What happens when you put an onion in water?

1. Diffusion: The onion's cells are semipermeable, meaning they allow water molecules to pass through while preventing larger molecules like sugars from escaping. As a result, water moves from the hypotonic environment outside the cells (pure water) into the hypertonic environment inside the cells (containing dissolved sugars and salts). This process is called osmosis, and it causes the onion cells to swell and become turgid.

2. Leaching of Compounds: The onion's cells contain various compounds, including sulfur compounds, enzymes, and pigments. As the cells swell with water, these compounds start to leak out into the surrounding water. This is why the water becomes cloudy and takes on the characteristic oniony odor.

3. Cell Disruption: As the onion cells continue to swell, their cell walls may rupture, releasing even more compounds into the water. This process can also cause the onion to soften and lose its shape.

4. Microbial Growth: The nutrients released from the onion can serve as a food source for microorganisms, such as bacteria and fungi. Over time, this can lead to the growth of mold or other microorganisms on the onion, especially if the water is not changed regularly.

It's important to note that the rate at which these processes occur depends on various factors, such as the temperature of the water, the type of onion, and the amount of time it is left in the water.