surface tension science fair experiment

7 Surface Tension Experiments To Try With Kids

• November 2, 2022
• Science Experiments

Here is a list of easy and fun surface tension experiments for kids. These surface tension experiments with water can help kids learn about static water and the forces within it.

Do you love the 4th of July milk fireworks?

What if you can create them using milk?

Have you noticed crazy little balls in your coffee mug while stirring it?

Well, it’s possible to recreate them! There are lots of other factors to know. So, let’s have a look at the seven science experiments that will help to understand physics in a better way while having fun at home.

1. Milk Fireworks        

This is an easy science activity that needs only a few raw materials and can prove to be a great boredom buster. 

Raw materials 

• A dish 
• Food coloring agents 
• Liquid dish soap

Required Steps 

• Take the dish and pour some milk into it.
• Now drop a few drops of coloring agents in the middle.
• Now take an earbud soaked in liquid dish soap and dip it into the middle with food coloring agents. 
• The colors get scattered in all directions like fireworks! 

Observation

Experiment Observing that adding little soap to the milk weakens its surface tension by pushing the milk molecules with its hydrophobic ends. Also, the food coloring agents are pushed along with them, and end up having a spectacular sight of  fireworks on liquids !

Note: You can conduct this experiment with milk at different temperatures such as warm and very cold to see whether this will make any difference to the behavior of the milk molecules.

2. Water BBS

This experiment demonstrates how crazy little balls notice in the coffee mug while stirring it.

• One cup of coffee
• One coffee stirrer
• Few drops of liquid soap

Required steps

• Take the coffee mug and stir it with the stirrer
• Maybe nothing will happen, and then mix a few drops of liquid soap

In this experiment, notice some little balls in the coffee mug, which are nothing but anti-bubbles. These bubbles are formed when a liquid is dropped turbulently into the same or another liquid.

These are thin films of gas enclosing a sphere of liquid that can appear and then get fully submerged in the liquid.

Unlike ordinary air bubbles, these anti-bubbles do not rise quickly on the top. Patient to see them as they are quite mesmerising.

3. Soap Boat

This science activity video on a  soap boat experiment  is all about the surface tension of water and the impact of soap on water.

• 1 dish containing water
• 1 little boat with a notch out of a card
• A few cotton buds
• Liquid soap
• Take the dish and place the little paper boat on the surface of the water
• Now, soak the cotton bud in liquid soap and touch its tip into the water to power your paper boat

In this experiment, the boat will start moving swiftly! Now, this happens when you touch the soap on the surface of the water. Soap weakens its surface tension and creates enough force to push the lightweight paper boat. Interesting to notice it!

4. Floating Card

• 1 open jar with a mesh screen on its mouth  
• 1 card 
• 1 jug of water
• Take the open jar with the mesh screen and pour water into it from the jug
• Now, take the card and place it gently in the mouth of the jar
• Invert the jar, and you will see that it will uphold the card!
• Next, gently remove your hand from the card
• Slid out the card from beneath the jar
• The jar will hold up the water mysteriously!

 Observation

Observations help to notice the  mysterious water suspension.  So, the science behind this  floating water trick  is nothing but the surface tension across the screen, which holds up the water.

There is also a role of cohesion to play in this science activity. It is the cohesion that causes surface tension. Here, water molecules remain joined together between each tiny opening of the screen mesh and form a thin invisible membrane that is strong enough to hold the water when the jar is inverted.

You can even stick some needles inside the jar! Interestingly, the surface tension will successfully prevent the water from falling in that case too! 

You can use this experiment as a magic trick before your friends and can, later on, explain to them the science behind the water suspension.

5. Suddenly sinking paper clips

This science activity video on  paper clip floating  and sinking is again about the surface tension of water.

• 1 glass containing water
• 1 paper clip
• 1 piece of tissue paper
• A small quantity of liquid soap
• Take the paper clip and place it on top of the water surface of the glass
• Try to balance it on the water surface
• If it sinks, take it out from the glass
• Now, place the piece of small tissue paper on the water surface and then put the paper clip on it
• Next, gently remove the tissue paper from beneath the paper clip as it will start floating on the water surface
• Now take the Q-tip and soak it in liquid soap and touch its tip into the water
• The paper clip will again sink at the bottom! 

Now, wondering why is the  paper clip floating on water soap?  Well, the reason is again the humble surface tension! 

In the second step, then try to make the paper clip float on the water surface, it sinks because the metal with which the clip is made is denser than the water. 

However, when placing it on a piece of floating tissue paper, it does not sink because now the surface tension of the water is supporting it.

Again, when you touch the water with soap, this surface tension gets reduced. So, the clip sinks like a brick into the glass. 

Also, let’s experiment with this interesting activity with different lightweight objects to see whether the same thing is happening again. 

