You will need:

• Alka-Seltzer tablets
• Cooking oil
• Food colouring
• A glass jar, cup, or clear plastic bottle
• For extra spooky fun, you can also add some ‘spider leg’ chocolate sprinkles!

Step 1: Fill your container 2/3 of the way with oil

Step 2: Add water until the container is ¾ of the way full. The water should settle at the bottom of the container.

Step 3: Add drops of food colouring one at a time, as many as desired

Step 4 (optional): Add the chocolate sprinkles

Step 5: Drop in an Alka-Seltzer tablet and watch your potion begin to brew!

The science behind it:

Water is a polar molecule, meaning that one end of the molecule is positively charged while the other end is negatively charged. Oil is a nonpolar molecule. Polar molecules only interact with other polar molecules, and the same goes for nonpolar molecules. So when a polar water molecule and a nonpolar oil molecule meet, they ignore each other completely, and the two liquids separate!

Alka-seltzer tablets are made of bicarb soda and citric acid. In their solid tablet form, the two chemicals remain separate. But when the tablet is dropped into water, the bicarb soda and citric acid combine to create carbon dioxide gas! When the gas rises, it takes some of the water (and spider legs) along with it.

Once bubbles of water and gas reach the surface of the, the gas escapes and the water falls back to the bottom of the beaker. Because no water is lost during the process, the reaction can be repeated again and again with a new tablet!