Buoyancy for Kids: Will it Sink or Float?
- Art Activities
Why does a heavy boat float while a small rock sinks? Would a buoy sink if an elephant sat on it? Sometimes objects sink because they’re heavy, but other times it’s because they are buoyant! This buoyancy for kids experiment helps explain why.
Read About Buoyancy First
One way to get your child interested and excited to explore buoyancy is to read a picture book about it. Scroll down to the end of this article for two book recommendations.
Get Started
The set up is simple. Start with a tall clear vase of water and a small collection of citrus, such as Wonderful Halos mandarins . They are a great snack time treat, and can be included in creative science projects to teach kids that healthy snacking is fun. Not to mention, Wonderful Halos are sweet, seedless and easy to peel, perfect for kids and adults!
With these supplies in hand, ask your child what he or she thinks will happen if they drop a mandarin in the water. Will it sink or float?
If you have a preschooler, you could also offer a small collection of objects such as rocks, seashells, or twigs and ask what they think will happen if dropped in the water.
Have paper and pencil ready in case you want to take notes.
More to Explore
A little while back we set up a floating egg experiment to explore buoyancy from a different angle. Once you’re done exploring the buoyancy experiment on this page, check out the floating egg experiment. All you will need are an egg, water, and a few cups of salt.
Back to buoyancy and citrus, here’s what you’ll need…
This article may contain affiliate links
To learn about density while making and testing predictions about sinking and floating.
- Wonderful Halos
- Tall Glass Jar
- Other objects to test for buoyancy
- Paper and Pencil for Note-taking (optional)
- Predict if the mandarin will sink or float
- Drop it in the water. What happens?
- Predict if the peeled mandarin will sink or float.
- Describe how the whole mandarin and peeled mandarin are different.
- Discuss theories about the phenomena that was witnessed.
Step 1: Select your fruit and drop it in the water.
Ask: What happens when you drop the mandarin in the water?
It floats! What? Why doesn’t it sink?
Ask: Why do you think it floats?
Step 2: Peel the fruit and drop it in the water. What happens?
It sinks! Why does this happen?
Ask: Why do you think the peeled mandarin sinks?
Next: Experiment with other fruits and objects. We tried a lemon: both unpeeled and peeled.
What we noticed
The lemon with a peel floated and peeled lemon sank, the same as our first test with the mandarins: with a peel floats and without sinks.
You may notice that some of the peeled mandarins actually float. What’s going on here? Why do some sink and some float? This is good question, and we’ll tackle it in just a moment.
After going through this process, I asked my daughter to make some guesses about what was happening. Here are her thoughts:
- The peel has air in it, which helps it float.
- When it’s peeled, there are gaps between the mandarin sections so water can get into it, making it sink.
- When it has a peel it’s like a buoy.
- A rock is heavier so it sinks and the peeled orange is heavier because the water fills it.
The Science Behind the Experiment
Imagine trying to push a beach ball into a pool of water. What happens? You will feel resistance from the water, won’t you? This upward force pushes from the water toward the ball. Now, if you drop an object such as a rock into water and it sinks, gravity is at play. In this case, the downward force of gravity is greater than the upward force of the water. If the upward force of the water is greater than the downward force of the object, the object will float.
Now, imagine that you jump into a pool while wearing a life jacket. What happens? Without the life jacket, your body might sink to the bottom, but with the life jacket it floats. The life jacket is filled with a light material that has lots of little air pockets. The pockets of air weigh less than the water it displaces, so the jacket (and you!) will float. Similarly, if you’ve ever tried floating on your back (without a life jacket), taking a big breath of air can help keep you buoyant because you’re adding air to your body.
The Mandarin Peel is Like a Life Jacket
The whole mandarin is like a person wearing a life jacket. The peel of the mandarin is filled with small air pockets that help the mandarin float, like a life jacket. Remove the peel and the cracks between the mandarin segments fill with water, making it more dense, making it sink.
So why do some of the peeled mandarins sink while others float? We have a few theories.
- Mandarins with dense segments will sink.
- Mandarins that have air in the segments will float.
- Sometimes water will get between the segments, adding more weight, making the mandarin sink.
- When the pith, or white part of the mandarin, isn’t fully removed, it can act as a barrier to water entering between the segments. This keeps the mandarin floating.
What happens when you change the density of the water by adding salt, baking soda, or sugar to it? Try the simple activity in this post to find out.
Recommended Books about Buoyancy
Who Sank the Boat? , Pamela Allen
Things That Float and Things That Don’t , David Adler
Thank you Wonderful Halos for sponsoring this post. All opinions are my own.
Clear explanation. Easy to understand for kids
Thank you for the kind comment, Anita 🙂
your Sink and Float slides really teach us a lot! REALLY!
I do this experiment often with groups of children to illustrate the importance of wearing a life jacket. Your photos and description are very well done. I will be sharing this page to help parents and teachers do their own buoyancy experiments and water safety talks. Please consider featuring a water safety story, such as Stewie the Duck Learns to Swim, in your links, as well as a link for more water safety education for families. Blessings, Kelly, Jack Helbig Memorial Foundation
Es muy chulo
[…] from the mixture actually grabs onto the raisin, which effectively increases the raisin’s buoyancy, or floating […]
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April 10, 2014
Salty Science: Floating Eggs in Water
A density demonstration from Science Buddies
By Science Buddies
Key concepts Density Mass Volume Concentration Buoyancy Water Introduction Have you ever wondered why some objects float in water and others sink? It has to do with the density of the objects compared with the density of the water surrounding them. If an object is less dense than the water around it, it will float. Because salt water is denser than freshwater, some things float more easily in the ocean—or extremely salty bodies of the water, such as the Dead Sea. You can make your own dense water by adding salt to tap water. In fact, if you add enough salt, you can make the water so dense that an egg will actually float in it! Explore how this works in this science activity. Background If you put an egg in a cup of tap water, it will sink to the bottom. Why is this? Because the density of the egg is higher than the density of tap water, so it sinks. Density is the mass of a material per unit volume. For example, the density of freshwater under standard conditions is approximately one gram per cubic centimeter. But, if you add enough salt to the water, the egg will actually float back up to the surface! Adding salt to the water increases the density of the solution because the salt increases the mass without changing the volume very much. When enough salt is added to the water, the saltwater solution's density becomes higher than the egg's, so the egg will then float! The ability of something, like the egg, to float in water or some other liquid is known as buoyancy. But just how much salt is needed to make an egg float? In this science activity you'll figure that out by making solutions with varying concentrations of salt in them. Materials
Measuring cup
Large container, such as a large bowl or cooking pot (It must be able to hold at least three cups.)
