
Sink or Float
The best of preschool water play activities.
— by julie hodos on January 28, 2025
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Not all preschool water play activities have to be frivolous fun, although there is a time and place for that. Some can be educational and play based as well! The sink or float science experiment is one of these that falls into the play based learning category.
My preschooler doesn’t even realize he’s learning even when we’re hypothesizing but maybe that’s because he enjoys arguing. The great part is that we don’t have to argue because the answer is right in front us. We simply have to test the item in the water. Read on for instructions to make this experiment educational and play based!
Additional resources.
Explore these preschool water play activities as well.
- For more preschool water play activities be sure to check out the rest of the week of learning in Ww is for Water. There you’ll find science experiments for learning about the water cycle, book suggestions, and a free printable sorting activity to teach your child about salt versus fresh water animals.
- Another favorite for my children is the Dancing Grapes science experiment. If you want to continue learning about density and water then this is the perfect activity. This science experiment deals with carbonated water counteracting a grape’s density until the grape reaches the surface, where the bubbles burst and then it returns to the bottom of the glass. Here it repeats the process as more carbonation bubbles cling to the grape.
Books to read.
Water is Water: A book about the water cycle by Miranda Paul and Over and Under the Pond by Kate Messner are excellent selections for an older preschooler. Water can be… by Laura Purdie Salas is a great choice for younger preschoolers.
Sink or Float
Materials needed for the best of preschool water play activities
Objects to test.
First you will need to determine objects that are allowed to get wet. These can look like toys, coins, keys, utensils, balls, grass, leaves, wood, rocks, ice, pinecones, and feathers. Whatever you’re okay with getting wet. Let your child help in finding and choosing items if you’re comfortable with telling them no. Otherwise you can preselect and gather items togehter.
Bigger isn’t always better, but in this case it is.
The next item you will need is a container to do the experimenting in. If you’re outside then consider what objects your child might gather up. Such as a very large stick. If you’re inside you can use a bowl, bathtub, or sink. Bigger isn’t always better, but I do enjoy using a kiddie pool for this activity.
The reason I suggest a bathtub or kiddie pool is because your child will probably have the presumption that the larger or heavier an object is the more likely it is to sink. You want to be able to easily put these false assumptions to the test. My son was very surprised when a coin sank to the bottom but the tree limb he dragged out of the woods, that was almost his size, floated.
2 hand towels.
Lastly, you will want two different colored towels. These will simply be a way to display and gather together similar items. Floating objects and sinking objects.
Instructions for the best of preschool water play activities
Set up Sink or Float
Begin by gathering items together and placing them by your container. Lay out the hand towels nearby. Now, fill the container with water.
A disclaimer here, be wise with supervision since this is a water activity. If it’s a smaller container inside, water can easily and quickly become a mess. If using a larger container like a bathtub or kiddie pool then you will definitely not want to leave it unattended. My kiddos were all under supervision while the kiddie pool was filled with water.
Hypothesize and test.
Before your child tests an object, ask them if they think it will float or sink. Let them test it. Once they see, have them take the object and place it on the designated towel. I have found it is easiest to designate the towels once we’ve begun. My kiddos are always too eager to begin and rarely listen. This way I’m not repeating myself.
Discussion.
After your child has worked through the objects you gathered, now is the time to discuss the two different groups. Consider the similar materials, wood objects float and metals sink. Plastic will not fit a certain mold. Some will float and some will sink, depending on the type. Some plastics are more dense than water and others are less dense. If an object is more dense then water, it will sink. If it is less dense then it will float.
The most important thing to remember in the discussion is that weight is not the same as density of an object. You can help drive this point home by comparing a piece of wood that is heavier than a coin.
Further experimenting
I strongly encourage this last step to see if your child has a new understanding for density. Even if they can’t put it in so many words, they can now logically consider the material of an item and make a more educated hypothesis.
My son’s disappeared into the woods to gather sweet gum seeds, as I said before a very large tree branch, and additional rocks. You can also have preset items ready to bring out if you are confined indoors or do not want to explain why some items cannot get wet. Consider things like a nail, craft pom-pom, wooden spoon, a game die, or lettuce leaves.
Preschool water play activities can be educational too.
My boys love playing in the water and with water! So this activity is perfect for taking something they love and making it a learning experience. And when thought out ahead of time and set up well, then it’s easy for mom or dad too!
Sink or float is one activity in Ww is for Water. Ww is for Water is a week of preschool lessons all centered around water. Learn about the water cycle and animals who live in water with a free printable. Check it out!
Creative activities for preschoolers.
Ww is for Water is a part of a 26 week preschool curriculum that is free and play based. Letter of the Week has been reimagined for all that home learning has to offer. Explore more at the button below.
Sink or Float
Activity Instructions
Materials needed
- Objects allowed to get wet (toys, coins, keys, utensils, balls, grass, leaves, wood, rocks, ice, etc.)
- Bucket of water or large bowl
- Two different colored towels.
Instructions
- Before beginning, think about the objects you want to use and gather them together. Save out a couple for the last part of the activity.
- Completing this activity outside is ideal but if that’s not an option then you can set this up in the kitchen or bathroom.
- The towels: designate one as the sink towel and one as the float. As your child tests different items, have them place the object on the appropriate towel.
- Allow your child to find objects and test.
- Once all objects have been tested, have your child examine the objects on each towel. Discuss the materials of each.
- Objects with a higher density than water will sink and objects with a lower density will float.
- Remember, density is not the same as weight.
- Now, have your child and yourself select a few more different objects and ask your child if they think it will float or sink before testing it based on the knowledge you now have.
- Discuss why they were right or wrong.
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