6. Penny Dropper

Have you ever wondered  how many drops of water can fit on a penny ?

Well, this super fun science activity will give all the answers. 

• 1 plastic dropper 
• Take the penny and place it on a flat surface
• Now take the dropper, fill it with water, and put a drop of water at the center of your penny
• Keep on adding water drops to the penny and count
• A dome shape made up of water drops will form on the penny 

The experiment makes us observe that a penny can hold several water drops before it eventually starts spilling over the coin. Here, it is the surface tension of water that prevents the water molecules from falling apart. So, the water molecules remain together and form a dome shape. Even Experimenting with other liquids such as saltwater, milk, and soapy water to figure out whether they yield the same result or not.

7. Leidenfrost Effect        

Have you ever heard about the  Leindenfrost effect ?

Well, it is a phenomenon where liquids, instead of getting evaporated, glided on the surface of a pan. This happens when the pan is heated beyond the boiling point of that liquid. 

This effect was named after the German doctor Johann Gottlob Leidenfrost (1715-1794), who described this effect. 

However, to do this exciting science experiment, you will need adult supervision as this involves heat hazards! 

• 1 empty pan
• One dropper
• Take the empty pan and put it on a stove.
• Next, add some water droplets into the pan one by one with the help of the dropper, and the water droplets will quickly evaporate. 
• Keep on adding the water droplets but now increase your speed. 
• Water droplets will now not evaporate. They will instead make small spheres gliding on the hot surface of the pan.

The observation makes us wonder how  does water dance on a hot pan . See, when heating the pan more than the boiling point of water, which is 100-degree Celsius, water drops vaporize quickly that it forms a layer of steam that insulates the rest of the water droplets are added from the hot surface of the pan. As a result, you end up watching the dancing water droplets. 

All the above activities can be done at home to develop a better understanding of some key concepts of physics. 

Dianna Cowern, also called physics girl presented a video of seven experiments or science tricks that offer surface tension, anti-bubble, cohesion, and lienenforst effect.

Courtesy: Physics Girl

https://www.youtube.com/watch?v=WsksFbFZeeU&feature=emb_logo

https://www.antibubble.org/

https://www.stevespanglerscience.com/lab/experiments/water-screen/

https://msdlt.instructure.com/courses/108/files/2571/download?wrap=1

https://www.rookieparenting.com/how-many-drops-of-water-can-you-put-on-a-penny/

https://www.sociologygroup.com/water-drops-dance-hot-plate/

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June 25, 2015

Measure Surface Tension with a Penny

A soapy science activity from Science Buddies

By Science Buddies

Learn about the secrets of soap in this surprising surface tension-testing activity!

George Retseck

Key concepts Chemistry Molecules Surface tension

Introduction Have you ever noticed on a rainy day how water forms droplets on a window? Why does it do that instead of spreading out evenly over the whole surface? You might not guess it but this property of water is also related to washing dishes and doing the laundry. How? It all has to do with something called surface tension. Try this activity to learn more!

Background You have probably noticed that if you look at a surface outside on a rainy day or spill some water inside, the liquid tends to form droplets that stick up from a surface instead of spreading out into an even sheet. This occurs because water is made up of many tiny molecules that are all attracted to one another. Molecules in the middle of a drop of water are pulled evenly in all directions by all the nearby molecules. Those near the droplet’s surface, however, are pulled mostly inward by the water molecules below them. This creates "surface tension." The surface of the water droplet is held together by the attraction between molecules.

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Now, think about washing dirty dishes or clothing. There will be lots of tiny little holes and cracks that water needs to get into to wash away dirt and grime, such as the spaces between the fibers of a shirt or between a plate and bits of dried food. In order for water to flow more easily into these small spaces, you need to decrease its surface tension. You can do this by adding soap, which is a surfactant (a material that decreases the surface tension of a liquid). In this activity you will see how soap decreases the surface tension of water by putting water droplets on top of a penny.

Medicine dropper or eyedropper

Glass, cup or small bowl

Dish towel or paper towel

Flat, level surface that can get wet, such as a kitchen counter

Paper and pencil or pen (optional)

Preparation

Place your penny on a flat, level surface that can get a little wet, such as a kitchen counter.

Fill a glass, cup or small bowl with tap water.

Fill the medicine dropper with water.

Now carefully add one drop of water at a time to the top of the penny. Hold the medicine dropper just above the top of the penny (not touching it) so each new drop has to fall a short distance before it merges with the drop on the penny. You can write down the number of drops you add if you like. How many drops of water do you think will fit on top of the penny? Watch the drop on top of the penny carefully as it grows. It should keep getting bigger and bigger until it touches the edges of the penny.

Keep adding drops (refill your medicine dropper as necessary) one at a time. How big does the drop on the penny get before it finally spills over the edges?

