Name ____________________________________ Date ___________________ Period ____________
SOLAR STILL
Can you survive on just saltwater and sun? On a deserted island, there's ocean water all around you - but you can't drink any because it's too salty.
Here's how to turn saltwater into fresh water using the sun (and gravity.)
Materials : large bowl, short glass or cup, tape, plastic wrap, small rock, salty water
Procedure :
1.
Pour about two inches of saltwater in a large bowl.
2.
Take an empty cup and put it in the bowl. The top of the cup should be shorter than the top of the bowl, but higher than the saltwater.
3.
Put plastic wrap over the top of the bowl. You may need to use tape to make sure the seal is tight.
4.
The last step is to put something heavy right in the center of the plastic wrap, over the empty cup that will weigh the plastic down and help you collect the water. Now you've made a solar still. It's called a still because it distills, or purifies, water.
5.
Leave your still outside in the sun. Leave it alone for a few hours, or even a whole day. The longer you leave it out, the more water you'll collect.
6.
When you're ready to check your still, take the plastic wrap off and look at the water that's collected in the cup. Do you think it's salty or fresh? You can taste it to find out. Measure how much you have collected using a graduated cylinder and record your results.

Parts:
What are the functions of these parts?
Parts
Rock
Plastic
Wrap
Bowl
Salty
Water
Function
Hint: Why does it need to be well sealed?
with another part?
Interactions:
How does one part of the system interact
2 parts How do they interact?
Plastic Wrap
Water
SYSTEM: SOLAR STILL
Cup
Systems Analysis:
1.
What is the boundary of the system? _______________________________________________
2.
Is the system open or closed? _____________________________________________________
3.
Explain your answer to number 2 in terms of energy and matter. _________________________
4.
What is one input of this system? __________________________________________________
5.
What is one output of this system? _________________________________________________
6.
Which energy transformation should occur in the Solar Sill?
A.
Light energy from the Sun becomes thermal (heat) energy in the salty water.
B.
Thermal (heat) energy from the Sun becomes chemical energy in the salty water.
C.
Thermal (heat) energy from the Sun becomes thermal (heat) energy in the salty water.
D.
Light energy from the Sun becomes chemical energy in the salty water.
7.
What type of substance is the salty water in the plastic bowl?
A. Mixture B. Element C. Molecule
8.
Why can’t you use filter paper to filter out the salt from the salt water?
D. Compound
9.
Evaporation is a process in the water cycle. Where does evaporation happen in the still?
A. When water gas turns into drops of water on the plastic wrap
B. When water in the plastic bowl becomes water gas in the air
C. When drops of water on the plastic wrap fall
D. When clean water collects in the metal cup

What type of bowl, cup and wrap did you use for your Solar Still? Clear or Colored Plastic
Large, Medium or Small Bowl Metal, Glass or Plastic Bowl Metal, Glass or Plastic Cup
How well did your water Solar Still work?
How much water collected in your cup? __________ Is it fresh or salty? ____________
Let’s compare results…
Class Data:
Amount of water
Family collected in mL
Large
Bowl
Med
Bowl
Small
Bowl
Clear
Wrap
Dark
Plastic
Glass
Bowl
Metal
Bowl
Plastic
Bowl
Glass cup
Metal cup
Plastic cup
Redesign : Can you redesign a still to work even better? Faster? Collect more water? Make at least 2 modifications to improve the efficiency of the system. Explain how your modifications are going to make the system work more efficiently. Base your explanation on data from your prototype, class data or research.
1. First modification…
2. Second modification…
Include a labeled drawing of your proposed redesigned still in your INB.