One half cup of table salt
Five cups that hold at least 16 ounces each
Permanent marker (if you are using plastic cups) or masking tape and a pen (to label nondisposable cups)
Three spoons for mixing salty solutions
Soup spoon for egg transfers
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Preparation
Take the egg out of the refrigerator and allow it to warm to room temperature. Be sure to always wash your hands after handling uncooked eggs because they may carry salmonella.
Pour one and one half cups of water into your large container.
Add one half cup of salt to the large container and stir to dissolve some of the salt (it will not all dissolve yet).
Add one more cup of water to the large container (making two and one half cups total) and stir to dissolve the remaining salt. The salt should be completely dissolved before you go on to the next step. It may take several (five to 10) minutes of stirring, so you may need to be patient. Why do you think it's important to start out with a solution that has such a high concentration of salt?
Arrange the five cups on a surface, going in a line from left to right. Label the cups 1 to 5. If you are using plastic cups, you can use a permanent marker to label them. If you are using nondisposable cups, you can use masking tape and a pen to label them.
Add three quarters cup of the salty solution you prepared to cup 1.
Add three quarters cup of plain tap water to cups 2 through 5. (Cup 5 will be plain tap water.)
Add three quarters cup of the salty solution you prepared to cup 2 and mix it. What is the salt concentration in cup two compared with cup one?
Add three quarters cup of the salt solution from cup 2 to cup 3 and mix it. What is the salt concentration in cup 3 compared with cups 1 and 2?
Add three quarters cup of the salt solution from cup 3 to cup 4 and mix it. What is the salt concentration in cup 4 compared with the other cups?
Use a soup spoon to place an egg in cup 5. Does the egg float?
Use the spoon to take the egg out and place it in cup 4. Does the egg float?
Repeat this process with cups 3, 2 and then 1. In which cup does the egg first float? If the egg floated in more than one cup, did you notice any difference in how it floated? What does this tell you about the density of the egg?
Extra: In this science activity you figured out, within a factor of two, how much salt it takes to float an egg. You could narrow down the range further by testing additional saltwater solutions to try and determine the egg’s density. To do this, start your solution with the salt concentration in which the egg first floated and make a new dilution series, as you did before. Now in which cup does the egg first float? What does this tell you about the density of the egg?
Extra: Repeat this activity using several more eggs, possibly both hard-boiled and uncooked eggs. Do you get the same results with other eggs or is there some variation between different eggs? For testing hard-boiled versus raw eggs, you should test the same egg, first raw and then after hard-boiling it to investigate any differences.
Extra: Find out how much salt there is in seawater. From the results of your activity, do you think an egg would float or sink in seawater?
[break] Observations and results Did the egg float in cup 1 and 2, but not in cups 3, 4 or 5? You likely saw that the egg floated best in cup 1, floated a little less in cup 2 (but part of it was above the surface) and did not float in the other cups. Cup 1 had the undiluted salty solution that you originally prepared, which was one half cup of salt in two and one half cups water total. The concentrations of the salt solutions in cups 2 to 4 were halved as you increased in cup number; for example, the concentration of the salt in cup 2 was half that of cup 1, and the concentration of the salt in cup 3 was half again of cup 2. (Cup 5 had plain tap water.) The egg should have sunk in cups 3, 4 and 5 because the density of the egg was higher than the density of the solutions (or plain tap water) in those cups. Cups 1 and 2 had more salt in them than the other cups (with cup 1 having the most salt), which means these solutions were denser. The egg should have floated (with part of it above the water surface) in these two cups because the solutions were denser than the egg. The actual density of the egg is in between the density of the solution in cup 3 and that in cup 2. More to explore What Is Density? , from Charles E. Ophardt, Elmhurst College Why Is the Ocean Salty? , from Herbert Swenson, U.S. Geological Survey Publication Fun, Science Activities for You and Your Family , from Science Buddies How Salty Does the Sea Have to Be for an Egg to Float? , from Science Buddies
This activity brought to you in partnership with Science Buddies
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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Buoyancy Experiment - Teach Kids About the Physics of Buoyancy Forces
Posted by Admin / in Physics Experiments
Teach kids the principle of buoyancy. Will a metal can magically float on top of water? Is floating due to a magical electrical field or the hydrogen bonding of the water at the surface? Not really. This experiment demonstrates the simple way in which the study of physics is used to determine if an object will float and how much force we can count on the water pushing up on an object that is placed in the water. The concept is simple and even the physics buoyancy equation is simple.
Items Needed for Experiment
- Aluminum can
- Tin snips or wire cutters
- Container larger than a can
- 2nd container larger than the first
- Medicine dropper
- Scale capable of measuring ounces or grams
- Small weights
EXPERIMENT STEPS
Step 1: Have an adult carefully use tin snips or wire cutters to cut the aluminum can in half lenthwise. Do not touch the exposed cut sides of the can because it will easily cut skin. Place some tape over the exposed cut side of the can so it can be handled without the risk of cutting anyone's hands.
Step 2. Carefully have an adult smash half of the cut aluminum can. Do not touch the exposed cut sides of the can because it will easily cut skin. Avoid leaving any air voids in the can.<
Step 3. Weigh the large container and record its weight.
Step 4. Weigh the cut alumium can on the scale in ounces or pounds. The can is light enough that the scale will need to read hundreths of a pound.
Step 5. Place the smaller container inside the larger container. Fill the smaller container nearly to the top with water. Try not to let any water spill from the smaller container into the larger container in this step. Drop in the smashed part of the aluminum can to demonstrate how it sinks to the bottom.
Step 6. Fill the water completely to the top in the smaller container. Fill it up slowly until not one more drop can be added.
Step 7. Place the cut aluminum (boat) into the water in the smaller container and allow the water to overtop into the larger container.
Step 8. Use the medicine dropper to remove some of the water from the smaller container without spilling any more water.
Step 9. Carefully remove the smaller container (with water and aluminum boat) from the larger container. Weigh the larger container with the excess water that spilled. The weight of the water is equal to the buoyancy force pushing up on the aluminum boat, making it float.
Step 10. Dump the water out of the large container and dry it out completely. Repeat Steps 6-9, but this time add some small weights or rocks inside the floating aluminum can. Weigh the water that spilled into the larger container. The weight of the displaced water is the buoyancy force that allowed the aluminum can and small weights to float.
SCIENCE LEARNED
A buoyant force acts on all objects that are either partially or fully submerged in a fluid. The fluid can be either a gas (air) or a liquid such as water. The buoyant force always acts upward on the object. How the buoyant force affects an object is usually conditional based on weight and size of the object and the density of the fluid that is displaced. For example, a buoyant force pushes a rock that lies on the beach upward from the air it displaces. It is not enough force to move the rock. A larger buoyant force pushes upward on the same rock if it were thrown into the ocean. This buoyant force would still not be enough to overcome gravity and it would sink to the bottom. A large piece of steel that is shaped into a boat is much heavier that the rock, but if enough water is displaced by the steel boat, it will float on the water.
