Surface Tension Calculator

What Is Surface Tension?

Surface tension is the energy per unit area at a liquid interface. It makes a liquid surface behave like a stretched elastic film and drives capillary rise in narrow tubes.

Capillary Rise Formula

For a vertical capillary tube of inner radius $r$, fluid density $\rho$, rise height $h$, contact angle $\theta$, and gravity $g$:

$$\gamma = \frac{\rho g h r}{2\cos\theta}$$

Water wets clean glass with $\theta \approx 0^\circ$, so $\cos\theta \approx 1$. For water at 20°C, $\gamma \approx 0.072$ N/m.

Frequently Asked Questions

What units does surface tension use?

SI surface tension is newtons per meter (N/m). Millinewtons per meter (mN/m) is common for small values.

What is contact angle?

Contact angle is the angle between the liquid surface and the solid wall at the three-phase line. Smaller angles mean better wetting and higher rise.

Why does a narrower tube rise higher?

Capillary rise is inversely proportional to tube radius in the Jurin equation, so smaller tubes produce taller columns for the same fluid.

Does temperature affect surface tension?

Yes. Surface tension usually decreases as temperature increases because intermolecular forces weaken.

When does this formula break down?

Very wide tubes, non-wetting fluids with large contact angles, or tubes where gravity dominates surface effects give negligible capillary rise.

Report

Surface Tension Calculator

What Is Surface Tension?

Capillary Rise Formula

Frequently Asked Questions

Related Tools

Recent Visits