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Drops Of Water On A Penny

Have you ever thought about how many drops of water can fit on a penny ? Try this fun science experiment with things found in your purse or pocket! Explore the surface tension of water with this fun and easy penny lab with the kids. We are always on the hunt for simple science experiments , and this one is just super fun and easy!

Explore How Many Water Drops On Penny

Add this simple penny lab to your science activities this season. If you want to learn about the surface tension of water, let’s dig in. While you’re at it, make sure to check out these other fun water science experiments.

Exploring water drops on a penny is a fantastic science experiment for kids because it’s simple and fascinating. By placing drops of water onto a penny, kids can observe how the water beads up and forms a dome-like shape, defying gravity.

This phenomenon occurs due to surface tension , the cohesive force that causes water molecules to stick together. Through this experiment, kids can learn about surface tension and how it affects the behavior of liquids. They can also experiment with variables such as the number of water drops or the penny’s cleanliness to see how it impacts the results. Additionally, this experiment can be efficiently conducted with everyday household items, making it accessible and engaging for scientists of all ages.

Water Drops On A Penny Project

You can also easily turn your penny experiment into a fantastic presentation along with your hypothesis. Check out the resources below to get started.

• Easy Science Fair Projects
• Science Project Tips From A Teacher
• Science Fair Board Ideas

Penny Lab Experiment In The Classroom

TIP: If you want to add a little variety to this experiment, swap out the pennies for nickels, dimes, and quarters. Ask your students to guess how many drops will fit on each coin. Record the date from the experiment and make a class graph chart with your results!

Additional ideas for penny lab hypotheses include using different liquids or clean vs. dirty pennies . What else can you think of when creating an experiment?

Get Your Free Printable Penny Lab Guide!

Penny Lab Experiment

Let’s investigate how many drops of water can fit on a penny. Grab your purse, turn over the couch cushions, or break out the piggy bank; it’s time to find some pennies to experiment with!

• Eyedropper or pipette
• Food coloring (makes seeing this in action MUCH easier, but is optional)
• Small bowls

Penny Experiment Set Up:

STEP 1: Add water to both of your bowls, and one of them, add green food coloring. This is optional if you want to see the drops a bit better.

STEP 2: Use an eyedropper or pipette to pick up and carefully drip one drop of water at a time onto the penny.

STEP 3: Count how many drops you can fit onto one penny until the water overflows.

We were able to get ours up to about 27! Go ahead and record the data for separate trials on the same coin. What can you conclude?

Why Do So Many Drops Of Water Fit On A Penny?

Were you surprised that a lot more drops of water fit on a penny than you predicted? We had 27 drops of water on ours!

What property of water allows the water to stick to the penny? Surface tension and cohesion are why you can get so many drops of water on a penny.

Cohesion is the “stickiness” of like molecules to one another. Water molecules love to stick together! Surface tension is the result of all the water molecules sticking together. Learn more about the surface tension of water !

Once the water has reached the edge of the penny, a dome shape begins to form. This is due to the surface tension forming a shape with the least amount of surface area possible (like bubbles )!

What happens if you use a different liquid like alcohol? Can you as many drops on a penny?

More Fun Penny Experiments

• Sink the boat challenge!
• Penny Spinners
• Green Pennies Experiment
• Paper Bridge STEM Challenge
• Lemon Battery STEM Project

Use the Scientific Method

This drops of water on a penny experiment is a fantastic opportunity to use the scientific method and record your experiment using the free mini worksheet pack below.

You can read about using the scientific method here , and find more information on the independent and dependent variables !

The first step in the scientific method is asking a question and developing a hypothesis.

Apply the scientific method to this drops-on-a-penny science activity and turn it into a surface tension experiment by choosing a question to investigate.

