Combine 1-1/2 cups of warm water, 2 cups of Elmer's glue and a few drops of food coloring and mix well in a large container or bowl. Add some glitter if you want sparkles. In a separate, smaller bowl or container, combine 1-1/3 cups of warm water and 2 tsp. of Borax and mix well until the Borax is fully dissolved. Combine both mixtures and mix with your hands until all of the liquid is absorbed.
Preschoolers can become familiarized with units of measurement and math concepts like simple fractions and greater than, less than. Introduce measuring cups, tablespoons, teaspoons, halves, quarters, etc. Discuss and compare the different types of measurements. Display the recipe and allow the children to help measure and make the flubber. It might be a good idea to have them practice with sand or water first. Measuring and mixing will also help them practice their motor skills.
Introduce children to the scientific method by having them make predictions and then explain that you will be testing the predictions with experiments. On a poster board write down their predictions to questions like whether it will sink or float, stretch or bounce. Have them think up questions that start with "What happens if you..." and guess the answer. Once the flubber is made, experiment and test those theories to determine if they were right.
Discuss with the preschoolers the properties of a solid and a liquid. Provide solid and liquid examples and include some that have similar qualities to flubber, like play dough, Silly Putty, clay and liquid glue. Make a Venn diagram or columns for "solids" and "liquids" on a poster board or chalkboard and ask the children to explain and assign each item. Have them compare and contrast each item to the flubber. Then discuss the flubber and let them try to figure out which category it belongs in. Once they each think they have their answer, explain that flubber belongs in both categories because it has the properties of both a liquid and a solid.