Gases, liquids, and solids Flashcards
Name some general gases and how they appear in the world
- surrounded by an atmosphere composed of a mixture of gases: air (78% N2 and 21% O2)
- Oxygen (O2) supports human life, chlorine gas (Cl2) is used to purify drinking water, acetylene gas (C2H2) is used in welding (Schweißen), carbon dioxide (CO2) and methane (CH4) are implicated in global warming
Name some properties of gases
- Many molecular compounds are gases
- All gases are composed entirely of nonmetallic elements.
- All gases have simple molecular formulas and low molar masses.
- A gas expands spontaneously to fill its container.
- The volume of a gas equals the volume of its container.
- Gases are highly compressible: upon pressure their volume decreases.
- Gases form homogenous mixtures with each other regardless of the identities orrelative proportions of the component gases.
(ex: water and gasoline vapor and liquid mixtures) - The characteristic properties of the gases arise because the individual molecules are relatively far apart.
- As a result, different gases behave similarly.
P=?
F=?
- Pressure, P, is the force, F, that acts on a given area, A:
- P = F / A
- Force: F = ma
How can the atmospheric pressure be measured?
-by use of a mercurey barometer
What do you know about the Standard atmospheric pressure?
-Standard atmospheric pressure, which corresponds :to the typical pressure at sea level, is the pressure sufficient to support :a column of mercury 760 mm in height
How do you calculate the pressure of a gas ( closed end)
-Pgas= Ph1
How do you calculate the pressure of a gas ( open end) if gas is moved to left?
-Pgas + Ph2= Pate (760mm hg)
How do you calculate the pressure of a gas ( open end) if gas is moved to right?
-Pgas =Ph2+ Pate (760mm hg)
How much torr is one pa? How much pa is one bar?
- 1 torr =133.322Pa
- 1pa= 0.00001bar
What does the Boyle’s Las say?
- The Pressure-Volume Relationship
- The volume of a fixed quantity of gas maintained at constant temperature is inversely proportional to the pressure
- > the more pressure the less volume (anti-proportional in Vp diagramm)
What does the Charles’s Law say?
- The Temperature-Volume Relationship
- The volume of a fixed amount of gas maintained at constant pressure is directly proportional to its absolute temperature
- > the higher the temperature the bigger the volume
What does the Avogadro’s Law say?
-The Quantity-Volume Relationship
-The volume of a gas maintained at constant temperature and pressure is directly proportional to the number of moles of the gas:
V = constant x n
What was Gay-Lussac’s observation and Avogadro’s explanation?
- observation: two volumes’ hydrogen one volume oxygen result two volumes water vapor (Wasserdampf)
- explanation: 2H2(g) + O2(g) ->2H2O (g)
What is the ideal gas equation?
- PV = nRT
- an ideal gas is a hypothetical gas whose pressure, volume, and temperature behavior is completely described by the ideal-gas equation.
- The term R is called the gas constant.
- Temperature must always be expressed in K!
Does the ideal gas equation accurately describe real gases?
- The ideal gas equation does not always accurately describe real gases
- Ordinarily, the difference btw ideal and real behavior is so small that we may ignore it
What is dalton describing`?
- Total pressure of a mixture of gases equals the sum of the pressures that each would exert if it were present alone
- Pt = P1 + P2 + P3 + …
Why is it the case with the Delton’s law?
-each gas in a mixture behaves independently, we can easily relate the amount of a given gas in a mixture to its partial pressure
What are the five rules of Kinetic-Molecular Theory?
-gases consist of large numbers of molecules
that are in continuous, random motion.
-The volume of all the molecules of the gas is negligible compared to the total volume in which the gas is contained
-Attractive and repulsive forces btw gas molecules are negligible
-Energy can be transferred btw molecules during collisions, but the average kinetic energy of the molecules do not change with time
-The average kinetic energy of the molecules is proportional to the absolute temperature. At any given temperature the molecules of all gases have the same average kinetic energy
What are the effects of:
- volume increase at constant temperature
- a temperature increase at constant volume
- 1.pressure decrease
- 2.pressure increase
What can we see in the deviations from ideal behavior?
- all real gases fail to obey the relationship to some degree
- Real molecules do have finite volumes and they do attract one another
When can the ideal behavior deviate?
- high pressure
- > volumes of particles become more and more
- low temperature
- > move more slowly, chance of attraction increases
Give the correction for volume in the van der Waals Equation
- nRT/V-nb
- b=constant describing the size of the gas particles
- n=moles
- (-nb) ->accounts for the volume occupied by the gas particles
Give the correction for molecular attraction in the van der Waals Equation
- (-n^2 *a/V^2) ->accounts for the attraction between the gas particles
- a= constant describing the strength of the attraction
- n=moles
Give The van der Waals Equation
-P= (nRT)/V-nb - ((n^2)*a)/V^2
On what does physical properties depend?
