer 20

This is when a liquid turns into a solid. As you suck the energy out of a liquid, there’s less energy available for the molecules to overcome the forces between the particles. As a result, the particles lock into place as a solid. This is what happens when you turn water into ice by cooling it down.

Question 21

vaporization

Answer 21

This is when you turn a liquid into a gas by adding energy to it - this added energy breaks apart the forces between the particles, allowing them to fly wild and free as gases.

Question 22

condensation

Answer 22

When you cool a gas enough, the particles no longer have enough energy to overcome the forces between them. At this point, the gas condenses into a liquid.

Question 23

sublimation

Answer 23

Sublimation is when a solid turns directly into a gas. This occurs when the vapor pressure of the liquid phase of the material is so high that the material goes directly from a solid to a gas without first turning into a liquid. You know how ice cream gets all disgusting and rubbery after it’s been in the freezer for a long time. That’s because the water sublimed out of it and only the rubbery other stuff is left over.

Question 24

deposition

Answer 24

When a gas turns into a solid. This happens when the gas loses energy and goes from the gas to the solid state. When ice cream grows ice crystals when it gets rubbery in the freezer, that’s because the water was deposited as ice crystals.

Question 25

evaporation and boiling

Answer 25

One example of vaporization is evaporation, which occurs when only a few molecules of the liquid have enough energy to become a gas – the pressure of the gas caused by the evaporation of these particles is called its vapor pressure. As the temperature of the liquid increases, evaporation increases and the vapor pressure of the liquid increases, too. When the vapor pressure of the liquid increases to where it’s the same as the atmospheric pressure, the liquid boils. An example of evaporation is when your goldfish dies because his bowl dried out.

Question 26

phase changes diagrams: lines, normal melting point, and normal boiling point

Answer 26

1. Each line that marks the border between two phase changes denotes the conditions under which both phases of matter can stably exist.
2. The temperature at which the compound melts at a pressure of one atmosphere. In this diagram, the normal melting point is 00 C.
3. The temperature at which the compound boils at a pressure of one atmosphere. In this diagram, the normal boiling point is 1000 C.

Question 27

phase change diagram triple point and critical point

Answer 27

1. The conditions of temperature and pressure at which all three phases of matter can stably exist. For water, the triple point is 0.06 atm and 0.010 C, which is why you’ve never seen all three phases of water in equilibrium.
2. The conditions of temperature and pressure past which it’s impossible to distinguish between the liquid and gas phase of the material. This occurs because the material has too much energy to stick together (which is true of gases) but is crammed so tightly together that intermolecular forces between the particles are strong. Under these conditions, the material is said to be a supercritical fluid.

Question 28

kinetic molecular theory of gases

Answer 28

The kinetic molecular theory of gases is a mathematical model that’s intended to quantitatively describe the behavior of gases. Unfortunately, the math that goes into such a model is really hard to do, and requires annoyingly huge quantities of computing power. Because we usually don’t feel like buying such gigantic computers (and because the model was invented in the mid-19th century, before computers were even born), the kinetic molecular theory uses some assumptions about the particles in gases to make the whole thing a little easier to deal with.

Question 29

postulates of the kinetic molecular theory

Answer 29

1. gas molecules are infinitely small
2. gas molecules are constantly moving, and never move preferentially in one direction
3. gas molecules undergo elastic collisions; when two hit each other, none of the energy is lost
4. the kinetic energy of a gas molecule is related to its temperature; the higher the temperature, the higher the kinetic energy
5. gases don’t experience intermolecular forces

Question 30

Why are gas molecules, “infinitely small?”

Answer 30

Because the particles in a gas are all really far away from each other, the volume of the particles in a gas is really small compared to its overall volume. Since the gas molecules take up a fantastically small percentage of its volume, we can just make the assumption that they’re infinitely small to make the math easier.

Question 31

diffusion/effusion

Answer 31

How gas travels can be described by either diffusion or effusion.

Diffusion is when gas travels through other gas. Effusion is when gas travels through a vacuum containing no other gas molecules.

Question 32

rate of diffusion

Answer 32

rate of gas A / rate of gas B = ∫molar mass of gas B / molar mass of gas A