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Sink or Float Experiment for Preschoolers

Last updated on October 28, 2019

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Set up a sink or float experiment  to teach toddlers and preschoolers about density and buoyancy. This play-based learning activity combines a science activity  and a water activity, and for some extra fun, we’re adding a colourful twist. 

My kids love science. Thankfully, there are tons of easy science activities that we can do at home to quench their thirst for scientific discovery. A simple sink or float activity is a great beginner science experiment that will introduce your toddlers and preschoolers to density and buoyancy .

Physics for Preschoolers

This sink or float experiment is a simple physics experiment that will encourage your child to make predictions and observations about buoyancy and density. Through their observations, they’ll learn that buoyant objects float and dense objects sink, and if they want to be true little scientists, they can even record their predictions.

Low-prep activity for indoors or out

We love to do this low-prep activity in the backyard when the weather is nice. I set up this particular sink or float experiment three days ago and the kids have set it up themselves every day since. We’ve been enjoying it on the patio so they can get as wet and wild as they like with it.

Indoors, kids can do this activity at the kitchen sink, in the bathtub or on the floor with a tub or basin filled with water.

Engage their senses with a colourful twist!

We love adding a packet of   jello powder or juice crystals to the water. Not only does this colour the water, it gives it a wonderfully fruity scent.

The kids get a thrill out of watching the water change colour, and the pop of colour and the scent have educational benefits as well : kids retain more information when more than one sense is engaged.

What you’ll need for a sink or float activity

• waterproof toys and household items (see suggested items below)
• a container to do the experiment in i.e. plastic tub, basin, pot, bucket etc.
• drinking straws (optional)
• Jello or juice crystals (optional)

Note:  If you’re doing this experiment indoors, place a plastic table cloth or some beach towels under the bin to soak up any spills.

Suggested items for a sink or float experiment:

Items that sink.

• metal utensils
• toy car/truck
• glass gemstones or marbles (not suitable for toddlers)

items that float

• stick or popsicle stick
• bathtub toys
• foam shapes
• rubber ball

How to do an educational sink or float experiment

Start off by collecting the items for your experiment. If you give your kids a list of things to collect, this  part of the activity can be a fun little scavenger hunt for your kids.

Fill a tub or bucket with lukewarm water.

If colouring your water, you can add it now or once the toys have been added.

Before adding your objects to the water, ask your children to predict which objects they think will sink and which will float.

In a classroom, this can be done by a show of hands in favour of an item sinking or floating. If you’re doing this activity with a large group, it can be fun to have a tally beside each item to indicate each child’s hypothesis.

Now, have the kids drop the objects, one by one, into the water one observe what happens.

Once all of the items are in the water, you can extend the activity by giving the kids drinking straws to blow the floating items around. This is a fun way to teach children about kinetic energy as the air they blow through the straw propels the floating items forward.

The science behind the sink or float experiment

Before explaining why items sink or float, ask your children why they think an object sinks or floats. They may guess it’s because of size or weight or construction.

Then, explain that items sink or float based on their density . Density is determined by how close or far apart molecules are within an item. Molecules are tiny and only visible by a microscope. You can refer to this article to help explain this  to your kids. I’ve also listed a few books below that you can read with your kids before doing the experiment.

You can also use this opportunity to explain why blowing through a straw moves the floating items around the bin (kinetic energy).

Once you have prompted their learning by explaining the science behind the activity, allow your children to replicate the experiment as many times as they please. This will help to solidify their knowledge and reap the benefits of play-based learning.

Since first doing our sink or float experiment, my kids have set up their own version of the activity every day since. It’s been amazing to see their fascination with such an educational activity.

More easy science activities:

Three Chemical Reactions for Kids

Water Displacement Experiment for Preschoolers

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Reader Interactions

Lindsay Robinson

April 14, 2020 at 11:22 pm

Hi, I really enjoyed reading about your lesson. Thank you for the ideas. Where did you get the clear plastic buckets?

Jackie Currie

April 16, 2020 at 8:59 am

I’m not sure where that bucket came from, but if you search for “clear ice buckets” on Amazon, there are quite a few options there, Lindsay.

December 10, 2021 at 3:50 pm

What if, before explaining why things sink or float, you help them figure out ways to test their hypothesis? For example, if they guessed size, can they figure out what size is the cutoff? Can they find any objects that sink at a size they predict would float, or vice versa? Same with weight or whatever other theory they come up with.

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Easy Sink or Float Experiment For Kids

Easy and fun science with a sink or float experiment. Open up the fridge and the pantry drawers, and you have everything you need to test what objects sink or float in the water with common household items. Kids will have a blast checking out the different ways they can test sink or float. We love easy and doable science experiments !

Sink or Float Experiment

We used items from the kitchen for our sink and float experiment. Plus, I am sure your child will be able to come with other fun things to test! You can even have them test a collection of their favorite items, too!

Watch the Video:

💡Read all about the science below! Take a look at more experiments you can do here!

• a large container filled with water
• different fruits and vegetables
• aluminum foil
• aluminum cans
• spoons (both plastic and metal)
• anything your kiddos want to explore

💡 Tip: You could also try peeling or slicing your vegetables. 

Free Printable Sink or Float Worksheets!

Grab our free printable worksheets for kids to record their observations! Find more [here] .

Instructions:

STEP 1. Before you start, have your kiddos predict whether the item will sink or float before placing the object in the water.

STEP 2. Place each object in the water one by one and observe whether it sinks or floats.

If the object floats, it will rest on the water’s surface. If it sinks, it will fall beneath the surface. Read the science info below about why some objects float and some sink.

Extension: Does Aluminum Sink or Float?

The aluminum can, and aluminum foil were some exciting things we tested in our sink or float activity . We noticed the empty can could float, but it would sink when pushed under the water. Also, we could see the air bubbles that helped it float. Have you seen the crushing cans experiment?

Project: Does a full can of soda float, too? Just because something feels heavy doesn’t mean it will sink!

The aluminum foil floats when it is a flat sheet when it is crippled into a loose ball, and even a tight ball. However, if you give it an excellent pound to flatten it, you can make it sink. Removing the air will sink it. Check out this buoyancy activity with tin foil here!

Project: Can you make a marshmallow sink? We tried it with a Peep candy. See it here. What about a paper clip? Check out this experiment here.

Why Do Objects Sink or Float?

Some objects sink, and some objects float, but why is that? The reason is density and buoyancy!

Every state of matter, liquid, solid, and gas, has a different density. All states of matter are made up of molecules, and density is how tightly those molecules are packed together, but it’s not just about weight or size!

Items with molecules packed tighter together will sink, while items made up of molecules that are not as tightly packed together will float. Just because an item is considered a solid doesn’t mean it will sink.

For example, a piece of balsa wood or even a plastic fork. Both are considered “solids,” but both will float. The molecules in either item are not packed together as tightly as a metal fork, which will sink. Give it a try!

