Mad Science: Glurch

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Supplies

  • Elmer’s Glue® (8 oz bottle of Elmer’s Glue-All)
  • Borax (a powdered soap found in the grocery store)
  • Large mixing bowl
  • Plastic cup (8 oz size works well)
  • Spoon
  • Measuring cup
  • Food coloring (the spice of life)
  • Water
  • Paper towel (hey, you’ve got to clean up!)
  • Zipper-lock bag (don’t you want to keep it when you’re done?)
  • Water

Process

Here’s the easiest way to make a big batch Elmer’s Slime. The measurements do not have to be exact but it’s a good idea to start with the proportions below for the first batch. Just vary the quantities of each ingredient to get a new and interesting batch of goo.

  1. This recipe is based on using a brand new 8 ounce bottle of Elmer’s Glue. Empty the entire bottle of glue into a mixing bowl. Fill the empty bottle with warm water and shake (okay, put the lid on first and then shake). Pour the glue-water mixture into the mixing bowl and use the spoon to mix well.
  2. Go ahead… add a drop or two of food coloring.
  3. Measure 1/2 cup of warm water into the plastic cup and add a teaspoon of Borax powder to the water. Stir the solution – don’t worry if all of the powder dissolves. This Borax solution is the secret linking agent that causes the Elmer’s Glue molecules to turn into slime.
  4. While stirring the glue in the mixing bowl, slowly add a little of the Borax solution. Immediately you’ll feel the long strands of molecules starting to connect. It’s time to abandon the spoon and use your hands to do the serious mixing. Keep adding the Borax solution to the glue mixture (don’t stop mixing) until you get a perfect batch of Elmer’s slime. You might like your slime more stringy while others like firm slime. Hey, you’re the head slime mixologist – do it your way!
  5. When you’re finished playing with your Elmer’s slime, seal it up in a zipper-lock bag for safe keeping.

What’s Happening

The mixture of Elmer’s Glue with Borax and water produces a putty-like material called a polymer. In simplest terms, a polymer is a long chain of molecules. You can use the example of cooking spaghetti to better understand why this polymer behaves in the way it does. When a pile of freshly cooked spaghetti comes out of the hot water and into the bowl, the strands flow like a liquid from the pan to the bowl. This is because the spaghetti strands are slippery and slide over one another. After awhile, the water drains off of the pasta and the strands start to stick together. The spaghetti takes on a rubbery texture. Wait a little while longer for all of the water to evaporate and the pile of spaghetti turns into a solid mass — drop it on the floor and watch it bounce.

Many natural and synthetic polymers behave in a similar manner. Polymers are made out of long strands of molecules like spaghetti. If the long molecules slide past each other easily, then the substance acts like a liquid because the molecules flow. If the molecules stick together at a few places along the strand, then the substance behaves like a rubbery solid called an elastomer. Borax is the compound that is responsible for hooking the glue’s molecules together to form the putty-like material. There are several different methods for making this putty-like material. Some recipes call for liquid starch instead of Borax soap. Either way, when you make this homemade Silly Putty you are learning about some of the properties of polymers.

Elmer’s Slime is very easy to make, but it’s not exactly what you’ll find at the toy store. So, what’s the “real” slime secret? It’s an ingredient called polyvinyl alcohol (PVA). The cross-linking agent is still Borax, but the resulting slime is longer lasting, more transparent… it’s the real deal.

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Mad Science: Oobleck

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Supplies

  • One box of cornstarch (16 oz)
  • Large mixing bowl
  • Cookie sheet, square cake pan, or something similar
  • Pitcher of water
  • Spoon
  • Gallon size zipper-lock bag
  • Newspaper or a plastic drip cloth to cover the floor
  • Water
  • Food coloring

