WHAT IS POLARITY?

You probably noticed that oil and water don’t mix. And the reason is a property called polarity.

We say that molecule is polar when there is a difference between electronegativity of its atoms. Electronegativity is a very important chemical property that tells us how easy is for an atom to receive electrons. Nonpolar molecules have no or very small difference in electronegativity of its elements.

But how is polarity connected to the fact that water and oil don’t mix?

Well, water is a polar molecule (hydrogen and oxygen form polar bonds) and oil is a nonpolar molecule (consisting of hydrogen and carbon which are of similar electronegativity).

Polar and nonpolar molecules really don’t like each other (they can’t form any chemical bonds) so they stick to their own group.

SCIENCE BEHIND THE LAVA LAMP EXPERIMENT

When we drop food coloring into the bottle, it doesn't mix with oil, but it does with the water. How come? It’s again the polarity thing. Colors are made of polar molecules, so they mix only with other polar molecules. We say that “like dissolves the like”. So if you remember that water is a polar molecule, anything that we can dissolve in it (like salt or sugar) must also be a polar molecule! Anything that dissolves in oil is nonpolar.

About Fizzing tablets

Fizzing tablets contain baking soda and citric acid. When they mix with water, they make carbon dioxide which we see as the bubbles in the water. Since it is a gas, it tries to escape the bottle so it moves upwards and on the way, it picks up some colored water. When it reaches the surface, it escapes, but the colored water returns all the way down to the other water molecules.