In all cases of buoyancy, the buoyant force acts against gravity. Archimedes Principle is used to predict the amount of buoyant force on a submerged or floating object. The Archimedes buoyancy theorem predicts that the buoyant force on a submerged object is equal to the weight of the displaced fluid. This makes sense because if an inflated ball that is floating on the water is pushed underwater and let go, the buoyant force will propel the ball upward until it jumps out of the water. The ball will return to the surface of the water and again float. The ball, however, does not completely float on top of the water. A small part of the bottom of the ball actually is underwater. When the ball is floating on the surface the weight of the ball and buoyant force are in equilibrium.
In the experiment, an aluminum can was used to demonstrate buoyancy force. Aluminum has a higher unit weight than water. Typically, aluminum weighs about 165 pounds per cubic foot, where water weighs only 62.4 pounds per cubic foot. A solid piece of aluminum will sink in water. This was demonstrated in the experiment by crushing a can and placing it in the water. The aluminum can that is cut in half, however, is able to float on the water. The amount of force can be verified by measuring the amount of water that spills out of the inside water container. From Archimedes Principle, the weight of the water is equal to the buoyancy force that acts on the bottom of the floating can. As more weight is added to the floating can, more water is displaced. This is because more force is needed to keep the can floating at the water surface.
The Archimedes buoyancy equation is:
Fb = (mass density x gravity x volume displaced)/gravity constant
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- Why We’re Unique
Egg Floatation, (Buoyancy)
Introduction: (initial observation).
Everyone has experienced the fact that things feel lighter under water than they do out of water. You may also have noticed that it is easier to float (swim) in salt water than fresh water.
This is due to a buoyant force upward. The buoyant force is equal to the weight of the liquid that the object displaces. If the liquid is denser, then the buoyant force is greater. Steel sinks in water, but floats in mercury.
Other possible titles for this project are:
1. Effects of Density 2. Visualize Density 3. Floatation Magic The third title is only good if you can successfully submerge the egg in the middle of the jar.
Dear This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “ Ask Question ” button on the top of this page to send me a message.
If you are new in doing science project, click on “ How to Start ” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.
Project advisor
Information Gathering:
Find out about floatation. Read books, magazines or ask professionals who might know in order to learn about the factors that may cause an object float or submerge. Keep track of where you got your information from.
(The information you gather – along with what you already know- together form your background information. ) This is a sample.
What is buoyancy?
Buoyancy is the tendency or capacity to remain afloat in a liquid or rise in air or gas. Buoyant objects have a lower density than the liquid or gas they are in. For example a blimp has a lower density than air and wood has lower density than water. That is why wood floats on water and blimps rise in the air.
What is density?
Density is the ratio of mass to volume in metric system. you can also think of that as the mass of 1 cubic centimeter of anything. The following examples will help you to understand and calculate the density.
Q. 150 cc of water is 150 grams. What is the density of water? (or the mass of 1 cc water).
A. Density of water= 150/150 = 1 g/cm³
Q. A piece of oak wood masses 35 grams and has a volume of 50 cubic centimeter. What is the density of oak wood?
A. The density of oak = 35g / 50cm³ = 0.70 g/cm³
Q. A piece of iron masses 157 grams and has a volume of 20 cm3. What is the density of iron?
A. The density of iron = 157g / 20cm³ = 7.85 g/cm³
To find the density of any object, you need to know the Mass (grams) of the object, and its Volume (measured in mL or cm³). Divide the mass by the volume in order to get an object’s Density .
Please note that cc (cubic centimeter, cm³) and ml (milliliter) are the same volumes; however, ml is only used for liquids while cc is used both for solids and liquids.
How does the egg density compare to water?
Eggs normally sink in water. In other words an egg has a higher density than water. The density of pure water is 1. This means that one milliliter of water weights one gram. The density of an egg is slightly more than one. So one milliliter of an egg is heavier than one gram. If we want to have an egg to float in water, we must increase waters density. To do this we can dissolve some salt or sugar or any other water soluble substance that has a higher density into the water. For example, since salt has a higher density than water, salt water has a higher density than pure water.
Followings are properties of table salt (Na Cl, Sodium Chloride).
Salt Properties:
- Crystals or white crystalline powder
- Transparent and colorless in crystalline form, rather like ice Crystallizes in the isometric system, usually in the form of cubes Soluble in water (35.6g/100g at 0°C and 39.2g/100g at 100°) Slightly soluble in alcohol, but insoluble in concentrated hydrochloric acid
- Melts at 801°C and begins to vaporize at temperatures just slightly above this
- boiling point 1,413°C
- Hardness of 2.5 on the MHo scale of hardness
- Specific gravity of 2.165
- Non combustible – Low toxicity
- Hygroscopic – absorbs moisture from damp atmospheres above 75% relative humidity.
As you see the density of salt is 2.165 which is more than double the density of water.
Applications of Buoyancy: One of the useful applications of buoyancy and Archimedes’ principle are to the experimental determination of density. ( See how )
Buoyancy has many industrial applications. By knowing and understanding buoyancy you can sink and float the material as you wish. You can do this just by changing the density of liquid. This method is especially used for separation of minerals. For example most copper ores have only about 2% copper and copper compound in them is mixed with lots of soil. Buoyancy is used to bring the copper ore to the surface where it will be separated.
Buoyancy is also the main factor in the following:
- Ice on a lake
- Swim bladders in fish
- Scuba divers
- Aquatic plants (such as water hyacinth)
Floatation is also a mineral separation process, which takes place in a water-mineral slurry. In this method the difference in density is used to separate the pure minerals from unwanted soil that has a different density.
Question/ Purpose:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement. Following are some sample questions/ purposes for this project.
The purpose of this project is to understand the effect of salt on the density of water and floatation of objects. The main question for this project is:
How does the amount of salt in water affect the floatation of egg? (Experiment 2)
Some other related questions are:
- Does the size of an egg affect its ability to float?
- Does the color of egg affect its ability to float?
- Does the size of a glass jar filled with water affect the ability of egg to float?
Need a problem statement? This is a sample:
Materials may sink or float in water depending on their density. We need to have some control on this condition and be able to sink or float them as we need. This is especially important for us when we are separating a few different materials and we want some of them sink and some others float.
Note: This method of separation is already being used to separate minerals from each other and metals from soil. It is also used in recycling where plastics, papers and metals must be separated from each other.
How to measure the density of liquids?
To measure the density of any liquid (like water, saltwater, orange juice, alcohol,..) you will need 2 things. First you need a measuring tool to precisely measure the volume of liquid in milliliters. Then you need a balance scale or gram scale to measure the mass of the liquid in grams. (Mass is the same as weight at sea level. In reality balance scales measure mass, not weight). When you have these two values, then you divide the weight by volume. The result will be the density. For example if 50mL of liquid weights 53 grams, then the density is 53/50=1.06 g/ml.
