Halloween is such a fun holiday which inspired many spooky STEM activities. Naturally we had a Halloween teamed Girl Scout meeting, with fizzling cauldrons, bloody lava lamps, sticky Oobleck and even spooky refreshments. We explored chemical interactions between opposites such as acid and base, or water and oil.
When acid and base are mixed together, they react to neutralize each other producing water and salt. Sometimes gasses are produced, for example when vinegar (acetic acid) and baking soda (sodium bicarbonate) are mixed together water and carbon dioxide gas is produced. This reaction is super fun when it's done in a cauldron with green vinegar and baking soda.
Oil is hydrophobic, which means it doesn't mix with water. The word hydrophobic comes from the Greek words water "hydro" and fear "phobia". We observed how oil and water do not mix by making a lava lamp. The girls added colored water into a beaker with oil. The oil and water created 2 separate layers and did not mix. They added Alka-Seltzer to the beaker and observed how water droplets move in the oil layer without mixing with the oil.
Finally we mixed cornstarch with water and food color to make goopy slimy Oobleck. The girls explored how the consistency changed from a liquid to Non-Newtonian fluid and back to liquid when they added water or cornstarch. Non-Newtonian fluids change their behavior when force is applied. For example, Oobleck behaves like liquid without force, but when force is applied it behaves like solid.
To conclude our activity we had pumpkin seeds, caramel apple and spooky grape juice. Dry ice was added to the grape juice, which transformed the juice into a fizzy drink oozing a spooky fog.