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7 Water Science Experiments for Preschoolers

Doing water science experiments with preschoolers is a great idea because it helps the little ones learn in a fun and interactive way. When they play with water, they get to see how things float or sink, how water moves, and even how it changes form, like when it freezes or evaporates. This hands-on learning helps kids understand the world around them, boosts their curiosity, and helps them develop important skills like thinking, questioning, and problem-solving, all while they’re having a blast with the water activities.

Here are easy water science experiments for preschoolers. Each activity is interactive, educational, and, most importantly, fun!

1. Dancing Raisins

Dancing Raisins Science Experiment

  • Age Group: 3-5 years
  • Time: 15-20 minutes
  • Materials: Clear glass, soda water, and a handful of raisins
  • Preparation: Fill a glass with clear soda, leaving some space at the top, and then add a few raisins to it.

The Experiment: This experiment introduces preschoolers to the concept of buoyancy and gas bubbles.

Begin by asking the children what they think will happen if we put raisins in water. Will they float or sink? After hearing their predictions, drop a few raisins into the glass of carbonated water. The children will observe the raisins sinking initially but then starting to dance up and down. Explain that this happens because the carbon dioxide bubbles in the water attach to the rough surface of the raisins. As more bubbles accumulate, they lift the raisin to the surface. Once they reach the surface, the bubbles pop, and the raisin sinks again, continuing this cycle and making the raisins “dance.”

This experiment demonstrates buoyancy and encourages observation skills, as children watch the raisins and bubbles interact. It’s a simple yet fascinating way to introduce young learners to basic scientific principles, encouraging them to ask questions and make predictions about the world around them.

2. Water Simmer and Evaporation

water simmers in pot


  • Age Group: 4-5 years
  • Time: 30 minutes (including observation time)
  • Materials: Small pot, stove (with adult supervision), water, marker, and a piece of paper.
  • Preparation: Fill the pot with water and mark the water level on the paper.

The Experiment: This experiment introduces preschoolers to the concepts of heat, what simmering water looks like, and evaporation.

With close adult supervision, place the pot of water on the stove and turn the heat to low, allowing the water to simmer gently. Explain to the children that when water gets warm, it starts to move and create tiny bubbles, which is called simmering. As the water simmers, some of it turns into steam and disappears into the air, a process known as evaporation.

Let the children observe the water level decreasing over time. This experiment offers a tangible way to understand how water can change form from liquid to gas and introduces the concept of the water cycle in a very simplified manner. It encourages children to observe the changes carefully, ask questions, and understand the effects of heat on water. Ensure to emphasize safety around hot surfaces and the importance of adult supervision when conducting experiments involving heat.

3. Rainbow Walking Water

Colorful Rainbow Water Walking With Paper Towels to Next Glass

  • Age Group: 3-5 years
  • Time: 20-30 minutes
  • Materials: Clear cups, water, food coloring, and paper towels
  • Preparation: Fill several cups with water and add a few drops of different food coloring to each cup to create various colored solutions.

The Experiment: This experiment allows preschoolers to explore color mixing and water transfer in a visually engaging way.

Arrange the jars in a circle and introduce a unique food coloring to the water in each one. Then, fold paper towels into thirds and submerge one end of each into a jar of water as shown in the image. After some time, the colors will ascend the paper towels, blending with the hue from the adjacent jar.

Encourage them to predict what will happen when they mix colors, such as blue and yellow or red and blue, and then let them experiment with mixing the colors by transferring water between cups. This teaches them about primary and secondary colors. It also helps develop fine motor skills and hand-eye coordination. The experiment can be extended by asking children to create their own color recipes and record their findings, fostering early scientific thinking and inquiry.

4. Sink or Float

objects floating and sinking in container with water
  • Age Group: 3-5 years
  • Time: 15-20 minutes
  • Materials: A large container filled with water, various small objects (e.g., cork, pebble, plastic toy, metal spoon)
  • Preparation: Gather all materials and ensure the container is filled with enough water for objects to float or sink.

The Experiment: This simple yet effective free STEM activity teaches preschoolers about density and buoyancy.

Start by discussing with the children whether they think each object will float or sink when placed in water. Allow them to hold and feel the weight of each object before making their predictions. Then, one by one, let them place the objects in the water to see the outcome. This hands-on activity encourages children to think critically about why some objects float while others sink, introducing basic concepts of density and buoyancy. It also enhances their observational skills and their ability to make predictions based on their understanding of the physical properties of different materials.

Explain, that everything around us, even water, is made of super tiny bits. Think of these bits like tiny building blocks. Some things have their blocks packed really tight, and others have them more spread out. If something has its blocks packed tighter than water’s blocks, it will sink. If its blocks are more spread out than water’s, it will float.

5. Colorful Water Symphony

  • Age group: 3-5 years
  • Time: 30 minutes
  • Materials: Clear glasses or jars, food coloring, water, a spoon.
  • Preparation: Fill each glass or jar with varying levels of water.

The Experiment: This experiment introduces preschoolers to the concept of sound and how it can be altered using water.

Start by arranging the glasses in a line on a table. Before the children arrive, fill the glasses with different amounts of water. Add a few drops of food coloring to each glass to make the experiment more visually engaging; each glass should have a different color.

Once the setup is ready, gather the children around the table and explain that they will be making their own music with water. Show them how to gently tap the side of each glass with a spoon and listen to the sounds. Explain how the amount of water in each glass changes the pitch of the sound it makes when tapped. The more water in the glass, the lower the pitch will be, and vice versa.

Encourage the children to experiment by tapping the glasses in different sequences to create their own water symphony. This hands-on activity teaches your preschoolers about sound while they observe how water can be a visual and auditory medium for scientific exploration. As they engage with the experiment, they’ll learn basic principles of sound waves and how they are affected by different mediums, in this case, water, in a fun and interactive way.

6. Celery Food Coloring Experiment

Rainbow Celery Experiment
  • Age Group: 3-5 years
  • Time: 1-2 days
  • Materials: Celery stalks with leaves, clear glasses, water, and food coloring (multiple colors)
  • Preparation: Fill each glass halfway with water and add a few drops of different food coloring to each glass.

The Experiment: This experiment offers a vivid exploration of capillary action, showing how plants absorb water.

Begin by explaining that just like how we drink water with straws, plants have their own natural “straws” called capillaries, which they use to drink water from the ground.

Insert a celery stalk into each glass. Ask the children to predict what will happen to the celery and why they think so. Over the course of a day or two, the children will observe the celery stalks changing color, especially noticeable in the leaves. This change occurs as the colored water travels up the stalk through tiny tubes in the celery, called xylem, demonstrating capillary action.

Engage with the children about how the water moves against gravity, and discuss the importance of water for plants. This experiment teaches kids scientific concepts and fosters patience and observation skills, as the children will need to wait and watch the changes over time. I think it is a fantastic way to connect natural scientific phenomena with everyday observations, like why leaves might change color after a rainstorm or how plants stay nourished and grow.

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