If the object is denser than water, it will sink. If it’s less dense, it will float!

Check out more easy density experiments.

Buoyancy is the ability of an object to float or rise in a fluid, such as water or air. It occurs because the upward force exerted by the fluid (liquid or gas) is greater than the downward force of gravity acting on the object.

In simpler terms, buoyancy is how well something floats. Generally, the greater the surface area, the better the buoyancy. You can see this in action with our tin foil boats !

In our sink or float experiment below the vegetables that float are buoyant because the upward force of the water is greater than their weight, helping them stay on the water’s surface. Those that sink are denser than water.

TIP: Discuss how some vegetables might have air pockets inside them, contributing to their buoyancy.

Try This: Do Vegetables Sink or Float?

Generally, fruits and vegetables with higher water content are more likely to float, while those with lower water content or denser structures may sink. Here are some examples:

Fruits and Vegetables That Tend to Float:

These fruits and vegetables have a higher water content and often contain air pockets, making them less dense than water and more likely to float.

Fruits and Vegetables That Tend to Sink:

• Sweet potatoes
• Avocado (when submerged)
• Winter squash

These fruits and vegetables are denser and have less water content, making them more likely to sink in water.

It’s important to note that there can be variations within each type of fruit or vegetable, and factors such as size, ripeness, and the presence of air pockets can influence whether they float or sink. Conducting a simple sink or float experiment with a variety of fruits and vegetables can be a great way to explore these ideas further.

More Fun Water Experiments

Check out our list of science experiments for Jr Scientists!

• Walking Water Experiment
• What Materials Absorb Water?
• What Dissolves In Water?
• Saltwater Density Experiment
• Do Oranges Sink or Float?
• Freezing Water

Printable Science Projects For Kids

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• Be a Collector activities pack  introduces kids to the world of making collections through the eyes of a scientist. What will they collect first?
• Know the Words Science vocabulary pack  includes flashcards, crosswords, and word searches that illuminate keywords in the experiments!
• My science journal writing prompts  explore what it means to be a scientist!!
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Science Projects > Physics & Engineering Projects > Learn About Sinking & Floating Objects  

Learn About Sinking & Floating Objects

All objects, including liquids, have a mass-to-volume ratio known as density. Density is a measurement for how compact (close together) the molecules in the object are.

In the first sink or float experiment, you’ll predict the density of common household objects. In the second oil in water experiment, you’ll analyze the density of common liquids.

Floatable Objects Experiment

Sink or float.

You probably already know that some things will float in water and some will not. Do you know why that is? Sometimes the best way to find out if something will sink or float is just to try it—and that is exactly what you’ll do in this “floatable objects” experiment! Gather up some objects from around your house to test their sinking or floating abilities. Make sure all of the items you pick can get wet!

What You Need:

• a large container of water (or fill up a sink or bathtub)
• lots of small objects of different weights and materials (plastic, metal, wood, foil, Styrofoam)
• a few larger objects
• HST worksheet

What You Do:

1. Look at the objects you collected. Draw a picture of each one in the boxes on the left side of the worksheet.

2. Make a prediction about each object – do you think it will sink or float in the tub of water? (To make a prediction means to say what you think will happen.) Mark your prediction on the worksheet for each item (circle float or sink).

3. Drop the objects into the water one at a time. Watch what happens to each one. Did you predict correctly? Circle “float” or “sink” next to each object on the sheet to show the results of your experiment.

What Happened:

Even though some of your items seemed very light (things like a paperclip or a button), they still sank in the water. Some objects that might have seemed sort of heavy (like a wooden block) probably floated.

That is because whether an object sinks or floats in water doesn’t just depend on its weight or size. It also depends on its density. Density is a measure of how solid something is. All things are made up of tiny particles called molecules. If the molecules inside an object are very close together, the item is solid, or dense. If the molecules are farther away from each other, the object is less dense, or less solid. An example of a very dense item is a penny. A cork is less dense.

A penny, paperclip, or button sank because the materials they are made of (metal for a paperclip and penny, plastic for a button) had more density than water. (Their molecules are closer together than water molecules are.) A cork, piece of wood, or Styrofoam floated because those materials have less density than water. All the objects that were less dense than water floated in the water! Objects that were more dense than the water sank.

Oil in Water Experiment

Liquid density.

Do you know why oil floats on water? Would an object that sinks in oil be able to float in water? Try this experiment to find out and learn more about density.

• 1-cup glass measuring cup
• vegetable oil
• food coloring
• small objects (we used a raisin, grape, cork, button, penny, screw, and piece of wax)

2. Add 1/3 cup of corn syrup so that the level of liquid in the cup rises to the 2/3 cup mark.

3. Add 1/3 cup of oil to fill the cup to the 1 cup mark.

4. Watch what happens. The layers should separate so that the corn syrup is on the bottom, the oil is on top, and the water is in the middle.

5. Guess where each of your objects will land when dropped into the cup, then test them out one at a time.

The corn syrup was the most dense liquid, so it sank to the bottom of the cup. The water was less dense than the corn syrup, but more dense than the oil, so it settled on top of the corn syrup. The oil was the least dense, so it floated on top of the water!

The objects that you dropped into the cup had different densities. Each object sank into the cup until it got to a liquid that was more dense than it. The cork was not very dense at all, so it floated on the surface of the oil. The wax fell into the oil, but not all the way to the water, so it was more dense than the cork, but not as dense as water. The grape and the raisin fell to the bottom of the water layer, but not into the corn syrup. That means that they were less dense than the corn syrup, but more dense than the water! The penny and screw were very dense; they sank all the way to the bottom of the corn syrup!

To learn more about the properties of water, check out our Science Lesson, Learn About Water .

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Fun with Mama

Toddler and preschool activities

Written by Nadia T • Feb 8, 2024 • 4 Comments

Sink Or Float Experiment + Worksheet

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 ?

Table of Contents

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 container/water table – we used the Ikea Flisat table.
• 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

More Science Experiments

Nadia is a mom of 4, with a passion for making childhood education fun through play. She encourages parents to spend quality time with their kids through fun kids activities and enjoys art, traveling, and doing activities with her children.

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August 29, 2021 at 10:37 am

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.

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Play to Learn Preschool

A delightful preschool experience

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Sink or Float Experiment

This sink or float experiment is a preschooler’s dream! Students remain engaged in an inquiry-based learning project, full of surprises and sensory experiences that they will talk about all year long.

Predicting Outcomes in Preschool

Predicting is an exciting skill that comes with practice. In preschool, students predict what will come next in class based on the routines established throughout the year. They may also predict if their baseball team will win an upcoming game based on how they’ve played in the past. Recognizing what has previously happened to predict what might happen is a skill that can be put to the test in the preschool classroom in a number of ways.

