substances whose constituent atoms, molecules, or ions are held rigidly together in a definite way, giving hte solid a definite volume and shape
liquids
constituent atoms or molecuels are held together less strongly, giving hte liquid a definite volume but a changeable and indefinite shape
gases
constituent atoms or molecules have little attraction for one another and are therefore free to move about in whatever volume is available
__ and __ account for more than 99% by volume fo dry air. The remaining 1% is largely __, with trace amounts of several other substances also present. __ is present (.0385%)
nitrogen
oxygen
argon
carbon dioxide
Gas mixtures are always __, meaning that they are __.
homogeneous
uniform in composition
Unlike liquids, which often fail to mix with one another and which may separate into distinct layers--oil and water, for example-- gases always mix completely
a. true
b. false
a. true
Gases are __. When pressure is applied, what happens to the volume?
Solids and liquids, however, are nearly __, and even the application of great pressure does what to their volume?
compressible
the volume of a gas contracts proportionately
incompressible
changes their volume only slightly
Why does homogeneous mixing and compressibility both occur?
because molecules in gases are far apart
Mixing occurs because what?
In solids and liquids, molecules are packed closely together, where they are affected by various __ and __ forces that can __ their mixing.
individual gas molecules have little interaction with their neighbors and the chemical identities of those neighbores are irrelevant
attractive
repulsive
inhibit
One of the most obvious characteristics of gases is that they exert a measurable __ on the walls of their container.
pressure
What is pressure?
What is the formula?
force exerted per unit area
P=F/A= (m x a)/ A
where F is force, A (area), m(mass), a (acceleration)
The SI unit for force is the __, and the SI unit for pressure is the __.
Newton (N)
pascal (Pa)
The mass of air in the atmosphere pressing down on the Earth's surface exerts what we call __.
atmospheric pressure
Because the pascal is an inconvenient size for most chemical measurements, the alternative pressure units __, __, and __, are most often used.
mm of mercury (mm Hg)
atm
bar
the __, also called a __. is based on atmospheric pressure measurements using a mercury _.
mm Hg
torr
barometer
Explain a barometer.
a long, thin tube that is sealed at one end, filled with mercury, and inverted into a dish of mercury; some mercury runs from tube into dish until downward pressure of the mercury insidethe column is exactly balanced by the outside atmospheric pressure, which presses on the mercury in the dish and pushes it up the column
In a barometer, the empty space above the mercury in the sealed end of hte tube is a __.
vacuum
Knowing the density of Hg and the acceleration due to gravity, its possible to calculate hte __.
pressure exerted by the column of mercury 760 mm in height
Why is the bar convenient?
It is a power of ten of hte SI unit pascal
Gas pressure inside a container is often measured using an open-end __, a simple instrument similar in principle to the mercury barometer.
manometer
explain a manometer.
U-tube filled with Hg, with one end connected to a gas-filled container and the other end open to the atmosphere
the difference between the pressure of the gas in the container and the pressure of the atmosphere is equal to the difference between the heights of hte mercury levels in the two arms of the U-tube
Manometer:
If the gas pressure inside the container is less than atmospheric, the mercury level is __.
If the gas pressure inside the container is greater than atmospheric, the mercury level is __.
higher in the arm conncted to the container
higher in the arm open to the atmosphere
True or False:
Different gases show remarkably different physical behavior regardless of chemical makeup.
False:
Different gases show remarkably similar physical...
The physical properties of any gas can be defied by four variables: __(4)__
The specific relationships among these four variables are called __, and a gas whose behavior follows the laws exactly is called an __.
pressure (P)
temp (T)
volume (V)
amount (number of moles- n)
gas laws
ideal gas
Boyle's Law
volume of a fixed amount of gas at a constant temperature varies inversely with its pressure
ex: if gas pressure is doubled, hte volume is halved
in other words: the volume of an ideal gas varies inversely with pressure
When V and P are plotted at constant temp and moles (Boyle's Law), what will the graph resemble?
hyperbola
Charles' Law
volume of a fixed amount of an ideal gas at a constant pressure vries directly with its absolute temperature
if gas temp in kelvin is doubled, the volume is doubled
in other words: volume of an ideal gas varies directly with absolute temperature
How was absolute zero determined?
using Charles's law and plotting volume versus temperature
Avogadro's Law
the volume of an ideal gas at a fixed pressure and temperature depends on its molar amount. (The volume of an ideal gas varies directly with its molar amount.)
If the amount of the gas is doubled, the gas volume is doubled; if halved, the volume is halved.
