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

Ball in the air

The air stream doesn't allow the ping-pong ball to fall.


http://www.youtube.com/watch?v=mExwPCvNRJ0

An eddy in a bottle

To make our experiment we need two plastic bottles of one and a half litres.

First, drill a hole in the two bottles corks.
Then, fill one of the bottles with water to about three quarters and join the two plugs per cylinder.
To unite the two bottles it can be used a tape.

It is very important the union between the bottles.

When the water on the bottles is empty is upper, it seems that the water does not fall easily to the bottle bottom, but if we give a circular motion to the bottle top and creates a swirling, water falls easily.

By placing the bottles on top, water doesn’t fall to the bottom because of the compressed air trapped in the bottle which is down. It can pass through it, as there is no room for it.

When the eddy is generated by moving the top bottle, it is communicated the air in both bottles and the water in the top bottle falls easily into the bottom bottle.

by Yulia

Ruler and newspaper

To make our experiment we need a ruler made of plastic, a sheet of newspaper and a heavy object.

First we place the ruler on a table so that the middle part of the ruler is on the edge of the desk. If we drop a heavy object on the part that stands out we see that the ruler falls down from the table.

We repeat now the experiment by placing a newspaper sheet extended on the part of the ruler that is on the table. If we draw now the same object on the part that stands out we see that the ruler doesn't fall to the floor.

What makes the ruler stop? Is it an invisible hand or perhaps the weight of the newspaper sheet?

The correct answer is the pressure and the strength in the atmosphere on the newspaper sheet.

It´s very easy and you can do it at home. Will you do it there?

by Marta and Claudia

The water that is not wet

To make the experiment we need:

1) A glass
2) A piece of paper
3) A big countainer with water

We have to fill a countainer with water, then we put a piece of paper at the botton of the glass so that, it won´t fall when we turn it down. Later,we turn round the glass and we put it with the paper into the borron of countainer. It´s so important not to till the glass.

Finally, we take the glass out of the countainer and we check that the piece of paper isn´t wet.

The explanation is quite simple the air contened into the glass blocks the water to enter and arrive to the piece os paper which is at the botton of the glass.

by Marta and Isabel

An eddy in a bottle

In order to make our experiment we needed two plastic bottles of 1´5 liters.

In the first place, we perforated a hole of 1 cm in the corks of the two bottles. Soon we filled one of the bottles with water until approximately three fourth parts and if united the two bottles by the corks. In order to unite the two bottles insulating tape can be used. Is very important a good union between the bottle.

When the bottle with water is on the empty bottle it is observed that the water does not fall easily to the inferior bottle, but if we give a circular movement to the superior bottle is generated an eddy and the water falls easily.

When placing the bottle in the superior part, water does not fall by the little compressibility of the air locked up in the inferior bottle that does not leave space to the water that falls. When the eddy is generated when moving the superior bottle, it is put in communication the air that is in both bottles and the water of the superior bottle falls easily in to the inferior bottle.

Colegio Sagrado Corazón (Esclavas)
Sevilla (Spain)