• What will happen next in the story? (Predictable patterns are HUGE in preschool books !)
• What do you get when you mix red with yellow ?
• Do you think sandpaper is rough or smooth? Which of your 5 senses helped you make that prediction?

Does It Sink? Does It Float?

This sink or float experiment is perfect for the beginning of the preschool year because it teaches important, familiar vocabulary (many students know the word float from swimming) and requires very minimal preparation. Begin by talking about the terminology ( sink and float ). Show a variety of objects and allow students to hold each one. Discuss predictions for each item. Why do you think it will float? (“It’s very light.”) Why do you think it will sink?

Ideas Items to Test:

• Pencils & crayons
• Spoons (both plastic and metal)
• Lemons & Limes (Check out this cool article about these!)

Ask the students to make predictions and post them on a pocket chart tally marks or name cards. For each item, count the number of students who think it will sink versus the number that thinks it will float. This is an excellent time for a bit of math review using words like more or less .

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Let the Fun Begin!

Once predictions have been made, it is time for the fun to really start! If possible, take the experiment outside or protect an indoor area with a plastic table cloth as it will inevitably be a little wet. There is only a little setup and a few supplies needed to make this experiment one the students will not soon forget.

Supplies Needed for the Sink or Float Experiment:

• a bucket or tub of water
• items to test in the experiment

As a starting point, begin by allowing students to explore apples in the water. Exploration is a critical step in developing an understanding of a concept. Students may try and push the apple to the bottom, only to watch it float back up to the top.

Does the apple float or sink?

Once students have explored the apples, come back and discuss what they discovered as a class. Were their predictions correct? Remind students that predictions are guesses, and it is okay if they guessed wrong – that’s how we learn! Some students may even begin to make connections such as “I knew it would float. I went bobbing for apples last year.”

More Sink or Float Experiment Fun

Once students have had a chance to explore the buoyancy of the apple, the next step is to extend the learning. Challenge the students to go back inside the classroom and find something else that would float. Discuss why they think it would float. Is it similar to the apple in any way? These discussions are great ways to build connections.

Next, ask students to find things that will sink. This can be a bit more challenging. Many of the heavy things in the classroom (blocks, for example) that the students think would sink are made of wood, which floats. Guide students as necessary, then allow them to continue to search for similar items as needed.

Other Preschool Science Experiments

Sometimes, teachers are intimidated by planning science lessons because it sounds like a big and complicated project. Preschool science does not have to be that way, though! Just exploring the world around them is enough to spark a curiosity that will build knowledge for years to come.

Check out this Resource from my Shop!

Preschool Science Centers for the Year

Students will enjoy hands-on  SCIENCE CENTERS  all year long. Each unit includes a list of supplies for each topic, learning objectives, lesson ideas, as well as photos and activities that students will want to explore again and again! Encourage young learners to ask questions, make observations, and develop scientific thinking skills.

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Meaningful Activities for Learning & Creating

July 20, 2013 By Chelsey

Science for Kids: Sink or Float (with Free Printable)

Kids love discovering which items will sink or float ! It’s a great hands-on science activity for kids of any age and really gets kids thinking and predicting. Here’s how we set up our sink or float science project, as well as a free printable kids can use to record their observations.

Follow our Science for Kids Pinterest board!

This experiment was actually initiated by Lucy herself! She had approached me one day and asked if I could help get her a container of water to test out some objects she had collected.

Kids are naturally curious about floating and sinking, and this science activity provides the opportunity for children to make predictions and observations about floating and sinking with minimal help.   (This post contains affiliate links.)

Materials for Sink or Float Science:

• Large container filled with water
• Objects collected from around the house
• Free printable recording sheet  (optional)

• Walk around your house with your child and collect items you’d like to test out. (We collected these things: bristle block ,  plastic toy, crayon, cork, a spoon, and a rock.)
• Fill a large container with water. (We used a large plastic bin.)
• Find a place to conduct the science experiment where your child can easily reach the bin and where you don’t mind a bit of water possibly getting out.
• Have your child choose one object at a time.  Do you think it will sink or float? Why?   Have your child place the object in the water and observe what happens. (Optional: Record the result on the recording sheet. You can have your child draw a picture or write the name of the object or model writing and drawing the object yourself.)
• Repeat this for all the objects.
• Why do you think some objects floated and some sank? Is there anything the same about the objects that floated? How about with the objects that sank? 

Lucy had so much fun with this! It was fun to sit back and watch her excitement and curiosity grow as the activity went on. At one point she even came up with a new question, “I wonder what will happen if I push the floating things down to the bottom. Maybe they will stay there.” She discovered they still floated right back up!

• We took our experiment outside. That way there was no worry about a mess being made.
• I left this outside for a few days for the kids to experiment with on their own during play time.
• This would also be a fun center in a school classroom!

Want to go even further?

Even more activities to inspire creativity and critical thinking for various ages.

• Fill up a giant backyard pool with water and do this experiment with larger items.
• For older kids, introduce the terms density and buoyancy to explain what happened.
• Place an orange in your container of water to see if it floats. Peel the orange and try it again. What happened?
• Try the Floating Egg experiment found on Tinkerlab.
• Do our Dancing Raisin science experiment.

Find more STEM activities in our ebook! Learn more about it here , or b uy it now here !

STEM Experiment: Scientific Method Float or Sink Activity

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Oh the scientific method! Such a structured way to exploration but so helpful when taking on a big scientific project. Scientists and researchers use this method when trying to answer questions about our world. Following the scientific method allows researchers to have a guide that helps them organize all the information. Because let’s face it, nowadays the information at our fingertips is so huge! With this STEM experiment, you can help your children get an understanding of using the scientific method in a fun and educational way.

** Check out our Simple Science Project For Kids: Float or Sink for a simple play-based version of the Float or Sink experiment! Perfect for younger kids or if you are looking for a less structured activity. **

Having a tool like the scientific method is very useful. And introducing it to your kids will help them with problem-solving and analytical skills. It will give them a way to structure their thoughts when problems arise. It also shows them to take their time to think about the problem and analyze different perspectives before choosing the best solutions.

Some Background Information

The scientific method is used by scientists to structure their research and make the process of discovering something more efficient and effective.

The steps to the scientific method are the following:

As you can see, there are many steps before starting any experiment. By researching and writing down your hypothesis first you will be able to set up the perfect experiment to answer the question. You will also have some background knowledge that will help you when doing the experiment.

STEM Experiment: Let’s find out the Answer to…

The question.

So here is a question for your children:

Why do you think things float or sink?

They probably have some ideas and answers for this. Encourage them to write down their original thoughts so that you can compare them once you are done with the STEM experiment.

Here you can find a free printable to fill out as the experiment goes on.