• How many drops do you think will fit on a penny? (PREDICTION)
• What happens when one drop of water meets another drop? (OBSERVATION)
• Which coin held the most water? (EXPLANATION)
• Can you think of everyday examples of surface tension? (APPLICATION)

Helpful Science Resources To Get You Started

Here are a few resources that will help you introduce science more effectively to your kiddos or students and feel confident yourself when presenting materials. You’ll find helpful free printables throughout.

• Best Science Practices (as it relates to the scientific method)
• Science Vocabulary
• 8 Science Books for Kids
• All About Scientists
• Science Supplies List
• Science Tools for Kids

More Science Experiments To Try

Check out our list of science experiments for Jr Scientists!

• Walking Water
• Rubber Egg Experiment
• Why Do Things Float In Salt Water?
• Water Density Experiment

Printable Science Projects For Kids

If you’re looking to grab all of our printable science projects in one convenient place plus exclusive worksheets and bonuses like a STEAM Project pack, our Science Project Pack is what you need! Over 300+ Pages!

• 90+ classic science activities  with journal pages, supply lists, set up and process, and science information.  NEW! Activity-specific observation pages!
• Best science practices posters  and our original science method process folders for extra alternatives!
• Be a Collector activities pack  introduces kids to the world of making collections through the eyes of a scientist. What will they collect first?
• Know the Words Science vocabulary pack  includes flashcards, crosswords, and word searches that illuminate keywords in the experiments!
• My science journal writing prompts  explore what it means to be a scientist!!
• Bonus STEAM Project Pack:  Art meets science with doable projects!
• Bonus Quick Grab Packs for Biology, Earth Science, Chemistry, and Physics

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Drops on a Penny

Hydrogen bonds and surface tension give water some amazing properties. let's use them to see how many drops of water fit on a penny.

Print this Experiment

You might think that you can’t fit many drops of water on the surface of a penny. Pennies are just so small! In the Drops on a Penny experiment, though, you’ll experience surface tension and cohesion at their finest. How many drops of water can you fit? There’s only one way to find out… by adding one drop at a time!

Experiment Videos

Here's What You'll Need

Eyedropper or pipette, let's try it.

Wash and rinse a penny in tap water. Dry it completely with a paper towel.

Place the penny on a flat surface. The flatter the surface, the better this experiment is going to go.

Use an eyedropper or pipette to draw up water.

Carefully, drop individual drops of water onto the flat surface of the penny.

Keep track of the water drops as you add them, one at a time, until water runs over the edge of the penny. You’ll probably be surprised by the number of drops you get on there!

How Does It Work

There are two properties at work in this experiment: cohesion and surface tension. Cohesion is the attraction of like molecules to one another. In this case, the like molecules are the H20 molecules in the water drops. Surface tension is a special term we use to describe the cohesion between water molecules.

Water’s cohesion and surface tension are special because of hydrogen bonds. Hydrogen bonds are formed by the hydrogen atoms of one molecule being attracted to the oxygen atoms of another molecule.

The cohesion and surface tension of water becomes apparent when the drops of water you add to the penny reach the penny’s edge. Once the water has reached the edge, you begin to see a bubble or dome of water forming on top of the penny. The bubble shape is a result of the water molecules clinging to one another in an optimal shape (just like the bonds on the surface of a blown bubble).

Take It Further

Extend this experiment by trying different coins such as dimes, nickels, or quarters.

Science Fair Connection

Demonstrating the cohesive properties of water is pretty cool, but it isn’t a science fair project.  You can create 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 liquids such as vegetable oil, salt water, soda, etc. How does this change the number of drops the penny can hold?
• Try testing surfaces with different shapes. Do circular surfaces hold the same amount of water as rectangular surfaces with approximately the same surface area?

That’s 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 liquids, make sure that the other factors are remaining the same.

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Drops on a Penny Experiment

Have you ever noticed on a rainy day how water forms droplets on a window? Why doesn’t it spread out evenly over the whole surface? It has to do with something called surface tension. In this activity, you’ll experience surface tension and cohesion by testing how many drops of water you can you fit on a penny. You might be surprised considering pennies are so small! There’s only one way to find out…

Objectives:

• Describe the cohesive and adhesive properties of water.

