To make our experiment we need a plastic bottle of 1.5 liters, a sheet of paper and some matches. First is a pair of holes in the plastic bottle at the beginning and another near the glass. Then take the sheet and cut a rectangle of 10x15 cm. Roll of paper for a small cylinder about 15 cm long. Finally the tube is inserted through a hole above the paper bottle. When you turn on the tube of paper with a match is made and a small flame is observed, on the other end of the tube leaving a dense column of smoke, falling into the bottle. On the outside, no smoke. If you cover the bottom hole with a finger to see how the smoke comes out next paper. Explanation: By burning the tube portion of the paper is apparent in the form of particles with gases that are formed during combustion and the air is smoky. Under normal circumstances, the smoke is drawn to the burning hot air (convection currents) In our experiment, the smoke that is produced inside the tube along its journey. Inside the bottle is not hot air, so that when smoke comes out the bottom end of the tube there is no convection and upwelling of smoke (more dense than air) precipitates at the bottom of the bottle.
Barnutiu S, Blaga A, Gaidos C, Chira F, Temes C
Scoala Gimnaziala "Gheorghe Lazar" , Zalau, Romania