Lab2. Vulcani visti da dentro

Ingredienti: Una bottiglia di olio vegetale

Un barattolo di vetro

Acqua

Colorante alimentare

Una pastiglia di Alka-seltzer, o di un altra sostanza effervescente.

Procedimento: 

Riempire il barattolo di vetro per 1/5 di acqua 

Aggiungere alcune gocce di colorante alimentare 

Riempire il resto del barattolo con olio vegetale

Aspettare qualche minuto fino a che acqua ed olio non saranno ben separati 

Lasciar cadere nel barattolo la pastiglia effervescente 

Cosa avviene? 

Water and oil aren’t exactly the best of friends. Because of their shape and the way their atoms stick together, they prefer keeping to themselves rather than mixing with one another. The Greek root for water is ‘hydro’, so we say that water is ‘hydrophilic’ (loves water) while oil is ‘hydrophobic’ (afraid of water). Because a drop of water has more mass than the same sized drop of oil, gravity pulls on it with more force, pulling it to the bottom.

Fizzing tablets contain a mix of chemicals, including sodium bicarbonate and citric acid. Nothing happens when they’re added to oil, but when added to a solvent like water, the sodium bicarbonate separates and reforms with the citric acid to form sodium citrate. In the process, it also creates some carbon dioxide gas and a few water molecules. In your jar, the tablets reacted once they had sunk down into the water at the bottom, where they created bubbles that trapped and carried drops of water up through the oil to create your lava-like eruption.