Got Milk?
This weekend, if you have some milk in
the fridge then you are well on your way to investigating polymers
and surface tension. The following are 2 science experiments
involving milk to try. Have fun and let me know your results!
Making Plastic from Milk
You'll need some milk and white
vinegar, plus something to heat your mixture. The stove or microwave
will work! Heat 1 cup of milk until it is steaming (if you use the
microwave be sure to watch it carefully!). Put 4 teaspoons of vinegar
into a mug. Once your milk is ready, add it to the mug. Stir the milk
and vinegar slowly. What happens?
You'll see clumps, or curds beginning
to form. Once there are many curds, allow the mixture to cool for a
while. When it is cool enough to handle drain the extra liquid off of
the curds and then put them on some paper towels. Be sure these
towels are on a tray or a surface that you don't mind getting wet.
Press the paper towel down on the curds to continue to soak up extra
liquid. Knead the curds into a ball of dough- voila! milk plastic! If
you want to make something out of your plastic, you should form it
within an hour of mixing up your curds. Add food coloring or glitter to
the wet dough, shape it and allow it to dry. Dried plastic
can also be decorated with paint or markers.
So what happened here? Plastics are all
made up of chains of repeating molecules, or polymers. Plastic can be
made of chains of the same molecules or different ones. The milk you
used in your experiment contains many molecules of casein protein.
The vinegar is an acid and when you added it to your milk it helped
the casein proteins unfold and reorganize themselves into a long
chain- a polymer! The plastic you made is called casein plastic and
was commonly used in the early 1900's through the 1940's to make many
plastic items. Neat!
There are many variations of this
experiment. www.sciencebuddies.org and www.sciencebob.com are just 2
great sites for science experiments like these!
Tie-Dye Milk: A Surface Tension
Experiment
You'll need some milk, a shallow dish
or pan, a q-tip, dish soap and food coloring. Pour enough milk to
cover the bottom of your pan. Mix up about a half a cup of water and
a squirt of dish soap in a different container. Drip several
different drops of food coloring on the surface of the milk. Take the
q-tip and dip it in the soapy water, then touch it to the surface of
the milk. What happens?
Magic!? No, but still very cool. The
soap on the q-tip breaks the surface tension of the milk. Surface
tension is a force that holds a liquid together like a skin. When the
surface tension was broken in your dish of milk, it allowed food
coloring and more milk to escape from underneath the surface to the top, making a swirling
motion.
If you enjoy mixing up creations like
this in your kitchen check out www.kitchenpantryscientist.com for all
sorts of experiments.
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