Osmosis
Osmosis is the movement of water through a barrier from where there is more water to where there is less.
A bowl of water sits next to a bowl of saltwater, connected by a damp cloth. Water moves through the cloth from the plain-water side to the saltwater side. The plain-water bowl slowly empties while the saltwater bowl fills up. Water always flows toward the side with less water in it.
Explaining osmosis by grade level
Think about seeds sitting in salty water. The salt pulls water away from the seeds. The seeds dry out and cannot sprout. Plain water lets seeds soak up all the water they need to grow. That is why salt water hurts plants.
Projects that explore osmosis
Osmosis is the movement of water through a barrier from where there is more water to where there is less. In this experiment, you stand seed rolls in plain water, salt water, and sugar water. The liquid wicks up through the paper towel barrier into the seeds. Plain water has the most free water available, so osmosis pulls more water into those seeds than into seeds sitting in salt or sugar solutions.
Osmosis moves water through a barrier from more water to less. You water identical plants each day with different amounts of salt mixed in. Salt dissolved in soil water means less free water on the outside of root barriers. Plants watered with plain water showed no harmful effects because their roots had plenty of free water to pull inward.
Osmosis moves water through a barrier from where there is more water to where there is less. Here, twelve cauliflower plants are split into four groups, each watered with a different solution: Epsom salt (MgSO4), table salt (NaCl), potassium chloride (KCl), or plain water (H2O). When salt dissolves in water, it reduces the free water available outside the root barrier. That means roots in salt solutions pull in less water. Over ten days, only the plain water group grew taller, and it also produced the longest roots at 12.4 cm. Table salt caused the biggest height loss, an average drop of 1.12 cm.