Once the drop spills over the penny’s edge, use a towel to completely dry off the penny and surrounding surface. How many drops of water were you able to add before the water ran over the penny’s sides?

Mix a small amount of dish soap with your tap water.

Now, repeat the experiment using soapy water. Do you think you will be able to add more drops or less before the liquid spills over the sides of the penny? Again, slowly add one drop at a time. How big does the drop of water on top of the penny get before it breaks and flows over the edges?

Extra : Try the experiment with different liquids or other things you can find in your kitchen. (Make sure you have an adult's approval to use any liquids before you handle them.) How do different soaps and detergents like hand soap or laundry detergent compare with one another? What about other liquids like milk or juice? Which ones make the biggest (or smallest) drops? With the most or least number of drops?

Extra : Try using something other than a penny to collect the droplets. What happens if you use different materials, such as the flat top of a small plastic bottle cap or a button?

[break] Observations and results You should find that plain tap water produces a much larger, stable drop of water on top of the penny than the soapy water does. This is because plain tap water has higher surface tension, so the surface is "stronger" and can hold together a larger drop. Adding soap lowers the water’s surface tension so the drop becomes weaker and breaks apart sooner. Making water molecules stick together less is what helps soaps clean dishes and clothes more easily.

More to explore Sticky Water , from Exploratorium Soap , from Exploratorium Measuring Surface Tension of Water with a Penny , from Science Buddies Surface Tension Science: Build a Raft Powered by Soap , from Scientific American Science Activities for All Ages! , from Science Buddies

This activity brought to you in partnership with Science Buddies

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Science Projects > Physics & Engineering Projects > Water Experiments  

Water Experiments

Surface tension experiments.

Surface tension is one of the most important properties of water .

It is the reason that water collects in drops, but it’s also why plant stems can “ drink water ,” and cells can receive water through the smallest blood vessels.

You can test multiple surface tension experiments using just a few household items.

What You Do:

1. Start with a cup of water and some paperclips. Do you think a paperclip will float in the water? Drop one in the cup to find out. Since the paperclip is denser than the water, it will sink to the bottom of the cup.

Now find out if you can use surface tension to float the paperclip. Instead of dropping the paperclip into the cup, gently lay it flat on the surface of the water.

(This is tricky — it may help to place a piece of paper towel slightly bigger than the paperclip in the water. Then lay the paperclip on top of it. In a minute or so, the paper towel will sink, leaving the paperclip floating on top of the water.)

2. Even though the paperclip is still denser than the water, the strong attraction between the water molecules on the surface forms a type of ‘skin’ that supports the clip.

3. Now put a drop of dish soap in the water. This will bind with the water molecules, interfering with the surface tension .

The paper clip will sink. You can try floating other things on top of the water also – pepper floats well until you add dish soap. Can you find any other light items that will float?

Surface tension creates the ‘skin’ on top of the water, but it is also what causes water to stick together in drops.

Observe how these drops stick together by experimenting with water and a penny. All you need is a cup of water, a penny, and a medicine dropper .

First make a prediction: how many drops of water do you think you can fit on the top surface of the penny? Add one drop. After seeing how much room it takes, do you want to rethink your first prediction?

Now continue carefully adding drops until the water spills off the penny. Try this three times, recording the number of drops each time, and then find the average number of drops that can fit.

Surface tension is the reason you can fit so much water on the penny. The water molecules attract each other, pulling together so the water doesn’t spill.

Try this experiment with different-sized coins. Predict how many drops you can fit on a quarter compared with the penny.

For one final surface tension experiment, start with a full glass of water. Predict how many pennies you can add to the water without the glass overflowing. Gently add pennies one by one. Because of surface tension, the water will rise above the rim of the glass before it spills! Compare your original prediction with the number of pennies you were able to add.

Freezing Point

Have you ever wondered why rivers and lakes freeze in the winter, but oceans do not? In this experiment we will see that it is the presence of salt in the ocean that makes it less likely to freeze.

What You Need:

• 1-gallon freezer bag
• 1-quart freezer bag
• crushed ice
• thermometer

1. Fill the gallon freezer bag half full with crushed ice. Add one cup of salt and seal the bag. Put on some gloves and knead the ice and salt until the ice has completely melted.

2. Use the thermometer to record the temperature of the saltwater mixture. Even though the ice has melted, the temperature should be less than 32°F (0°C).

3. Now put about an ounce of water in the quart freezer bag. Seal the quart bag and then put it in the saltwater mixture in the larger bag. Seal the larger bag also and leave it until the water inside the quart bag freezes.

How did the water freeze when surrounded only by saltwater?

The salt broke apart the bonds between the water molecules in the ice, causing it to melt, but the temperature remained below the freezing point for pure water.

Salt (and other substances dissolved in water) will always lower the freezing point .

