Why Do Bones Break? Science Experiment for Kids

broken salt dough bones

Most of the time, our bones stay in place when we jump and move around. Whew! But why do bones sometimes break?

To help kids understand why bone fractures can happen, try a simple science experiment!

This bone fracture activity is based on a project from the Human Body Learning Lab anatomy book for kids. Ask lots of questions and have lots of fun throwing and smashing salt dough bones.

What causes bones to break?

Sometimes, a hard hit or fall can cause a break. Whether or not a bone breaks depends a few factors.

A person’s age

Younger kids have more cartilage, which is more flexible than bone. Cartilage can bend a little so they can cushion the weight of things pressing against it. Elderly people have less cartilage, and bones can get weaker with age.

How far a person fell

The higher the fall, the more likely a fracture could happen, like from a tall ladder. The lower the fall, the less likely a bone might break, like from a couch.

young person with more cartilage, old person with less cartilage

What the person fell on

pillows can cushion falls and protect bones from breaking

Pillows and padding can cushion and protect bones from breaking. On the other hand, hard surfaces like concrete and brick can be more risky. That’s why gymnasts do cartwheels and flips on soft, bouncy floors!

How fast the person fell or was hit

A very fast speed can be more dangerous to bones. For example, a car accident after a high-speed chase could cause many bones to break.

Bone fracture science experiment for kids

Human Body Learning Lab book - Salt Dough Bones recipe

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How to make salt dough bones

Full recipe and steps for making Salt Dough Bones can be found in Human Body Learning Lab, the best anatomy book for kids!

Learn why and how bones break


Notice the texture of the salt dough bones when it has just cooled from the oven. Then feel the bones after they have been sitting on the countertop for a few days.

Ask questions

Do the bones feel softer, harder, or the same after they have been sitting out?

Are certain parts of the salt dough bones softer or harder?

Do bigger bones or smaller bones take longer to bake?


Try dropping the bones with different heights, speeds, and surfaces.

Try baking the bones at different temperatures and seeing if this causes the bones to break or stay strong.

Try adjusting the ratio of the ingredients, such as adding more flour or less water. Does this change the texture and firmness of the bones?

Video demonstration

Watch pediatrician Dr. Betty Choi demonstrate this fun bone experiment!

Learn more about your amazing body!