This sink or float experiment for kids is a great way to learn about weight, buoyancy, and density. Children will predict whether the object will sink or float in water and then can write their prediction on the free sink or float worksheet.
We LOVE doing science experiments for kids, and while this activity is geared towards kids 3-7 years old, it’s fun for a large variety of age groups. This is because the older they get, the more “creative” they’ll get with the items that they want to use to sink if they sink or float
Related: Have you tried making Ice Cream In A Bag?
Sink Or Float Experiment + Worksheet
If you’re looking for a way to add some interesting aspects to home learning or even homeschooling, this is a fun experiment for the kids. You just need to gather up some simple household items and have your child look at them and make their predictions.
Once they get the hang out of it, they’re going to be using this reference in their everyday lives. Maybe the next time you go swimming, they’ll ask if they’ll sink or float when they jump in the pool? Isn’t it great how everything learning can be used easily in everyday life?
You’ll find that a simple Science experiment such as this sink or float experiment is an easy way to get the kids working together, without even really trying.
Why do objects sink or float?
1. Density: Density is a measure of how much mass is contained in a given volume. Objects with greater density than water will sink, while those with less density will float. For example, metals like iron are denser than water, so they sink.
2. Buoyancy: Buoyancy is the upward force exerted by a fluid (in this case, water) on an object immersed in it. This force opposes the weight of the object. Objects that are less dense than water displace an amount of water equal to their weight, causing them to float. Objects that are denser than water displace less water than their weight, so the buoyant force is less than the object’s weight, causing it to sink.
3. Shape and Volume: The shape and volume of an object also play a role in whether it sinks or floats. Even if an object is denser than water, it may float if it has a shape that allows it to displace enough water to generate buoyant force greater than its weight. This is why some boats, made of materials denser than water, float—they are designed to displace a large volume of water, creating enough buoyant force to keep them afloat.
Materials required for the sink or float activity:
You’ll need some materials to get started with this experiment. But also feel free to use other items that you have in your home as well.
- Water
- Water container/water table – we used the Ikea Flisat table.
- Cardstock
- Objects to use. Choose a combination of items that will sink and those that will float. Items like a button, pencil, flower, crayon, apple, rubber duck, small ball, leaf, pear, etc.
- Printable (found at the bottom of this post, if you’d like to have your student record their predictions and results.)
Which objects sink?
- Metal objects such as paper clips, keys, or screws
- Rocks or pebbles used for sensory play or decoration
- Glass items such as marbles or small glass beads
- Some types of wooden blocks or manipulatives
- Playdough or clay sculptures
- Some types of plastic toys that are denser or heavier
- Coins or tokens used for counting or sorting activities
- Some types of art supplies like ceramic or pottery pieces
These items are usually denser or heavier than water, causing them to sink when placed in water during sink or float experiments or sensory play in preschool classrooms.
Which objects float?
Preschool classroom items that often float include:
- Rubber or plastic toys (such as ducks, boats, or figurines)
- Foam letters or shapes used for learning activities
- Plastic building blocks or manipulatives
- Empty plastic containers or bottles
- Corks or stoppers from various art or craft supplies
- Styrofoam cups or plates used during snack time
- Floating bath books or water-friendly storybooks
- Some types of crayons or markers with plastic casings
These items are typically lightweight and have a lower density compared to water, allowing them to float easily during sink or float experiments or water play activities in preschool classrooms.
Set up the sink or float experiment
Since there is water involved, you might want to set it up outside or on your porch, but if you don’t have that option, don’t worry. You can easily lay down some towels on the floor and have this experiment inside, too.
Once you have gathered up those items, it’s time to get started. (Don’t forget to print out your worksheet below!)
The easiest way to get started is to have your child pick one item, feel the weight of it, write down the item on their sheet and then make a prediction about whether or not it’s going to sink or float.
Then, once they put it into the water, they need to follow that up by recording the correct action that happened.
Talk about this sink or float experiment and why they think that some things are sinking while others are floating. It’s a great way to extend the learning time and to have them active and involved as well.
Questions to discuss after the experiment:
- What did all the items that floated have in common? What about those that sunk?
Did you know that oil has a different density from water? We explored this concept in our fireworks In a jar oil and water science experiment
Other ways to use this sink or float experiment
Once your child gets the hang of how it works, you can even have it to where they’re using two items at the same time and trying to guess which one will sink faster than the other.
Or, have your children take turns and use creative play as though they’re scientists in a lab.
Let them use their imaginations as well when using this science activity!
Make sure to talk about items that are safe (and not safe to put in water) before they go exploring to find more items that can they can use in the sink and float experiment.
(and just in case, be right there with them supervising so that they don’t decide to test out your cell phone to see if it sinks or floats!)
Here’s what students will learn when engaging in sink or float activities:
1. Observation Skills: Preschoolers will learn to observe the behavior of different objects in water. They will notice whether the objects sink to the bottom or float on the surface.
2. Predictions: Engaging in sink or float activities encourages children to make predictions about whether an object will sink or float before testing it out. This helps develop their ability to make educated guesses based on prior knowledge and observations.
3. Cause and Effect: By testing various objects in water, preschoolers begin to understand the cause-and-effect relationship between an object’s properties (such as weight, shape, and density) and its behavior in water.
4. Classification: Students will learn to classify objects based on whether they sink or float. This helps them understand basic concepts of categorization and sorting.
5. Critical Thinking: Sink or float activities promote critical thinking as children explore why certain objects sink while others float. They begin to ask questions and seek explanations, fostering a curious and inquisitive mindset.
6. Comparing and Contrasting: Preschoolers will compare and contrast different objects based on their sinking or floating behavior. This helps them develop skills in recognizing similarities and differences.
7. Problem-Solving Skills: When an object behaves unexpectedly (e.g., a heavy object floats), children engage in problem-solving to understand why it occurred. This encourages them to think creatively and analytically to solve the puzzle.
8. Language Development: Engaging in discussions about sink or float activities enhances language development. Children learn new vocabulary related to buoyancy, density, and properties of objects as they describe their observations and share their findings with others.
9. Hands-On Exploration: Sink or float activities provide hands-on learning experiences that are essential for preschoolers’ cognitive and sensory development. Manipulating objects in water stimulates their senses and enhances their understanding of the physical world.
10. Curiosity and Wonder: Most importantly, sink or float activities spark children’s curiosity and wonder about the world around them. They become excited about science and discovery, laying a foundation for lifelong learning.
Don’t forget to print out your free worksheet printable here!
WHERE TO GET THE ACTIVITY
GET THE SINK OR FLOAT ACTIVITY HERE
Check out the Pop Rocks and Soda Experiment too!
Tips for this Sink and Float Experiment
Build your child’s confidence by letting them take over and fun the show. After learning for a short time, they’re going to be ready to take over and experiment.
Step back and become their “assistant” in the science lab. That way, they’re in charge of the experiment and you’re just there to help them as needed.
Having a towel handy to dry off items is also a good idea. Saves a big mess from happening!
Once your child has gone through all the items, use some math skills and count up how many items sunk versus how many items actually floated.
Don’t forget to change up the items and let them do this sink or float experiment over and over again!
Like Science activities for kids? Check out these as well:
- Water In A Bag Pencil Experiment – Water Experiment for Kids
- Rain Cloud In A Jar Science Experiment
- Walking Water Experiments For Kids
- How To Make A Lava Lamp Experiment
- Baking Soda Volcano Experiment
Just came across this and it was just what I needed. Can’t wait to use it with my primary classes. Thank you for creating it and I look forward to seeing all your TPT items.