This is why water in the ocean rarely freezes.

• Find out more about salt water by making a Solar Purifier

More Water Projects:

•   Liquid Density
•   Hot Water: Convection Science
•  Water Wheel

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Sink or Swim (Surface Tension)

What happens when you weaken the hydrogen bonds in water.

Print this Experiment

There are times in science where changing one variable can be the difference between fire and smoke, conducting and insulating, and in this case, sinking and swimming. In the Sink or Swim experiment, you’ll learn how adding one variable to water will change the amount of surface tension the water has. You’ll see that anything you add to water may quickly affect whether something sits on water or not.

Experiment Videos

Here's What You'll Need

Two glasses, let's try it.

Fill two glasses equally full with water.

In one of the cups, add about 1 oz (30 mL) of dish soap and gently stir the solution.

Create two identical balls of paper that can fit into your glasses of water.

Gently drop one paper ball into the plain water and drop the other paper ball into the glass with the soapy water solution.

You will quickly observe that the paper balls react differently to the two fluids. In fact, one paper ball begins to sink while the other sits atop the water!

How Does It Work

It may appear that one paper ball is floating on the water while the other ball sinks, but it isn’t entirely about density. Instead, what you are observing is a difference in the surface tension of the water. Soap is a surfactant, or a compound that lowers the surface tension of a liquid. Soap, in particular, decreases the surface tension of water by weakening the hydrogen bonds that make water such a special substance.

This lower surface tension has two direct effects when it comes to the paper ball. First, the lower surface tension means that the paper can’t sit atop the water’s surface, allowing more of the water to come in contact with more of the paper. Second, the weakened hydrogen bonds mean that the water is more likely to soak into the porous paper, making the paper much more dense and causing it to sink.

Science Fair Connection

Weakening hydrogen bonds is fun, but it isn’t a science fair project yet.  You can create a a science fair project by identifying a variable, or something that changes, in this experiment.  Let’s take a look at some of the variable options that might work:

• Try testing different amounts of soap. You can time the amount of time it takes for the paper ball to be completely submerged.
• Try to find the best surfactant possible. Try different brands of soap, or even other solids and liquids to see which acts as the best surfactant.
• Try changing the shape or size of the paper.  Time how long it takes different sizes or shapes to be submerged.

Those are just a couple of ideas, but you aren’t limited to those! Try coming up with different ideas of variables and give them a try.  Remember, you can only change one thing at a time.  If you are testing different surfactants, make sure that the other factors are remaining the same!

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Racing Lolly Sticks – Surface Tension Experiment

June 26, 2013 By Emma Vanstone 7 Comments

How do you make a lolly stick race across water? Would you believe me if I told you all you needed was a drop of washing-up liquid ( dish soap ) and some water to do a fun surface tension experiment ?

Racing lolly sticks – surface tension experiment

You’ll need.

A large container – we used our water table, but a bath would work too.

Washing up liquid – dish soap

Wooden lolly stick

Instructions

Fill your container with water. You only need it a couple of cm deep.

Place the lolly stick on the water. It should float.

Add a little washing-up liquid at one end of the stick. It should zoom off.

Why does this work?

This simple science investigation is a great demonstration of surface tension . When you have a container full of water, the water molecules below the surface are pulled together equally in all directions, but those on top are pulled together more tightly, as they don’t have water molecules above them. This draws them together to form a kind of ‘skin’ that we call surface tension. It is the surface tension that stops the lolly stick from sinking. When washing-up liquid is dropped onto the surface of the water it disrupts the arrangement of the water molecules, decreasing the surface tension behind the stick.

Water molecules move from areas of low surface tension to high surface tension, and so the lollystick stick moves.

More surface tension investigations

Make a small boat and investigate to see whether disrupting the surface tension of the water makes it move.

Ask a friend to blow waves over the surface of the water with a straw, investigate whether the surfboard still moves when washing up liquid is added.

Set up a lollystick race for multiple children!

Another way to demonstrate surface tension is to disrupt cocktail sticks in a bowl of water or to make a hole in a layer of pepper on water !

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If you enjoyed this experiment, we’ve got lots more science for kids you’ll love.

Try our STEM Challenges , fun experiments for science at home or science fair ideas .

Last Updated on September 8, 2023 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

June 28, 2013 at 2:23 pm

This is a great summer science activity!

July 04, 2013 at 4:19 pm

What a neat and fun lesson!! Thank you for sharing at Sharing Saturday!!

July 20, 2013 at 8:36 pm

Oh I never knew that. I’ve been collecting lollipop sticks and I’m sure my boys will love this activity.

March 28, 2014 at 10:19 am

October 08, 2015 at 6:13 pm

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Surface Tension Experiments

Learn about the surface tension of water with our simple definition below. Try these fun surface tension experiments at home or in the classroom. As always, you’ll find fantastic and easy-to-do science experiments .