- physical state
- intermolecular forces
Name some properties of gas
- assumes (übernehmen) both the volume and shape of its container
- is compressible
- flows readily (leicht, breitwillig)
- diffusion within a gas occurs rapidly
Name some properties of liquids
- assumes the shape of the portion of the container it occupies
- does not expand to fill container
- is virtually incompressible
- flows readily
- diffusion within a liquid occurs slowly
Name some properties of solid
- retain its own shape and volume
- is virtually incompressible
- does not flow
- diffusion within a solid occurs extremely slowly
Describe gases on molecular- level
- total disorder
- much empty space
- particles have complete freedom of motion
- particles far apart
Describe liquids on molecular- level
- disorder
- particles or clusters of particles are free to move relative to each other
- particles close together
Describe crystalline solids on molecular- level
- ordered arrangement
- particles are essentially in fixed positions
- particles close together
Describe the transformation of gases, liquids, solids
- gas when cooled or compressed becomes liquid
- liquid when cooled become solid
- liquid when heated or reduced pressure become gas
- solid when heated become liquid
What is an ion-dipole force? Where does it occur?
-An ion-dipole force exists btw an ion and the partial charge on the end of a polar molecule
-Polar molecules are dipoles; they have a positive end and a negative end
-Ex: HCl is a polar molecule because of the difference in the electronegativities of
the H and Cl atoms
What is an dipole-dipole force? When does it occur; when effective; which is stronger ion-dipole or dipole- dipole?
- A dipole-dipole force exists btw neutral polar molecules
- Polar molecules attract each other when the positive end of one molecule is near the negative end of another
- Dipole-dipole forces are effective only when polar molecules are very close together
- > They are generally weaker than ion-dipole forces
Where does hydrogen bonding exist?
-exists btw the hydrogen atom in a polar bond (particularly an H-F, H-O, or H-N bond) and an unshared electron pair on a nearby electronegative ion or atom (usually an F, O, or N atom on another molecule)
Effects of hydrogen bonding on water
- Water has a high melting point, a high specific heat, and a high heat of vaporization.
- > the intermolecular forces btw H2O molecules are abnormally strong
What happens when water becomes ice?
- When water freezes, the molecules assume an ordered, open arrangement, leading to a less dense structure
- This structure of ice permits the maximum number of hydrogen-bonding interactions btw the H2O molecules
What are the words condensation, sublimation, deposition, vaporisation standing for? Which of them are endothermic/ exothermic?
- condensation -> from gas to liquid (exo)
- sublimation -> from solid to gas (end)
- deposition -> from gas to solid (exo)
- vaporisation -> from liquid to gas (end)
- melting-> from solid to liquid (end)
- freezing -> from liquid to solid (exo)
Give the heating curve for water
-from -25 to 0 -> ice
-0 -> ice and liquid water (melting)
-100 -> liquid water and vapor (vaporization)
- 100 to 125 -> water vapor
(-in °C)
Which forms can solid have?
- Solids can be either crystalline or amorphous (noncrystalline).
- A crystalline solid is a solid whose atoms, ions, or molecules are ordered in well-defined arrangements
ex: quartz and diamond - An amorphous solid is a solid whose particles have no orderly structure. They lack well-defined faces and shapes
ex: rubber and glass
The repeating unit of solid is known as?
-the unit cell
When is something called primitive cubic, body-centered cubic, and face-centered cubic?
- primitive cubic -> if the constituent particles are present only at the corners
- body-centered -> if the constituent particles are present at the corners and at one body- center
- face-centered -> if the constituent particles are present at the 6 face centers along with corners
- > NaCl, Zinc blende, Cu
Name the form of unit particles, forces between particles, the properties, and examples of molecular solid
- atoms or molecules
- dipole- dipole forces, London dispersion forces, hydrogen bonds
- fairly soft, low to moderately high melting point, poor thermal and electrical conduction
- Argon, Ar; methane, CH4; sucrose, C12H22O11; Dry, Ice CO2
Name the form of unit particles, forces between particles, the properties, and examples of covalent network solid
- atoms connected in a network of covalent bonds
- covalent bonds
- very hard, very high melting point, often poor thermal and electrical conduction
- Diamond, C; quartz, SiO2
Name the form of unit particles, forces between particles, the properties, and examples of ionic solid
- positive and negative ions
- electrostatic attractions
- hard and brittle, high melting point, poor thermal and electrical conduction
- typical salts- for example, NaCl, Ca(NO3)2
Name the form of unit particles, forces between particles, the properties, and examples of metallic solid
- atoms
- metallic bonds
- soft to very hard, low to very high melting point, excellent thermal and electrical conduction, malleable (formbar) and ductile (biegsam)
- all metallic elements- for example , Cu, Fe, Al, Pt