To measure the volume of the liquid you may use a graduated cylinder, a graduated burette or a graduated pipette. For example if you have a 10mL pipette, you can fill it up to the 10mL marking and transfer the liquid to a cup or weighing dish. If you need 50ml you can repeat that 5 times.
How to make a 5% saltwater?
Weight 5 grams of salt and transfer it to a 100 ml graduated cylinder. Then add water up to the 100ml marking. Swirl the cylinder until the salt is fully dissolved.
Instead of a 100 mL graduated cylinder you can use any other measuring cup or beaker as long as it is marked for 100mL capacity.
With the same method you can make any other concentration of saltwater. For example if you start with 7 grams of salt and add water up to the 100mL marking, then your solution will be a 7% solution.
You can also increase the solute (salt) and solvent (water) at any ratio. For example in our 5% saltwater example you could use 50 grams of salt and add water up to the 1000mL marking.
Identify Variables:
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other. This is how you define the variables for the main question of this project (tested in experiment 2)
The independent variable (the one that we set; also known as manipulated variable) is the amount of salt in water.
The dependent variable (also known as responding variable) is the status of the egg in water (sink, submerge, float).
The control variable is water temperature. (We control the temperature because variations in temperature may cause variations in the density of water. Make sure all water or saltwater you use are at room temperature, and do all experiments in the same day and in the same room.)
Another way of defining the dependent variable is :
The dependent variable (also known as responding variable) is the density of salt-water.
Hypothesis:
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
Following is a sample hypothesis for the above question.
Since the density of salt is more than the density of water, adding salt to water will increase the density of the mixture (solution). If the density of water becomes more than the density of the egg, then the egg will float. (Experiment 2)
Experiment Design:
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Experiment 1: What is the density of egg?
Introduction: The density of pure water is 1. In other words the weight of 1ml water is 1 gram (ml=milliliter=1:1000 Liter) . Objects with a density of less than 1 will float on the water. Objects with a density of more than 1 will sink to the bottom of water. In this experiment we test the density of egg.
Place a 1000ml graduated cylinder on a scale and fill it up with 200ml of pure water. Record the total weight of the cylinder and water.
Carefully place an egg in the cylinder. Record the volume increase and weight increase.
Divide the weight increase by volume increase to find out the density of the egg.
In one experiment, the volume of the egg was 51ml and the weight was 57 grams. So the density of egg will be calculated as: Density of egg=57 : 51 = 1.176 g/cc
cc means cubic centimeter. cc is the same as milliliter.
What is the density of your egg?
Experiment 2: How much salt will it take to make an egg float ?
This is the main experiment for this project
Introduction:
In order to find the salt concentration that floats the egg, status of an egg in water samples with different amounts of salt can be examined.
For this experiment you will need:
- A plastic or glass jar,
- A measuring cup or graduated cylinder to measure the amount of water
- A gram scale to weigh the salt. Gram scale is a scale that can measure in grams. (Also see the Materials and Equipments section in this project guide)
- Fill 2/3rd of a clear plastic or glass jar with water. Measure and record the amount of water that you are using for this experiment. You will need either the volume or the mass (weight) of water.
- Carefully place an egg at the bottom of that jar. Egg will simply sink and remain at the bottom.
- Prepare some salt. For every 1000 grams of water (one liter), have about 500 grams salt. The salt that you are using must be in the form of fine crystals or powder so it can dissolve easily. Record the mass of salt that you are starting with.
- Start adding some salt and stir the solution carefully.
- Continue that until the egg starts to rise. Measure the amount of salt that is left over and use that to calculate the amount of salt that is used. (Subtract remaining amount from initial amount)
- Use the amount of water and the amount of salt that is used to calculate the concentration of salt water that can float an egg.
Concentration=(mass of salt)/(mass of salt + mass of water)
In other words first you add the mass of salt and the mass of water to calculate the total mass. You will then divide the mass of salt by total mass of salt water.
Need a Control Group?
Place a similar egg in another container of water, but don’t add any salt to that. That will be your control group. You will observe that the egg in the control group does not float, so you will be sure that the floatation of egg in your experimental container is due to the added salt.
Need a Data Table or Results Table?
The result of this experiment is one single value, so you will not need a data table. If you need a data table for your project, you can repeat your experiment 3 or 4 times and enter the results in a table. For example you may get a small white egg, a large white egg, a small brown egg, and a large brown egg. Try the experiment with each of these eggs and write the results in a table like this:
| Small White | |
| Large White | |
| Small Brown | |
| Large Brown |
Make a bar graph:
You can use a bar graph to visually present the results in the above table. Make one vertical bar for each type of egg you try. Write the name or the type of egg under each bar. The height of each bar will represent the salt concentration that floated that egg. For example make a 21 cm tall bar to show the concentration of 21%.
This is a common question asked about this experiment:
1. How much salt will it take to make an egg float?
2. What’s my controls?
1. We don’t provide results. Keep adding salt until the egg floats. Keep track of the amount of salt you are adding.
2. Control is another container of water and egg that you do nothing with that. In other words you don’t add any salt. In this way when the egg starts to rise in the container that you are adding salt, you can be positive that adding salt caused the egg to rise, not an unknown environmental condition.
Experiment 3: How does salt affect the density of water?
In this experiment you will measure the density of water without salt and with different amounts of salt. (If you need a graph for your science project, this is the experiment that you need to do.)
For this experiment you need a metric scale that measures grams. You will also need a measuring cylinder to measure the volume of salt water.
Make different salt solutions starting from 1% (By weight or by volume; you choose!) salt and go up to 25% salt.
For each solution measure the density and record it in your results table.
To measure the density, measure the weight and the volume of the water and then divide the weight by volume. (Measure the weight in grams and measure the volume in milliliters or cubic centimeters).
Your results table may look like this:
| Salt Solution (by weight) | Density |
| 0% | 1 |
| 1% | 1.0054 |
| 2% | |
| 3% | |
| …. | |
| ….. | |
| 25% | 1.1554 |
How to make a 5% by weight salt solution? To make a 5% solution, you weight 5 grams of salt and then add water to that to make it 100 grams.
If you are good in math, you can also calculate the density of different salt solutions.
If you want to measure it and you don’t have much time, just measure the density of 5%, 10%, 15%, 20% and 25% salt solutions. Since the graph is linear (Straight line), it makes no difference how many different salt solutions you test.
You use the above table to make a graph. In the graph, you mark the point that the density of solution is the same as the density of egg. That is where the egg can remain submerged without sinking to the bottom or floating on the top.
This is a sample graph that shows the relation between the concentration of salt and the density of saltwater.