Time to Research

Research is usually done by reading and reading and more reading of scientific papers, journals and relevant material. We are not going to do this 🙂 We will move the research along by asking our kids some questions. So let’s get your kids brain to work a bit:

• Think of objects that float/don’t float, what are they made of? How big are they?
• Do you float in water? Can you make yourself float more or less? (By filling your lungs with air and holding your breath you will float more)
• Show them a list of materials, do you think materials matter?
• Show them different sized objects or images of objects, do you think size matters?
• What other things do you think affect the ability of an object to float or sink?

Write down a Hypothesis you want to test

Now that you have brainstormed about why an object floats or not you can make a hypothesis or more than one! But first, what is a hypothesis?

• A hypothesis is an idea or explanation for something that needs to be proved
• A hypothesis tries to answer the question of your research (in this case, why do things float or sink?)
• A hypothesis is proved through experiments and testing

Some ways you can express your hypothesis:

• Things made out of _______ float/sink
• Things that are ___________ float/sink
• Floating depends on ______________

Time to test those Hypotheses

Once you’ve made a hypothesis, ask your child how you could test it. Here are a few examples of experiments you could do with them but feel free to come up with your own!

First step in any experiment is to gather the materials you are going to test and any tools you might need. For any experiment you are going to need:

• Objects to test (different sizes, materials and shape)
• Water, in a bucket, in the sink, in the bathtub, in a small outdoor pool
• Paper and pencil to write down your findings

Ways you can experiment and make your children think about the hypotheses:

• Categorize the objects you have collected and test their floating ability by pairs:

           ○ same material, different size

           ○ same material, different shape

           ○ same size, different weight

• Get plastic containers and fill them with different materials and test the floating capabilities, for example:

          ○ empty container

          ○ container filled with cotton (what happens when cotton gets wet?)

          ○ container filled with sand

          ○ container filled with water

          ○ container filled with sticks

          ○ container filled with coins

          ○ container filled with stones

• Do the same with a glass container

There is a list of materials and object ideas in the guide for inspiration. Let them experiment and play 🙂 there is no rush to finish the activity! Don’t forget to write down your findings so you can analyze them later!

Let’s analyze those Resultats

Now it’s time to look back on your STEM experiment and the results to see if your hypothesis was correct. You can ask the hypothesis back in question form and see if the results support it! Other questions you can ask to discover why certain objects float:

• Does wood/plastic/metal/stone float?
• Does shape or weight matter?
• What containers could float? Which ones would sink? What was inside of them?

Conclusion Time

So did you find out why things float? Did you test your hypothesis? Did you get some fun ideas about other things you could test with this method? Did more questions pop up as you experimented? Welcome to the STEM world! The questions never end 🙂 and this is oh so important for your children to experience. How to answer questions using the scientific method is a must in the STEM world. If you want a more detailed answer to why things float you can download the printable guide, there is an explanation at the end. But I’m sure that you will have a pretty good idea about the answer from all that scientific experimenting you will do 😉

So to finish up the activity you can talk about what you discovered and if there are more things you would like to research together. If you have any topics you would like me to cover just comment below and I’d be happy to write a post about it in the future. I hope you enjoyed this activity and had fun experimenting and discovering how our world works.

For more information about STEM and how to transform your STEM activities at home, check out these posts:

• 5 tips to transform STEM activities at home
• What is STEM and why is STEM learning important?

Check out other fun STEM activities to sneak in some STEM learning:

• STEM activity: Build a pyramid and learn about shapes
• STEM project: Engineer a house out of natural materials
• STEM challenge: The Tower of Random Things
• STEM water play: 8 fun activities to try this summer
• STEM Road Trip Experiment

Happy STEM learning!

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Sink or Float Experiment: Physics for Kids

By: Author Jacquie Fisher

Posted on Published: August 20, 2019

Categories Kids Activities & Crafts , Science Experiments

Kids will LOVE this easy sink or float science experiment that doubles as a great outdoor activity!

Welcome back to our Summer Science series hosted by Edventures with Kids and Inspiration Laboratories! 

So far, we’ve covered —

• biology { books about plants, animals & humans },
• geology { rock, volcano and fossil activities } and
• astronomy { marshmallow constellations }. 

This week, we’re focusing on physics and boy, was it hard to narrow down what we wanted to do!  There are so many areas of our lives that are governed by the principles of physics — like the fact that we don’t all just float away due to gravity 😉

But we finally decided on a great science experiment that involves water and your favorite fruits — super simple & a great outdoor activity too!

Sink or Float Experiment for Kids

Physics is the area of science that focuses on matter and energy.  The areas of mechanics, light, heat, sound, electricity, magnets and forces are all broad areas of physics. 

I know — it’s a HUGE part of science and life. 

So where do you begin? 

With kids, the easiest place to begin is with life experiences. 

Talk about the force of gravity when they drop something.  Or explore the idea of sound waves and why it’s easier to hear someone talking when they are right next to you vs. when they are in another room.

And I often rely on some good books — because they always bring up great questions!  Here’s a few that we really love including their affiliate links that are perfect when discussing physics concepts:

For this specific experiment, there are a few awesome books that help explain the concepts of density, buoyancy and physics:

Things that Float and Things that Don’t – with fun illustrations and a story format, this book helps kids ages 4 – 8 years to understand why some items float and some sink in water.  I also love that it introduces how to make predictions too!!

What Floats? What Sinks? is a colorful exploration into these physics concepts!  This nonfiction book has gorgeous photographs, clear explanations, a glossary and fun physics activities for kids ages 5 – 9 years old.

We love the Let’s-Read-and-Find-Out Science series!  The book Forces Make Things Move is a great look into the various forces that exist around us. 

Kids will learn about concepts like gravity and friction in a fun and tangible way.  It’s also a great refresher for us parents who haven’t talked about physics since that high school science class 😉

Older kids can also enjoy exploring science with Ms. Frizzle and the class.  Once they outgrow the Magic School Bus picture books, try the chapter book series which shares more details about the various science topics. 

The Classic Sink & Float Experiment: Science Concepts

I can’t believe that I haven’t shared a hands-on sink & float activity yet!  This is one of those things that kids do all the time — they LOVE to play with items in water. 

First, the physics behind sink & float:

We’ll be testing two physics concepts during this activity. 

The first is density — the weight of an item in relation to it’s volume.   Volume is how much space something takes up — so Dad has a larger volume than the kids.

The easiest way to explain density is that everything is made up of molecules — the closer together those molecules are, the more dense the item. 

Try not to let kids get caught up in saying “if it weighs more, it will sink”. 

Something doesn’t need to weigh a lot to sink — for example, give them a really small rock and a really large rock.  They will both sink because they are both dense.

The second concept that you can introduce is buoyancy. 

Buoyancy is the upward force that supports items in water.  This is why we feel lighter when we’re in a pool — there’s actually a force helping to keep us supported and afloat.

