what is the constant in the floating egg experiment

Floating Egg Experiment

Will an egg float in fresh or salt water.

Will an egg float in fresh or salt water? The Floating Egg Experiment is an easy hands-on investigation that can be done in your own kitchen! I have used this lab before as a class demonstration, group lab investigation, and with my own kids at home. There are several science terms and concepts that can be taught in this experiment including density, solutions, mixtures, saturation, concentration, mass, and the list goes on. Scroll to the bottom to download your own Floating Egg Experiment Lab Sheet!

*Don’t miss out on the Salt Water Density Lab featuring a free observation lab sheet too! And be sure to check out all of our FREE Science Resources including our Labs & Experiments !

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Floating Egg Experiment Introduction

Before conducting the experiment, there are a few things you should cover with your students to create a meaningful learning experience. First, spend time talking about the terms below. We discuss the meaning of salinity and a homogeneous mixture amongst other concepts. Since this investigation is demonstrating the difference in density between salt water (oceans) and fresh water (rivers, lakes, ice), it works well with our Water Distribution Unit .

Important Terms and Facts

– Salinity describes the amount of salt dissolved in water. Saline water is water with salt dissolved in it.

– A homogeneous mixture is a type of mixture where a solute (salt) is dissolved into a solvent (water). This type of homogeneous mixture is called a solution .

– Density is the amount of mass in volume. Volume is the amount of space something takes up.

– Buoyancy is a force on an object making that object rise or move forward.

Floating Egg Experiment Lab Sheets

Write hypothesis.

Once you have introduced the key terms in the Floating Egg Experiment, make sure the students are given the following facts and the FREE FLOATING EGG EXPERIMENT LAB SHEETS.

Water has a density of 1 g/mL (g/cm3).
Objects will float in water if their density is less than 1 g/mL.
Lastly, objects will sink in water if their density is greater than 1 g/mL.

After giving your students this information, guide them to write a hypothesis for the posing question, “Will an egg float in salt or fresh water?”

For example, their hypothesis could read like this:

If I add 1 TBSP of salt to every ½ cup of fresh water, a raw egg _____________________________ float.

Students will plug in the words, “will” or “will not,” in the blank of the hypothesis.

Identify Variables

Identifying variables in an experiment is something that takes most students practice. It is a good idea to continuously review the following terms. Check out our Scientific Method unit to get more practice.

Manipulated Variable – variable that is different in the experiment. It is the thing that is manipulated. *In this case, the manipulated variable is the amount of salt added to the water.

Responding Variable – variable that is being tested. It responds to the manipulated variable. *Hence, if the egg floats or not.

Controlled Variable – variable(s) in the experiment that do not change or remain the same. *In this lab, the glasses and raw egg are the controlled variables.

Review the experiment before conducting...

For you teachers, it is always advisable to try an experiment out first to ensure that it works the way it is supposed to. There is nothing worse than demonstrating in front of a group of students for an experiment to flop! It has happened to the best of us… yes, it has happened to me! Watch this video I found on YouTube to get a step by step of the experiment. It is pretty easy to demonstrate.

I have used this experiment for years with the exception of the salt water with the fresh water on top. That aspect of the experiment was new to me. So, I too tried this at home before showing it to my students. *I wonder if it will work with glasses that aren’t quite so narrow at the bottom? Let’s see…

Gather Materials

The materials list is likely to all be found within your kitchen. I love experiments that do not require a tricky supply list. So, gather 3 raw eggs, water, salt, a spoon, 3 clear glasses, and a measuring cup and tablespoon come in handy.

Fresh Water first and then Salt Water

I always start demonstrating the egg sinking in the fresh water first. Next, you will show how adding salt to the fresh water will change its density. Thus, the egg will now float in the denser salt water. In the Egg Floating Experiment, I use 1 tablespoon of salt per 1/2 cup of water. This enables the students to measure more precisely. Some kids need the restrictions.

*On their lab sheets, students will draw and record observations and make conclusions.

Extended Learning...

This aspect of the Floating Egg Experiment is a new for me. I never did this in years past, but what a great addition. You can choose to demonstrate this last glass or the students can continue to follow the procedures on their lab sheet. In the end, take the time to talk about the science behind this experiment. This is where the science comes all together!

What's the Science behind it?

It’s very important that before, during, and after an experiment that you are explaining the science behind the experiment. If you skip this step, then the lab becomes merely a fun hands-on activity with no real science connections. The experiments are meant to help the students get past the surface and begin to soak in the abstract and unseen science behind it.

Glass #1 – The egg sunk to the bottom in glass #1 because the egg is more dense than the water. Hence, the egg has more mass in its volume than the water does.

Glass #2 – The egg floats in salt water because the salt water is more dense than the egg. This means that the salt water has more mass in its volume than the egg does. The salt adds mass to the volume of the water creating a more dense liquid.

Glass #3 – When the egg is put in the cup, the glass is only half full with a mixture of salt and water. This causes the egg to float in the salt water instead of sinking. When plain water is added to the salt water, the egg remains in the middle of the glass because of density. The plain water is the least dense, then the egg, and the most dense is the salt water at the bottom of the glass.

*When the floating eggs are pushed into the salt water, the eggs float right back up to the top of the salt water. This is due to buoyancy. The force of the salt water causes the egg to rise back up.

DOWNLOAD FLOATING EGG EXPERIMENT LAB SHEETS

Check out these other free resources.

