Experience the mesmerizing feel of watching a lava lamp, with its large colored bubbles sinking, rising, and morphing.
The action you see is caused by the density and polarity of the substances.
Density is the measurement of how compact a substance is – how much of it fits in a certain amount of space. Because water is more dense than oil, it will sink to the bottom when the two are put in the same container. Density is also affected by temperature – the hotter the liquid is, the less dense it will be.
Polarity prevents oil and water from mixing together. Water molecules are “polar” because they have a lopsided electrical charge that attracts other atoms. Just like in magnets opposites want to attract allowing water to mix with other liquids. Oil molecules are non-polar, they don’t have a positive or negative charge, so they are not attracted to the water molecules at all. This is why oil and water do not mix!
The Alka-seltzer reacts with the water to produce carbon dioxide gas bubbles. These stick to the water droplets. The water/gas combo is less dense than the oil, so they rise to the top of the flask. At the top, the gas bubbles pop and escape into the air, allowing the dense water to sink back to the bottom again.
Be sure to ask for permission and ask for help when you need it! Have fun and be safe!