I frequently recommend that you try this experiment in the tub while your kids are taking a bath but since we’re dealing with fruit, you might want to use a large pot or bowl instead of the tub (then you’ll be able to eat the fruit later 😉

Sink & Float Experiment: Hands-on Physics for Kids

Ok, time to get wet! 

Head to the fridge or your local Farmer’s Market and grab some fruits and veggies — we used a variety of small and large items (it’s just more fun that way).  You’ll also need a large bowl or pot filled with water.

BEFORE you let the kids drop anything in the water, print off our Sink & Float worksheet (below) so kids can make a few predictions about what fruit & veggies will sink or float.

Let the kids hold each of the items you will test.  Ask them “Do you think it will sink or float?” 

Talk about the idea of density and which items they think are very dense vs. not so dense. Then have the kids circle their prediction for each item. 

This is a really important step in any science experiment — forming predictions and testing to see the results!

Now the fun — drop each of the items into the water to see what happens!

Circle the results for each item — how many did you predict correctly? 

We were 50/50 for our small fruit items.  My daughter realized that blueberries both sink and float.  And strawberries float too!  When we cut them open, you can see that the middle (core) of the strawberry is hollow.

Both peppers and nectarines float!  Peppers were an easy guess but necterines took a little thought (the pit being hollow was our learning experience). 

Here’s where we can really see buoyancy at play — see how the pepper floats on the top of the water but the nectarine floats below the surface?  That shows us how the force of buoyancy affects items differently depending on their density.

And a melon is one of the coolest things to test (well, that and pumpkins but we don’t have any of those yet). 

Melons can be really large compared to the other items and sometimes feel pretty heavy (easy to trick the kids with this one 🙂

And yep, it floats!

Grab a copy of the Sink & Float worksheet along with some of your favorite fruits & veggies and test out some physics with your kids this week 😉

More Cool Science Experiments for Kids

There are so many ways to discover the different areas of physics! Try a few of these activities including affiliate links to some of our favorite science items:

• If your kids enjoyed this activity, try this STEM Challenge: Building Boats that Float !
• Try easy physics experiments with the Sick Science: 9 Easy Experiments kit
• Hop over and explore color and temperature with Inspiration Laboratories this week.
• Explore all types of physics concepts with the Physics Workshop activity kit !

Be sure to see all of the booklists & activities in our Science for Kids series!

Books & Websites that explore Plants, Animals & the Human Body

Backyard Earthworm Experiments

The Science of Rocks, Fossils and Volcanoes

Digging for Dinosaurs — Learn to be a Paleontologist

Explore the Night Sky – Marshmallow Constellations

Books about Space

Solar System Activities for Kids

Fantastic Forces & Water Rockets

Does your Food Sink or Float?

Create Your Own Wizard’s Lab

Make a Cup Cake (Chemistry of Baking)

Blowing Up Balloons/Blowing Out Candles

Kids Activities that Explore Ecology

Learning about Biomes

Create an Under the Sea World: Exploring Ocean Zones

Mama's Must-Haves

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Sink or float experiment

Explore density and buoyancy with this super simple sink or float experiment for kids. It’s exactly what it sounds like: Simply gather testable materials and a tub of water and test whether an object floats or sinks!

Preschool activities can be super engaging, can offer learning opportunities, and be super simple too. Small children can be introduced to the scientific method of researching, hypothesizing, experimenting, analyzing, and concluding through this simple sink or float activity. See what we tested below!

What is a sink or float experiment?

This is an excellent activity for young scientists – Especially those who love playing outside! Learn why we think science for kids is so important in this post.

This activity is a very simple and visual way to teach children about the scientific concepts of density and buoyancy. Depending on the age of your children or students, you’ll want to modify the science language you use. In preschool, I would ask “do you think your object will sink or float?” and “why do you think this object will float?”

For older kids, you can begin talking about density and buoyancy as well as deeper hypothesizing and analyzing. What makes an object buoyant? How can you predict the density of one object compared to the next? Etc.

Download these worksheets before starting!

This is a great standalone activity. Your little ones will learn without writing things down. But, if you want a worksheet to supplement it, you can download my Float or sink experiment worksheet from my Teachers Pay Teachers store for free. Or, if you just want to focus on learning the scientific method, I have my Scientific Method   worksheet listed there for free too.

You can also download the first one from the PDF below.

Creating the sink or float experiment: What you’ll need

This is meant to be a child-led activity, so the materials needed will vary from one kiddo to the next. Just make sure the items are safe and that they’re allowed to be tested (unlike your cell phone or favorite watch, for example).

Here is what you will need:

• You could also use the kitchen sink
• Whatever objects your children would like to test (we used a flower, a rock, a stick, a leaf, and a pinecone)

How to create the sink or float experiment

This is one of my most simple science experiments. All your kids have to do is this: Collect materials to test, hypothesize (make an educated guess) about which will float and which will sink, and then test one item at a time!

This is a fun way to encourage your children to be involved in the scientific process as they gather materials, practice testing ideas, and share their observations as they tell you which things sink and which things float.

Extended learning: Sink or float science

A simple extension to this is to challenge your little scientists to build the strongest aluminum foil boat that they can. Then, once it’s built, fill a container with water, place the boat on the water, and see how many pennies or marbles (or whatever other items you have a surplus of) you can stack on the boat before it starts sinking.

We hope you enjoy this really easy sink or float experiment! It’s the perfect science activity for a sunny day (or as an indoor activity – but keep a mop close!). Extend learning by asking kids to write or draw what they discovered. For a math component, you could do some graphing with the results, too.

Other experiments you could try

We’ve been conducting lots of science experiments lately! Here are some you might want to check out:

• What melts ice the fastest? 3 STEM activities for kids
• Which color absorbs the most heat?
• Ice insulation STEM challenge

More science posts

Searching for more science experiments and science-related activities to do with your little ones? Check out this category to see all of our posts about science for kids!

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Fantastic Fun & Learning

Fun learning activities and things to do with kids

Sink or Float Science Activities

By Shaunna Evans 6 Comments · This content may contain affiliate links.

We’ve been incorporating a lot of open-ended explorations into our preschool activities. These sink or float activities are an engaging way for kids to explore the properties of different materials. They are great science investigations for toddlers and preschoolers.

I love how Ashley from Life with Moore Babies encouraged her kids to collect  their own objects for this  Does it Float or Sink?  activity.

These  Sink or Float Activities for Toddlers  from Mom Inspired Life include some great objects that I hadn’t thought of experimenting with before.

In  Science for Kids: Sink or Float , Chelsey from Buggy and Buddy helps her daughter put together her own science investigation along with a great free printable.

This Sink and Float Water Play with Natural Materials is perfect for toddlers on hot summer days.

This Does it Sink or Float? – Pirate Style activity is perfect for little learners.

Teach your kids about surface tension in this Make a Paperclip Float experiment.

