why do hot molecules move faster than cold molecules? why?
414204
hot molecules contain greater potential energy and as this converts to ke at a faster rate they can move around a lot faster
481035
its the other way round. a thing is hot if its molecules are moving with a higher thermal velocity (prop to T^1/2). if you heat something its molecular vibrations go up in turn increasing its temperature.
693920
Any chemical reaction is based on a flow of energy.  Provide more energy and you can then make the reaction faster, as the energy is more abundant to allow the compounds to react, and each molecule will then get to the proper energy level required to react at a faster rate.
402851
Thermal convection involves the transfer of heat away from something warm by action of the air in contact with it.  This occurs because the air near the object is heated by direct contact with it.  As a gas, the air molecules move faster when heated and drive the nearby molecules farther apart.  This makes the number of molecules in any particular volume become less that the more distant, cooler air.  Thus the density of the heated air becomes less, making it buoyant compared with the cooler air.  Thus, gravity makes the warm air rise away from the warm object, carrying away some of its heat.  The process continues as new, cooler air then comes into contact with the warm object.
815552
It's all about quantum mechanics. Molecules can have a temporarially set speed at which they rotate, expand and contract, or move, but they can not go just a little bit slower or a little bit faster, their speeds are constant unless there is not enough energy to stay at a speed, or enough to "jump" speeds. I believe Philip Ball can describe it best:\n\nWhen a molecule absorbs light, it's energy increases- it gets "hotter," by which I mean that the molecule may shake, jiggle, or spin more vigorously. It is then said to have been "excited" by absorption. The reason why molecules absorb photons of light at some frequencies but not at others is that their motions are determined by the rules of  quantum mechanics, which place restrictions on which motions are allowed. We saw in chapter one (My note: I'm typing this straight from the book, but I can't show all of chapter one) that the electrons in atoms and molecules are not free to adopt any old orbit around the nuclei, with correspondingly arbitrary energies; instead, they are confined to a ladder of specific energy levels, with the energies in between the rungs being forbidden. The electronic energy levels are said to be quantized. In the same way, the energies of the motions that the molecules execute in space may also be quantized. The two-atom oxegyn molecule O2 for example, both rotates (tumbles end over end) and vibrates (the bond between the two atoms stretching and contracting) in free space. The energies associated with these motions may take only certain values, forming a ladder of energy levels like those for the electron energies. As the energies of rotation and vibration depend respectively on the speed of rotation (the number of revolutions per second, say) and the frequency of vibration (the number of in-and-out oscillations per second), the latter two quantities are quantized too. The o2 molecule, terefore, can vibrate only at specific frequencies and spin only at specific speeds. \n\nPhew, that was alot of typing! Yes, I did get that straight out of the book, I didn't copy-paste. He then goes on to explain how the larger an object is, the colser the energy levels are, so there is no real "forbidden zone", and therefore the object can accelerate gradually.\n\nEdit : Sorry about the typos, I'll pick them out as I find them.
978480
Yes, in some specific circumstances, hotter water freezes faster than colder water.  All explanations are still hypotheses and there is no fully proven explanation yet for why.  It's known as the Mpemba effect.
629453
warm water dissolves ice faster than warm air because it can transfer and absorb heat faster than warm air of the same temperature
255271
Yes you are correct.Different substances are different because of  their molecular structure and the constituents of each molecule. Molecules are well bound together in solids than in fluids (gases and liquids). The molecules are free in gases.\n Further the molecules are not at rest and are in vibrations.When the substance is heated  the average energy of a molecule  increases which tend to decrease the bindings of the molecules.\nGenerally by heating , a substance  chnges from solid to liquid and then to gaseous state.We call this as physical change.\nWhen the energy is  strong enough to break the  molecules into its constituent elements new compounds are produced we call it as chemical change.\nIn effect heat  has many things to do with their bondings
71275
Heat is the kinetic energy of molecular motion. The molecules of a hot object are in rapid motion; the hotter, the higher the average speed and the greater the thermal energy. If the object is gaseous the motion consists of free-path travel and collisions with other molecules. If it is liquid the paths between collisions are shorter, and if solid the motion is vibrational with no secular movement.
770931
yes the kinetic velocity is incresed....due to the phase change...this is why we give energy for the liquid to vapourise to increase the energy of each molecule and seperate them ...for the motion to be faster
718611
The soda has more heat than the ice.  Heat energy travels from areas of greater heat to lesser heat.  The heat energy in the soda leaves the soda to go to the ice which in turn melts the ice, and leaves behind a cooler soda.\n\nHeat moves....cold doesn't.
