Quite a few of the things we use every day are made of plastic. And they are usually made in a factory using chemicals. But hiding in your fridge and cabinets are two ingredients that, when put together, make a simple kind of plastic that can be molded and decorated.

QUESTION

How do you make plastic?

WHAT YOU NEED

• Pint of milk

• Adult

• Saucepan

• Mixing spoon

• 1-teaspoon measure

• White vinegar

• Sieve

• Large pan

• Rubber gloves

• Water

WHAT TO DO

• Pour milk into the saucepan.

• Ask an adult to turn on the stove and put the saucepan on the stove.

• Simmer the milk, but don't let it burn.

• Carefully measure out 4 teaspoons vinegar and pour them into the milk. Don't touch the hot pan.

• What do you see in the pan? Stir the mixture.

• Ask an adult to turn off the heat and set the pan aside to let the mixture cool.

• Put the sieve into a larger pan.

• Ask an adult to pour the mixture into the sieve, letting the liquid run down the drain. What do you have left in the sieve?

• Put on the gloves and wash the blobs under cool running water. When they're cool, press them with your hands. What do they feel like? What do they smell like?

• Now you have your own plastic. Make it into some fun shapes and let it dry for a day. Then you can decorate it!

WHAT'S HAPPENING

Milk contains a protein called casein. This protein is not something you can taste in regular milk. But when you add an acid, such as vinegar, and heat, the protein turns into lumps. These lumps are similar to the plastic used in almost everything we own. This chemical change is a big one—don't eat the lumps, they're not made of milk anymore and it's not safe!

YOUR NOTES

Describe the smell and feel of the plastic you just made.

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What did you make with your plastic? Draw a picture of it here.

protein: an essential part of the food we eat that helps our bodies grow healthy and strong.