Digestive System Science Experiment: How Does Bile Break Down Fat?


This week we continued our study of the digestive system. We covered the liver and pancreas. The liver makes bile, which is used by our bodies to break down fat in the small intestine. We did this science experiment to show how bile works.


Milk (at least 2% fat)

Food Coloring

Dish soap

cotton ball


Pour milk into a dish. Put a drop of food coloring in different spots in the milk, far away from each other. Squirt a little dish soap onto the cotton ball and then place it soapy side down in the dish. You will immediately notice the food coloring drops start to swirl around.


Why does this happen? Soap contains a chemical similar to what is found in bile. It surrounds the fat in the milk and tries to break it into smaller pieces. This is what it does to dirt also, which is why we use it to wash our clothes and dishes. As the soap swirls around the fat in the milk, trying to break it down, the food coloring gets moved around as well. You can watch it continue to swirl as the soap tries to do its job. This is what happens in your small intestine as well. The bile surrounds fat particles to break them down.


This is a very simple experiment to illustrate part of the digestive process. Happy homeschooling to you and your family!

15 thoughts on “Digestive System Science Experiment: How Does Bile Break Down Fat?

    1. They soaked the cotton in dish soap which has chemical components closely related to file and the food coloring represents fats. It is to show you what happens in the stomach. The same way the soap in the wash breaks up dirt off our clothes.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s