Did you know that you can tell whether an egg is raw or boiled without cracking the shell? It is called the egg spin test and it is really easy and fun to try at home or in the classroom.

How to Tell if An Egg is Hard Boiled

My kids (and I) were excited to learn about this simple egg experiment which came in handy in our home recently. As we were preparing for some serious egg decorating, we lost track of which bowls contained raw egg or boiled egg.

Related: More science projects

Without having to crack an egg, we used egg physics to help us solve our problem in the form of the egg spin test.

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Egg Spin Experiment: Raw vs. Boiled Egg

I did a little research and found a simple way to figure out which of the eggs were boiled and which of the eggs were still raw with a simple spin an egg.  This helpful egg hack is also a great way to teach a little science lesson for the kids.

Supplies Needed for Egg Spin Test

• Eggs – raw & boiled
• Flat surface

Egg Spin Test Instructions

Step 1 – Find a Test Surface

Place the egg in question on a flat surface.

Step 2 – Spin an Egg

Grip it between your thumb and fingertips, and then gently spin it. Emphasize “gently” with your kids, because a raw egg spinning off the table can get messy…I speak from experience!

Step 3 – Stop the Egg Spin

While the egg is spinning, touch the egg lightly enough to make it stop spinning, and then lift your finger off.

Results of Spin Test: Is it a Boiled Egg? Is it a Raw Egg?

If the egg is hard boiled:

If the egg is boiled, the egg will stay in place.

If the egg is raw:

If the egg is raw, it will amazingly start spinning again.

So what in the world is going on?

This Egg Spin Experiment Works Because of Egg Physics!

This is a perfect example of inertia and Newton’s Law of Motion:

An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force.

Newton

So, something in motion will stay in motion until acted upon by another force.

1. Egg and Shell Spin Together When Egg is Raw

The egg shell and its content are spinning along together. When you stop the egg from spinning, you stop the egg shell from moving, but the inside of the raw egg is liquid and just keeps spinning around.

Eventually, the friction of the egg shell will slowly stop the liquid center from spinning, and the egg will come to rest.

2. Egg Mass is Solid when Egg is Boiled

Inside the hard boiled egg, the mass is solid. When the egg shell stops, the center of the egg cannot move anywhere, so it is forced to stop with the egg shell.

Try this egg experiment with your kids, but before you explain to them how it works, ask them for a theory on why the raw egg or boiled egg spins differently.  

Egg Test

Many people think of an “egg test” as whether to tell if you have a fresh or spoiled egg without cracking the shell. Since we are running all sorts of science experiments around the un-cracked egg today, why not look at that too!

Remember, simple egg freshness tests aren’t always accurate and can sometimes give you the wrong result as to egg freshness. To really make sure your egg is fresh, the best thing to do is check the expiration date on the carton and store the eggs properly.

Egg Test Methods

• Egg float test: Place the egg gently in a glass filled with water. If the egg sinks to the bottom, it is fresh. If the egg floats, it is not fresh.
• Egg sniff test: Smell your egg. If it has an unpleasant odor, it is not fresh.
• Egg crack test: While your egg is on a flat surface, crack the shell and observe your egg. If you can see the yolk is round and upright, the egg is fresh. If you see the yolk is flattened with thin, spread out white around it, it is not fresh.
• Egg shell test: Hold your egg up to the light. If the shell appears thin and fragile, the egg is likely older and not fresh.

How does the egg spin test work?

When we spin a raw egg, it will wobble or not spin smoothly because the liquid inside is moving around. But when we spin a boiled egg, it will spin smoothly and quickly because the inside of the egg is solid. The solid yolk and egg white make the boiled egg spin nicely like a top. So, by spinning an egg and seeing how it moves, we can tell if it’s raw or boiled.

Which physics lesson does the egg spin test illustrate?

The egg spin test can help us understand the concept of balance and motion.

When we spin an egg, we observe how it moves and spins. If the egg is fresh, it spins smoothly and quickly because the weight inside is evenly distributed. This shows us that balance is important for objects to spin properly.

On the other hand, if the egg is not fresh, it may spin slowly or wobble because the weight inside is not balanced.

This teaches us that balance affects how things move. By experimenting with the egg spin test, we learn about the connection between balance and motion.

Where can I find other simple science experiments for my kids like the egg test?

As luck would have it, we wrote the book on simple science experiments! Literally. Check out The 101 Coolest Simple Science Experiments on Amazon!

More Egg Science Experiments for Kids

• Try the egg drop challenge idea – one of the best egg science fair ideas!
• Squeeze egg in hand experiment shows the balance eggs have between being strong and being fragile.
• How to make scrambled eggs inside the shell.
• Egg in vinegar experiment to make a naked egg.
• Hatching supermarket eggs?
• Egg starts with E and we have other letter e crafts and activities.
• Did you know that traditional paints were actually egg paint?

Were you able to use the egg spin experiment to see if your egg was raw or boiled? Did it work?