Easy Surface Tension Experiments

Here are some fun ways to demonstrate the surface tension of water. Plus, all you need is a handful of common household supplies. Surface tension is a combination of chemistry and physics . Let’s play with science today!

Magic Pepper and Soap Experiment

Sprinkle some pepper in water and make it dance across the surface. This fun pepper and soap experiment will teach kids about the surface tension of water.

Bubble Snakes

Find out how you can blow up a gigantic bubble snake, all with the help of surface tension.

Drops Of Water On A Penny

A fun science activity with pennies and water. How many drops of water do you think you can get on a penny? The results might surprise you and all because of surface tension!

Floating Paperclip Experiment

How do you make a paperclip float on water? Learn about the surface tension of water with a few simple supplies.

Magic Milk Experiment

Try this color-changing milk and soap experiment. Like water, the dish soap breaks the surface tension of the milk, allowing the food coloring to spread out.

Geometric Bubbles

Explore surface tension while you blow bubbles! Make your own homemade bubble solution too!

Paper Clips In A Glass

How many paper clips fit in a glass of water? It’s all to do with surface tension!

Skittles Experiment

Why don’t the skittles colors mix in water? Explore how surface tension of water makes effects the process. Also set this up with M&Ms.

Soap Powered Boat Experiment

Explore surface tension up close as kids observe firsthand how soap influences the movement of a small boat on the water’s surface.

Bonus Activity: Water Drop Painting

Not an experiment as such but still a fun activity that combines science and art. Paint with water drops using the principle of surface tension of water.

What Is Surface Tension Of Water?

Surface tension exists on the surface of water because water molecules like to stick to each other. This force is so strong that it can help things sit on top of the water instead of sinking into it, like our pepper and soap experiment below.

The high surface tension of water allows a paper clip, with much higher density, to float on water. It also causes drops of rain to stick to your windows and is why bubbles are round. The surface tension of water also helps propel water-striding insects on the surface of ponds.

💡 Also, learn about capillary action !

Scientist Agnes Pockels discovered the science of surface tension of fluids simply by doing the dishes in her kitchen.

Despite her lack of formal training, Pockels was able to measure the surface tension of water by designing an apparatus known as the Pockels trough. This was a key instrument in the new discipline of surface science. In 1891, Pockels published her first paper, “Surface Tension,” on her measurements in Nature.

What is the scientific method?

The scientific method is a process or method of research. A problem is identified, information about the problem is gathered, a hypothesis or question is formulated from the information, and the hypothesis is put to test with an experiment to prove or disprove its validity. Sounds heavy…

What in the world does that mean?!? The scientific method should be used as a guide to help lead the process.

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Surface Tension Experiments for Kids

Activities » Science » Surface Tension Experiments for Kids

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Are you looking for simple, yet fascinating science experiments that your kids can do at home? Why not explore the topic of surface tension with some fun activities and experiments? Surface tension is an interesting phenomenon that captures the imagination of even young children.

With just a few materials, they will be able to conduct hands-on experiments to observe and understand surface tension in action.

In this post, we’ll talk about what surface tension is, provide examples of relevant everyday objects as well, and explain four engaging experiments you and your kids or students can try out today! Let’s get started!

As you can probably guess from all my science-related posts lately, my sons are a bit, shall we say, obsessed with science experiments right now. For example, we love the dancing milk experiment and love doing experiments with try ice !

What are 5 examples of surface tension?

Surface tension is the property of a liquid that allows it to resist external forces that could increase its surface area. Here are five examples of surface tension in action:

• Water Striders: Water striders are insects that can walk on the surface of water due to the surface tension of water. Their legs do not break through the surface because of the cohesive forces between water molecules.
• Capillary Action: Surface tension is responsible for capillary action, where liquids can rise or fall in narrow tubes or porous materials against the force of gravity. This phenomenon is seen in plants’ ability to draw water from the soil into their roots.
• Droplets Forming on Leaves: When you see water droplets forming on the surface of leaves or other hydrophobic (water-repellent) surfaces, it’s due to surface tension. The cohesive forces of water cause it to bead up rather than spread out.
• Soap Bubbles: Soap bubbles are held together by surface tension. The soap molecules in the bubble’s film reduce surface tension, allowing the bubble to form and hold its shape.
• Droplets on a Needle: When you touch the surface of water with a fine needle, it can cause water to form a droplet at the tip of the needle. This is due to the surface tension of water trying to minimize its surface area.

Surface tension plays a significant role in various natural phenomena and everyday experiences, as demonstrated by these examples.

Surface Tension Science Experiment for Kids

Science is hands-on and fun for kids. The great part is that kids learn something while doing experiments that they enjoy! With a little bit of knowledge, you can easily bring this learning into your home and classroom.

