When an egg is submerged in corn syrup, it undergoes notable changes that reveal scientific principles. This common household experiment demonstrates how different concentrations of substances interact across a barrier, providing a tangible way to explore concepts governing many biological processes. The experiment typically involves a de-shelled egg, allowing its inner membrane to serve as the barrier.
The Visible Transformation
After a day or two, an egg submerged in corn syrup undergoes noticeable changes. The most noticeable change is a significant reduction in size; the egg gradually shrinks, becoming smaller than its original dimensions. Its surface, once plump and firm, may appear somewhat wrinkled and flaccid, indicating a loss of internal volume.
The flexible inner membrane, which was taut at the beginning, becomes loose and baggy around the shrunken contents. The corn syrup around the egg may also appear slightly more diluted or watery than it was initially. These physical changes occur without external force.
The Principle of Osmosis
Osmosis describes the movement of water molecules across a semipermeable membrane. This membrane acts like a selective filter, allowing small molecules, such as water, to pass through freely while blocking larger molecules. Water naturally moves from an area where its concentration is higher to an area where its concentration is lower. This movement aims to equalize the concentration of solutes, or dissolved substances, on both sides of the membrane. The net flow of water continues until equilibrium is approached, or until opposing pressures prevent further movement.
The Role of Concentration Gradients
The egg in corn syrup experiment demonstrates osmosis. The egg’s inner membrane functions as the semipermeable barrier. Inside the egg, the egg white is approximately 90% water, while corn syrup is significantly more concentrated, containing about 25% water and a high percentage of sugar. This creates a substantial concentration gradient, meaning there is a much higher concentration of water inside the egg compared to the corn syrup outside.
Driven by this gradient, water molecules spontaneously move from the area of higher water concentration (inside the egg) to the area of lower water concentration (the corn syrup). This net outward movement of water causes the egg to lose mass and shrivel, leading to its deflated appearance. The sugar molecules in the corn syrup are too large to pass through the egg’s semipermeable membrane, so only the water moves, resulting in shrinkage.
Variations and Broader Implications
The process can be reversed by placing the shrunken egg from the corn syrup into plain water. Water molecules will then move from the higher concentration in the plain water into the lower concentration inside the egg, causing it to swell and regain its original plump shape. This demonstrates the reversible nature of osmosis and reinforces the concept of water movement based on concentration differences. Osmosis is a fundamental process with implications in everyday life and biology.
Examples include plant roots absorbing water from the soil, which have a higher water potential than the root cells. Additionally, osmosis is responsible for why our fingers wrinkle after prolonged exposure to water, as skin cells absorb water. The rehydration of dried fruits like raisins when soaked in water also illustrates this principle, as water moves into the raisin cells which have a higher sugar concentration.