what is water tap experiment

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

37 Water Science Experiments: Fun & Easy

We’ve curated a diverse selection of water related science experiments suitable for all ages, covering topics such as density, surface tension, water purification, and much more.

These hands-on, educational activities will not only deepen your understanding of water’s remarkable properties but also ignite a passion for scientific inquiry.

So, grab your lab coat and let’s dive into the fascinating world of water-based science experiments!

Water Science Experiments

1. walking water science experiment.

This experiment is a simple yet fascinating science experiment that involves observing the capillary action of water. Children can learn a lot from this experiment about the characteristics of water and the capillary action phenomenon. It is also a great approach to promote scientific curiosity and enthusiasm.

Learn more: Walking Water Science Experiment

2. Water Filtration Experiment

A water filtering experiment explains how to purify contaminated water using economical supplies. The experiment’s goal is to educate people about the procedure of water filtration, which is crucial in clearing water of impurities and contaminants so that it is safe to drink.

Learn more: Water Filtration Experiment

3. Water Cycle in a Bag

The water cycle in a bag experiment became to be an enjoyable and useful instructional exercise that helps students understand this idea. Participants in the experiment can observe the many water cycle processes by building a model of the water cycle within a Ziplock bag.

4. Cloud in a Jar

The rain cloud in a jar experiment is a popular instructional project that explains the water cycle and precipitation creation. This experiment is best done as a water experiment since it includes monitoring and understanding how water changes state from a gas (water vapor) to a liquid (rain) and back to a gas.

Learn more: Cloud in a Jar

5. The Rising Water

The rising water using a candle experiment is a wonderful way to teach both adults and children the fundamentals of physics while also giving them an exciting look at the properties of gases and how they interact with liquids.

6. Leak Proof Bag Science Experiment

In the experiment, a plastic bag will be filled with water, and after that, pencils will be inserted through the bag without causing it to leak.

The experiments explain how the plastic bag’s polymer chains stretch and form a barrier that keeps water from dripping through the holes the pencils have produced.

Learn more: Leak Proof Bag Science Experiment

7. Keep Paper Dry Under Water Science Experiment

The experiment is an enjoyable way for demonstrating air pressure and surface tension for both adults and children. It’s an entertaining and engaging technique to increase scientific curiosity and learn about scientific fundamentals.

Learn more: Keep Paper Dry Under Water Science Experiment

8. Frozen Water Science Experiment

The Frozen Water Science Experiment is a fun and engaging project that teaches about the qualities of water and how it behaves when frozen.

You can gain a better knowledge of the science behind the freezing process and investigate how different variables can affect the outcome by carrying out this experiment.

9. Make Ice Stalagmites

10. Bending of Light

A fascinating scientific activity that explores visual principles and how light behaves in different surfaces is the “bending of light” water experiment. This experiment has applications in physics, engineering, and technology in addition to being a fun and interesting method to learn about the characteristics of light.

11. Salt on a Stick

This experiment is an excellent way to catch interest, engage in practical learning, and gain a deeper understanding of the characteristics of water and how they relate to other substances. So the “Salt on Stick” water experiment is definitely worth trying if you’re looking for a fun and educational activity to try!

Learn More: Water Cycle Experiment Salt and Stick

12. Separating Mixture by Evaporation

This method has practical applications in fields like water processing and is employed in a wide range of scientific disciplines, from chemistry to environmental science.

You will better understand the principles determining the behavior of mixtures and the scientific procedures used to separate them by performing this experiment at home.

13. Dancing Spaghetti

Have you ever heard of the dancing spaghetti experiment? It’s a fascinating science experiment that combines simple materials to create a mesmerizing visual display.

The dancing spaghetti experiment is not only entertaining, but it also helps you understand the scientific concepts of chemical reactions, gas production, and acidity levels.

14. Magic Color Changing Potion

The magic color-changing potion experiment with water, vinegar, and baking soda must be tried since it’s an easy home-based scientific experiment that’s entertaining and educational.

This experiment is an excellent way to teach kids about chemical reactions and the characteristics of acids and bases while providing them an interesting and satisfying activity.

15. Traveling Water Experiment

In this experiment, you will use simple objects like straws or strings to make a path for water to pass between two or more containers.

Learn more: Rookie Parenting

16. Dry Erase and Water “Floating Ink” Experiment

The dry-erase and water “floating ink” experiment offers an interesting look at the characteristics of liquids and the laws of buoyancy while also being a great method to educate kids and adults to the fundamentals of science.

Learn more: Dry Erase and Water Floating Ink Experiment

17. Underwater Candle

In this experiment, we will investigate a connection between fire and water and learn about the remarkable factors of an underwater candle.

18. Static Electricity and Water

19. Tornado in a Glass

This captivating experiment will demonstrate how the forces of air and water can combine to create a miniature vortex, resembling a tornado.

Learn more: Tornado in a Glass

20. Make Underwater Magic Sand

Be ready to build a captivating underwater world with the magic sand experiment. This experiment will examine the fascinating characteristics of hydrophobic sand, sometimes referred to as magic sand.

21. Candy Science Experiment

Get ready to taste the rainbow and learn about the science behind it with the Skittles and water experiment! In this fun and colorful experiment, we will explore the concept of solubility and observe how it affects the diffusion of color.

Density Experiments

Density experiments are a useful and instructive approach to learn about the characteristics of matter and the fundamentals of science, and they can serve as a starting point for further exploration into the fascinating world of science.

Density experiments may be carried out with simple materials that can be found in most homes.

This experiment can be a great hands-on learning experience for kids and science lovers of all ages.

