• Pixel-art sticker of Osmox, personifying Osmotic Pressure, with the caption “Water Crosses To Even Things Up.”

IndexHeat & EntropySticker

Osmox

Osmotic Pressure Physics

\[\Pi = c R T\]
$4.99 USD
$4.99 USD
Sale Sold out

Meet Osmox, a U-shaped tube who watches water cross a membrane to even things up. Osmotic pressure equals concentration times the gas constant times temperature: a 0.1 mol per litre sugar solution at 25 °C pushes about 2.5 × 10⁵ Pa, roughly two and a half atmospheres. Pixel-art kiss-cut sticker in 2, 3, 4 and 6 inches; equation, symbols and sources in the physics panel below.

Size
Surface

Flat $6 shipping worldwideMade to order, ships in 2–5 business days

Details

Size3″ × 3″

3″ × 3″ kiss-cut sticker.

Shipping

Flat $6 shipping on every order, worldwide, whatever's in it.

Delivery times & where we ship

Returns & replacements21 days

Every item is printed to order, so we can’t accept returns or exchanges for change of mind, or if you ordered the wrong size or colour.

Print defect, misprint, damage or the wrong item? We’ll send a free replacement, or a refund if you prefer. Report it within 21 days of delivery with a photo; no need to send it back.

Full refund & replacement policy

The physics

Meet Osmox, a U-shaped tube who watches water cross a membrane to even things up.

A semipermeable membrane lets small water molecules through but blocks larger dissolved molecules such as sugar. If pure water is on one side and sugar solution on the other, more water moves into the solution than comes back out. The level on the sugar side rises until the extra weight of liquid pushes back hard enough to stop the flow.

The pressure needed to stop it is the osmotic pressure, Π = cRT. For a sugar solution of 0.1 mol per litre at 25 °C, that is 100 mol/m³ × 8.314 J/(mol·K) × 298 K ≈ 2.5 × 10⁵ Pa, about two and a half times atmospheric pressure.

Even a modest solution can push surprisingly hard, which is why the formula looks just like the ideal gas law.

Osmosis keeps plant cells firm, decides how much water our own cells take up, and is reversed in desalination plants, where high pressure forces water out of seawater through a membrane.

Equations

\[\Pi = c R T\]
SymbolMeaningUnit
\(\Pi\) osmotic pressure \(\mathrm{Pa}\)
\(c\) concentration of dissolved particles \(\mathrm{mol/m³}\)
\(R\) molar gas constant \(\mathrm{J/(mol·K)}\)
\(T\) absolute temperature \(\mathrm{K}\)

Sources

  1. OpenStax Chemistry 2e — Colligative Properties
  2. NIST CODATA — molar gas constant R

Field notes

View all
  • Pixel-art illustration for this Pixelated Physics post: a pixel pendulum bob character swinging over a circular floor marked with pixel pegs, a few pegs knocked over showing the swing plane slowly turning, a pixel Earth spinning in the window

    How Does a Foucault Pendulum Prove Earth Rotates?

    A long pendulum’s swing plane slowly turns relative to the floor. Foucault showed in 1851 that the turn is Earth’s rotation made visible. The rate is 360° times the sine...

    How Does a Foucault Pendulum Prove Earth Rotates?

    A long pendulum’s swing plane slowly turns relative to the floor. Foucault showed in 1851 that the turn is Earth’s rotation made visible. The rate is 360° times the sine...

  • Pixel-art Einstein ring: a foreground galaxy bends the light of a galaxy directly behind it into a circular ring of arcs centered on it

    How Does Gravity Bend Light? Einstein Rings and...

    Gravity bends light because spacetime is curved. The 1919 eclipse measured the Sun’s deflection; Einstein’s 1936 note foresaw stellar lenses; modern telescopes image Einstein rings. Here is the physics without...

    How Does Gravity Bend Light? Einstein Rings and...

    Gravity bends light because spacetime is curved. The 1919 eclipse measured the Sun’s deflection; Einstein’s 1936 note foresaw stellar lenses; modern telescopes image Einstein rings. Here is the physics without...

  • Pixel-art illustration for this Pixelated Physics post: three abstract pixel mascots of early quantum ideas: a glowing light-packet character, a tiny atom with stepped orbit rings, and a fuzzy uncertainty cloud, climbing a staircase of energy levels

    Who Started Quantum Mechanics? Planck, Bohr and...

    Quantum theory did not begin with one paper. Planck quantized energy in 1900, Bohr quantized the atom in 1913, and Heisenberg’s 1925 matrix mechanics plus the 1927 uncertainty relation made...

    Who Started Quantum Mechanics? Planck, Bohr and...

    Quantum theory did not begin with one paper. Planck quantized energy in 1900, Bohr quantized the atom in 1913, and Heisenberg’s 1925 matrix mechanics plus the 1927 uncertainty relation made...

1 3
View all