This Will it Sink or Float? Is a great easy science experiment your kids will love.

This Salt Water Density Experiment For Kids is a fun twist on the classic sink or float experiment. Extend this experiment by testing to see if there is a difference between raw and and hard-boiled eggs in this egg floating science experiment .

Use leftover fruit to test these Fruity Boats .

This Garden Sink or Float Activity will be an instant hit with your kids.

FREE PRINTABLE SINK OR FLOAT RECORDING SHEET

Design your own Sink or Float Science Experiment with this free printable recording sheet.

Gather materials and experiment to see whether they sink or float. Then recording the results by drawing or writing in the free printable sink or float recording sheet.

 Complete the form below to get your free printable sink or float recording sheet.

More Math and Science Activities with Fizz, Pop, Bang!

Fizz, Pop, Bang! Playful Science and Math Activities is designed to bring hands-on fun to math and science play. It’s full of engaging and powerful learning opportunities in math and science, shared through ideas that incorporate art, play, sensory learning and discovery, for a whole-brain approach.

It includes 40 educational projects and 20 printables including a set of build-your-own 3D shape blocks, engineering challenge cards and a range of math games.

Learn more about Fizz, Pop, Bang! or you can buy it now !

Reader Interactions

March 29, 2022 at 3:37 pm

We love all your hard work. It makes learning fun!! Thank you.

August 14, 2013 at 8:03 am

My son loves sink and float! Would you share these today if you have a moment? I would love to see you over there!

August 17, 2013 at 9:00 pm

Would love to share. Thanks for the invite.

August 13, 2013 at 4:18 pm

Thanks for including our experiment!

Mary Catherine

August 13, 2013 at 12:52 pm

Shauna, what a lovely collection of open-ended science! As always, I love discover & explore and FFL!!

August 17, 2013 at 9:08 pm

Thanks, Mary Catherine!!

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Sink or Float: A Science Experiment for Young Learners

Do toothpicks float? Does a plastic spoon sink? In this fun and easy Sink or Float Science Experiment, your little ones will find out which types of objects float and sink with this exciting  science project . Your kids will get to practice making hypotheses about what they think will happen to each object and then test whether they are right through experimentation.

*Post contains affiliate links; see  disclosure  for additional details.

Ready to get started with this fun buoyancy activity contributed by the team at  Education.com ? Let’s get started!

Experiment for Young Learners

What you need:.

• Plastic dishpan
• 5-7 Small household items. Examples include a paper clip, plastic spoon, coin, toothpick and sponge
• Notebook or binder paper
• Marker or Pen
• 2 sheets of construction paper

What You Do:

1. To set up for the project, place the newspaper on a table.  Write the word “Sink” on one sheet of construction paper and the word “Float” on the other. and the other piece with the word “Float.” Put the objects on the newspaper.

2. Review the meaning of the words “sink” and “float” with your child.  Explain that we are going to do an experiment to see which of the objects sink down when they are placed into water and which ones float.

3. Ask your child to guess which objects will sink and which one will float.  Place each object next to the appropriate sheet of construction paper based on the prediction.

4. Divide a piece of binder paper into thirds vertically. Ask your child to draw each object on a piece of binder paper and write her prediction next to each object in the middle column of the paper (sink or float). On the right column of the paper, add a label that says “Result”.

5. Next, add some water into the plastic dishpan. Choose one of the objects and place it into the water. Observe whether it sinks or floats and record the result on the binder paper next to each prediction. Repeat this for each of the remaining objects.

6. Have your child compare the prediction for each object to the result. If any of them do not match, discuss why your child thought about those objects and what she learned. Your child should now have a better understanding of what types of objects sink and float!

More Sink or Float Learning

Want some other ideas to help with teaching buoyancy to your young learner? Here are a few resources to add to your Sink or Float Science time:

• Buoyancy Worksheets from Education.com – These worksheets are great for documenting the experiment or piquing interest a day or two before doing it with your kiddo. While you’re there, be sure to check out their other free worksheets . I’ve been using them in our homeschool for years! :)
• Magic School Bus Season 2, Episode 13 – You can buy the Season 2 DVD on Amazon, stream the episode through your Netflix subscription, or buy the individual episode through Amazon Prime Video.
• Reading Ideas for early learners – Things That Float and Things That Don’t by David A. Adler, Float by Daniel Miyares, The Magic School Bus Ups and Downs by Joanna Cole, and  What Floats in a Moat? by Lynne Berry.

Lastly, if you’d like to find more inspiration for tackling preschool at home, see our Ultimate Guide to Homeschooling Preschool. :)

Privacy Overview

Will It Sink or Float?

This simple sink or float science experiment is great for kids of all ages! It’s a fun way to work on making predictions, testing hypotheses and drawing conclusions. And, as a big bonus, it’s perfect for Valentine’s Day.

Snag your set below and then hop over and grab even more STEM fun with our Epic STEM Challenge Bundle!

This post contains Amazon affiliate links.

Getting Ready

To prep, I grabbed a bag of conversation hearts and seven clear glasses. Then, I raided our pantry for every liquid I could find: apple juice, white vinegar, molasses, olive oil, water, maple syrup, etc.

Then, I printed off the free sink or float prediction sheet (below) and grabbed a pencil for Middle Brother to use when he filled it out.

Middle Brother (age 4) LOVES  science experiments!  Therefore, he was eager to jump in and start working. We filled each cup with a different liquid and labeled them with a strip of Scotch Expressions Tape .

I helped him write down the name of each liquid on the chart. Then, focusing on one liquid at a time, he predicted whether the conversation heart he would drop in later was going to sink to the bottom or float on top. I marked his hypotheses with an “X.”

The most exciting part came next: finding out the results! We grabbed our cup of molasses, the first liquid on our list, and Middle Brother dropped in a conversation heart.

He was thrilled to see the heart plop on top of the sticky liquid and just float.

We marked the column “float” with a circle to show it was the actual result and talked about how it differed from his prediction (that the heart would sink).

Moving from one liquid to the next, Middle Brother continued testing his hypotheses and recording his results just like a grown up scientist.

The Science Behind It

Everything is made up of molecules – teeny tiny particles that can only be seen with a microscope.

If those molecules are packed very closely together, they are more dense. If the molecules are spread apart, they are less dense.

Each of our liquids had a different density. As a result, when we dropped the conversation heart on top of a liquid, it would float on top if the liquid was more dense than the candy heart.

If, however, the liquid was less dense than the candy heart, it would sink to the bottom.

Ready to Experiment?!

Snag your set below and then hop over and grab even more STEM challenges kids will LOVE with our Epic STEM Challenge Bundle!

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Orange Buoyancy Kids’ Science Experiment

Looking for a quick kids’ science experiment that’s sure to wow little scientists?! This simple buoyancy activity requires just a few common household supplies. Kids will love learning why things sink and float in this easy, hands-on experiment!

