Easy solar still science experiment you can do with your children: Free Water!

     Often as parents we get asked the curious "why" question that we don't quite know how to answer. One of the possible solutions is to conduct a small, and very easy, experiment and let them see for themselves the direct result of evaporation. At the same time you both will learn a valuable outdoor skill. Creating pure drinking water from nothing.
     Ideally the experiment should begin in the morning or late morning in order to give the sun the best opportunity to demonstrate evaporation clearly. Before you start, there are some supplies you will need:

• A small cup, any cup. Even in the forest you should be able to find something someone threw out like a soda can or plastic water bottle that you can form into a cup. 
• A sheet of plastic from a hardware store or home supply store. This is the stuff you usually would use to protect your furniture from paint splatter. Look for at least 1 mil thickness up to 3.5 mil thickness. 
• Something to dig with. Anything will work, even your hands. 
• Rocks. You'll need a handful of decent sized rocks to support the and one small rock about 1 inch in diameter. 

Now you'll need to find an open area that is in direct sunlight most of the day. Be sure to make sure you have permission to use whichever area you choose.
Now for the fun part! (See attached photos for a visual description)
Step 1: Dig a hole about 2 feet wide and 2 feet long and 6-8 inches deep (or deeper if you can)
Step 2: Place the cup in the center of the hole and cover the entire hole with the plastic sheet.
Step 3: Place rocks/soil on the sheet edges to keep in place then place ONE small rock DIRECTLY over the cup in the center of the plastic.
The last step is the hardest part. It's been really easy up until now...
Step 4: Wait, wait, wait. You may as well go enjoy your day doing something else because the experiment will take a good part of the day.
     At about five o'clock in the afternoon go back to your solar still site. Take a look at the plastic. This is a good time for parents to have their child describe what they see or maybe jot it all down in a journal. What they will be looking at is a hole that earlier had been dry...or looked like it was dry. The sheet will have a fair amount of condensation on it...and the cup will have WATER! Carefully remove the plastic sheet and voila! There is your fresh, pure, clean drinking water.
     Explain to your child that water was present in the soil before and they simply couldn't see it. The sun had attempted to evaporate the moisture in the soil but the moisture was blocked by the plastic before it could get up into the sky. The trick of putting the cup in the center and weighing down the plastic used gravity to allow the evaporated water, which then condensates, to drip into the cup to create pure drinking water.
     I hope you have enjoyed the experiment. I'm sure your child enjoyed spending time with you and learning something in the meantime.

Helpful hints:

• This is a great survival skill and can work in any climate except Arctic, where the water will freeze and you may as well melt snow to drink. 
• Make sure the hole is dark colored inside to promote heat buildup and evaporation. Dark colored leaves can help if the soil is lightly colored. Just line the hole with the freshly picked leaves from nearby trees. 
• Use an old food tin to place a piece of plastic in and keep it in your backpack when camping. You never know when you might need it. Plus you will already have a cup (the tin) when you need it!