ONLY FOR GROUP 3

by Spain 1 group 3

We can’t see the glass stick because in the bottle there is glycerin. The glycerin and the glass as a material have got the same refractive index. And if they have the same refractive index, we can only see one thing we can't distinguish them: everything happens as if there is only one medium. In this case the bottle. So, we can’t see these two things, we can only watch see the glycerin. And it is similar to water because it is transparent.

OK (2nd Revision). N.Hoang

Spain 1

(Pais Vasco)

by French group 3:

  When the glass is turned upside down, the pressure forces that are applied towards the glass' opening part aren't compensated. The weight of water inside the glass (downwards) is much weaker than the the pressure forces (upwards). Hence, the intensity of the pressure force is strong enough to keep the water inside the glass. Due to the atmospheric pressure, the water doesn't fall off the glass. Water is not solid. When water drips, some air bubbles can create in the liquid, and this in-draught allows water falling off of the glass when the card has disappeared. Thanks to the card, the creation of bubbles within the liquid is stopped. Therefore, to be able to fall, the water contained has to struggle with a pressure force almost a hundred times bigger than its own weight.

To be reviewed

I don't agree totally with your explanation...unless it is not clear. See this website http://culturesciencesphysique.ens-lyon.fr/ressource/QSpression.xml

N.Hoang

2nd revision

by Spain 2 group 3

Barium hydroxide in liquid state when reacts with carbon dioxide produces barium carbonate, it is a white solid substance. When CO2 is introduced into the Ba(OH)2(aq) solution we can see white precipitate forming at the interface between the source of the CO2 and the aqueous solution. 

OK

ML Tibaldeschi

Spain 2

(Valencia)

by Italian group 3

If you prepare an aqueous extract of red cabbage leaves you can observe color change in the solutions having different pH.

Some substances are classified as either an acid or a base. Think of acids and bases as opposites—acids have a low pH and bases have a high pH. For reference, water (a neutral) has a pH of 7 on a scale of 0–14. Scientists can tell if a substance is an acid or a base by means of an indicator. An indicator is typically a chemical that changes color if it comes in contact with an acid or a base.

As you can see, the purple cabbage juice turns red when it mixes with something acidic and turns green when it mixes with something basic. Red cabbage juice is considered to be an indicator because it shows us something about the chemical composition of other substances.

What is it about cabbage that causes this to happen? Red cabbage contains a water-soluble pigment called anthocyaninthat changes color when it is mixed with an acid or a base. The pigment turns red in acidic environments with a pH less than 7 and the pigment turns bluish-green in alkaline (basic) environments with a pH greater than 7.

Red cabbage is just one of many indicators that are available to scientists. Some indicators start out colorless and turn blue or pink, for example, when they mix with a base. If there is no color change at all, the substance that you are testing is probably neutral, just like water.

The water dissolves certain pigments found in red cabbage, the '' anthocyanins '' (or'' Anthocyanins ''), which can function as pH indicators, assuming different colors in the presence of acidic or basic substances. So if you put a lemon in a vial of liquid of red cabbage the liquid changes color and becomes red because the acidity of lemon is between 2 and 3. While if you put a substance less acidity like bicarbonate the liquid becomes blue.