If you consider a very small object such as a grain of pollen, in a gas, then the number of atoms and molecules striking its surface would also be relatively small. Would the grain of pollen experience any fluctuations in pressure due to statistical fluctuations in the number of gas atoms and molecules striking it in a given amount of time?
Yes. Such fluctuations actually occur for a body of any size in a gas, but since the numbers of atoms and molecules are immense for macroscopic bodies, the fluctuations are a tiny percentage of the number of collisions, and the averages spoken of in this section vary imperceptibly. Roughly speaking the fluctuations are proportional to the inverse square root of the number of collisions, so for small bodies they can become significant. This was actually observed in the 19th century for pollen grains in water, and is known as the Brownian effect.
Phet explorations: gas properties
Pump gas molecules into a box and see what happens as you change the volume, add or remove heat, change gravity, and more. Measure the temperature and pressure, and discover how the properties of the gas vary in relation to each other.
Section summary
Kinetic theory is the atomistic description of gases as well as liquids and solids.
Kinetic theory models the properties of matter in terms of continuous random motion of atoms and molecules.
where
$P$ is the pressure (average force per unit area),
$V$ is the volume of gas in the container,
$N$ is the number of molecules in the container,
$m$ is the mass of a molecule, and
$\overline{{v}^{2}}$ is the average of the molecular speed squared.
Thermal energy is defined to be the average translational kinetic energy
$\overline{\text{KE}}$ of an atom or molecule.
The temperature of gases is proportional to the average translational kinetic energy of atoms and molecules.
The motion of individual molecules in a gas is random in magnitude and direction. However, a gas of many molecules has a predictable distribution of molecular speeds, known as the
Maxwell-Boltzmann distribution .
Conceptual questions
How is momentum related to the pressure exerted by a gas? Explain on the atomic and molecular level, considering the behavior of atoms and molecules.
Problems&Exercises
Some incandescent light bulbs are filled with argon gas. What is
${v}_{\text{rms}}$ for argon atoms near the filament, assuming their temperature is 2500 K?
Average atomic and molecular speeds
$({v}_{\text{rms}})$ are large, even at low temperatures. What is
${v}_{\text{rms}}$ for helium atoms at 5.00 K, just one degree above helium’s liquefaction temperature?
(a) What is the average kinetic energy in joules of hydrogen atoms on the
$\text{5500}\text{\xba}\text{C}$ surface of the Sun? (b) What is the average kinetic energy of helium atoms in a region of the solar corona where the temperature is
$6\text{.}\text{00}\times {\text{10}}^{5}\phantom{\rule{0.25em}{0ex}}\text{K}$ ?
The escape velocity of any object from Earth is 11.2 km/s. (a) Express this speed in m/s and km/h. (b) At what temperature would oxygen molecules (molecular mass is equal to 32.0 g/mol) have an average velocity
${v}_{\text{rms}}$ equal to Earth’s escape velocity of 11.1 km/s?
The escape velocity from the Moon is much smaller than from Earth and is only 2.38 km/s. At what temperature would hydrogen molecules (molecular mass is equal to 2.016 g/mol) have an average velocity
${v}_{\text{rms}}$ equal to the Moon’s escape velocity?
$\text{458}\phantom{\rule{0.25em}{0ex}}\text{K}$
Nuclear fusion, the energy source of the Sun, hydrogen bombs, and fusion reactors, occurs much more readily when the average kinetic energy of the atoms is high—that is, at high temperatures. Suppose you want the atoms in your fusion experiment to have average kinetic energies of
$6\text{.}\text{40}\times {\text{10}}^{\u2013\text{14}}\phantom{\rule{0.25em}{0ex}}\text{J}$ . What temperature is needed?
Suppose that the average velocity
$({v}_{\text{rms}})$ of carbon dioxide molecules (molecular mass is equal to 44.0 g/mol) in a flame is found to be
$1\text{.}\text{05}\times {\text{10}}^{5}\phantom{\rule{0.25em}{0ex}}\text{m/s}$ . What temperature does this represent?
Hydrogen molecules (molecular mass is equal to 2.016 g/mol) have an average velocity
${v}_{\text{rms}}$ equal to 193 m/s. What is the temperature?
Much of the gas near the Sun is atomic hydrogen. Its temperature would have to be
$1\text{.}5\times {\text{10}}^{7}\phantom{\rule{0.25em}{0ex}}\text{K}$ for the average velocity
${v}_{\text{rms}}$ to equal the escape velocity from the Sun. What is that velocity?
There are two important isotopes of uranium—
${}^{\text{235}}\text{U}$ and
${}^{\text{238}}\text{U}$ ; these isotopes are nearly identical chemically but have different atomic masses. Only
${}^{\text{235}}\text{U}$ is very useful in nuclear reactors. One of the techniques for separating them (gas diffusion) is based on the different average velocities
${v}_{\text{rms}}$ of uranium hexafluoride gas,
${\text{UF}}_{6}$ . (a) The molecular masses for
${}^{\text{235}}\text{U}\phantom{\rule{0.25em}{0ex}}$${\text{UF}}_{6}$ and
${}^{\text{238}}\text{U}$$\phantom{\rule{0.25em}{0ex}}{\text{UF}}_{6}$ are 349.0 g/mol and 352.0 g/mol, respectively. What is the ratio of their average velocities? (b) At what temperature would their average velocities differ by 1.00 m/s? (c) Do your answers in this problem imply that this technique may be difficult?
Questions & Answers
Do somebody tell me a best nano engineering book for beginners?
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
In this morden time nanotechnology used in many field .
1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc
2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc
3- Atomobile -MEMS, Coating on car etc.
and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change .
maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.