Process

  1. Pour approximately 1/4 of the box (about 4 oz) of cornstarch into the mixing bowl and slowly add about 1/2 cup of water. Stir. Sometimes it is easier (and more fun!) to mix the cornstarch and water with your bare hands.
  2. Continue adding cornstarch and water in small amounts until you get a mixture that has the consistency of honey. It may take a little work to get the consistency just right, but you will eventually end up mixing one box of cornstarch with roughly 1 to 2 cups of water. As a general rule of thumb, you’re looking for a mixture of roughly 10 parts cornstarch to 1 part water. Notice that the mixture gets thicker or more viscous as you add more cornstarch.
  3. Sink your hand into the bowl of “quicksand” and notice its unusual consistency. Compare what it feels like to move your hand around slowly and then very quickly. You can’t move your hand around very fast! In fact, the faster you thrash around, the more like a solid the gooey stuff becomes. Sink your entire hand into the goo and try to grab the fluid and pull it up. That’s the sensation of sinking in quicksand!
  4. Drop a plastic toy animal into the cornstarch mixture and then try to get it out. It’s pretty tough even for an experienced quicksand mixologist.
  5. Slap TestPour the mixture onto the cookie sheet or cake pan. Notice its unusual consistency when you are pouring it onto the pan. Stir it around with your finger, first slowly and then as fast as you can. Skim your finger across the top of the glop. What do you notice?

    Try to roll the fluid between your palms to make a ball. You can even hold your hand flat over the top of the pan and slap the liquid glop as hard as you can. Most people will run for cover as you get ready to slap the liquid, fearing that it will splash everywhere.

    According to theory, the mixture should stay in the pan. Yeah, right! If your cornstarch water mixture inadvertently splatters everywhere, you will know to add more cornstarch. When you are finished, pour the glop into a large zipper-lock plastic bag for later use.

IMPORTANT – READ THIS! The cornstarch will not stay mixed with the water indefinitely. Over time, the grains of cornstarch will separate from the water and form a solid clump at the bottom of the plastic storage bag. It is for this reason that you must not pour this mixture down the drain. It will clog the pipes and stop up the drain. Pour the mixture into a zipper-lock bag and dispose of it in the garbage.

What’s Happening

The cornstarch and water mixture acts like a solid sometimes and a liquid at other times. This concoction is an example of a suspension – a mixture of two substances, one of which is finely divided and dispersed in the other. In the case of the cornstarch quicksand, it’s a solid dispersed in a liquid.

When you punch the cornstarch quicksand, you force the long starch molecules closer together. The impact of this force traps the water between the starch chains to form a semi-rigid structure. When the pressure is released, the cornstarch flows again.

All fluids have a property known as viscosity – the measurable thickness or resistance to flow in a fluid. Honey and ketchup are liquids that have a high resistance to flow. Water has a low viscosity.  Sir Isaac Newton said that viscosity is a function of temperature. So, if you heat honey, the viscosity is less than that of cold honey. The cornstarch and water mixture and quicksand are both examples of non-Newtonian fluids because their viscosity changes when stress or a force is applied, not when heat is applied.

Mad Science: Kid Friendly Elephant Toothpaste

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Supplies

  • 16 oz empty plastic soda bottle (preferably with a narrow neck such as those made by Coca-Cola)
  • 1/2 cup 20-volume hydrogen peroxide (20-volume is 6% solution, purchased from a beauty supply store)
  • Squirt of Dawn dish detergent
  • 3-4 drops of food coloring
  • 1 teaspoon yeast dissolved in approximately 2 tablespoons very warm water
  • Funnel
  • Foil cake pan with 2-inch sides
  • Safety glasses
  • Lab smock

Process

  1. Have students put on their safety glasses and lab smock.  Each student should have in front of them a cake pan, plastic bottle, Dawn in small cup, food coloring, 1/2 cup peroxide, and the dissolved yeast mixture.
  2. Stand the bottle up in the center of the cake pan. Put the funnel in the opening. Add 3-4 drops of food coloring to the peroxide and pour the peroxide through the funnel into the bottle. Show a water molecule diagram and a peroxide molecule diagram, pointing to the extra oxygen that will be set free in the reaction.
  3. Add the Dawn detergent to the peroxide in the bottle.
  4. Pour the yeast mixture into the bottle and quickly remove the funnel.
  5. The students can touch the bottle to feel any changes that take place.

