When you put a gummy bear in vinegar, it swells up significantly over 24 to 48 hours, growing to roughly double its original size or more. The gummy bear absorbs the liquid through a process called osmosis, and the vinegar’s acidity also begins to break down the gelatin structure, giving the bear a softer, mushier texture than it started with.
Why the Gummy Bear Swells
A gummy bear is mostly gelatin, sugar, and a small amount of water. When you drop it into a cup of vinegar, the gelatin acts as a semipermeable membrane, meaning water molecules can pass through it but larger molecules like sugar cannot easily move out. Since the gummy bear has a high concentration of sugar and other dissolved substances inside, and the vinegar solution outside is mostly water (vinegar is about 95% water), water flows inward to try to balance the concentration on both sides. This movement of water through a membrane from a region of lower solute concentration to higher solute concentration is osmosis.
The result is a gummy bear that puffs up as it absorbs liquid. It can grow to two or even three times its original volume depending on how long you leave it soaking. The bear also becomes noticeably squishier because the gelatin matrix is now saturated with liquid rather than holding its firm, chewy structure.
How Vinegar Differs From Plain Water
If you run this experiment side by side with a gummy bear in plain water, you’ll notice some differences. A gummy bear in water also swells through osmosis, often growing even larger than the one in vinegar. That’s because vinegar contains acetic acid and dissolved molecules that make it a slightly more concentrated solution than pure water, so the osmotic pressure driving water into the bear is a bit lower.
The more interesting difference is texture. The acetic acid in vinegar starts to break down the gelatin protein that gives the gummy bear its shape. After 24 hours, a vinegar-soaked bear tends to feel softer, more fragile, and more easily torn apart compared to a water-soaked bear, which usually holds together better. The vinegar bear also picks up a sour smell and tangy taste (though eating experiment materials isn’t recommended since they’ve been sitting out).
What to Expect Hour by Hour
In the first few hours, you’ll see the gummy bear start to look slightly puffier and the surface becomes a bit cloudy or pale as liquid begins moving in. By the 8 to 12 hour mark, the bear is noticeably larger and the color has faded because the same amount of dye is now spread through a bigger volume of gelatin. The texture shifts from firm and chewy to rubbery and soft.
By 24 hours, the bear has reached close to its maximum size. It’s bloated, translucent, and fragile enough that picking it up carelessly can tear it. If you leave it for 48 hours or longer, the vinegar continues weakening the gelatin and the bear may start to lose its shape entirely, collapsing into a blob rather than holding a bear outline. Some of the gelatin dissolves into the surrounding liquid, which is why the vinegar may look slightly cloudy.
Running This as an Experiment
This is one of the most popular science fair and classroom experiments because it’s cheap, visual, and demonstrates a real biological concept. Osmosis is exactly how your cells regulate water: cell membranes are semipermeable just like the gelatin in a gummy bear, allowing water to pass through while keeping larger molecules in place. Your body uses this process constantly to move water where it’s needed.
To get the most out of the experiment, set up several cups with different liquids: plain water, vinegar, salt water, and sugar water. Measure each gummy bear’s length, width, and mass before dropping them in, then measure again at 12 and 24 hours. Salt water produces the most dramatic contrast. Because saltwater has a higher concentration of dissolved particles than the inside of the gummy bear, water actually flows out of the bear, causing it to shrink. This reverse result makes the osmosis concept click for most people.
A few practical tips: use the same brand and color of gummy bear for each liquid so you’re comparing fairly. Regular-sized bears work fine, but the larger “mega” gummy bears make the size changes easier to see and measure. Glass cups or jars let you observe changes without disturbing the bears. And use enough liquid to fully submerge each bear, since any part sticking out above the surface won’t absorb evenly.
Why the Bear Doesn’t Dissolve Completely
Gelatin is a protein derived from collagen, and while vinegar’s acidity weakens the bonds holding gelatin molecules together, household vinegar (typically around 5% acetic acid) isn’t strong enough to fully dissolve the protein network in a reasonable timeframe. The gelatin strands form a tangled mesh that traps water inside, which is why the bear swells rather than simply falling apart. Over several days the structure degrades enough that the bear loses definition, but it won’t vanish entirely the way a piece of candy would dissolve in water. If you used a stronger acid, the breakdown would happen faster and more completely.