Surface tension experiments can be both fun and educational for kids. These experiments help children understand the concept of surface tension, which is the property of the surface of a liquid that allows it to resist an external force due to the cohesive nature of its molecules.

Surface Tension Science Activities

#1 – floating paper clip.

You’ll need a bowl of water, a paper clip, and a tissue or small piece of aluminum foil. Kids can place the paperclip gently on the surface of the water. They’ll observe how the water’s surface tension allows the paperclip to float.

#2 – Magic Milk

For this experiment, you’ll need a shallow dish, milk, food coloring, and liquid dish soap. Pour a small amount of milk into the dish, add a few drops of different food coloring, and then add a drop of dish soap in the center. Kids will be amazed as they watch the colors race to the edges of the dish due to changes in surface tension.

#3 – Floating Needle

Gather a bowl of water and a sewing needle. Slowly and carefully place the needle on the surface of the water. Kids will see that the needle can float on the surface due to surface tension.

#4 – Soap Boat

This experiment requires a small piece of aluminum foil, a bowl of water, and a bar of soap. Kids can cut the aluminum foil into the shape of a small boat and place it in the water. Then, they can carefully touch the soap to the water near the boat, and they’ll observe how the boat moves due to changes in surface tension.

#5 – Water Droplets on a Coin

Kids can place a clean, dry coin on a flat surface and carefully add water droplets one at a time using a dropper. They’ll notice how the water forms droplets and doesn’t immediately spread out due to surface tension.

#6 – Soap Bubbles

Making soap bubbles is a classic surface tension experiment. You’ll need a solution of water and dish soap and a bubble wand or straw. Kids can dip the wand or straw into the solution and gently blow it to create bubbles. They’ll learn how surface tension creates the thin film of the bubble.

#7 – Floating Pepper

Fill a bowl with water and sprinkle a small amount of pepper on the surface. Kids can then dip their finger, which has a tiny bit of liquid dish soap on it, into the water near the pepper. They’ll observe the pepper moving away from the soap as the surface tension is disrupted.

#8 – Water Bridge

Place two identical cups close together on a flat surface and fill them with water. Use a straw to create a bridge between the two cups by carefully touching the surface of the water in each cup. Kids will see a water bridge forming due to surface tension.

Remember to always supervise kids during these experiments, especially when handling small objects and liquids, and ensure they understand the safety precautions involved. These experiments can help children learn about the properties of water and surface tension in an engaging and hands-on way.

Easy Surface Tension Experiment with Dish Soap

* I used a circular bowl first, then we used a longer Pyrex bowl, which worked better because there was more space for the boat to speed off

• Cut a triangle from the card stock for your “boat”
• Fill your bowl with water*
• Gently place the triangle on top of the water (introduce the concept of surface tension)
• Place a small amount of dish soap on a finger
• Dip the fingertip into the water behind the “boat”
• Observe the boat speed off
• Encourage and ask questions

What is the Science Behind Surface Tension?

Surface tension is a fascinating phenomenon in fluid dynamics that arises due to the cohesive forces between the molecules of a liquid. It’s responsible for several interesting behaviors and effects, such as the ability of small insects to walk on water, the formation of droplets, and the shape of liquid surfaces.

Here’s a brief overview of the science behind surface tension:

• Molecular Cohesion: Surface tension is primarily a result of the cohesive forces between liquid molecules. These forces are primarily caused by intermolecular interactions, such as van der Waals forces and hydrogen bonding, depending on the nature of the liquid. These forces cause molecules at the surface of the liquid to be attracted to their neighboring molecules beneath the surface.
• Unequal Forces: Molecules inside the liquid experience cohesive forces from all directions because they are surrounded by other liquid molecules. However, molecules at the surface do not have molecules above them to balance the cohesive forces. This imbalance in forces results in a net inward force, which acts to minimize the surface area of the liquid.
• Energy Minimization: Nature tends to minimize the energy of a system. In the case of a liquid, minimizing the surface area minimizes the energy associated with the surface. As a result, liquids naturally form shapes that minimize their surface area, which is usually a sphere for small droplets or a flat surface for larger bodies of liquid.
• Mathematical Expression: Surface tension is quantified by a physical property called surface tension coefficient (symbolized as σ), which is measured in units of force per unit length (e.g., N/m or dyn/cm). It represents the amount of force required to increase the length of a liquid interface by a unit amount. The higher the surface tension, the more difficult it is to increase the surface area of the liquid.
• Effects of Surface Tension: Surface tension is responsible for various everyday phenomena, such as the formation of water droplets, capillary action (the rise of liquids in narrow tubes), the ability of small objects to float on the surface of water, and the shape of liquid menisci in narrow containers.
• Contact Angle: When a liquid wets a solid surface, the angle at which the liquid meets the solid is called the contact angle. The contact angle is determined by the balance between adhesive forces (liquid-solid interaction) and cohesive forces (liquid-liquid interaction) and is influenced by surface tension.
• Surfactants: Substances known as surfactants (surface-active agents) can reduce surface tension by interfering with the cohesive forces between liquid molecules. Surfactants are commonly used in detergents and soaps to help break up and remove dirt and grease from surfaces.

