Does smoke rise or goes down?

To make our experiment we need a bottle of plastic of 1´5 litres, a sheet of paper and a few matches.

First we make a couple of holes in the bottle of plastic, one in the top part and another one near the base of the bottle.

Them we take the sheet paper and cut away a rectangle of 10x15 cm (10 times fifteen). We coil the paper to obtain a small cylinder of approximately 15 cm of length. Finally the small tube of paper interferes for the top hole of the bottle.

On having ignited the small tube of paper with a match a small flame is formed and is observed that for another end of the bead goes out a column of very dense smoke that falls down inside the bottle. In the exterior scarcely there is smoke.

If we cover the low hole with a finger, the small tube of paper goes out and smoke doesn’t go out.

Explanation:

On having burned the small tube it departs from the paper it is clear in the shape of particles that, together with the gases that formed in the combustion and the air they form the smoke.

In normal circumstances, the smoke ascends dragged by the warm air of the combustion.

In our experiment, the smoke that takes place is produced in the interior part of the small tube travels along it. Inside the bottle, there is no warm air, so that, when the smoke goes out for the low end of the small tube there aren’t produced rising currents of convection and the smoke, denser that the air, it rushes to the bottom of the bottle.

by Clara, Beatriz and Inés

Spaghetti tightrope walker

Material: one spaghetti


1 Stand the spaghetti placed about your two hands.
2 It moves slowly one of the hands towards the other one without inclining the spaghetti.
3 Regardless of the hand that moves the two end up together in the center of the spaghetti that will remain in balance without falling.

Explanation:

By moving the hands, spaghetti slides without falling, keeping the gravity center between the fingers.

by Antonio and Antonio

A bottle with a hole

In order to make our experiment, we only need a bottle of water with it’s cap.

We make a small hole in a plastic bottle, about a half of its height, and we fill it full of water, while we are covering the hole.

If we remove our finger from the hole, no water comes out, but if we remove the cap of the bottle, the water starts to come out. But why?

If the cap is put, the internal pressure on the hole is equal to the external pressure and that’s why the water doesn’t come out of the hole.

But, if we remove the cap, we allow that the air comes into the top of the bottles, breaking the previous balance. The internal pressure on the hole is greater than the external pressure, so the water comes out of the bottle.

by Irene and Rafael

Fakir baloon

This is an experiment where we can see that if the same force is distributed over a bigger surface then pressure is smaller. Since what makes the balloon explode is pressure, the more "punaises" lesser will be the pressure exerted on the balloon. With only one "punaise" the balloon will explode.

Reaction of Sodium and Water

The helicopter

Cartesian Diver