Ch 11 Section 2 Flashcards
Robert Boyle discovered that gas pressure and volume are
related mathematically
the observations of Boyle and others led to the development of the
gas laws
the gas laws are simple mathematical relationships between the
volume, temperature, pressure, and amount of a gas
Robert Boyle discovered that doubling the pressure on a sample of gas at constant temperature reduces its
volume by one-half
reducing the pressure on a gas by one-half allows the volume of the gas to
double
the pressure of a gas is caused by moving molecules hitting the
container walls
if volume of container is decreased but same number of gas molecules is present at the same temperature then there will be more molecules per
unit volume
the number of collisions with a given unit of wall area per unit time will …. and therefore…
increase as a result; pressure will also increase
plotting values of volume versus pressure for a gas at constant temperature gives a
curve
the general-volume pressure relationship illustrated is called
boyle’s law
boyle’s law states that the volume of a fixed mass of gas varies inversely with the pressure at
constant temperature
Boyle’s la can be expressed as : PV=
k
P is
pressure
V is
volume
k is a
constant
Since P and V vary inversely, their product remains the
same
because two quantities that are equal to the same thing are equal to each other, the relationship between changes of pressure and volume can be expressed as: P1V1 =
P2V2
P1 and V1 are
initial conditions
P2 and P2 are a
different set of conditions
given three of the four values P1, V1, P2, and V2, you can use this equation to calculate the fourth value for a
system at constant temperature
if pressure is constant, gases expand when
heated
when temperature increases, the volume of a fixed number of gas molecules must increase if the pressure is to
stay constant
at the higher temperature, the gas molecules move
faster
they collide with the walls of the container more frequently and with more
force
the volume of a flexible container must then increase in order for the pressure to
remain the same
the quantitative relationship between volume and temperature was discovered by the French scientist
Jacques charles in 1787
Charles’s experiments showed that all gases expand to the same extent when heated through the
same temperature interval
charles found that the volume changes by 1/273 of the original volume for each
celsius degree, at constant pressure and initial temp of 0 degrees celsius
the same regularity of volume change occurs if a gas is cooled at
constant pressure
the kelvin temperature scale is a scale that starts at a temperature corresponding to
-273.15 degrees celsius
-273.15 degrees celsius is the lowest one
possible
the temperature -273.15 degrees celsius is referred to as absolute zero and is given a value of
zero in the Kelvin scale
K =
273.15 + degrees C
gas volume and kelvin temperature are
directly proportional to each other at constant pressure
charles’s law states that the volume of a fixed mass of gas at constant pressure varies directly with the
Kelvin temperature
charles’s law:
V =
k=
V = kT
V/T= k
the value of T is the
kelvin temperature
The ratio V/T for any set of volume-temperature values always equals the same
k
the form of charles’s law that can be applied directly to most volume temperature problems involving gases is:
V1/ T1 = V2/ T2
V1 and T1 represent
initial conditions
V2 and T2 represent a
different set of conditions
when 3 of the 4 values T1, V1, T2, and V2 are known, the equation can be used to calculate the fourth value for a
system at constant pressure
the energy and frequency of collisions depend on the average
kinetic energy of molecules
for a fixed quantity of gas at constant volume, the pressure should be directly proportional to the
Kelvin temperature, which depends directly on average kinetic energy
for every kelvin of temperature change, the pressure of a confined gas changes by
1/273 of the pressure at 0 degrees C
Gay-Lussac’s law: the pressure of a fixed mass of gas at constant volume varies
directly with the Kelvin temperature
Gay-Lussac’s law is expressed as :
P =
k=
P = kT
P/T= k
in gay lussac’s law k is constant that depends on the
quantity of gas and volume
for given mass of gas at constant volume, the ratio P/T is the same for any set of
pressure-temperature values
unknown values can be found using the following form of gay-lussac’s law:
P1/ T1 = P2/ T2
a gas sample often undergoes changes in temperature, pressure, and volume all at the
same time
the combined law expresses the relationship between
pressure, volume, and temperature of a fixed amount of gas
combined gas law: k=
PV/ T
in combined gas law, k depends on the
amount of gas
combined gas law can also be written as:
P1V1/ T1 = P2V2/ T2
each of the gas laws can be obtained from the combined gas law when the
proper variable is constant
boyle’s law is obtained from the combined gas law when
temperature is constant
because T1 = T2, T1 and T2 will canel out on both sides of the combined gas law equation, giving
Boyle’s law
