When the temperature is colder, is the air less dense or more dense?

Question

When the temperature is colder (or when it decreases), is the air less dense or more dense?

Answer 1

Air density is the number of gas molecules in a given volume of space. When air is cooled, the molecules slow down and require less and less space. When air is heated, the molecules move much faster, bounce off each other with much more energy, and require more space.
You can demonstrate this for yourself:
Take three balloons. blow them up so that they are the same size (and hold roughly the same amount of air).
Place the first on in the freezer for about half an hour.
Place the other balloon in some hot water (be careful!)
Leave the third balloon at room temperature. This is your control.
Compare the three balloons. Compared to the control (room temperature) balloon, the frozen balloon will have shrunk in size (less volume), while the heated balloon will have expanded (greater volume).
Each balloon contains roughly the same amount of gas molecules.
The cold balloon now has more air molecules per cubic unit of space and has become more dense than the control.
The heated balloon has grown in volume, and there are fewer air molecules per cubic unit of space, and it has become less dense.

Answer 2

Denser, of course.
To illustrate this: In Johannesburg, South Africa, when the B-747 was ready to take off for its flight to Frankfurt, Germany, it sometimes waited a couple of hours on the ground. Yet passengers landed earlier in Germany.
That is because, in the summer, it gets very hot there and it usually ends by rain showers that cool down the air. With cooler and denser air, the aircraft can carry more fuel and doesn't need to land and refuel underway, thus landing earlier in Frankfurt.

Incidentally, all aircraft instruments are calibrated to the Standard Atmosphere, which is 15 degrees centigrade. So yes, we fly lower in the winter. But not that much that it matters for safety.

Answer 3

As the temperature decreases, the particles dont move as much and are closer together, so the material is more dense.

Water is a special case; when water freezes, it actually expands and becomes less dense. This is because of the way the water molecules position themselves into a lattice.

Answer 4

Air molecules in hot air have more energy and move faster. This means more of them collide with each other, forcing air to expand. Expanded air is less dense than thicker cold air.

Answer 5

Humid air will be dense and dry air will be denser .This is because humid air is lighter than dry air.Humid air is already less dense and it will reach dence status on cooling whereas, the dry air is already in dense conditon and it will become more dense on cooling.

Answer 6

In S.C.I think that it depends on the humidity,weather it is high pressure or low pressure and if you are a G.Bush fan or you listen to stock car races on the radio or what you had to smoke,on and on and on and ?Never mind.

Answer 7

Cold- more dense
Hot- less dense.


But i dont get that when it comes to ice cubes, because ice cubes float..

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