What’s Happening

The reaction creates foam that shoots up out of the bottle and pools in the pan. After a minute or so, it begins to come out in a moving stream that looks like toothpaste being squeezed out of a tube. The students can play with the foam as it is just soap and water with oxygen bubbles. The bottle will feel warm to the touch as this is an exothermic reaction.

Mad Science: Lava Lamp

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Supplies

  • tall, skinny clear jar or container
  • vegetable or mineral oil (mineral oil is clear, the vegetable oil is yellowish)
  • water colored with food coloring
  • salt or epsom salts or Alka-Seltzer tablets

Process

  1. Create lamp by pouring 1 part water to 3 parts oil into container
  2. Break up Alka-Seltzer tablets (if using them)
  3. Slow pour salts or drop Alka-Seltzer pieces into container and observe the results

What’s Happening

First of all, you confirmed what you already knew… oil and water do not mix. The molecules of water do not like to mix with the molecules of oil. Even if you try to shake up the bottle, the oil breaks up into small little drops, but the oil doesn’t mix with the water. Also, food coloring only mixes with water. It does not color the oil.

When you pour the water into the bottle with the oil, the water sinks to the bottom and the oil floats to the top. This is the same as when oil from a ship spills in the ocean. The oil floats on top of the water. Oil floats on the surface because water is heavier than oil. Scientists say that the water is more dense than the oil.

Here’s the surprising part… The Alka-Seltzer tablet reacts with the water to make tiny bubbles of carbon dioxide gas. These bubbles attach themselves to the blobs of colored water and cause them to float to the surface. When the bubbles pop, the color blobs sink back to the bottom of the bottle.

Mad Science: Jell-glOw

fluorescent-jello

Supplies

  • Jell-O packet
  • Water
  • Tonic Water (contains quinine)
  • bowl
  • spoon
  • black light

Process

  1. Make Jell-O according to package directions, replacing half or all of the water with tonic water (the tonic water will make Jell-O taste bitter)
  2. Shine a black light onto Jell-O and observe results

What’s Happening

No matter what flavor/color of Jell-O you use, it will glow bright blue under the black light. This is the fluorescence of the quinine in the tonic water.

Mad Science: Fizzing & Foaming

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Supplies

  • 1Tbs baking soda
  • 1Tbs liquid dish soap
  • 3/4cup water
  • 1/4cup vinegar
  • food coloring
  • 12oz drinking glass
  • cookie sheet

Process

  1. Set glass on cookie sheet
  2. Add baking soda, soap, and food color to glass and stir
  3. Quickly pour vinegar into glass and observe the results

What’s happening

The experiment baking soda and vinegar is one of the most popular. However, it is deceptively simple: what appears to be one reaction is actually two, happening in quick succession. This reaction is an example of a multi-step reaction.

What actually happens is this: the acetic acid (that’s what makes vinegar sour) reacts with sodium bicarbonate (a compound that’s in baking soda) to form carbonic acid. It’s really a double replacement reaction. Carbonic acid is unstable, and it immediately falls apart into carbon dioxide and water (it’s a decomposition reaction). The bubbles you see from the reaction come from the carbon dioxide escaping the solution that is left. Carbon dioxide is heavier than air, so, it flows almost like water when it overflows the container. It is a gas that you exhale (though in small amounts), because it is a product of the reactions that keep your body going.

By adding the soap, you create millions of tiny bubbles of trapped carbon dioxide. Because the bubbles take up space, they quickly overcrowd each other and overflow the container.

Mad Science: Epsom Crystal Spikes

 

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Supplies

  • black construction paper
  • scissors
  • pie tin, cake pan, or shallow bowl
  • warm water
  • epsom salts (found in first aid aisle)

Process

  1. Cut paper to fit bottom of pie tin
  2. Add 1Tbs epsom salt to 1/4cup warm water and stir until dissolved
  3. Pour onto black paper and allow liquid to evaporate (sunny day works best)
  4. Observe results

What’s happening

When you add epsom salt to water, the salt dissolves. When the water evaporated, the salt forms crystals shaped like long needles. If you tried regular salt instead of epsom salt, what changes would you see?  Are they the same or different?