Materials and Equipment:
Material used for this project may vary based on the experiments that you choose and the equipment that are available to you. Following are a list of material and equipment used in the above experiments:
- 3 fresh (uncooked) eggs
- a bag of salt (2 lbs). Buy kosher salt or cooking salt from a local grocery store. water
- three beakers or any other clear jar
- 500 ML graduated cylinder MiniScience Part#AS2203
- Balance scale (gram scale). It is used to weigh the eggs.
See samples of balance scale at MiniScience.com or klk.com
If you cannot obtain a scale:
If you cannot obtain a scale for your experiments, you may try to use a measuring scoop instead. The results will not be very accurate if you use measuring scoops; however, they are good enough for you to complete your project. Make sure to write about your measuring method in your report in order to explain inaccuracy of results. To convert scoops to gram, use the following:
- 1/4 teaspoon tablesalt is almost 1.5 grams.
- One teaspoon tablesalt is almost 6 grams.
- One tablespoon tablesalt is almost 20 grams.
Results of Experiment (Observation):
Egg easily sinks in a drinking water (Right beaker) , but it floats in a concentrated salt water (Middle beaker) . We were also able to make a salty water that keeps the egg submerged (Left beaker) .
For the purpose of display, prepare three deferent jars. First jar will have pure water, Second jar will have saturated salt water and the third jar will have a salt water that has the same density of egg so the egg will remain in the middle.
When the density of the water is exactly the same as the density of egg, it would be difficult to make the egg stay in the middle. It may sometimes come up and sometimes go down. In the above picture, in order to force the left egg to stay in the middle, we filled 1/2 of the jar with saturated salt water. Then we added some pure water to the top of that without steering. Egg will sink in the top half and will stop as soon as it gets to the saturated salt water.
Calculations:
While you add salt to the water, record and calculate the amounts of water and salt for every condition. To do that, first add the mass of water to the mass of salt. For example if you used 700 grams of water and 150 grams of salt, the total is 850. This will be the total mass of the solution.
Then divide the mass of salt by the total mass of the solution. In this case you divide 150 by 850 and the results is 0.18 (or 18%). With this result you may conclude that salt water with concentration of 18% or more can float a fresh egg.
Numbers provided in this example are not real experiment results.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did. In your conclusion you must write how much salt and how much water are required in order for an egg to float.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
Following are samples of related questions:
- Can floatation experiment be performed with other materials such as beans and seeds and minerals?
- Can floatation be used as a separation method? (Can you separate sands from seeds or beans with this method?)
Possible Errors:
The temperature of water also effects its density. Warmer water has less density than cold water. The salt that you buy may not be pure salt. Salt manufacturers normally add other materials to the salt to absorb moisture. If your salt water appeared to be milky, leave it for a few hours until the white milky material added to the salt will precipitate. Then carefully transfer the clear salt solution to a new jar.
References:
Visit your local library and find some physics books with discussions in “Liquids”, “Density” and “Buoyancy”.
Following are some web resources:
http://www.iit.edu/~smile/ph9708.html
The Buoyancy Experiment
http://www.gpc.peachnet.edu/~pgore/Earth&Space/buoyancy.html
Q: Why you have used three different size of beakers shown in the picture? A: That is what we had available, but size of beaker or container has no effect on results.
Q: Where can I find, or what could be a substitute for the 500ml graduated cylinder and the balance scale (gram scale)?
A: You have many choices. Online they are available at MiniScience.com and other scientific suppliers. Locally, you may have a scientific supplier or photography supplier or teachers store that sell these. Balance scale is also available as kitchen supplies and in some pharmacies. Use a balance scale with precision of 0.1 gram or better.
Q: what is the problem statement of this project ?
A: This project does not have a problem statement. Instead it has a purpose. You can make up a problem statement if you wish. Any problem that is caused by low density of water can be used as the problem statement for this project. For example one problem is that many children each year drown in pools. Can adding salt to the pool increase buoyancy and reduce drowning? Is it better to fill up the swimming pool with fresh water or salty seawater?
Q: who is the first person to experiment egg buoyancy?
A: There are billions of objects in the world and egg is just one of them. No one will waste time to record who first did the buoyancy test in every one of these objects. Even if they do, it might be wrong. Buoyancy tests have been performed in many different seeds, many woods, plastics, metals, and minerals.
Q: What is the value of the project to society.?
A: The society benefits from the products that are made, filtered or improved by buoyancy method. Buoyancy is used to separate copper minerals, Zinc minerals and many others. It can also be used to clean seeds and beans from sand and other plant parts.
Q: How your findings can be used?
A: Your findings may be used to float eggs, beans or other materials with the purpose of separation and cleaning.
Q: I am having problems coming up with a good Hypothesis for this project the teacher wants my child to use the word buoyancy in her Hypothesis. How would I rewrite the problem statement and formulate a hypothesis based on what I have researched.
Problem: …………. Hypothesis: IF ……. Then …….. Because ……….
We are working with the experiment number 2 where would I find a gram scale.
A: Possible problem: We need to separate the eggs from stones by floatation. Possible Hypothesis: IF we add salt to the water THEN the buoyancy force of water will increase BECAUSE the density of salt is more than the density of water.
Gram scales are sold online and in some electronic stores and office suppliers.
It is always important for students, parents and teachers to know a good source for science related equipment and supplies they need for their science activities. Please note that many online stores for science supplies are managed by MiniScience.
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Science Experiments
Floating Egg Science Experiment
Can you make an egg float in water? In this simple science experiment, we take just a few minutes to test the laws of density and discover just how easy it is to make an egg float!
Below you’ll find detailed instructions and our demonstration video as well as the scientific explanation of “why it works.” We’ve also included a more ideas to explore the concept a bit further.
JUMP TO SECTION: Instructions | Video Tutorial | How it Works
Supplies Needed
- 2 Tall Drinking Glass
Floating Egg Science Lab Kit – Only $5
Use our easy Floating Egg Science Lab Kit to grab your students’ attention without the stress of planning!
It’s everything you need to make science easy for teachers and fun for students — using inexpensive materials you probably already have in your storage closet!
Floating Egg Science Experiment Instructions
Experiment Setup – Start with some observations about the eggs. Note that they are both raw eggs and have a similar size and weight. Then ask some questions. Do you think that the eggs will sink or float when placed in water? Do you think it’s possible to make them float? If so, how? Write down your hypothesis (prediction) and then follow the steps below.
Step 1 – Fill a tall drinking glass about 3/4 full of water and carefully place the egg into the glass. What happens to the egg? That’s right, it sinks to the bottom.
Did you know there is a way to make it float? Continue on in the experiment to find out how.
Step 2 – Fill another tall drinking glass about 3/4 full of water.
Step 3 – Add 3 Tablespoons of salt to the water and stir until it is completely combined. What do you think will happen if you place the egg into the glass with the salt water? Write down your hypothesis (prediction) and then test it to see if you were right.
