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In this activity, learners create a mixture of water, alcohol and permanent marker ink, and then add salt to form a colored alcohol layer on top of a colorless water layer.

Learners make a refrigerator that works without electricity. The pot-in-pot refrigerator works by evaporation: a layer of sand is placed between two terra cotta pots and thoroughly soaked with water.

This activity explores the basic workings of a siphon, which is the core technology that makes toilets work.

Learners use a commercially available toy to experiment with density. They fill a chamber in the toy submarine with baking powder and release it into a tank of water.

Visitors mix water and sodium bicarbonate (baking soda) in a large flask. They then add citric acid to the mixture and stopper the flask. The resulting reaction creates carbon dioxide gas.

Visitors separate a mixture of pebbles, salt crystals, and wood shavings by adding water and pouring the mixture through a strainer.

Visitors mix urea with water in one flask and mix calcium chloride with water in another flask. They observe that the urea flask gets cold and the calcium chloride flask gets hot.

Visitors prepare six solutions combining vinegar and ammonia that range incrementally from acid (all vinegar) to base (all ammonia).

Visitors observe a bottle with a balloon attached around the mouth. The bottle contains a solution of yeast, sugar, and water.

This is written as a display, but can easily be adapted to a hands-on activity. Learners discover how all the parts of a diaper work together to keep babies dry and comfortable.

Learners make a simple battery out of "sandwiches" of aluminum foil, pennies, and a salt water-soaked paper towel.

In this activity (on page 2 of PDF), learners create a low-tech refrigerator that requires no electricity to keep food from spoiling.

Learners build a filter from old soda bottles and dirt. They create polluted water, and pour it through their filter to clean it.