Moo Glue

Materials:

* 2 small paper drinking cups

* 1 tablespoon of white vinegar

* 1/4 cup 2% milk

* 1 pinch of baking soda

* spoon for stirring

* 2 paper towels or coffee filters

* 1 pair safety scissors

* black and white construction paper

* tablespoon measure

Procedure

Pour 1/4 cup of 2% milk into one of the paper cups. Add 1 tablespoon of vinegar. Stir for 1 minute. Do you see evidence of a chemical change?

Drape a paper towel or a coffee filter over the second cup. Push the middle of the towel down to form a space so that the mixture can be poured in.

Pour the curds and whey (the whey is the clear liquid part that separates out) and let it filter until the whey has gone through the paper towel into the cup.

Very gently squeeze the rest of the whey from the curds into the cup. Discard the whey down the sink.

Scrape (with a clean spoon) the curds into the empty cup. Add a pinch of baking soda and stir well. Allow 6 hours for the glue to dry completely.

What is going on here?

The glue you have made is from a protein called casein. The casein is a natural polymer, which is a huge molecule made from many repeating units. This protein is usually dissolved as part of the milk. When vinegar is added to milk, a chemical change transforms the protein into a solid. This is similar to what happens when you cook an egg and is called "denaturing" a protein.

When the milk coagulates or clumps up like this it has turned into curds and whey. Milk soured in this way is more digestible: it is like cottage cheese, but more sour.

The same process helps turn casein into cheese, plastics, jewelry, and even house paint. The protein molecules are very long and stringy and lots of "sticky" points on their surfaces, which allow them to act as a glue