looking for why smoke rises in the heat and why it falls in the cold, must be good for college paper.?
139288
I think this would be a good topic for a college paper, especially if you go into the details and work it all out carefully. \n\nThe previous answer is correct. I might add a few comments to help, however. \n\nIt comes down to density, and buoyant forces. If there is an unbalanced force against something, then it will accelerate because of Newton's second law. If the force from below on a parcel of air is less than the force of that parcel of air downwards (due to its weight, and pressure from air column above), then the parcel of air will sink. And if the force from above is less than the force from below, the parcel of air will rise.\n\nThe smoke is composed of gases and suspended particles in the air that can be quite small (small enough to be about the same size as the wavelength of light, and cause selective scattering, creating phenomena such as a blue moon). \n\nTherefore, smoke can rise or fall, depending on the forces acting on a parcel of air containing the suspended smoke particles. \n\nThe density of the air, and the pressure it exerts, depends on the temperature. A good first step is to assume that the air parcels satisfy the Ideal Gas Law, PV=NRT, where P is the pressure of the parcel, V is the volume, T is the temperature,  R is the universal gas constant, and N is the number of molecules. \n\nThe pressure at the bottom of an air column of uniform density gas of height h is rho*g*h, where rho is the density and g is the acceleration of gravity. \n\nThere is a lot of material about this on the internet and in other places. Hopefully our comments are enough to get you started on this, so you can analyze this carefully and write a nice paper.\n\n----------\n\nAddendum:\n\nAs the next answer states, and as in the reference, the constant n is typically used for number of molecules and the constant N is typically used for number of moles. I apologize.\n\nSo it is \n\nPV=NRT, or alternatively, PV=nkT\n\nwhere k is the Boltzmann constant. See the reference attached.
228532
Cigarette 730 770 776 84o\n\nThe temperatures of centrally ventilated cigarettes are somewhat lower (10-20 deg.C.)
959596
It's 55 degrees in Massachusetts today! What arctic air? Still a heatwave by my standards. Everything I know about canadians I learned from watching Trailer Park Boys.
696793
I graduated a few years ago and I do not smoke, but I hope you can use this:\nMy brother smokes (tobacco and pot) and is attempting his junior year for the 2nd time. His GPA is a 2.0. My sister and I never smoked and graduated with 3.5 and 3.6 respectively. My sister is a vet tech and a sophmore in college and I have a bachelors in organic chemistry. I cannot work at the moment, as I am pretty pregnant, but I was working as a paramedic.\n\nGood luck with your project!
933014
All decent explanations so far; I hope I can add to what has already been posted.\n\nLiquid and Ice most definitely can exist at the same temperature and Ice can be and often does get colder than 0C.\n \nFirst of all the Triple Point of water is the pressure and temperature at which Ice, Liquid Water and Water Vapor exist at the same time in equilibrium.  Vapor is the right word, not steam although you can argue that the only time that Water Vapor and Steam are the same thing is at a very low pressure.  The Triple point of water only happens at a near perfect vacuum, 0.0063 ATM to be precise.\n\nAdding Salt to water will lower the freezing point, but then it isn't water anymore, it's salt water.  Even so, Liquid Salt Water and Ice Salt Water can also exist at the same place and time at the same temperature, slightly below 0C.  But let's stick to water.\n\nIce can easily be lower than 0 degrees.  Consider a bucket of water, liquid water sitting outside and the air temperature is -10C.  Little by Little, as the liquid reaches 0.0098 C, liquid starts to become ice.  The ice crystals form in the bucket, around the walls of the bucket and on the surface first.  The air is still -10C so the bucket, the liquid and the ice will keep getting colder.  The ice on the surface will drop to slightly below 0C but very slowly since it is still absorbing the heat of the not-yet-frozen water.  Eventually, the entire bucket of water will be frozen and will be just below 0C.  First the walls of the bucket will reach -10C (same as the air tempertaure).  The ice near the walls of the bucket and on the surface will reach -10C first, continually absorbing the heat energy from the relatively warmer ice near the center of the bucket.  Until finally, the entire bucket of ice is steady at -10C.  That is until the sun comes out or the day gets warmer.\n\n\nAnd by the Way, dry ice is not water, it's frozen CO2 (Carbon Dioxide)\n\nOne more thing, at a near perfect vacuum, you can actually cool liquid water to less than 0C without it freezing.  Never tried that but I did accidently freeze a beer last night...
819795
Sorry I'm the kind of teacher you parents despair of because thats the kind of home work I'd set.  My class have to design and make a thermal insulator to stop ice melting this week!!!\n\nTry this link it might help\nhttp://www.volcanolive.com/model.html
757999
Hot smokey air rises, cleaner air with more oxygen is lower.  Maybe just enough to get out.
933723
You don't need a chemical reaction.\nFrozen carbon dioxide, known as dry ice, can do the job.\nIt's in a thermos container, but as soon as it touches the air, it sublimates into gaz, producing the smoke. (To make more, put it in water instead.)  And it's heavier than air, so it stays close to the ground.  And it's not expensive!
376885
The heat causes waves in the air that affect the passage of light becuase the density is different than the surrounding air.  Same happens if you look at the fron of an  air horn like at a football game. But it's the opposite, it's caused by extreme cold.
113745
You should be able to find the answers on these web pages:\n\nhttp://www.uni.edu/~iowawet/H2OProperties.html\nhttp://dl.clackamas.cc.or.us/ch106-06/thermal.htm\nhttp://daphne.palomar.edu/jthorngren/latent.htm
689682
check this site. it might help.. though i think this is a course outline for fire fighting students
838604
If you trust yourself not to burn the place down, you could light some candles. The flame will burn the carbon particles in the smoke and make it clear up quicker.
194124
Because the air spreads out, and as it spreads out it retains less heat.\n\nAnd while cold air does sink and hot air rises, as cold air does get lower in altitude it warms up, and hot air cools as it rises. \n\nI live in the foothills west of Denver so I see the rising/falling air thing firsthand. In the winter we get this air that 50 miles to the west was part of a blizzard. As it descends the mountains, it dries out and heats up sometimes bringing temperatures in the middle of the winter into the 60's or 70's.
219472
Because cold air has a tendency to sink !!!
525325
The clouds trap the heat.  Heavy cloud cover makes for warmer temperatures and higher humidity.  Less cloud cover is the opposite.  Er go the phrase "clear and cold".
137459
Differential heating causes hot air to rise and other air has to take its place so that in turn causes wind.  Weather is very complicated and is affected by many variables.
1063614
It is not air that takes a spherical shape in water but rather the water forces it to take that shape. This is because of surface tension - the same reason why drops of water tend to be shperical. It is the state with least potential energy implying the most stable state.\nIn case of smoke in air, the same thing does not happen as neither air nor smoke does not have any surface tension (being gases, rather mixtures of gases, they are not cohesive unlike water or any liquid for that matter). The simply diffuse into each other randomly (and aided by air currents) however, smoke being a hot mixture of gases, tends to rise higher, hence the wierd upgoing patterns formed by smoke.