Osmosis in Sodium Polyacrylate
–
When the potato is put into the dis
tilled water, it will absorb the water. The water is trying to dilute the salt inside the potato.
– When the potato is put into salty water, it will lose water. The water in the potato moves towards
Side Note: Uses for sodium polyacrylate include high absorbancy disposable diapers and moisture absorbent
for automobile and jet fuels. When the superabsorbant polymer is distributed in sandy soil, it improves the
soil’s ability to retain moisture and improves its ability to support agriculture. This polymer absorbs about 300
times its weight of tap water (800 times its weight of distilled water because the ions in tap water reduce the
absorbing properties of the polymer). The addition of the salt (sodium chloride) breaks the "gel" polymer
apart as water leaves the polymer
to dilute the salt concentration outside the polymer network. Examples of Osmosis in Beans and Fruits
• Show the students the dried beans and the beans that have been soaking in water overnight, the soaked
and the unsoaked dried fruit.
• Explain to them that water was absorbed through osmosis.
Example of Osmosis in “Orbs”
• Show students the orbs and tell them they are the same as a product sold in gardening stores
• Put the “orbs” into a clear 10 oz cup and add water so that it is about ¾ full. Tell students they can
observe the orbs over the next few days (leave with teacher).
• Tell the class that the orbs can be reduced to their original size by putting them on a plate and left to dry
for several days. They can then be rehydrated and used again. Some can be sprinkled with salt and
water observed being drawn out.