Time Required:

• 10-15 minutes if using only pennies and only water

Credit: Science World

Lesson Files

• Drops on a Penny Lesson Plan (.pdf)

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Materials Needed for this Lesson Plan

• Drops on a Penny Kit

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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.

Drops on a Coin

Activity length, 10-15 mins., activity type, discrepant event (investigatable).

In this demonstration, students' assumptions are challenged as they observe the power of surface tension in water droplets.

Although a water molecule has an overall neutral charge, the actual structure of a water molecule makes it a polar molecule (it has a positive end and a negative end). The two hydrogen atoms are slightly positive, and the oxygen atom is slightly negative. A weak link occurs between the negatively charged oxygen atom of one water molecule and the positively charged hydrogen atoms of a neighbouring water molecule. This weak link is called a hydrogen bond . The polarity of the water molecule can also cause it to be attracted to molecules of other polar substances.

There are two types of "stickiness" in this demonstration: cohesion and adhesion.

The attraction between water molecules is called cohesion . The cohesive force that occurs between water molecules is so strong that, at the water's surface, it creates a "skin", which is known as surface tension . Surface tension is strong enough to support insects that crawl across the water's surface, like water striders (Gerridae).

The attraction of water molecules to other substances, like soil or glass, is called adhesion . As drops of water are added onto a penny, the adhesive force between the water and the penny keeps the water from falling off.

Cohesive forces are strong, but not unbreakable. As a water drop builds up and out, usually bulging over the sides of the penny, the cohesive forces will eventually be overcome by the force of gravity on the water molecules. The "skin" will burst, and all of the water will spill off.

The cohesive forces between polar molecules are stronger than those between non-polar molecules, such as those in oil or syrup. That's why you can make a bigger "pile" of water than of oil or syrup.

Describe the cohesive and adhesive properties of water.

Per Student or Pair: 5 cent coin or penny an eyedropper water mineral/baby/olive oil corn syrup

Key Questions

• How many drops of water they think a coin can hold? Were your predictions correct?
• Does it matter if the coin is heads or tails?
• Will syrup/oil hold more or less drops than water? Why?
• How is it possible to get so many water drops on a coin?
• What causes the ‘skin’ on the surface of the big droplet?
• Would a 10 cent coin hold more or less drops? Why?
• Teacher Tip: Younger students may believe a 10 cent coin holds more because it is worth more despite being smaller.
• Place a coin on a table or desk.
• Holding the eyedropper close to the surface of the coin, carefully squeeze water droplets onto the coin, one at a time. The droplets should pool up on the coin, creating a big droplet of water. Get the students to count the drops.
• Stop squeezing when the droplet on the coin breaks up and overflows. The count is the number of drops that the coin could hold before the one that caused the coin to overflow.
• Wipe off the coin or use a new one.
• As before, gradually add drops of oil or syrup to the surface of the coin using the eyedropper. Get the students to count the drops.

Teacher Tip:  To make sure your count is accurate, hold the eyedropper far enough above the coin so that the drop has to fall a short distance before fusing with the droplet on the coin.

• Perform this as a student activity, rather than just a demo.
• Add a drop of soap/detergent to the water you use. It reduces the surface tension causing a dramatic reduction in the number of drops that will fit on the coin.
• Start with a full glass of plain water (with a dry rim to prevent the water from dripping down the side of the glass). How many coins can we add to the water without the glass overflowing?
• Gently add coins one by one. Because of surface tension, the water will rise above the rim of the glass before it spills (just like the initial experiment). Compare your original prediction with the number of coins you were able to add.

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Jeff is a senior graphic designer at Science World. His illustration work has been published in the Walrus, The National Post, Reader’s Digest and Chickadee Magazine. He loves to make music, ride bikes, and spend time in the forest.

