# Is Water Sticky? (DD-296)

> Water molecules attract one another through hydrogen bonds. At the surface, molecules have neighbors only below and beside them, so they're pulled inward, and the surface behaves like a stretched film. That's surface tension, and water's is high for a liquid, about 72 millinewtons per meter at room temperature. Attraction between like molecules is called cohesion; attraction to other surfaces, like glass or a plant's xylem walls, is adhesion. Together they drive capillary action. Surface tension shapes drops, lets some insects stand on water and dominates fluid behavior in microgravity, where water forms floating spheres. The footage shows water beading on a coin and drops on surfaces.

- Department: Science
- First published: 2024-08-11
- Last updated: 2024-08-11
- Permalink: https://detailenjoyer.com/case/is-water-sticky/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-296-F01**: Surface tension comes from water molecules pulling on each other. _(Write-up · Exhibit A (Hydrogen bonds))_
- **DD-296-F02**: Adhesion is attraction to other surfaces. _(Write-up · Exhibit C (Cohesion vs. adhesion))_

## Write-up

A coin can hold a dome of water above its edge. Cohesion holds water to water; adhesion holds it to other things.

1. **Hydrogen bonds**: Water molecules attract each other through hydrogen bonds.
2. **A stretched film**: Surface molecules are pulled inward, so the surface acts like a film.
3. **Cohesion vs. adhesion**: Cohesion is water-to-water attraction; adhesion is attraction to other surfaces.
4. **Capillary action**: Cohesion and adhesion together drive capillary action.
5. **In microgravity**: Without gravity, surface tension pulls water into spheres.

## Related case files

- [Marangoni Motion (DD-024)](https://detailenjoyer.com/case/marangoni-motion/): I paired it with what happens when surface tension varies
- [CASCADE (DD-269)](https://detailenjoyer.com/case/cascade/): I linked more water physics

## Reel vs. record

- **Note**: 'Water molecules strongly adhere to each other': I'd use 'cohere'. Cohesion is attraction between water molecules; adhesion is attraction to other materials.
- **Note**: 'This adhesive force is crucial...': both cohesion and adhesion matter for water moving up plants.

## Video: Is Water Sticky?: A Coin Can Hold a Dome of Water Above Its Edge

- Duration: 24.5 s · Published: 2024-08-11
- File: https://detailenjoyer.com/assets/videos/C-jWAiCJb1O.mp4

### Transcript

DID YOU KNOW? Surface tension in water is a result of its cohesive properties where water molecules strongly adhere to each other due to hydrogen bonding. This cohesion creates a "skin" on the water's surface that is resistant to external forces. This adhesive force is crucial in many natural processes including the formation of water droplets and the movement of water through plants. In technological applications it affects how liquids behave in different environments such as in microgravity or on hydrophobic surfaces. NOW YOU KNOW!

## Questions & answers

**Q: What attracts water molecules to each other?**  
A: That's the root of surface tension. _(Source: Write-up · Exhibit A (Hydrogen bonds) · Wikipedia: Surface tension)_

**Q: Why does the surface act like a film?**  
A: They lack neighbors above. _(Source: Write-up · Exhibit B (A stretched film) · Wikipedia: Surface tension)_

**Q: What's attraction to other surfaces called?**  
A: Cohesion is water-to-water. _(Source: Write-up · Exhibit C (Cohesion vs. adhesion) · Wikipedia: Surface tension)_

**Q: What do cohesion and adhesion drive together?**  
A: It lifts water in narrow tubes. _(Source: Write-up · Exhibit D (Capillary action) · Wikipedia: Surface tension)_

**Q: What shape does water take in microgravity?**  
A: Surface tension pulls it round. _(Source: Write-up · Exhibit E (In microgravity) · Wikipedia: Surface tension)_

## Sources

- [Wikipedia: Surface tension](https://en.wikipedia.org/wiki/Surface_tension)

## Cite this case file

Easterling, Marcus. "Is Water Sticky?." The Detail Department (DetailEnjoyer), case file DD-296, last updated Aug 11, 2024. https://detailenjoyer.com/case/is-water-sticky/