Follow the simple step-by-step below and then grab 30 more easy-to-follow science experiments kids will beg to repeat (plus a no prep science journal to keep track of their results!) in our shop !

Playing in pools, floating down rivers, and bobbing about the ocean in their PFDs…

This summer has given us plenty of opportunity to see buoyancy at work in everyday life.

My kiddos loved figuring out just what helps keep them afloat with this oh-so-simple twist on the classic sink or float experiment.

And I loved that this experiment took mere minutes to complete!

Getting Ready

This experiment was ridiculously easy to set up!

I grabbed a tall glass vase (a large bowl works, too), an orange, and water and we were ready to roll.

Kids’ Science: Sink or Float?

I called over my kids and asked them if they thought the orange would sink or float in water.  They both predicted that the orange was heavy and would sink.

Next, I had each child pour water in the vase until it was about 3/4 full.

Then, we plopped the orange in to see if their guess was correct.

The kiddos were pretty amazed to find out they were wrong and the orange actually floated!

After they tried to sink it by pushing and poking it under the water, I removed the orange and asked them to peel it.

I asked them if they thought the PEELED orange would sink or float and they both guessed that it would still float because it was now smaller with the peel removed.

Wrong again!  The orange sank to the bottom.

Now they were thoroughly confused.  They continued to take the peeled orange in and out of the water to see if they could somehow get it to float again but no matter how hard they tried, nothing worked.

The Science Behind It

Why is it that a peeled orange sinks even though it is lighter than an unpeeled orange?  The secret lies in its peel!

Buoyancy is the tendency of an object to float or sink in water or any other fluid.

Whether an object is buoyant is determined by Archimedes’ Principle which states that any object in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object.

When the orange is placed in water, there are two forces working on it in opposite directions: gravitational force pulls the orange down while buoyant force pushes it up.

Gravity pulls the orange down with a force equal to the weight of the orange, while buoyant force pushes the orange upward with a force equal to the weight of the water that the orange displaced.

If the orange can displace a volume of water that equals (or is greater than) the weight of the orange, then it will be buoyant and float.

While making the orange weigh slightly more, the peel of an orange helps displace enough water to make the unpeeled orange buoyant.

The peel is also full of tiny pockets of air that make the unpeeled orange less dense than water – and the orange floats.

When you remove the peel, the orange no longer displaces enough water to overcome gravitational force. The orange becomes more dense than water and it sinks.

To really make this experiment relevant to my kiddos, I explained that the peeled orange was similar to them in a pool.  When they curl into a ball and make themselves smaller, they sink to the bottom.

But since their life jacket is made of foam and contains tons of air pockets, when they put one on, they can suddenly displace more water while becoming less dense, and they easily float.

More Simple Science Kids Will Love

Inspire kids to LOVE science with 30 more jaw-dropping experiments they’ll beg to repeat! Grab 30 easy-to-follow science experiments (plus a no prep science journal to keep track of their results!) in our shop !

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Things That Float or Sink in Water

Identifying things that float or sink in water is a common science assignment. The project is straightforward enough for young children, but predicting whether a substance or object floats can become complicated because it involves both the density of the material and the buoyancy of an object. For example, ice floats on water. Steel is dense, so it typically sinks, yet ships made of steel sail on the seas every day.

Here is a list of substances that float or sink on water, based on density, and a look a how buoyancy lets even dense materials float.

List of Things That Float or Sink on Water (Density)

Density is the mass per unit of volume of a substance. The more mass there is in a volume, the higher the density. The density of water is about 1 gram per milliliter (g/ml) or 1 gram per cubic centimeter (g/cm 3 ). So, things that are less dense than water float on it, while substances that are more dense than water sink in it. For numerical values, consult a list of densities of common substances . Otherwise, the list of things that float are all materials with a density less than 1 g/ml, while the list of things that sink all have a density greater than 1 g/ml.

List of Things That Float

• All gases : Air, oxygen, hydrogen, nitrogen, carbon dioxide and other gases float on water. Even the densest gas, tungsten hexafluoride, has a density of 0.0124 g/ml and floats on water.
• Lithium metal
• Sodium metal
• Rotten eggs

List of Things That Sink

• Dishwashing liquid
• Heavy water
• Heavy water ice cubes
• Magnesium metal
• Aluminum foil
• A black hole

Does Poop Float or Sink?

Human feces (poop) either sink or float, depending on a few different factors. Mostly, poop is denser than water and sinks. However, it floats if a person’s diet is high in fiber or the stool contains a lot of gas or fat. While not necessarily indicative of a medical condition, floating poop can be indicative of an infection, pancreatitis, or irritable bowel syndrome.

Even a dense object floats its shape gives it buoyancy. Buoyancy is the upward force exerted on an object submerged in a fluid (liquid or gas) that opposes the weight of the object. This force is due to the pressure difference between the top and bottom of the object, which creates a net upward force.

According to Archimedes’ principle, the buoyant force on an object equals the weight of the fluid displaced by the object. If the weight of the fluid displaced is greater than the weight of the object, the object floats. If the weight of the fluid displaced is less than the weight of the object, the object sinks.

Note that it does not matter how much water is below an object (assuming it is not touching the bottom). An object floats equally well in shallow water as in deep water. Also note that adding more weight to a floating object changes the balance of forces. So, if you pile enough mass onto a floating object, it eventually sinks.

A good example of a dense object that floats is a metal ship. Despite being much heavier than water, steel cargo ships and tankers float because the shape of the hull displaces a large volume of water, creating a buoyant force that supports their weight.

Prove It For Yourself

While it’s counterintuitive that heavy objects float if they displace enough water, it’s easy to prove it for yourself. Take a sheet of aluminum foil and crush it tightly into a ball. It sinks if you throw it into a bucket of water because aluminum is more dense than water. But, if you fold up the edges of a sheet of foil to form a makeshift boat, the aluminum floats.

Common Misconceptions About Floating

There are several common misconceptions about how floating works. The following statements are false:

• Light objects float and heavy objects sink, regardless of their size or shape.
• A floating object is completely above the surface of the liquid.
• Objects only float because they contain trapped air.
• Objects float better in deep water than in shallow water.
• Bolz, Ray E.; Tuve, George L., eds. (1970). “§1.3 Solids—Metals: Table 1-59 Metals and Alloys—Miscellaneous Properties”. CRC Handbook of tables for Applied Engineering Science (2nd ed.). CRC Press. ISBN 9781315214092.
• Lima, Fábio M. S. (2014). “A downward buoyant force experiment”. Revista Brasileira de Ensino de Fisica . 36 (2): 2309. doi: 10.1590/S1806-11172014000200009
• OECD (2012). “Test No. 109: Density of Liquids and Solids”. OECD Guidelines for the Testing of Chemicals , Section 1. ISBN 9789264123298. doi: 10.1787/9789264123298-en
• Serway, Raymond; Jewett, John (2005). Principles of Physics: A Calculus-Based Text . Cengage Learning. ISBN 0-534-49143-X.