Step 5 – Next carefully place the second egg into the glass with the salt water. What happens to the egg? That’s right, it floats. Take a moment to make some observations. Why do you think one egg sinks and the other egg floats?
Find out the answer in the how does this experiment work section below.
Video Tutorial
How Does the Floating Egg Science Experiment Work
Why does the egg sink in regular tap water, but float in saltwater? The answer lies in the density of water!
Density is a measure of the mass per unit volume of a substance. Simply said, how much “stuff” in a given volume. Water has a density of 1 g/mL (g/cm3). Objects will float in water if their density is less than 1 g/mL. Objects will sink in water if their density is greater than 1 g/mL.
The egg will sink in regular tap water because the density of the egg is greater than the density of water. The egg’s density is only slightly higher than water at 1.03 g/mL, but that is enough to make the egg sink.
When you add salt to the water, you are increasing the density of the water by adding more mass (or stuff) in the given volume. You don’t really change the volume of the water by adding salt. By adding enough salt, you increase the density of the water so that it is higher than the density of the egg and the egg will float!
Other Ideas to Try
Try this experiment again, but instead of using an egg use a potato slice or a carrot slice. You will have to play around with the amount of salt you add to the water because all objects have their own unique density. Add salt a tablespoon at a time and mix well until you cannot see any salt in the solution, then add your object to see if it floats or sinks. Remove your object and keep adding salt until you can get your object to float. To make it a true science experiment, create a data table to keep track of how much salt you add to the solution.
I hope you enjoyed the experiment. Here are some printable instructions.
- Drinking Glass
Instructions
- Fill a tall drinking glass about 3/4 full of water
- Place the egg into the glass of watch and watch it sink
- Fill another tall drinking glass about 3/4 full of water
- Add 3 Tablespoons of Salt and stir until combined
- Place the egg into the glass and watch it float
Reader Interactions
April 3, 2019 at 2:58 pm
i love this experiment
January 23, 2020 at 11:14 pm
I really loved doing this experiment with my class
August 26, 2020 at 2:59 pm
The egg floats because the density of the salt water changes to be greater than the egg and the density of the egg becomes less dense so then the egg floats. But when you put an egg in tapwater the density of the egg is greater than the density of the tapwater which makes the egg sink.
January 20, 2022 at 11:33 am
bro I loved this experiment it was amazing!!! I tried it out with my friends and it worked! Thank you!
February 10, 2022 at 7:19 pm
this is very helpful thank you
March 7, 2022 at 9:56 am
i loved this experiment : )
April 16, 2023 at 11:35 am
I love doing this experiment at home
May 1, 2023 at 9:00 am
It’s amazing thank you for sharing.
November 3, 2023 at 10:18 am
This is my science fair experiment! YAY!
November 25, 2023 at 7:41 am
wow what a great experiment m!!!
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SCIENCE EXPERIMENTS FOR KIDS
Explore buoyancy with foil boats.
In this experiment, kids will learn that sometimes it’s good to rock the boat
Tested, edited & approved by:
Bryan Holmes , Former Assistant Director of Education
This animal is not on exhibit in the habitats. It is one of our Animal Ambassadors and is used in public and school programs.
Download a PDF of this experiment
Will it float? You might have heard your kids ask this question as they held your keys over the toilet. So put that curiosity to work with this fun project that uses foil “boats” to teach them about buoyancy without sacrificing your prized possessions.
Using foil and some common household containers, your little sea captain will learn about buoyancy by investigating relationships between surface area, volume, weight, and displacement. No keys will be harmed in the conducting of this experiment.
GATHER THIS:
- Aluminum foil (heavy duty works best)
- Empty containers in different shapes, such as bowls, cups, yogurt tubs, tennis ball tubes, small boxes, etc.
- A large tub of water
- Small weights (marbles, nuts, bolts, and washers)
THEN DO THIS:
- Rip off a square of foil. You can use more or less if you want.
- Form the foil over one of your shapes.
- Pull the foil from the container so that it maintains its new shape.
- Float your foil like a boat in the tub of water!
- Add weights slowly to your boat to find out how much it can support before it sinks.
- Try different shapes, or try creating a boat without a mold!
- How do you make a boat that holds up the most weight?
- Is it better to have a small bottom and tall sides, or a wide bottom and small sides?
- Does a sheet of aluminum foil float if you don’t shape it? What if you crumple it up, or fold it up into a tiny square?
WHAT IS HAPPENING?
Buoyancy is a net upward force caused by displacement. A boat displaces a certain amount of water based on its weight and shape. If the weight of the boat is less that the weight of the water it displaces, it floats! If the boat weighs more than the water it displaces, it will sink.
WHAT THIS TEACHES:
Skills: Observation, Measurement, Modeling, Experimenting
Themes: Buoyancy, Forces, Engineering, Water
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- Nov 18, 2019
10 Simple Experiments for Density and Buoyancy and Air Pressure
Updated: Jun 24, 2020
Develop an understanding of air pressure, buoyancy, and density using a series of hands-on labs.
When I’m teaching a science concepts like air pressure and density my goal is to help kids build mental models of what’s going on. Whenever possible I try to start with something they can touch and feel and experience. Here’s a simple sequence we did in my classroom. I hope you can see how students’ understanding builds.
1. Air is Stuff: Air Pressure Experiment with Water
This activity is a good place to start. When you try to pour water into the jug, it won’t go in. This is a concrete way to show that air is stuff. This always surprises and puzzles kids and encourages them to play. And when they’re intrigued, kids engage with difficult material more easily.
This is where we begin our study of buoyancy. Can you see where this will lead?
If you don’t get the idea that air is stuff, you won’t believe that it has weight. And if you don’t believe that air has weight, you won’t see how it can produce pressure. And if you don’t understand how air produces pressure, you won’t be able to see how it creates buoyancy. And if you don’t understand how buoyancy works, then it’s tough to grasp the concept of density. Sure, you can memorize the formula for density, but what does that tell you about density? BTW what IS the formula for density? And will it be on the test?
2. Matter Presses: Understanding Pressure
Once we proved to ourselves that air is stuff, we’ll play with the concepts of weight and pressure. This activity is free on my website. If you’re interested in a copy, you can sign up here.
This is a super simple activity to show kids how the weight of an object (our body) doesn’t change as you change your position (squatting, sitting, standing on tiptoe), yet its pressure does. It’s a concrete way for kids to feel the connection between the concepts of weight and pressure.
We’re just getting started on our investigation into density, buoyancy, and air pressure. These three concepts are related, and it’s helpful to study them together. In this activity, kids see how pressure comes from weight. We’ll continue that line of thought in the next couple of activities.
3. Streamlines: Water Pressure Experiments with a Water Bottle
Have you tried this experiment? It’s easy, a little messy, and super fun. Plus, kids find it intriguing, so that’s a huge point in its favor.