John 4:14 – But whosoever drinketh of the water that I shall give him shall never thirst; but the water that I shall give him shall be in him a well of water springing up into everlasting life.

Salty Science: Floating Eggs in Water

A density demonstration from Science Buddies

By Science Buddies

Key concepts Density Mass Volume Concentration Buoyancy Water Introduction Have you ever wondered why some objects float in water and others sink? It has to do with the density of the objects compared with the density of the water surrounding them. If an object is less dense than the water around it, it will float. Because salt water is denser than freshwater, some things float more easily in the ocean—or extremely salty bodies of the water, such as the Dead Sea. You can make your own dense water by adding salt to tap water. In fact, if you add enough salt, you can make the water so dense that an egg will actually float in it! Explore how this works in this science activity. Background If you put an egg in a cup of tap water, it will sink to the bottom. Why is this? Because the density of the egg is higher than the density of tap water, so it sinks. Density is the mass of a material per unit volume. For example, the density of freshwater under standard conditions is approximately one gram per cubic centimeter. But, if you add enough salt to the water, the egg will actually float back up to the surface! Adding salt to the water increases the density of the solution because the salt increases the mass without changing the volume very much. When enough salt is added to the water, the saltwater solution's density becomes higher than the egg's, so the egg will then float! The ability of something, like the egg, to float in water or some other liquid is known as buoyancy. But just how much salt is needed to make an egg float? In this science activity you'll figure that out by making solutions with varying concentrations of salt in them. Materials

Measuring cup

Large container, such as a large bowl or cooking pot (It must be able to hold at least three cups.)

One half cup of table salt

Five cups that hold at least 16 ounces each

Permanent marker (if you are using plastic cups) or masking tape and a pen (to label nondisposable cups)

Three spoons for mixing salty solutions

Soup spoon for egg transfers

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Preparation

Take the egg out of the refrigerator and allow it to warm to room temperature. Be sure to always wash your hands after handling uncooked eggs because they may carry salmonella.

Pour one and one half cups of water into your large container.

Add one half cup of salt to the large container and stir to dissolve some of the salt (it will not all dissolve yet).

Add one more cup of water to the large container (making two and one half cups total) and stir to dissolve the remaining salt. The salt should be completely dissolved before you go on to the next step. It may take several (five to 10) minutes of stirring, so you may need to be patient. Why do you think it's important to start out with a solution that has such a high concentration of salt?

Arrange the five cups on a surface, going in a line from left to right. Label the cups 1 to 5. If you are using plastic cups, you can use a permanent marker to label them. If you are using nondisposable cups, you can use masking tape and a pen to label them.

Add three quarters cup of the salty solution you prepared to cup 1.

Add three quarters cup of plain tap water to cups 2 through 5. (Cup 5 will be plain tap water.)

Add three quarters cup of the salty solution you prepared to cup 2 and mix it. What is the salt concentration in cup two compared with cup one?

Add three quarters cup of the salt solution from cup 2 to cup 3 and mix it. What is the salt concentration in cup 3 compared with cups 1 and 2?

Add three quarters cup of the salt solution from cup 3 to cup 4 and mix it. What is the salt concentration in cup 4 compared with the other cups?

Use a soup spoon to place an egg in cup 5. Does the egg float?

Use the spoon to take the egg out and place it in cup 4. Does the egg float?

Repeat this process with cups 3, 2 and then 1. In which cup does the egg first float? If the egg floated in more than one cup, did you notice any difference in how it floated? What does this tell you about the density of the egg?

Extra: In this science activity you figured out, within a factor of two, how much salt it takes to float an egg. You could narrow down the range further by testing additional saltwater solutions to try and determine the egg’s density. To do this, start your solution with the salt concentration in which the egg first floated and make a new dilution series, as you did before. Now in which cup does the egg first float? What does this tell you about the density of the egg?

Extra: Repeat this activity using several more eggs, possibly both hard-boiled and uncooked eggs. Do you get the same results with other eggs or is there some variation between different eggs? For testing hard-boiled versus raw eggs, you should test the same egg, first raw and then after hard-boiling it to investigate any differences.

Extra: Find out how much salt there is in seawater. From the results of your activity, do you think an egg would float or sink in seawater?

[break] Observations and results Did the egg float in cup 1 and 2, but not in cups 3, 4 or 5? You likely saw that the egg floated best in cup 1, floated a little less in cup 2 (but part of it was above the surface) and did not float in the other cups. Cup 1 had the undiluted salty solution that you originally prepared, which was one half cup of salt in two and one half cups water total. The concentrations of the salt solutions in cups 2 to 4 were halved as you increased in cup number; for example, the concentration of the salt in cup 2 was half that of cup 1, and the concentration of the salt in cup 3 was half again of cup 2. (Cup 5 had plain tap water.) The egg should have sunk in cups 3, 4 and 5 because the density of the egg was higher than the density of the solutions (or plain tap water) in those cups. Cups 1 and 2 had more salt in them than the other cups (with cup 1 having the most salt), which means these solutions were denser. The egg should have floated (with part of it above the water surface) in these two cups because the solutions were denser than the egg. The actual density of the egg is in between the density of the solution in cup 3 and that in cup 2. More to explore What Is Density? , from Charles E. Ophardt, Elmhurst College Why Is the Ocean Salty? , from Herbert Swenson, U.S. Geological Survey Publication Fun, Science Activities for You and Your Family , from Science Buddies How Salty Does the Sea Have to Be for an Egg to Float? , from Science Buddies

This activity brought to you in partnership with Science Buddies