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Recycled Boats – Sink or Float

September 16, 2019 By Emma Vanstone 1 Comment

Recycled boats are fun to make a great for exploring the concept of buoyancy or for little ones just very basic sink or float activity.

A sink or float experiment makes a great first science activity for preschoolers ( always watch them carefully around water ) and a fun first attempt at making a prediction or hypothesis for older children.

If you want to structure the activity like a real experiment you can also introduce the concept of variables where you only change one variable for each test. For example, use the same boat, but change the object inside. You can then follow that by using the same object but different boats and record the results.

What you need to make a recycled boat

Empty containers

Old magazines or newspaper

Double sided tape

Large container filled with water for testing

How to make a recycled boat

This bit is up to you! We made our recycled boats very basic, but you could make yours as fancy or simple as you want.

Red Ted Art has lots more homemade boat inspiration too!

Preschool floating and sinking science project

For younger children start by asking them to test different objects to see if they sink or float. Once they’ve tried a few ask them to predict whether the next one will sink or float. Empty ( and full ) water bottles, large stones, plastic or metal toys and pine cones are good things to start with.

The next challenge is to try to find a way to make an object that sank, float. One way to do this is to place it in a boat. Plasticine boats, aluminium foil boats or recycled boats like we made should work perfectly.

We had some lemons hanging around so made some lemon boats too, you can also make boats from melon, oranges, limes and other fruits with a thick skin. They float because the skin is full or air bubbles, which reduces the density.

Sink or Float – explore further

Find out how to make a lemon sink and why lemons float with this activity.

We love to theme our activities. Sink or float pirate style is always popular.

Keep it simple with a LEGO sink or float activity .

For older children discover why some objects float and some sink and find out how to make a ball that sinks, float!

For a slightly different sink or float experiment pour a layer of vegetable oil over water and try to guess which objects from a selection will float on each layer .

Last Updated on April 21, 2021 by Emma Vanstone

Safety Notice

Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

Reader Interactions

September 16, 2019 at 8:41 pm

I really enjoyed this experiment, and testing it out with my four year old daughter. We had fun constructing the boat and even though she did realize it, developing a hypothesis.

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The Global Montessori Network

• Sink and Float

This activity is designed for 3-6-year-old children. This science activity allows children to explore the concept of sink or float. 

The Objective of Sink or Float Activity

In this activity, children can play, experiment, and discover what types of objects float and sink in water and why during a hands-on activity.

Why Do Objects Sink or Float?

• Weight: The weight of an object is the measure of gravitational force acting on that object. Heavy objects sink, and lighter objects float
• Buoyancy: The buoyancy of an object placed in liquid measures the upward force of the liquid acting on that object. When the upward force acting on an object in liquid is greater than the downward force of gravity (or its weight), the object floats, and vice versa. 
• Density: Objects denser than water will sink, and objects less dense than water will float. 

Benefits of Sink and Float Activity 

This activity enables the child to promote scientific thinking, such as cause and effect, observations, comparison, reasoning, data gathering, experimentation, and evaluation.

• It helps in language development by introducing various objects that can sink or float.
• It develops the OCCI: order, concentration, coordination, and independence.
• It coordinates and controls hand-eye movement.

Material Required for Sink or Float Activity

• A large container filled with water
• Two containers to sort floating and sinking objects
• ones that float: feather, Lego, bath toy, crayon, ping pong ball, plastic utensil, pencil, etc. 
• Ones that sink: toy cars, coins, metal spoon, eraser, dry pasta, etc.
• Towel to wipe spilled water

How to Introduce Sink and Float Activity to the Child?

Bring the activity from the shelf and organize the material needed. Invite the child to perform the activity and differentiate objects that can sink and float in water. Ask them to sort the objects and put them in their respective containers. Demonstrate the activity slowly and carefully so that the child can see and understand each movement.

• Fill the container with water.
• Using tweezers, take an object from the basket and place one item into the water at a time.
• Ask the child, “does it float or sink?”
• Let the child observe whether it floats or sinks.
• Remove them from the water with the tweezers.
• Place the object into the corresponding labeled container.
• Repeat the exercise with every object.
• Talk about why some objects sank, and others didn’t.
• Discuss the weight, size, and material the object is made of and how this influences the floating ability. Let the children relate to the density, buoyancy, and weight of the object.
• This sensory experiment encourages children to be curious, observe closely, and notice patterns. 
• Clarify the doubts that a child may express.

Questions to be Asked to Children While Performing the Sink and Float Activity

• Look at the objects that sank. Do they have anything in common with one another? 
• Look at the objects that are floating. Do they have anything in common?
• What is the reason objects float or sink?

Variation of Sink or Float Activity

Materials required:.

• a pair of scissors, 
• Few coins or beads, 
• Bucket full of water

How to Introduce this Variation of Sink and Float Activity?

• Take the tinfoil and cut small squares out of the tinfoil shape then slowly put the cutout and float it on the surface of the water. 
• After that, place coins or beads one by one in the center of the foil.
• Keep placing coins one by one on the tinfoil until the tinfoil sinks to the bottom of the container. 

Questions to be Asked While Introducing the Sink and Float Activity

• What was the number of coins you could place on the tinfoil? 
• What is the maximum number of coins you can get by arranging the coins differently on the tinfoil? 
• Whether the shape of your tinfoil float is changed, how many coins can you get?

Fun Facts about Sink and Float Activity 

• The density of liquids varies as well. You can make a mixture of corn syrup, oil, and water by mixing them together. Since corn syrup is the densest, it sinks to the bottom. Because of its lightness, oil floats to the top of the container, whereas water is in the middle.
• An object’s shape can also affect whether it sinks or floats. When you put a ball of clay in water, it sinks immediately. However, Clay will float if it is flattened out into a raft shape.
• It is also possible for objects filled with air to float. Iron sinks into the water but a boat made of iron will float on water because of the air which is filled inside the boat.

Watch the video to learn more about the science behind the floating and sinking of objects. 

Related Video Resources

• Tilt of the Earth’s Axis
• Life Cycle of a Butterfly
• The Coming of Life

To watch more science video lessons, click here . 

Video created by: by Alejandra Jurado

• Why sink and float experiment is important?

The sink and float activity helps the child to understand the concept of buoyancy and density. They will learn that buoyant objects float and dense objects sink as they observe.

• What is the meaning of float and sink?

An object floats if its density is less than water. It means that the upthrust of water on an object is greater than its weight. Objects that have a density greater than water sink.

• Do things float better in salt water?

The ocean or extremely salty bodies of water, like the Dead Sea, are denser than freshwater, which is why some things float more easily there.