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Water Drops on a Penny – Science Experiment

Have you ever wondered how many drops of water you can put on a penny before the water spills. Okay, what’s your guess? I asked my children the same question today, and their guess was 5 or 6. So, we decided to give it a try and my kids were amazed to see the results. This is a super fun and quick science experiment to do at home, and it only needs come coins and water.

Materials for Water Drops on a Penny

• Different type of coins – penny, nickel, dime and quarter
• Eyedropper or Syringe
• paper and pencil

Instructions

• Fill the eyedropper or syringe with water.
• Rinse a penny and dry it completely.
• Place the penny on a plate with a flat surface.
• Guess how many drops you can place on a penny before the water spills. Write your guess on a paper.
• Attempt to drop water on the penny , one drop at a time, and count the amount of drops
• Record the results on the piece of paper next to the number you’ve guessed. How did they compare ? Have you been close in your estimated guess?

The Science behind it

Water molecules are attracted to each other, called cohesion. This attraction creates a bond on the surface called “surface tension.”. When the water reaches the rim of the penny, it begins to bulge over the surface as the molecules cling together. It is due to the surface tension forming a shape that has the least possible surface area. Eventually, gravity overcomes this force as the pile rises and the water spills over the side of the penny.

Further Extension

• Try using a nickel, dime or a quarter. What you predict is going to happen ?
• What do you think will happen if you used another liquid ( Milk, oil, soapy water etc )

Let’s stay connected. Follow my blog facebook page  My World Their Way

Here are some more science experiments to try

• BROKEN PENCIL SCIENCE
• HOW DO YOU EXPLAIN AIR RESISTANCE
• HOW DOES A STRAW WORKs | AIR PRESSURE
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Happy experimenting !

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Reader Interactions

February 8, 2021 at 7:01 pm

This is really neat! My seven year old is really into science and I think he would really enjoy this!

February 9, 2021 at 5:32 am

This is awesome! We love cool science experiments at my house!

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Penny Experiment with Water Drops

A penny experiment that demonstrates how water tension works and water can hold together in a dome shape – a super simple science experiment for kids!

Drop water on a penny and it just runs over the side, right?

Maybe not…

Maia was excited to show us a penny experiment she learned at school that demonstrated how water can hold together in a dome shape. This super simple science experiment requires only a penny, some water, and a dropper.

The Penny Experiment in Action

She showed us how we could carefully squeeze a drop of water at a time onto the top of the penny…

…and the droplets would combine to form a bubble of water.

Maia thought it looked a little like a snow globe (one of her favorite things).

We each tried the penny experiment to see how many drops of water it would take before it reached its limit. Because once it did, the water bubble burst and flowed over the edge of the penny.

Pretty cool, eh? We all had fun with this one. I think it’s definitely worth keeping it in mind for a rainy afternoon. Or just when you need a quick and easy activity for the kiddos.

By the way, if you want the technical explanation for why this works and what’s going on with the water, check out Steve Spangler Science .

3 More Favorite Simple Science Experiments for Kids

• The Rainbow Milk Science Experiment
• Make Painted Daisies
• Make a Baking Soda Volcano

P.S. Want even more science? Here’s my collection of The Best Kids Science Experiments to Try at Home .

Pin It for Later 

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Drops on a Penny

Introduction: Drops on a Penny

Overview: In this activity, kids will predict how many drops of water will fit on the head of a penny before overflowing. This very simple experiment gives children an introduction to the scientific process. At the beginning, kids will make a prediction. Then they will conduct an experiment and collect data. At the end, they will compare their results with their predictions.

Skills focus:

• Experimenting
• Collecting data
• Communicating/sharing ideas

Recommended ages: 4 and up

Estimated time: a minimum of 15 minutes

Step 1: Supplies

For this activity, you will need (per child):

• Eye dropper
• Small jar of water
• Tray or plate to work over

Shared materials:

• Rags or paper towels
• Pencils and paper

Step 2: Record Predictions

Begin by asking children to make a prediction about how many drops of water they think will fit on the head of a penny. Model the idea of a "prediction" and reassure them that it is not a test, it is simply a guess based on what they think. Record everyone's predictions.

