Tuesday, November 20, 2012

Glow in the Dark Gak

Gak is something almost everyone has made, but here are some instructions on how to make glow in the dark gak.  At the end of this entry, explore some of the science behind gak and glow in the dark toys.

For this experiment you'll need:  white glue, borax, water, spoons, containers for mixing, and green phosphorescent  pigment (available for purchase at www.douglasandsturgess.com)

Add 1/4 water and 1 tsp. of borax to one container.

Add 1/4 cup water and 1/4 cup white glue to a second container.

Make sure that both mixtures are fully combined and dissolved.

Add 1/2 tsp. green phosphorescent pigment to the glue and water mixture.  Stir well.

Add the water and borax mixture to the white glue, pigment, and water mixture.

Stir quickly to combine the two.  Strands should begin to form as the mixture thickens.

Stop stirring once all the water is dissolved.

The resulting mixture is gak.  This elastic, putty-like goo is fun to squish around and play with.

This gak is special because it glows bright green in the dark.  Keep it charged up by holding it under a bright light.  Keep the gak stored in a plastic bag so it doesn't dry out.  The pigment tends to "settle" out of the gak, so knead it every once in a while to keep it all combined.

It is likely that this gak isn’t the first glow in the dark item you’ve seen.  Glow in the dark toys such as plastic stars, key chains, and yoyos are everywhere.  How do all of these items glow in the dark?  Glow in the dark items all include chemicals calls phophors.  There are many different types of phosphors, but they all work in the same way.  Recall that atoms have a center made up of neutrons and protons.  Flying around this center are quickly moving electrons.  Electrons are sometimes farther away or closer to the center, depending on the amount of energy they have.  You may have noticed that glow in the dark items will glow less brightly over time, but “charging” them under a light makes them glow again.  When you hold the item under the light, the light gives the electrons energy, allowing them to move farther away from the pull of the center of the atom.  With time the electrons eventually relax and move closer to the center again, release the extra energy as light.

When atoms combine together, a molecule is formed.  Molecules can be many different shapes and sizes.  A familiar molecule is H20, or water.  Water is a small molecule made of two hydrogen atoms and one oxygen atom.  Sometimes small molecules combine to form one long chain.  This long chain is called a polymer.  Just like a chain, a polymer is made of the same repeating unit.

Gak is formed when polymers are created.  When you stir the gak up, you should notice that it appears stringy like melted cheese.  Those are the polymers forming!  The white glue provides a type of monomer called a hydrocarbon; sodium borate in borax causes these monomers to link together into a polymer.  However, gak is very squishy and flexible.  This is because the polymer chains can be easily broken and remade.  The polymers are held together by weak hydrogen bonds; it does not take much effort, or energy, to break apart and rebuild these bonds.

Tissue Paper Hot Air Balloon

Perhaps you've seen hot air balloons for sale as science demonstrations/experiments that you fill up with hot air from a hair dryer and let float to the top of the room.  This product can be easily recreated on a smaller scale with tissue paper.  This project is a great way to demonstrate and learn about gases and density.

You'll need: 5-6 sheets of tissue paper, a strip of paper, a glue stick, a marker, scissors, and  a hair dryer.

The first step is to layer 5-6 sheets of tissue paper and fold them in half lengthwise.

Use a marker to draw a half tear drop shape.

Cut along the line and unfold the layers.  Each one will be a panel for the hot air balloon.

Using a glue stick, or wet glue thinly applied with a paintbrush, glue one edge (marked in the picture above) and layer another panel on top. Pres down firmly to seal the edge.

Once the glue has dried, unfold the two panels to inspect for any holes.  Make sure to seal up any gaps.

Fold enough panels (5 pictured here, but depending on your teardrop shape you may need more or less) to create a round hot air balloon body.  Since the seams are facing outward, it is easy to repair any gaps and to fit in the last panel.

Glue a strip of paper inside the opening of the hot air balloon.  The paper strip should fit snugly over the hair dryer end you plan on using.  This paper strip gives the balloon support and make it easy to inflate.

With the hairdryer on low, fill the balloon with hot air.  You will need to use one hand to keep the hot air balloon on the hair dryer, but don't press too tightly.  It is necessary that some air escape out the bottom opening rather than creating a hole elsewhere.  Once the balloon is filled with hot air, is should rise a little and slowly drift back down to the ground.

The hot air balloon you built out of tissue paper works under the same scientific principle that enables real hot air balloon to fly: warmer air rises in cooler air.  It might seem like air is just empty space, but the air around us is a type of matter called a gas.  Matter comes in three states: solids, liquids, and gases.  Each state is made up of tiny particles called atoms.  In a gas, the atoms are spread out and bouncing around constantly.  A gas will fill also a container of any size or shape.