Surface tension is a result of the attractive forces between liquid molecules, which causes the surface of a liquid to behave like a stretched elastic membrane. It plays a crucial role in many natural and industrial processes and is a fundamental concept in fluid mechanics.

Other Surface Tension Experiment Ideas

• Experiment with different substances in the water (black pepper, for example, gives a great demonstration of soap deterring germs
• Explain how the dish soap weakens the surface tension of the water. So, the tension is stronger in front of the “boat”.
• Use different liquids
• Utilize different shapes (talk about velocity and physics)
• What happens with more dish soap? More water? A bigger “boat”?
• Have “boat” races
• Experiment with different objects to see if the water’s surface tension can support various objects (such as a paper clip)
• Sink/Float work

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Easy Science: Surface Tension Water Drop Races

Science experiments don't need to be complicated! A water drop race is a simple science project is a great was to pass the time when you need a quick distraction for your kids. It can be part of an in-depth classroom exploration into the concept of surface tension and molecule cohesion.

What is Surface Tension?

Surface tension is

the property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules. The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension. The molecules at the surface of a glass of water do not have other water molecules on all sides of them and consequently they cohere more strongly to those directly associated with them. USGA

A classic kids surface tension experiment is the one where you drip water drop by drop onto a penny. You can also observe surface tension by floating a paper clip on the surface of water.

Bugs also use surface tension to hang out on ponds and streams. Leaves during a rain storm also demonstrate water's cohesive nature.

For this water drop race experiment, surface tension is responsible for the spherical shape of the water droplets. The waxy paper keeps the water from being absorbed away by the surface they sit on.

However, even if your child is too young to grasp the concepts of surface tension and the bonding properties of water molecules, it's still a super fun indoor activity that will make kids say, "Cool!!!"

Water Drop Surface Tension Experiment

How to conduct water drop races

You will need: one straw per scientist glass of water water dropper wax paper or parchment paper

Observations

Kids will start to notice ways in which they can control their water drops. Young scientists can explore surface tension strength by blowing air through the straw extra hard, which will cause larger water drops break up into smaller water beads.

Kids will also learn how to blow water beads together to merge them into larger droplets. No doubt, they will have fun sucking water drops up the straw and blowing them back out! My kid loved blowing his off the table to "plop" on the floor! ( It's just water, after all. )

Conclusions

Whether or not you use this surface tension experiment to go into depth about how water molecules, tension and cohesion work, water drop races provide lots of entertainment!

I absolutely loved how this project has the added bonus of keeping the kids busy for an extended period of time without a lot parental involvement. And because it's just a small amount of water that is used, you won't have to worry about everything getting wet or the kids making a big mess to clean up!

More water experiments

• Water refraction is just like magic!
• Amaze your kids with a leak proof hole in a bag!
• Make a coin jump off a bottle
• All our favorite indoor water activities

I First Published this idea 3/16/09.

Reader Interactions

Leptir says

June 04, 2010 at 9:14 am

Looks like fun 🙂 I'll probably try it in my classroom with kids. Thanks for sharing 🙂

MaryAnne says

June 04, 2010 at 12:15 pm

What an excellent activity! Thanks for the idea =)

June 05, 2010 at 1:44 am

Christy says

June 05, 2010 at 5:33 pm

My kids will love this! Thanks.

Raising a Happy Child says

June 09, 2010 at 11:14 am

I have to try it out - wind races have been popular here, but we haven't done them with water.

September 12, 2016 at 5:29 pm

Hi! I'm about to launch a year-long science course for young kids at some of the local schools. I love this idea! It will be a PERFECT fun activity to end the "Surface tension" lesson with! We'll be doing some fun experiments to bring the concept home to the kids, and this is just what I needed! Thanks so much Erica!

September 14, 2016 at 12:16 pm

Glad the idea was useful!

Julie C Billow says

April 17, 2017 at 12:45 am

I just tried this out myself and had fun! Try adding some color to the experiment by drawing on the waxed paper with markers and then watch as the water drops blow through the colors and absorb them. Fascinating!

April 19, 2017 at 11:07 am

I love that idea!

March 09, 2018 at 3:22 pm

Used this today with my preschool kids. Many had fun watching the water break apart and go back together. I added food coloring to the water and used freezer paper ??

Rebecca says

March 28, 2019 at 3:00 pm

We used color waters and blew the the color water droplets into each other to see what colors they turned into. The kids loved it.

