Air has a mass: An "empty" bottle is full of air: You can see and hear air flowing out of an ampoule, when you hold it under water. When you discharge a bottle of bear or an ampoule with soap water gas bubbles are formed inside.
Using a 50-ml syringe and a digital scale you can measure the mass of air.
 
 
Material + 50,0 g weight
Syringe without air
Syringe with 50 ml air

5. Scales and syringes: Weighing air
Material (left photo)
sterile disposable syringe (50 ml), transparent sticky tape, stop-cock for closing, digital pocket scale (70g/0,01g), weight (50,0g), nail (5 cm), tongues, candle, matches, beaker with water.
Preparation of the syringe
1. Protect the marking of the syringe by covering it with transparent sticky tape.
2. Tightly screw an open stop-cock into the syringe. Fill it with 50 ml of air.
3. Heat a nail above the flame of a candle. Press it through the piston to fix it at the 50-ml mark.
4. Remove the nail. Press the air out of the syringe.
 Experiment
5. Close the stop-cock. Pull the piston to the 50-ml mark.
6. Fix it in this position pressing the nail through the hole in the piston..
7. Weigh the "empty" syringe on a digital pocket scale (Photo 2). Write down the mass.
8. Take the syringe from the scale. Open the stop cock. Re-weigh (Photo 3).
9. Repeat 5. and 6.
10. Dip the syringe with the stop-cock under water. Open it.
 Write down you observations, explain them.

back.............. ......,,....first publication: 22.01.2009.. ..................... last modification: 08.04.2010