Gummy bears, made from sugar, gelatin, and water, offer a fascinating glimpse into fundamental scientific principles when exposed to different liquids. These candies can also serve as a simple model for understanding how certain substances interact with water. Observing what happens to a gummy bear when it is immersed in salt water reveals a common biological process.
The Science of Osmosis
Osmosis describes the movement of water molecules across a semi-permeable membrane. A semi-permeable membrane is a barrier that allows smaller molecules, like water, to pass through it, but restricts the passage of larger molecules, such as dissolved sugars or salts. This movement occurs from an area where water molecules are in higher concentration to an area where they are in lower concentration. Within this process, a solution consists of a solvent, which is the substance that dissolves another, and a solute, which is the substance that gets dissolved. Water is often referred to as the “universal solvent” due to its ability to dissolve many substances. Osmosis works to balance the concentration of these solutes on both sides of the membrane by moving the solvent, typically water, until equilibrium is reached.
The Gummy Bear Experiment: What You Observe
When a gummy bear is submerged in salt water, the gummy bear typically shrinks or shrivels. Its texture also tends to become firmer or tougher than its original state. The candy might appear to lose some of its vibrant color as well. This reduction in size and alteration in texture can be observed over a period of several hours. The extent of shrinking depends on the concentration of salt in the water; a higher salt concentration generally leads to a more pronounced decrease in the gummy bear’s volume and mass. These visual outcomes provide direct evidence of water movement away from the gummy bear.
Explaining the Gummy Bear’s Transformation
A gummy bear, being composed largely of gelatin and sugar, behaves like a semi-permeable membrane. The internal structure of the gummy bear contains a certain concentration of dissolved sugars and other components. When placed in salt water, the water outside the gummy bear has a higher concentration of dissolved salt and thus a lower concentration of free water molecules compared to the water inside the gummy bear. This creates a concentration gradient, prompting water molecules to move from the area of higher water concentration (inside the gummy bear) to the area of lower water concentration (the salt water solution). This type of solution, where the external environment has a higher solute concentration than the inside of the object, is known as a hypertonic solution. As water exits the gummy bear, it loses volume and shrinks.
Beyond Salt Water: Varying Outcomes
The principle of osmosis explains different outcomes when gummy bears are placed in various liquids. If a gummy bear is submerged in plain fresh water, it will absorb water and swell, becoming larger and softer. This occurs because fresh water is a hypotonic solution, meaning it has a higher concentration of water molecules than the gummy bear, causing water to move inward. Conversely, if a gummy bear is placed in a highly concentrated sugar water solution, the outcome might be less dramatic than in plain water, or it could even shrink slightly depending on the sugar concentration. If the sugar solution outside the gummy bear is hypertonic relative to the gummy bear’s internal composition, water will still leave the gummy bear. The concentration of solutes in the surrounding liquid dictates the direction of water movement and the resulting changes in the gummy bear.