How many observations can you make? Note how the lower streams are shooting farther than the upper ones. What could you conclude from that?
Click here (or on a pic) for middle school labs on this topic.
This is a visual example showing how pressure comes from weight. The greater push comes from the taller column of water. Kids can prove this to themselves by comparing bottles of different diameters and heights. It’s easy to conclude that it’s only the height of the water that changes the shape of the squirt.
This activity gives good evidence that the water sitting above the hole produces the pressure. This is a direct correlation to air pressure, which comes from the weight of Earth’s air sitting on top of you.
The difficulty with understanding air pressure is that we ignore the surrounding air. We rarely think of air as sitting on us. It’s invisible so we forget it’s there. Time to roll the tape from activity #1 . Air is stuff. It’s always there and we need to remember this to understand air pressure.
If you climb a mountain to a place where there’s less air above you, there’s less pressure. And vice versa, the lower you go, the higher the pressure. We call sea-level standard pressure, but if you go below sea level (into a cave for instance) air pressure increases.
[Students may know that air high in the atmosphere is thinner than that near sea level. While that’s important, it’s a separate issue and we don’t deal with it yet.]
This is part 3 of our conceptual journey—we’ve determined that air is stuff and we’ve connected weight to pressure. The definition of stuff is that it has weight and takes up space. And if air has weight, it must be able to produce pressure by sitting on stuff.
And what keeps air sitting on Earth? The same force that keeps every other substance sitting on Earth… gravity! Just because it’s light and thin and invisible doesn’t make it immune to gravity. Gravity gives air its weight and air’s weight produces pressure. It’s that simple. The complicated part is that we haven’t trained our brains to think in those terms. We forget that air is there and we forget that air is stuff. So it’s helpful to refer to experiments that kids have completed—like trying to pour water into a sealed bottle (experiment #1 ). The water won’t go in because the bottle is already full… of air.
And this is our job as teachers—to help kids think like scientists.
4. Nature Abhors a Vacuum: Playing with Suction Cups
Now that we’re beginning to get an idea of where air pressure comes from, what if we could change it? What if we could change the pressure around an object? How would that affect it? In this activity, we play with suction cups. Their shape allows them to trap some air and then change their volume.
If their volume increases but the amount of air inside stays the same, the pressure will drop. Now the inside pressure is less than the outside pressure. It’s this small difference that makes suction cups stick. The higher outside air pressure is pushing them against the surface, keeping them attached.
This is a good activity to delve into the idea that pressure can come from two different sources. We’ve already looked at what causes the outside, or atmospheric, pressure (air’s weight).
And now we’re looking at the pressure which comes from the air pushing against the sides of the container. All gasses exhibit this pushiness. This is a more common understanding of air pressure and one that confuses kids when they’re learning about atmospheric pressure.
5. Nature Abhors a Vacuum: Playing in the Tub
Who hasn’t tried this? Umm, a lot of kids apparently. Part of our job as science teachers is to help kids play with materials so they can discover concepts on their own. Play builds a library of phenomena and experiences that kids can refer to when unpacking their understandings. Here they see how they can lift a full, upside-down cup and it doesn’t empty. It remains full until the rim of the cup breaks the surface of the water. They can use a bottle of any shape or size and see the same results.
What keeps the water in the cup?
Water seeks its level by falling to the lowest point. But for water to leave this cup, a vacuum would have to form in the space since there’s no way for air to enter. The surrounding air pressure pushes on the surface of the water and holds the water in the cup.
What if the cup were very tall, wouldn’t the pressure from the water in the cup overwhelm the atmospheric pressure? Yup!
Normal air pressure is about 15 pounds per square inch. For a one inch column of water to weigh 15 pounds, it would need to be about 32 feet high.
Above 32 feet a vacuum would form and the water would not stay higher than that. This is the basis for early barometers. These were made with mercury because it’s super dense and therefore short enough to fit inside a room. Making a water barometer is a cool experiment if you have the time and space for it.
Do you see the barometer here? The sealed tube of mercury is inverted into an open dish of mercury, just like the experiment we did with the cup and water. As the room’s air pressure rises and falls because of changing weather, the height of the mercury will rise and fall.
(Click the image to go to the full painting)
6. Determining Density: An Experiment for Kids
This is the classic way to find the density of an object. While you can use anything that sinks, I prefer polymer clay. It’s sold under brand names Fimo and Sculpey, but there are off-brands too. The beauty of this clay is that it doesn’t dry out, doesn’t leave a residue, and you can use it in water.
But why clay? By using clay, you can show that density is a quality of a substance. It doesn’t change if you have more or less of the substance. Kids can calculate the density for two or three different-sized lumps to prove this to themselves.
Click the image to go to the lab directions.
7. How do Boats Float? A Buoyancy Lab
You can understand floating and sinking in two ways:
First, you can look at the way pressure changes with the depth or height of a fluid. As we saw in Activity #3 above, the pressure in a fluid depends on how deep the fluid is. The deeper you are, the higher the pressure is. So, if you’re standing in water, the pressure at your feet is higher than near your head. This difference in pressure causes a force that pushes you upward.
Do you float? It depends. You also have a downward force (your weight) so these two forces work against each other and the larger one wins.
Another way to look at sinking and floating is to realize that water holds up the water above it. If you could remove a chunk of water and replace it with another object of identical size, will that object float or sink? It depends. If the object weighs more than the same volume of water, then it will sink. If it weighs less, it will float. And if it weighs exactly the same, it will neither float nor sink but stay where you put it.
It’s this second idea that we’re exploring here. We’re determining how much water an object displaces and whether that amount of water weighs more or less than the object. The cool thing about this procedure is that you can use it with floating objects. Here the boat displaces an amount of water. If we collect and weigh this water, we see that it weighs more than the entire boat. Here we're using polymer clay which is cool because it won't float if it's a solid ball, but it does float if its shaped like a boat. You could also use a square of foil to shape an aluminum foil boat but it's a little less forgiving when trying to reshape it multiple times..
So the weight of the boat (a downward force) is less than what the water can support (the upward force) and the boat floats. If we loaded the boat with weights, it would still displace the same amount of water. When would it sink? At the point when its weight increased beyond the weight of the displaced water.
I like this setup because it’s simple and cheap to make and is easy to store.
8. Air Is Compressible: How to Deflate a Marshmallow
This activity uses two different pumps—one that pumps air into a bottle and one that pumps air out of a bottle. Can you think what beverage you might use each for?
I love using marshmallows for this since they’re soooo visual. This always draws a WOW from kids and they want to do it over and over. When you pump air in, the marshmallows contract and when you pump the air out, they expand. The marshmallows fatigue over time, but you can use them a few times for sure.
Here we’re back to exploring the idea that air pressure is a function of how much gas is inside a confined space. If you add more molecules to the space, the pressure goes up and if you take some out, the pressure drops. This doesn’t explain surrounding (ambient) air pressure or why that rises and falls, but it’s an important part of understanding.