183221
All molecules above absolute zero (0 Kelvin or approximately minus 273 degrees Celsius) have some form of heat energy (aka enthalpy).  This is distributed over four different types of "motion".  These are known as Translational, Rotational, Vibrational and Electronic.  To effect each of these takes increasing amounts of energy   \n\nYou've asked about Translational energy.  Heat energy gets converted to kinetic energy.  When there is insufficient kinetic energy (ie: too cold), molecules remain as solid (frozen) in a lattice. Once the melting point has been reached then the molecules have enough kinetic energy to break from their solid structure and can move freely about one another (liquid).  If enough heat energy is applied that individual molecules have enough energy to escape one another, then they boil off and become a gas.  Different gases have different boiling points.  Water boils at 100 degrees Celsius to become steam.  Nitrogen boils at something like minus 170 degrees Celsius.  So, at Standard Temperature and Pressure, 298.15K (25 degrees Celsius) and 760mmHg (1 Atmosphere), Nitrogen is roughly 200 degrees above boiling point.  This is why it can move so fast.\n\nRotational Energy: As the name suggests, energy required to spin a molecule about an axis such that, while spinning, it changes orientation (ie: N2 is a linear molecule so spinning on the axis along the triple bond doesn't count).\n\nVibrational Energy: Energy spent bending molecules (they do that too!)\n\nElectronic energy: this one is less motion of the molecule than of the electrons jumping orbitals.  Electronic energy is responsible for things like fluorescence and, if too much energy is applied to a molecule then the bound electron can escape and break the bond (resulting in degradation of the molecule).
785758
Any mass of gas has temperature T. That means that the gas molecules have average kinetic energy of E=E1=m1*v1^2/2=E2=m2*v^2/2 no matter what molecules are present in compound.\nThus E1/E2=1=(m1*v1^2)/(m2*v2^2) or v1/v2=sqrt(m2/m1)=sqrt(13/12)=1.04; hence the ‘lighter’ would move 4% faster than ‘heavier’.\nTo be more particular you have to consider rotation of molecules and their thermal capacities, but these effects are not substantial in our case.
468561
In terms of molecular motion, molecules of a gas have higher kinetic energy (moving energy)than molecules of a solid do.\n\nBecause molecules of a gas have higher kinetic energy, they always move fast and they don't stay solid at any particular moment you observe (that's why you can walk through gaseous environment because molecules of a gas don't stay into a solid layer to stop you). Because they are freely moving like that, it will be energetically favorable to dissolve gas into other medium.\n\nIn contrast, molecules of a solid stay connected to each other (crystal lattice,...). When you want to dissolve a solid to other medium, you have to break up the bonds between molecules of the solid. Breaking up molecular bonds is energetically unfavorable; in other words, it takes up energy to break up chemical bonds and energy is not always available to do that. In the case of molecules of gas, they're already freely moving so at some moments, they just wander off and dissolve.
936982
http://www.badastronomy.com/mad/1997/hightemp.html\n====================================\nThis is actually not an easy question! It depends on what you mean by temperature. Here on Earth, in our cozy blanket of air at one atmospheric pressure, we think of temperature as how hot something is. But on a microscopic level, that really means how vigorously molecules and atoms are bumping into each other. The faster they move, the harder they bump, and the higher the temperature. \nHowever, have you ever wondered why water at 70 degrees Centigrade might scald you, but air at that temperature won't? Air is less dense than water, so it carries less energy total even if the temperature is the same. The atoms are jiggling just as fast, but there are fewer of them. \n\nI bring this up because there can be ridiculously high temperatures in the Universe, but they don't mean much! For example, the Voyager probe measured a temperature of over one billion degrees in the magnetosphere of Uranus. Imagine! But really what it was measuring were particles moving extremely quickly. If you stood (well, floated) in Uranus' magnetosphere, you wouldn't suddenly vaporize. On the contrary, you'd freeze! The particles may be very very hot, but there simply aren't enough of them for them to heat you up. \n\nSo to answer your question, probably the hottest temperatures reached in the Universe today are in the cores of supernovae (stars that explode), or possibly in the mysterious gamma ray bursters, extremely energetic explosions the cause of which no one knows. But the hottest temperature of all time would have been the Big Bang: since it had all the matter and energy squeezed into one point, it must have had nearly infinite temperature! \n==========================================\n\nhttp://www.phys.utk.edu/sorensen/pub/PAD_CV.htm\n\n Based on data from CERN in Switzerland we have finally been able to detect the emission of direct photons from heavy ion reactions. The implications of this discovery are huge. First of all: based on the slope of the transverse momentum spectrum we can deduce, that the photons are emitted from a fireball at a temperature above 300 MeV, which must be the hottest temperature ever measured of any object!! A temperature of 300 MeV correspond to a temperature of more than 5 trillion degrees on the Fahrenheit scale. More importantly, this discovery strongly suggests that the so-called Quark Gluon Plasma must have been created in the early stages of the fireball. Our discovery was prominently featured during the press conference at CERN in Spring 2000 and was mentioned in the front page feature in New York Times describing the potential discovery of the Quark Gluon Plasma at CERN. Phys. Rev. Lett. 85 (2000) 3595
327488
hi,\n\nas i remember:\n\n - molecules behave as rigid objects (spheres, if you like)that move according to newtonian physics\n\n -  collisions between molecule/molecule and molecule/container are perfectly elastic (i.e. energy is conserved in all collisions)\n\n  - the size of the particle is much less than their typical separation (i.e. collisions are infrequent).  this leads to the related feature that there are no long-range interactions betweeen molecules.\n\n - the average kinetic energy of a collection of molecules is a function of only the temperature.
426143
Ice floats on water because it is less dense than water.\n\nAs water cools past 5 degrees celsius, the density of the water actually decreases.  Since ice is water molecules at <0 degrees celsius, it is less dense than liquid water ( greater than 0 degrees), so it floats.\n\nfrom a molecular point of view, the H2O molecules in ice is equally spaced apart, whereas H20 in liquid state are able to slide past each other (i.e. closer to each other), so it is more dense than ice.