22. Super Cool Lava Lamp Experiment

The awesome lava lamp experiment is an entertaining and educational activity that illustrates the concepts of density and chemical reactions. With the help of common household items, this experiment involves making a handmade lava lamp.

Learn more: Lava Lamp Science Experiment

23. Denser Than you Think

Welcome to the fascinating world of density science! The amount of matter in a particular space or volume is known as density, and it is a fundamental concept in science that can be seen everywhere around us.

Understanding density can help us figure out why some objects float while others sink in water, or why certain compounds do not mix.

24. Egg Salt and Water

Learn about the characteristics of water, including its density and buoyancy, and how the addition of salt affects these characteristics through performing this experiment.

25. Hot Water and Cold-Water Density

In this experiment, hot and cold water are put into a container to see how they react to one other’s temperatures and how they interact.

Sound and Water Experiments

Have you ever wondered how sound travels through different mediums? Take a look at these interesting sound and water experiments and learn how sounds and water can affect each other.

26. Home Made Water Xylophone

You can do this simple scientific experiment at home using a few inexpensive ingredients to create a handmade water xylophone.

The experiment demonstrates the science of sound and vibration and demonstrates how changing water concentrations can result in a range of tones and pitches.

Learn more: Home Made Water Xylophone

27. Create Water Forms Using Sound!

A remarkable experiment that exhibits the ability of sound waves to influence and impact the physical world around us is the creation of water formations using sound.

In this experiment, sound waves are used to generate patterns and shapes, resulting in amazing, intricate designs that are fascinating to observe.

28. Sound Makes Water Come Alive 

These experiments consist of using sound waves to create water vibrations, which can result in a variety of dynamic and captivating phenomena.

29. Water Whistle

The water whistle experiment includes blowing air through a straw that is submerged in water to produce a whistle.

This experiment is an excellent way to learn about the characteristics of sound waves and how water can affect them.

Water Surface Tension Experiments

You can observe the effects of surface tension on the behavior of liquids by conducting a surface tension experiment.

By trying these experiments, you can gain a better understanding of the properties of liquids and their behavior and how surface tension affects their behavior.

30. Floating Paperclip

In this experiment, you will put a paper clip on the top of the water and observe it float because of the water’s surface tension.

31. Water Glass Surface Tension

Have you ever noticed how, on some surfaces, water drops may form perfect spheres? The surface tension, which is a characteristic of water and the cohesive force that holds a liquid’s molecules together at its surface, is to blame for this.

32. Camphor Powered Boat

The camphor-powered boat experiment is a fun and fascinating way to explore the principles of chemistry, physics, and fluid mechanics. In this experiment, a miniature boat is used to travel across the water’s surface using camphor tablets.

33. Pepper and Soap Experiment

The pepper in a cloud experiment is a simple and interesting activity that explains the concept of surface tension. This experiment includes adding pepper to a bowl of water and then pouring soap to the mixture, causing the pepper to move away from the soap.

Learn more: Pepper and Soap Experiment

Boiling Water Experiments

Experiments with boiling water are an engaging and informative way to learn about physics, chemistry, and water’s characteristics.

These investigations, which include examining how water behaves when it changes temperature and pressure, can shed light on a variety of scientific phenomena.

It’s important to take the proper safety measures when performing experiments with hot water. Boiling water can produce steam and hot particles that are dangerous to inhale in and can result in severe burns if it comes into contact with skin.

34. Make It Rain

This experiment can be accomplished using basic supplies that can be found in most homes, make it an excellent opportunity for hands-on learning for both kids and science lovers.

Learn more: Make it Rain

35. Fire Water Balloons

Learning about the fundamentals of thermodynamics, the behavior of gases, and the effects of heat on objects are all made possible by this experiment.

36. Boil Water with Ice

The Boiling Water with Ice experiment is an engaging and beneficial approach to learn about temperature and the behavior of water. It can also serve as an introduction for further discovery into the wonderful world of science.

37. Boil Water in a Paper Cup

The “boil water in a cup” experiment is an easier but powerful approach to illustrate the idea of heat transmission by conduction. This experiment is often used in science classes to teach students about thermal conductivity and the physics of heat transfer.

Similar Posts:

• 68 Best Chemistry Experiments: Learn About Chemical Reactions
• Top 100 Fine Motor Skills Activities for Toddlers and Preschoolers
• Top 50 Fun Food Science Experiments

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The Biology Corner

Biology Teaching Resources

Penny Lab: Soap and Surface Tension

Most science classes begin the year with an exercise on the scientific method .  It can be difficult to plan a short activity that will reinforce the main ideas of developing and testing a hypothesis.  This lab is simple and doesn’t require much in the way of materials: pennies, water, and pipettes (and paper towels for clean-up). 

Each section of the activity correlates to scientific processes.  Students develop a hypothesis, gather and analyze data. Then communication their results.

There is a question about independent and dependent variables, which some students may not be familiar with. You can help them with this part by reviewing or explaining those terms.

The final question asks them to pose other questions they might ask about surface tension.  They might wonder, for instance, if other substances can affect the surface tension or if temperature has an effect. 

If you have enough time, you could have them develop a new experiment to answer those questions.  Some students may need guidance here, they are usually not comfortable with posing their own questions, likely because most of their experience involves them answering questions that have been posed *to* them.

I created a version of this lab that focuses on the biological importance of surface tension as it relates to a water strider .  It is similar to this one, but includes a short video showing a water strider and asks students to make connections between the animal and water properties.

My AP Biology class does a more advanced version of this activity that includes statistics:  “ Investigation: Properties of Water with Statistics “

Grade Level: 6-9 Time Required:  15 – 20 minutes

Shannan Muskopf