Step 3: Experiment & Data Collection

Before the experiment gets underway, you may need to demonstrate how to use an eye dropper-- this is a complicated fine motor skill for some kids.

Once kids feel comfortable with the eye dropper, they can add one drop of water at a time to the head of the penny. Have them count each drop, this is their data collection. The drops will run together and form a thick layer of water on top of the penny. Have kids make observations-- what does it look like? What will happen next?

Eventually, the water will spill off of the penny. Have everyone record the number of drops they got up to.

Step 4: Discussion

Compare people's predictions with their results. Did it take more or fewer drops than they predicted? Was anyone surprised? Did everyone get the same results? Talk about what students might have done that resulted in the wide range of results (bigger vs smaller drops, dropping from high up vs closer, etc).

Step 5: Keep Going!

Encourage kids to ask their own questions and design their own experiment to test. Here are some ideas to get you started:

• Try it on the tail side of the penny.
• Try it with a different coin
• Try using a liquid other than water.
• Experiment with different temperatures of water.
• What happens when you add things to the water? (salt, soap, food coloring, etc)

Share you experiments with us! What worked? What didn't work so well? Leave us a comment.

The Science Kiddo

Tuesday, january 20, 2015, surface tension | drops of water on a coin + free printable.

• Set the coin on a flat surface.
• Fill a plastic pipette with water.
• Carefully squeeze out water drop by drop from the pipette onto the coin. Count how many drops fit on the coin before the dome breaks and the water spills over.
• Keep track of your results on this free printable table ! There is room to do three trials for each coin so you can average the trials together to see which coin holds the most water!

32 comments:

This is fun! Going to do it with my kids later today! Thank you for sharing it with us #pintorials

AWESOME! Have so much fun :)

Wow! This looks like a pretty cool experiment!

Hey thanks!

This is an awesome experiment! What fun! I love fun and easy experiments. I am definitely sharing this on my STEM board. Thanks so much for sharing!

Thank you for stopping by and for sharing!!

Thanks for sharing your article on the Hip Homeschool Moms Hop. I chose it as my favorite article from last week's Hop, so you are featured on this week's Hop! Don't forget to stop by and grab your "I was featured on Hip Homeschool Moms" button! Your article has also been added to our Science Board on Pinterest :-) We are looking forward to seeing more articles from you in the future!

Thank you so much, I am so honored! And I was so touched by what you said on the featured article about hands-on activities and my website :) I love stopping by the Hip Homeschool Hop every week to see what is new.

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How is the Surface Tension of Water Affected By Soap?

Introduction: Surface tension refers to water's ability to "stick to itself". Surface tension can be measured and observed by dropping water (drop by drop) onto a penny. The number of water drops that can fit on a penny will surprise you.

1. Initial Observation: Observe surface tension by seeing how many drops of water can fit on a penny. ____

Experimental Question : How does soap affect the water's surface tension? Develop a hypothesis that answers the experimental question. Write this statement below.

2. Test your hypothesis by comparing the number of drops of tap water that can fit on a penny to the number of drops of soapy water that can fit on a penny. Because water drops may vary depending on how well you drop the water, it is best to run many trials and take an average. Record your data in the table below. *Be sure to dry your penny between trials.

3. Communication is an important part of science. Compare your datat with 4 other groups.

Are there any groups that had significantly larger numbers than what you were able to get? Propose an explanation for why one group may have been able to get more drops on their penny than you.

4. Analyze the data and draw conclusions .

a) Identify the independent (manipulated) variable and the dependent (responding) variable in your experiment.

b) Write a sentence that explains how soap affects the surface tension of water based on the results of your experiment.

5. Questioning : Now that you have an idea about how soap affects surface tension. What other questions can you develop (and even test) about surface tension. Write at least two follow-up questions that could be tested using the penny technique.

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