March 29, 2019 at 8:08 am

What a fantastic idea!

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Simple Science Fair Experiment for Kids About Surface Tension Facts Video

Buggy and Buddy

Meaningful Activities for Learning & Creating

November 4, 2013 By Chelsey

Science Experiments for Kids: Exploring Surface Tension

We always enjoy all types of  science experiments for kids ! Our latest science experiment is all about exploring the surface tension of water and other liquids. This simple experiment for kids really intrigued my 5 year old and inspired her to come up with all kinds of ideas!

Follow our Science for Kids Pinterest board!

Whenever I  present my kids with  science experiments, my main goal   is to inspire them to make predictions and critically think about the world around them.  Exploring the surface tension of water and other liquids really motivated Lucy to come up with her own predictions and ideas!  (This post contains affiliate links.)

Materials for Exploring Surface Tension

• Cooking oil (We used canola oil.)

1. Use the eye dropper to place a few drops of water on some wax paper. Observe the drops closely. What do you notice?

2. Use another eye dropper to place some drops of cooking oil near the water drops. Compare the cooking oil to the water. How are they the same? How are they different?

3. Look closely at other liquids like rubbing alcohol on the wax paper. Compare and contrast all the liquids.

4. Try poking the water drop with a clean toothpick. What happens?

5. Now poke the water drop with a  toothpick that has been dipped in dish soap. What happens? Why do you think this happened?

After completing the previous steps, Lucy enjoyed trying out her own ideas. She tried placing drops of oil on top of water drops and tried mixing them together. Then she tried poking the different liquid drops with clean and soapy toothpicks. She was so intrigued!

What’s Going On?

The water drop on the wax paper looks kind of like there’s a skin around it. When you poke it with a clean toothpick, nothing happens, but, when you poke it with a soapy toothpick, the water spreads out.

Drops of water stick to each other. That’s why the surface of the water drops appear to have a skin-like layer on them.  This is called surface tension. Soap decreases the water’s surface tension causing it to spread out.

Want to Go Even Further?

Related activities to extend the learning for various ages.

• Here’s another experiment having to do with the surface tension of water~ Paperclips in Water .
• Try a similar experiment. See how many drops of water can sit on the surface of a penny using a dropper. Was it what you expected?
• Observe how the drops of other liquids look on the wax paper.

Be sure to check out STEAM Kids book and ebook for even more creative STEM and STEAM ideas!

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Science project, effect of temperature and salinity on surface tension of water.

Surface tension is a property of liquids. Liquids have a limited ability – called surface tension - to resist an external force. For example, when a liquid forms a lens-shaped meniscus in a graduated cylinder, the surface tension of the liquid is resisting the force of gravity. Because of surface tension, we observe objects float on liquids and insects walk on the surface of lakes, even though they may be far denser than the liquid. Surface tension is the product of Van der Waal forces. Since Van der Waal forces exist between the molecules of a single substance such as water, they are called inter-molecular forces. This force causes the molecules on the surface of a liquid to cling together, almost as if they were acting like a sheet of plastic wrap.

How do temperature and salinity affect surface tension?

• 2 clear glass 250 ml beakers (other types of transparent glassware can also be
• 1 gallon of distilled water
• Aluminum foil cut into small squares measuring approximately 1 cm x 1 cm
• White rice (size of grain does not matter)
• Access to refrigerator
• Access to a hotplate or microwave
• Thermometer
• Graph paper
• Measuring spoon
• Label one beaker “NaCl” (NaCl stands for sodium chloride - otherwise known as salt). Label the other beaker “pure water.”
• Fill both beakers with 250 ml of distilled water.
• Add 3 tablespoons of table salt to the beaker labeled “NaCl.” Stir until the salt is dissolved.
• Put both beakers in the fridge. After a half hour check the temperature of the liquids. Keep them refrigerated until the temperature of the water drops to 15° C.
• Float a piece of aluminum foil on the surface of the water. See if you can place individual grains of rice on top of the foil. You may want to use a tweezers to grasp the rice grains. How many rice grains can be placed on the foil in the pure water beaker before they sink? How many grains can be placed on the foil in the saltwater beaker before they sink? Write down your results.
• Let the beakers sit on a counter until the water is room temperature. Repeat step5.
• Using a hot plate, heat the water until it is 35°C. If you do not have a hotplate, use a microwave, heating the water for 5-second intervals and checking the temperature after every 5 seconds. Repeat step 5. Try this again when the water is 40°C, 45°C, 50°C, and 55°C.
• Graph your results. The y-axis of your graph can represent temperature and the x- axis can represent number of rice grains. Surface tension is less if fewer grains of rice are needed to upset the aluminum. Which has less surface tension – saline or pure water? How does temperature affect surface tension?