Hot air balloons are called so because they are filled with hot air.  Real hot air balloons use a flame to heat the air inside, and you used a hair dryer to heat up the air inside the one you built.  Gases behave in ways that can be predicted by a set of rules called the ideal gas laws.  One of those laws, Charles’s Law, states: V1/T1=V2/T2.  This is just a mathematical way of saying that the volume of a gas increases with temperature.  Higher temperatures mean more energy, so imagine the air molecules moving faster and spreading out more to take up a larger space.  So, when we heat up the air inside, we are increasing the volume.  This creates air that is less dense than the cooler air around it.  Density is mass per unit volume, so since we have the same amount, or mass, of air, and increase the volume, density decreases.

Flash Pickling

A large, plastic syringe can be used to create pickles almost instantly. The syringe is used a create a difference in pressure that causes the pickling solution, vinegar, to quickly permeate the cucumber pieces.  For this quick experiment you'll need: a cucumber, a knife, a large plastic syringe, and flavored vinegar (apple cider and rice wine make tasty pickles).

Chop a cucumber into small 1/2" pieces and place several inside the syringe tube.

Insert the plunger and use it to draw up enough vinegar to fill the syringe 2/3 to 3/4 full.  Make sure to get out as much air as possible.

Place your thumb very firmly over the syringe opening and use the other hand to forcefully depress the plunger.

Keeping your thumb firmly sealed, withdraw the plunger and keep it extended for about one minute.  This may cause a small amount of discomfort to your thumb.

Remove the plunger and empty out the contents of the syringe.  These cucumber pieces are now saturated with the vinegar, and they should taste like fresh pickles.

Pickling has long been a way to preserve fresh foods such as vegetables, fruits, and eggs.  These foods would typically rot and spoil rather quickly if they weren’t eaten or kept cold.  Pickling came in handy before the refrigerator was invented, and it is still popular today because pickles are so tasty!  Mold, insects, and bacteria are common factors of rotting and spoiled food.  Pickling foods creates an acidic, anaerobic environment that is inhospitable to these factors.  Vinegar is an acid, meaning it has a low pH and tastes sour.  By covering the pickles in liquid brine, an anaerobic environment is created.  Anaerobic means without air.  Just like us, insects and other food spoilers need air to breathe.  The anaerobic environment keeps the pickles fresh and safe to eat.

Flash pickling with the syringe creates instant pickles whereas you need to wait 1-3 weeks for refrigerator pickles.  The key to this time difference is pressure.  Boyle’s law states that pressure and volume are inversely related in a closed system (as long as temperature remains the same).  By covering the syringe opening with your thumb, you are creating a closed environment.  When the plunger is withdrawn, the volume is increased.  This means that the pressure lowered, creating a partial vacuum.  When you relax the syringe and release your thumb, the fluid vinegar rushes into the cucumber pieces, creating almost instant pickles.  For the pickles sitting in the fridge, they must wait patiently for osmosis to take its course.

Fusing Plastic Bags

Fusing plastics bags is a really easy and great way to make use of all those extra plastic grocery store bags lying around.  All you need is some parchment paper, a few plastic bags, scissors, a towel, and and iron.  The resulting product has a vinyl-like feel and is perfect for making wallets and even tote bags.

The first step is to flatten out the plastic bag and cut off the bottom and the top handles.

Place a large towel down on a flat surface.  An ironing board works as well, but this will give you a larger work space.  On top of the towel, place a large sheet of parchment paper.  Fold the flattened bag in quarters and place it on top of the parchment paper.

Lay another sheet of parchment paper on top of the folded plastic bag.  With an iron set to medium or "rayon" setting, firmly and smoothly press down and iron over the plastic bag for about 15-20 seconds.

Remove the iron, wait about 10 seconds for the plastic to cool, and check out the fused plastic.  It might need to be ironed a little bit more (especially around the edges).  If there are holes in the plastic bag, the iron is either too hot or you ironed it too long.  This can actually create a cool web-like affect when layered over  a different colored sheet of fused plastic.  Target bags melt/fuse really easily and create large sheets, hence the change in pictures.

Once you have several sheets of fused plastic, repeat the process to fuse them all together.  Place the messiest bag in the middle since it won't be seen.  Any designed you'd like to be visible should be placed outwards.  Depending on thickness, this will take a minute or two to fully fuse.

Trim off the uneven edges to create an rectangle.

If you want to make a wallet with designs, fuse a plastic bag of a contrasting color and cut shapes out of it.  Fuse these shapes onto the rectangle.

You will fold the wallet in half and fuse the edges together to create a pouch.  To to this, cut a smaller sheet of parchment paper that will fit inside the wallet and will allow only the edges to fuse.

