How to... make bones bend!

In this bite sized science experiment you will learn what makes bones hard and how you can tie a knot in one! Always remember to ask your parent or guardian to help you.

What you'll need:

1 large jar some long, thin chicken bones – washed and clean some vinegar

Step 1 Try bending a few of your chicken bones - what happens? Put your chicken bones in the jar and fill with enough vinegar to cover the bones completely. Now leave the jar somewhere safe for 1 week.

Step 2 Now you can remove the bones from the vinegar.  Try to bend them and see what happens now (be careful of any sharp edges!)  Can you tie them into a knot or twist them into a strange shape?  When you have finished playing with them either tie them up into a tangle, or make a picture with them.  Leave them somewhere safe for a few days to dry.  Once they have dried they will be permanently bent into shape!

Find out more...

As you might know, bones have something in them called calcium.  This is attached to carbon and oxygen atoms to give a form of calcium called calcium carbonate.  This calcium carbonate is what makes bones hard and strong (that is why you are often told to drink milk when you are young).  When the bones are in the vinegar, the calcium carbonate and the vinegar (which is a weak acid) react.  If you look at the jar over the week you will even be able to see the reaction taking place (look for small bubbles on the surface of the vinegar).
These bubbles are carbon dioxide gas, which is formed by the reaction between the calcium carbonate and vinegar.  Without the calcium carbonate in the bones they become much softer.  This is why we can bend them and tie knots in them.  By leaving the bones out in the air they will become hard again.