V/n= k at constant T and P
One mol of an ideal gas occupies a volume, called the __, of 22.414 L at 0 degrees C and exactly 1 atm pressure.
standard molar volume
All three gas laws can be combined into a single statement called the __,which describes how the volume of a gas is affected by changes in pressure, temperature, and amount. When the values of any three of the variables P, V, T, and n are known, the value of the fourth can be calculated using the __. The proportionality constant R in the equation is called the __ and has the same value for all gases.
ideal gas law
ideal gas law
gas constant
Ideal Gas Law Formula
V= (nRT/P)
OR
PV=nRT
The specific conditions of 0 degrees Celcius and 1 atm pressur are said to represent __.
standard temperature and pressure (STP)
The name __ implies that there must be some gases whose behavior is __. In fact, there is no such thing as an ideal gas that obeys the equation perfectly under all circumstances.
ideal gas law
nonideal
All real gases are __ to some extent and deviate slightly from the behavior predicted by the gas laws.
nonideal
How are densities calculated?
by weighing a known volume of a gas at a known temperature and pressure
Using the __ to find the volume at __ and then dividing the measured mass by the volume gives the __ at __.
ideal gas law
STP
density
STP
__, and therefore __, can also be calculated using the ideal gas law.
molar masses
molecular masses
Just as the gas laws apply to all pure gases, regardless of chemical identity, they also apply to __ of gases, such as air. The __, __, __, and __ mixture are all related by the __.
mixtures
pressure
volume
temperature
amount of a gas mixture
ideal gas law
Because the pressure of a __ at constant temperature and volume is proportional to its __, the pressure contribution from each individual gas in a mixture is also proportional to __.
pure gas
amount
its amount in the mixture
In other words, the __ exerted by a mixture of gases in a container at constant V and T is equat to the __ of each individual gas in the container, a statement known as __.
total pressure
sum of the pressures
Dalton's law of partial pressures
Dalton's law of partial pressures
Ptotal= P1+P2+P3+.. at constant V and T, where P1, P2,.. refer to the pressures each individual gas would have if it were alone.
The individual pressure contributions of the various gases in the mixture, P1, P2, and so forth, are called __ and refer to the pressure each individual gas would exert if it were alone in the container.
partial pressures
The concentration of any individual component in a gas mixture is usually expressed as a __.
mole fraction
What is the mole fraction?
the number of moles of the component divided by the total number of moles in the mixture
Mole Fraction Equation.
Moles of component/ Total moles in mixture
Assumptions of the Kinetic-molecular theory:
One
a gas consists of tiny particles, either atoms or molecules, movng about at random
Assumptions of the Kinetic-molecular theory:
two
The volume of the particles themselves is negligible compared with the total volume of the gas. Most of the volume of a gas is empty space.
Assumptions of the Kinetic-molecular theory:
Three
The gas particles act independently of one another; there are no attractive or repulsive forces between particles
Assumptions of the Kinetic-molecular theory:
Four
Collisions of the gas particles, either with other particles or with the walls of a container, are elastic. That is, the total kinetic energy of the gas particles is constant at constant T.
Assumptions of the Kinetic-molecular theory:
Five
The average kinetic energy of the gas particles is proportional to the Kelivin temperature of the sample
Gas pressure
a measure of the number and forcefulness of collisions between gas particles and the walls of their container
Temperature
The higher the temp at constant n and P, the what?
a measure of the average kinetic energy of the gas particles
faster the gas particles move and the more room theey need to move around in order to avoid increasing their collisions with the walls of the container
Total pressure of a fixed volume of gas depends only on the __.
T and the total number of moles of gas n
There is a __ among particles in a gas, a distribution that flattens out and moves to higher speeds as __.
broad distribution of speeds
temp increases
Why is the actual path followed by a gas particle a random zigzag?
an individual gas particle collides with another particle and bounces off in a different direction
For helium at room temp and 1 atm pressure, the average distance between collisions, called the __, is only about 1000 atomic diameters.
mean free path
What are some consequences of the constant motion and high velocities of gas particles?
gases mix rapidly when they come in contact
mixing of different molecules by random molecular motion with frequent collisions
diffusion
gas molecules escape without collisions through a tiny hole into a vacuum
effusion
Graham's law
the rate of effusion of a gas is inversely proportional to the square root of its mass, m
- the lighter the molecule, the mroe rapidly it effuses
Explain why differeent gases at the same temperature have the same average kinetic energy?
because temperature is a measure of average kinetic energy and is independent of the gas's chemical identity
Why is diffusion more complex than effusion?
because of the molecular collisions that occur
True or False:
The behavior of a real gas is the same as that of an ideal gas.
Explain your answer.
false:
different from that
kinetic-molecular theory assumes the volume of the gas particles themselves is negligible comapred with the total gas volume. This is valid at STP, but not at other ones.
It also says that there are no attractive or repulsive forces; there are!
Both ways in which the behavior of real gases deviates from the ideal gas law can be dealt with mathematically by a modificaiton of the ideal gas law called the __, which uses two correction factors, called a and b. Four legions of the atmosphere.
van der Waals equation
The temperature in the __, the region nearest the earth's surface, decreases regularly.
troposphere
After the troposphere is the __, then the __, and the __.
stratosphere
mesosphere
thermosphere
What are the main causes of air pollution?
release of unburned hydrocarbon molecules and the production of NO during combustion of petroleum products in older industrial plants
What is acid rain?
results primarily from production of sulfur dioxide
