why is it that hot air rises but when you go up in the atmosphere it gets colder? hot air is less dence than cold air but cold air is above hot air... how is this?
The saying "heat rises" is an acknowledgement of the fact that warmer air has a lower density than the surrounding atmosphere, and therefore, being of lower density, it will rise. This rising is limited however - think about it - if there were no limit to hot air rising, then the entire atmosphere would float out into space. The reason it is "cold" in the upper atmosphere is actually because of a lower air density. Remember that our concept of "temperature" as measured by a thermometer is actually the energy of the collisions between atoms. If you have a high density of atoms and you put thermal energy into the system you will raise the temperature. In the upper reaches of the atmosphere, the decreasing density means that even if the temperature were constant, it would FEEL like the temperature was going down. This lowering of temperature with altitude is called the "lapse rate" and a standard lapse rate is about 3deg Fahrenheit per 1000 feet. This can change from 1-5 degrees F depending on variables like pressure, humidity, etc. If you want to learn more about it, search for information on the tropopause. Air molecules in our atmosphere are constantly in motion. They are constantly banging into each other and into things around them. When you blow up a balloon, the air molecules bang into the insides of the balloon and that is what makes the balloon expand. This motion is a form of kinetic energy. Things that moves and have mass have kinetic energy. Air molecules move and have mass, so they have kinetic energy. Air temperature is essentially a measure of the average kinetic energy of the air molecules. The faster the molecules move, the higher their kinetic energy and therefore the higher their temperature. The slower they move, the lower their kinetic energy and temperature. If they stop moving altogether, the temperature drops to Absolute Zero which is -273 degrees Centigrade. It's called Absolute Zero because that is the coldest you can get. You can't move slower than not moving at all. now there is one more concept to explain to understand why it is colder at higher elevations. It covers the conversion between one type of energy and another. In this case, it is the conversion from kinetic energy to potential energy. We already discussed that kinetic energy is related to speed. The faster something moves, the more kinetic energy it will have. Now consider what happens when you throw a ball into the air. The higher it goes, the slower it goes. Eventually, it slows to the point where it stops and starts heading back to the earth. When the ball slows down, it loses kinetic energy, but it is gaining potential energy. The form of potential energy that the ball gains is in the form of height. It took energy to raise the ball, and that energy came from the kinetic energy. So now to answer the question. When the warm air rises, the speed of those air molecules slows down just like a ball that is thrown into the air slows down. The molecules convert their kinetic energy into potential energy when they rise into the air just like the ball did. And since temperature is a measure of kinetic energy, the lower kinetic energy means a lower temperature.
oh yeah... and absolute zero is almost completely an irrelevant topic for this subject, or any for that matter, because its completely impossible to acheive and theres no way to prove that it actually exists...i think...lol
not irrelevant at all, Temperature is a physical quantity which gives us an idea of how hot or cold an object is. The temperature of an object depends on how fast the atoms and molecules which make up the object can shake, or oscillate. As an object is cooled, the oscillations of its atoms and molecules slow down. For example, as water cools, the slowing oscillations of the molecules allow the water to freeze into ice.(like in the upper cirrus clouds) In all materials, a point is eventually reached at which all oscillations are the slowest they can possibly be. The temperature which corresponds to this point is called absolute zero. Note that the oscillations never come to a complete stop, even at absolute zero. There are three temperature scales. Most people are familiar with either the Fahrenheit or the Celsius scales, with temperatures measured in degrees Fahrenheit (º F) or degrees Celsius (º C) respectively. On the Fahrenheit scale, water freezes at a temperature of 32º Fahrenheit and boils at 212º F. Absolute zero on this scale is not at 0º Fahrenheit, but rather at -459º Fahrenheit. The Celsius scale sets the freezing point of water at 0º Celsius and the boiling point at 100º Celsius. On the Celsius scale, absolute zero corresponds to a temperature of -273º Celsius. Scientists especially those who study what happens to things when they become very, very cold - commonly use the Kelvin scale, with temperatures measured in Kelvin (K). This scale uses the same temperature steps as the Celsius scale, but is shifted downward. On this scale, water freezes at 273 K and boils at 373 K. Only on the Kelvin temperature scale does absolute zero actually fall at 0 K. The accompanying diagram compares the three temperatures scales. Just because you can't see it in every day to day life doesnt mean it doesnt exist! Is it arguable? yes but so is God.
where do you get your info??? absolute zero IS when molecules completely stop.....this is why i say its irrelevant to the subject. because the subject is why its colder higher in the atmosphere... nothing on earth reaches absolute zero, therefore its irrelevant...
NO problem man do your research before you make such bold statements. Definition of Absloute zero is:Absolute zero is a fundamental lower bound on the temperature of any macroscopic system. It is a temperature of 0 K, −273.15 i½C, or −459.67 i½F. It is unachievable in practice but it exists as a limit for real physical phenomena, and it was inferred by extrapolation from kinetic theory, and from other considerations in theoretical physics.
Alternate definitions are that absolute zero is the temperature at which no further energy can be extracted from a physical body, or the temperature at which the entropy change of an adiabatic process vanishes. On the other hand, defining it as the temperature at which all motion ceases would go against quantum mechanics requirements which state that even at absolute zero SOME MOTION REMAINS!
"It is unachievable in practice".....you said it..... i also AGREE that it is a THEORY..... so i guess we're both right.....LOL
also, for arguments sake (LOL), when i say "deny it, please" i am reffering to its impracticality as it relates to EARTH, u know, that one place where $hit DOESN'T reach absolute zero.......
ditto...lol, it was actually kind of a fun argument....im glad someone on here is also decently educated and willing to call me out when they spot something that doesnt seem right....lol