9. Out with a Bang: Heat Causes Expansion
This is another not-to-be-missed activity that your students will want to try over and over. It’s simple and quick. I let them do it themselves, though I supervised closely.
Add a centimeter or two of water to an empty can. Place it on a hot plate until the water is at or near boiling. Using tongs, remove the can and invert it into a bowl of water. BANG! The can collapses instantly.
What’s going on? As you heat the water, it turns to gas and drives out much of the air that was filling the can. Since the water vapor is hot, it doesn’t take much to fill the can. When you place the can into the water, it cools and the water vapor condenses. The pressure in the can drops dramatically (since it’s sealed and no air can get in) and the higher outside air crushes the can.
Sometimes the can doesn’t get crushed, but fills with water. Can you see why? Here, the air pressure pushes water into the can until the air pressure inside and outside are equal. It’s the same explanation but with a different outcome. And if this happens, you can reuse the can for another try!
10. Local Pressure: Heat Causes Expansion
This is the last in our lineup. Here we add some very hot water to a milk jug and swirl it around to heat the plastic. Next we dump out the water and cap the jug and wait. Before long the jug implodes. It’s not as dramatic as the previous demo but it gets the point across. I appreciate doing different setups that focus on the same concepts. It helps solidify ideas.
Plus, we’re scientists, we repeat stuff.
As much as possible, we begin with concrete experiences that kids use to construct their understanding based on what they’re seeing. A sequence like this forms the basis of our comprehension and gives us something to discuss and return to again and again.
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We have a few theories. Mandarins with dense segments will sink. Mandarins that have air in the segments will float. Sometimes water will get between the segments, adding more weight, making the mandarin sink. When the pith, or white part of the mandarin, isn't fully removed, it can act as a barrier to water entering between the segments.
Ever wonder why you can float in a pool? Or how in the world a cargo ship made of heavy steel, carrying many tons of cargo, doesn't sink? A Greek scientist n...
Negative Buoyancy and Sinking Bodies. In the first experiment we did earlier, the iron weight sank below the water as it was lowered. The 6 kg iron weight we used displaces water. However the weight of the water displaced is only 2 kg. So according to the principle of Archimedes, the buoyant force is 2 kg acting upwards on the iron weight.
Add one half cup of salt to the large container and stir to dissolve some of the salt (it will not all dissolve yet). Add one more cup of water to the large container (making two and one half cups ...
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 ...
The Cartesian diver science experiment illustrates Boyle's law and buoyancy. The Cartesian diver is a classic science experiment that demonstrates the principles of buoyancy and pressure in a fun and engaging way. Named after the French mathematician and philosopher René Descartes, the experiment has been fascinating students and enthusiasts for centuries.
Avoid leaving any air voids in the can.<. Step 3. Weigh the large container and record its weight. Step 4. Weigh the cut alumium can on the scale in ounces or pounds. The can is light enough that the scale will need to read hundreths of a pound. Step 5. Place the smaller container inside the larger container.
We recommend using the latest version of Chrome, Firefox, Safari, or Edge. When will objects float and when will they sink? Learn how buoyancy works with blocks. Arrows show the applied forces, and you can modify the properties of the blocks and the fluid.
Buoyancy is the tendency or capacity to remain afloat in a liquid or rise in air or gas. Buoyant objects have a lower density than the liquid or gas they are in. For example a blimp has a lower density than air and wood has lower density than water. That is why wood floats on water and blimps rise in the air.
Watch the Floating Egg Science Experiment Step by Step Instructions. How Does the Floating Egg Science Experiment Work. Why does the egg sink in regular tap water, but float in saltwater? The answer lies in the density of water! Density is a measure of the mass per unit volume of a substance. Simply said, how much "stuff" in a given volume.
Buoyancy is a net upward force caused by displacement. A boat displaces a certain amount of water based on its weight and shape. If the weight of the boat is less that the weight of the water it displaces, it floats! If the boat weighs more than the water it displaces, it will sink.
First, you can look at the way pressure changes with the depth or height of a fluid. As we saw in Activity #3 above, the pressure in a fluid depends on how deep the fluid is. The deeper you are, the higher the pressure is. So, if you're standing in water, the pressure at your feet is higher than near your head.
Materials and Equipment. 2-liter soda bottle (1) Water bottle, standard size, approximately 500-700 mL (1) Razor blade or knife. Drill with a 3/32-inch drill bit; be sure to confirm, but this size should create a hole that will fit the paper clip you'll be inserting. Scissors.
Hey There! Today's video is on BUOYANCY and why some objects FLOAT and some SINK! It's filled with experiments that you can do at home!!The videos mentioned ...
What is buoyancy? How does salt affect buoyancy? Learn all about density and buoyancy in this easy science experiment for kids from The Good and the Beautifu...
This lesson on buoyancy, along with this lab, can help older kids work on applying the knowledge this experiment gave them. Try it risk-free for 30 days Supplemental Science: Study Aid
For Primary, Elementary and middle School Students and Teachers. Buoyancy Experiments. Definitions. Buoyancy is a force applied by a fluid on a body immersed in the fluid. Archimedes' principle: The buoyancy force exerted on a body immersed in a fluid is equal to the weight of the fluid displaced by the body. Background Information.
07/01/24 Homework Help, Science Experiments A molecule is a group of atoms bonded together. Density is how close together the molecules of a substance are or how much mass a substance has in a given space.Buoyancy and density are related. Density affects how much an object might float, or be buoyant, or sink.
Have your teacher download the free Lesson Guides below so the entire class can explore buoyancy with some practical hands-on experiments. Also, here are some helpful links to buoyancy experiments and learning tools. Have fun but don't sink! Buoyancy Science Experiments - by Julian; The Physics of Boats; Buoyant Boats - by AAAS
Figure 1. Ascending helium balloons. (Wikipedia, 2009.) This force, or buoyancy, is exactly the difference in the weight of the balloon and its contents (plus a ribbon, if one is attached), versus the weight of the volume of air displaced. Latex is a permeable membrane, which means it has very small holes that allow the helium atoms to escape.
When the swim bladder expands, it will increase in volume and therefore displace more water. This increases the fish's buoyancy and it will float upwards. When the swim bladder is deflated, the fish will sink as it is displacing less water and its buoyancy decreases. Divers use the same concept for their buoyancy control devices.
The experiment involved the controlled introduction of various fluids into the chambers, allowing researchers to study bubble formation, growth, and coalescence under microgravity conditions.
15 Density Science Experiments. By Amy Cowen on March 13, 2024 8:00 AM. Use these free science lessons, experiments, and activities to teach K-12 students about density. Sometimes students wrongly think that an object's density is the same as its weight or its mass. Instead, density refers to an object's mass in a given volume.