ONLY FOR GROUP 9

The coulour of the ink depends on the acid/base properties of the medium. In fact, the tap water is slightly alkaline (base)  and when the ink goes there, it mixes with the water and becomes transparent. The vinegar, as it is an acid, brings back the colour of the ink again and when you put the baking soda, as it is a base, it neutralizes the vinegar (and then the medium becomes alkaline) and the color of the ink dissapears again as the first time.

OK. 2nd revision (I 've made some corrections by myself). N.Hoang

Spain 1

(Pais Vasco)

Material used:

-Wool

-A can

-A balloon

We've watched your video and we think the can moves because of static electricity. When you scrubbed the balloon with wool, electrons moved. 
One was neutral (the can) and the other one (the balloon) had got a positive or negative charge. Let's imagine the balloon had now more electrons (so was negatively charged), the can electrons went to the opposite side, and near the balloon side, there was more positive charge so it results that they attracted each others (and, it seemed to be a little bit inclined ^^'). because two opposite charges attract themselves

in fact, in the can (globally neutral), the electrons move so that the part of the can next to the balloon present an opposite charge to the balloon. That's why these 2 objects are attracted (2 opposite charges attract themselves).

OK. 2nd revision N.Hoang
 

by Spain 2 group 9

We can observe that the oil and the water make like two layers. We observe that the colored ice stays in the middle, between the oil and the water.

The oil and the water did not mix because the density of the water is bigger than the density of the oil.The ice has more density than the oil so it goes down and it has less density than the water so it floats.

Ok - (P. Sirabella)

Spain 2

(Valencia)

by Italian group 9

The movement up and down of the egg is due to the Archimedes principle: when the density of the liquid is low, then the egg goes down, but if the density of the liquid increases then the egg emerges to the surface. In fact, the Archimedes force is opposed to the gravity, and is proportional to the heavyness (i.e. density) of the fluid occupied by the egg.