Casein Glue

We all know how it happens... you are right in the middle of an arts & crafts project and you run out of glue.  It can be so frustrating, but did you know that you probably have all of the things around your house that you need to make your own glue?  Here's how to do it.

What you need:  Glass jar (e.g., an empty pickle jar), metal pot (for the stove), water, nonfat milk, thermometer (a cooking thermometer will work well), white vinegar, a funnel, baking soda, a spoon, and an eye-dropper.

[Caution:  This experiment involves boiling some water on the stove.  Ask for a parent's help or permission to carry out that step.  As always, it is a good idea to where some safety glasses (maybe your parents have some from their home improvement projects you can use) when performing experiments.]

What to do:  Fill the metal pot half-way full of water and bring to a boil.  When the water boils, remove from heat.  Fill your glass jar almost 2/3 full with milk, and then fill the rest of the way (~1/3) with white vinegar.  Place the glass jar into the hot water bath and insert the cooking thermometer into the mixture of milk and vinegar.  Stir gently with the spoon, until the mixture reaches 60 degrees Celsius (140 degree Fahrenheit).

Once the mixture reaches 60 degrees C, use the funnel to filter off any liquid (the whey).  The whey can be discarded.  Retain the curds and transfer back into your glass jar.  Putting a paper towel in the funnel can help you separate the curds and whey more effectively.

Next, stir in 1/2 teaspoon of baking soda (sodium bicarbonate) to the curds.  Slowly add drops of water and stir until the mixture retains the consistency of standard white glue.  Once you have reached that point, your glue is ready to use!

How does it work? Milk contains fat, protein, and lactose, with a normal pH between 6.3 and 6.6.  At this pH, the protein in milk remains dispersed.  However, when the pH is lowered by the addition of an acid (vineagar = 5% acetic acid), the net charge of the proteins change and they begin to clump or aggregate.  The proteins clump together into casein, an insoluble mass, which precipitates out of solution.  This the curd that you separated from the whey.  The excess acid in the filtered curds is then netrualized by the addition of a base (baking soda = sodium bicarbonate = NaHCO3).  After that, you have casein glue!

Now, get back to those arts & crafts...plenty of glue to go around.  Thanks to Rebecca Denney at U.T.  Arlington for submitting this project to DISCUS.  Very cool one!

Electromagnetic Motor!

So, it's hot, and you are bored at home, or in need of a science fair idea, but you only have a battery, a magnet, some copper wire, pliers, and wire cutters.  Well, that's enough to make a simple homopolar motor.  A homopolar motor is a simple motor which uses a electromagnetic field to work.  It was invented in 1821 by Michael Faraday (if you have never heard this name, look him up...he did some really impressive things!).  This project is safe, fun, and easy to make...it will definitely impress your family and friends.

What you need:  You only need five things - a battery, a magnet, some copper wire, some wire cutters, and pliers to shape the wire.

What to do:  Cut a length of wire and use the pliers or your hands to shape it in various ways.  Be creative.  After you try your shape out, you can alter it, and try again to see what shapes work better than others.  It is good to have some type of central point in the shape that you can align with the top of the battery, and to make sure that the shape is long enough to reach down to the magnet.  Now, center the battery on the magnet (the negative pole of the battery should rest on top of the magnet).  Balance the copper wire shape on top of the battery.  Make small changes in the shape until it spins freely.  Feel free to develop the experiment by changing the size of the battery, the magnet, and/or the copper wire.  See what shapes spin fastest.  If you need some help, or just want to see the motor in action, check out this You Tube video put together by Nham Tran, a U.T. Arlington undergraduate chemistry major, who submitted this project to be featured by DISCUS.

How does it work?  One word - electromagnetism.  In this experiment, the battery provides the electircal current and the magnetic provides the magnetic field.  The combined current and magnetic field creates an electromagnetic force.  When the wire is balanced on the battery, the current travels into the wire and down to the magnet.  The electromagnetic force generated causes the wire to spin.  It will spin indefinitely, until the battery dies.

Have fun and tell us how it worked for you!

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