Why Is Milk White?: & 200 Other Curious Chemistry Questions (2013)

Why is honey so sticky?

Hydrogen bonds make honey sticky. Earlier you learned about hydrogen bonds (page 153). Unlike other some bonds, hydrogen bonds form between molecules instead of between atoms in a compound. The attraction between honey and your fingers is due to hydrogen bonds in the honey attracting molecules in your fingers.

Honey is mostly water, fructose, and glucose. The last two are simple sugars, also known as monosaccharides. These three ingredients make up 86 percent of honey, with other sugars making up the bulk of the rest. Sugars bind well to water. Almost all of the 17 percent of honey that is water is bonded (with hydrogen bonds) to sugar, so that little water remains to support bacteria or molds. This is why honey needs no refrigeration.

The hydrogen bonds between the sugars and the water make the honey viscous, so it pours slowly and feels thick. Those same bonds make it stick to your fingers. But water also bonds to your fingers with hydrogen bonds but doesn’t feel sticky. What is the difference?

When your fingers get wet, they do tend to stick to one another a little bit more than when they are dry. But water does not stick very well to itself, so when you pull your wet fingers apart, a little water remains on each finger. The water sticks to your fingers more than it sticks to itself.

Honey sticks to itself far more than water does. You can see this when you pour the two liquids out of a cup. The honey takes a long time to pour out.

When the honey sticks to your fingers, it also sticks to itself. You have to use more force to pull your fingers apart than if they were just wet with water. We call that feeling “sticky.”