Get Fresh (Water)

Note: Adult supervision is required for this activity

What You Need:

250 mL water
5 mL salt
A glass or enamel pan with lid
2 clean glasses What To Do:

Put 250 mL of tap water into the pan.
Add 5 mL of salt and stir until dissolved.
Pour a small amount (about 10 mL) of salt water into one of the cups.
Put the lid on the pan and bring the water to a boil on the stove.
When the water is boiling, carefully remove the lid and turn it over.
Pour the water drops on the underside of the lid into the empty glass.
Replace the lid to collect more water drops.
Repeat Steps 5 to 7 until you have about 10 mL of water in the glass.
Remove the pan from the stove.
Set the cup of water aside to cool.
Taste the water in the two cups. How does it differ?

What's Going On? Water is a precious resource, but most of Earth's water is salty and can't be used for drinking. However, salt can be removed from water, as you saw in this activity. Water vapour evaporated then condensed on the underside of the lid, but salt can't do this, so it stayed inthe pan. This makes the water you collected drinkable. Scientists are currently experimenting with a similar procedure on a large scale in what are known as desalinization plants. So far, it is too expensive to be a practical way of getting fresh drinking water. What Else To Do: Some fish can live quite happily in salt water, but others can only survive in freshwater. Next time you're at the pet store, ask if they have salt-water fish for you to observe. Do you think the salt-water fish would survive if you put them in an aquarium filled with tap water? Why not?

Last Modified: 2004-12-10