A sink or float science project for preschoolers

Written by elle stober
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A sink or float science project for preschoolers
Ask children to make predictions about whether certain items will sink or float. (playing image by Renata Osinska from Fotolia.com)

Most preschoolers would be hard-pressed to define concepts like buoyancy and density, but letting them drop a variety of items into a tub filled with water gives them a sneak preview of such scientific tenets. Engaging in entertaining experiments such as a sink-or-float activity can help a child grasp other scientific concepts later on---and enjoy the process. Parents can bolster preschoolers' early scientific comprehension and exploration by giving them opportunities to experiment and ask questions.


Archimedes was a Greek astronomer, inventor, mathematician and scientist born in 287 B.C. in Syracuse on the island of Sicily. His discovery of the roles of density and buoyant force in determining whether something sinks or floats came quite by accident. Buoyant force---the opposite of gravity's pull---and density---the amount of mass found in a unit of volume---work in tandem with gravity to establish whether an item sinks or floats.

As Archimedes stepped into a bathtub full of water, some of the water splashed out over the sides. He deduced that the weight of the water he displaced evenly matched the buoyant force in the water. This discovery, now known as the Archimedes Principle, is applicable to every fluid.


For this sink-or-float activity, you will need a large tub, a marker, a piece of poster board that is 28 inches by 22 inches, a piece of clear contact paper and items that will sink or float. Try pieces of cork, metal and plastic bottle caps, toy boats, seashells, small sponges, feathers, paper, pebbles and empty and full containers. Draw a line down the centre of the poster board and label one side of the chart "sinks" and the other side, "floats." Cover the poster board with clear contact paper.

A sink or float science project for preschoolers
Let children drop each item in a tub or sink to see whether their sink-or-float predictions were accurate. (Toy boat in the bathroom sink image by Samu from Fotolia.com)


Give your children some of the gathered items and ask whether the items will sink or float. Help them put the item in the correct category. As children drop items into the tub of water, ask them to give their ideas about why some objects float and others don't. After testing each item, help them place the items in the appropriate category.


Sink-or-float activities teach preschoolers a bit about the scientific skills of prediction and observation. As they test their predictions, they can also work on early math skills by counting the items on each side of the chart. Sink-or-float activities can be used to teach preschoolers a few new vocabulary words, such as sink, float, observe, predict and conclusion. They can also enhance language skills. Perhaps most importantly, science activities can foster a positive approach to education by demonstrating that enjoyable aspects of everyday living---splashing, sorting, talking, watching and playing---are ways to learn.

A sink or float science project for preschoolers
Children can "record" their predictions on a chart. (blackboard image by Renata Osinska from Fotolia.com)


In an informal survey conducted among Head Start teachers by authors Kathleen Conezio and Lucia French, teachers said science activities engage preschool children along a wide range of developmental levels. Science activities correspond to children's innate interest in the world around them. Hands-on activities give teachers a chance to note and act on children's strengths and weaknesses; teachers also reported science activities encourage language and literacy skills and that problem-solving skills developed during science activities can extend to social settings.

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