Fold up the wallet and place a piece of parchment paper over the whole project (not pictured).  Concentrate on ironing the edges to melt them together.  Once it has cooled, the middle sheet of parchment should be easily removed.  Fold this in half to create a wallet that will fit in your pocket!

Here are some helpful tips to keep in mind:

    When ironing the plastic, make sure to work in a well-ventilated area.  Keep the windows and doors open!

 Always iron between parchment paper; otherwise, the plastic will melt onto the iron.
  Some grocery bags will work better than others.  Target and Safeway bags are very easy to work with.

 When folding the plastic bag, try to make sure any design is on the inside.  Some bags are printed with ink that will melt if ironed on the outside.  To be safe, before folding the bags in fourths reverse the bag so it’s inside out.
    If the wallet won’t stay folded in half, lightly iron the fold for 10 seconds to help it keep its shape.

Plastic grocery bags are a great material to fuse because it's thin and strong.  When a plastic grocery store bag is stretched in the direction of handles to bottom, the bag feels strong and resilient.  When the bag is stretched from side to side, it easily pulls apart and loses ts shape.  This is due to the chemical structure of polyethylene, the material that most plastic bags are made of. The polyethylene that makes plastic grocery bags is a polymer.  When plastic bags are made, the polymers are all lined up side by side in the same direction.  The polymers lay in the direction of handles to bottom.  Since grocery bags can be used to carry heavy items, the polymers are aligned this way to give the bags the most strength.  Imagine all these tiny chains laying next to each other and holding up the weight of a few cans of food.  It’s easy to stretch and deform the bag when it’s pulled from side to side because the chains of polymers are not connected in that direction.

Dying Flowers

Creating vibrant, colorful flowers from plain white flowers is really easy to do and a fun way to study plant vascular systems.  Any white or lightly colored flower will work well, but carnations are particularly fitting due to their sturdy nature and petal structure. Freshest flowers will soak up dye the fastest.

Materials needed: different colors of liquid food dye, white flowers, a sharp knife, and mason jars (cups work as well)

Fill the jars or cups with lukewarm water.

Add several drops of food dye to each jar.  The more food dye added, the more colorful the flowers will be.

Stir the dye into the water.

Cut the flower stems at an angle.  Shorter stems will cause the flowers to soak up dye more quickly.  Cutting the flower stems under water can prevent air bubbles from getting trapped in the stem's vascular system; these air bubbles can prevent the dye from being soaked up to the petals.

Set the flowers in the jars of dye.  After about an hour the petals will have a subtle hue.

Here are the flowers after 3 hours.

Here are the flowers after 24 hours.  They were left in the dye for another day without any huge difference.  Once the flowers are the color you desire, you can rinse the dye of the stems and place them in clean water.

It's possible to create flowers that are tie-dye or multiple colors by carefully splitting the stem and placing each part in a different container of dye.

The flowers can transfer the dye from the jars to the petals through their vascular system.  Most of the plants we see everyday are called vascular plants.  Trees, ferns, grasses, and flowers are all vascular plants.  These plants have special tissues that circulate water, minerals, and nutrients around the plant.  Water and minerals are first absorbed from the soil by the plant’s roots, which are then moved around by xylem.  Xylem and phloem are the two types of transport tissues.  Xylem form long tube-like vessels that help move water around the plant, while phloem carry the sugars made from photosynthesis. Both xylem and phloem also help support the plant and give it structure.

Several processes are involved in pushing the water and nutrients against gravity and up through the plant’s vascular system.  Three are as follows:
·          Capillary action, the attraction between a liquid and the tube it is in.  This is the force that pushes a liquid up a wick or a cloth with one end stuck in the water.
·         Transpirational pull:  Water in a plant’s leaves and other surfaces evaporates into the atmosphere.  This leaves a small pressure difference at the surface which gives a little pull to the top of the vascular system.
·         Root pressure:  Osmosis is the process of a liquid or gas moving through a membrane, such as a cell membrane, because one side has a higher concentration of solute.  Liquid moves into the roots of a plant through osmosis and this gives a little push to the bottom of the vascular system.  

With these processes, water and nutrients can be pushed up more than 100 meters in redwood trees!

By cutting the flower stems at an angle, more of the xylem is exposed to the dye, coloring the flowers more quickly.  The dyed water travels through the xylem to all parts of the plant.  The thin, white petals allow the dye to be seen very easily.  Celery stalks have very visible xylem; it’s that stringy fiber that makes it hard to chew sometimes.  Try soaking a celery stalk in dye and slicing it in half.  The individual xylem vessels will be easy to see.  The celery leaves will also end up colorful like the flower petals!