# How to weigh air

Density other than zero, not only solid substances and liquids, but also gases and also their mixes possess. It belongs also to usual air. If desired and existence of the corresponding equipment it can be weighed.

## It is required to you

• - tight, strong and not fragile vessel;
• - gate;
• - scales;
• - manometer;
• - vacuum pump;
• - tubes.

## Instruction

1. Take a tight, strong and not fragile vessel of the known volume. Open the vessel gate that its volume was reported with the atmosphere. Weigh it. The mass of the object will become result of measurement.

2. Connect a vessel to the vacuum pump. Pump out air up to the pressure about of one tenth atmospheric (10 in 4 degrees of Pa) that existence of molecules of gases in a vessel could be neglected. It is difficult to carry out pumping up to the smaller pressure in the conditions of usual laboratory. Close the gate.

3. Disconnect a vessel from the vacuum pump, and then again weigh. The pushing-out air force will reduce force operating from a vessel on a scale a little therefore the difference between the mass of the vessel and mass of the atmospheric air raising it will become result of measurement. The last is equal to the mass of the air which is in it before pumping out.

4. Open the gate, and the vessel will again be filled with air. You will subtract result of the second from result of the first measurement. You learn the mass of the air which is located in a vessel.

5. To learn vessel volume, completely fill it with water. After that pour out all water of it in measured capacity. Determine the volume of this water by a scale of measured capacity.

6. Transfer the mass of air and volume of a vessel to the SI system. Divide the first size into the second. You determine air density in kilograms on cubic meter.

7. Learn the current value of atmospheric pressure by means of a barometer. Write down with what pressure air density is measured. If desired take additional measurements in other days when pressure changes. Include results of all measurements in the table. Consider that density of air depends not only on its pressure, but also on structure. For example, the cities in it contain more heavy carbon dioxide. But influence it is so insignificant that it is possible to measure it not always.

Author: «MirrorInfo» Dream Team