Surface Tension Calculator - Laplace's Law Calculator

Surface Tension (σ):

Radius (r):

Pressure Difference (Pa): Pressure Difference (bar): Pressure Difference (psi): Pressure Difference (at): Pressure Difference (atm): Pressure Difference (Torr): Pressure Difference (hPa): Pressure Difference (kPa): Pressure Difference (MPa): Pressure Difference (inHg):

1. What is a Laplace's Law Calculator?

Definition: This calculator computes the pressure difference (\( \Delta P \)) across the surface of a spherical object based on Laplace's Law, using the formula \( \Delta P = \frac{2\sigma}{r} \), where \( \sigma \) is the surface tension, \( r \) is the radius, and \( \Delta P \) is the pressure difference.

Purpose: It helps engineers and scientists analyze pressure differences in applications like blood vessels, bubbles, and capillary action in physics and biology.

2. How Does the Calculator Work?

Calculations are based on Laplace's Law for spheres:

\[ \Delta P = \frac{2\sigma}{r} \]

Unit Conversions:

Category	Unit	Conversion to SI Unit
Pressure Difference	Pa (Pascals)	1 Pa
	bar	1 bar = 100,000 Pa
	psi (Pounds per square inch)	1 psi = 6894.76 Pa
	at (Technical atmospheres)	1 at = 98,066.5 Pa
	atm (Standard atmospheres)	1 atm = 101,325 Pa
	Torr	1 Torr = 133.322 Pa
	hPa (Hectopascals)	1 hPa = 100 Pa
	kPa (Kilopascals)	1 kPa = 1000 Pa
	MPa (Megapascals)	1 MPa = 1,000,000 Pa
	inHg (Inches of mercury)	1 inHg = 3386.39 Pa
Surface Tension	N/m	1 N/m
Radius	m (Meters)	1 m
	cm (Centimeters)	1 cm = 0.01 m
	mm (Millimeters)	1 mm = 0.001 m
	km (Kilometers)	1 km = 1000 m
	in (Inches)	1 in = 0.0254 m
	ft (Feet)	1 ft = 0.3048 m
	yd (Yards)	1 yd = 0.9144 m

3. Surface Tension of Liquids at 20°C

The following table provides surface tension values for various liquids at 20°C:

Liquid	Surface Tension (mN/m)
n-Heptane	16.0
n-Octane	18.4
Benzene	22.5
Toluene	22.55
Ethanol	22.60
Methanol	23.3
Water	28.9
Aniline	36.1
Glycerin	46.0
Mercury	72.75
Molten Sodium	476

Notes: These values are measured at 20°C in air. When you select a liquid, the corresponding surface tension value (in N/m) will automatically fill the input field. You can also enter a custom value in N/m.

4. Importance of Laplace's Law Calculation

Details: Accurate pressure difference calculations are crucial for understanding surface tension effects in biological systems (e.g., blood vessels, alveoli) and physical systems (e.g., bubbles, droplets).

5. Using the Calculator

Tips: Select or enter Surface Tension (N/m or choose a liquid), enter Radius (m, cm, mm, km, in, ft, yd), and ensure the shape is set to Sphere (default). Results include pressure difference in multiple units (Pa, bar, psi, at, atm, Torr, hPa, kPa, MPa, inHg).

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