Don’t worry to much if you don’t have whole milk or heavy cream. Nearly any milk will work and you can substitute half-and-half for the cream. Ideally you want ingredients with a high fat content because these will create a creamy texture when cooled. Remember that we’re just experimenting here, so try what you have on hand!

Ingredients

• 1/2 cup milk (Whole or 2% work best)
• 1/2 cup heavy cream (optional)
• 1/2 teaspoon vanilla
• 1 tablespoon sugar
• 4 cups crushed ice
• 4 tablespoons salt
• 2 quart size plastic bags
• 1 gallon size plastic freezer bag
• a hand towel or gloves to keep fingers from freezing as well

Basic Directions

Begin with mixing the milk, vanilla and sugar together in one of the quart size bags. If you want, you can mix this in a bowl first so that you get all the sugar dissolved. Seal the bag tightly, you want to try to get as much of the air out of the bag as you can. Too much air left inside may force the bag open during the mixing stage.

Place this bag inside the other quart size bag, again leaving as little air inside as possible and sealing well. By double-bagging, the risk of salt and ice leaking into the ice cream is minimized.

Put the two bags inside the gallon size bag and fill the gallon sized bag with ice, then sprinkle salt on top. Again, squeeze out as much air as possible and then seal the bag. Wrap the bag in the towel or put your gloves on, and shake and massage the bag, making sure the ice surrounds the creamy mixture. Five to eight minutes should be enough time to allow the mixture to freeze into ice cream.

When you are all done carefully open the bags and extract your ice cream. Enjoy!

If you’d like to experiment a bit more you can try substituting a mixture of heavy cream and your choice of milk. Mix up a few different batches and compare the texture of ice cream. Which to you think will have a smoother texture?

We suggest using freezer bags because they are thicker and less likely to develop small holes, allowing the bags to leak. You can get away with using regular plastic bags for the smaller quart sizes, because you are double-bagging. If you plan to do this indoors, we strongly recommend using gallon size freezer bags.

What does the salt do?

Salt forces the ice surrounding the bag of ingredients to melt. This “brine” solution or liquid that forms in the gallon bag absorbs the heat from the ice cream mix and gradually lowers the temperature of the mix until it begins to freeze.

If there were no salt added to the ice, it would melt at 32 degrees Fahrenheit and eventually the ice water and mix would come to equilibrium at 32 degrees. The ice cream mix, however, does not begin to freeze until its temperature falls below 27 degrees. Therefore, in order to freeze the mix, we need to add salt to the ice to lower the freezing temperature.

With 4 tablespoons of salt mixed with our ice, the brine temperature should remain constant at around 8 to 12 degrees Fahrenheit. This will give the rapid cooling and freezing that is essential to making smooth creamy ice cream.

Start by cleaning out the bottle and filling it with about 2 inches of water. Now pour in the vegetable oil to nearly the top. In order to color your lava, you will need to add several drops of food coloring. Notice that the food coloring does not mix or color the oil as the drops sink.

Materials:

• Plastic bottle (any size)
• Vegetable Oil
• Water
• Effervescing antacid tablet
• Food Coloring

What to do:

1. Fill the plastic bottle with 2 inches of water.
2. Fill the rest of the way with vegetable oil.
3. Put in 5 or 6 drops of food coloring.
4. Drop in an effervescing antacid tablet and you just made your very own lava lamp.
5. Try putting a flashlight under the bottle see what the lava lamp looks like now!

What is the Science?
Oil will not mix with water it is an example of a hydrophobic molecule. The term hydrophobic literally means water fearing from the Greek language hydros “water” and phobos “fear”. Food coloring is a hydrophilic molecule. The term hydrophilic literally means water loving from the Greek language hydros “water” and philic “friendship”. The food coloring has the ability to mix or transiently bond with the water (H2O) through hydrogen bonding. When you place the effervescing antacid tablet into the bottle it will dissolve in the water and form bubbles of carbon dioxide gas. The gas rises and takes some of the colored water along with it to the surface of the oil. When all of the gas has escaped out of the top of the bottle the water droplet falls back to the bottom of the bottle.

What to do:

1. Mix 1 cup hot water and 1.5 tsp. of Borax until dissolved. Set aside.
2. Mix 2 cups of clear glue and 2 cups of warm water together in a plastic bowl.
3. Using a metal spoon, slowly pour Borax mixture into the glue mixture while stirring quickly. Stir until the mixture leaves the side of the bowl. Slime will be sticky. Knead the mixture until it is no longer sticky. The more you work with it the easier it will become.

What’s the science?

Slime is an excellent example of a polymer. Polymers are large molecules consisting of repeating identical structural units connected by covalent chemical bonds. Polymers can be naturally occurring or manmade. Manmade polymers are materials like nylon, polyester, and polystyrene. Examples of naturally occurring polymers are proteins in our body like tubulin and actin. These proteins make up microtubules and microfilaments that serve as structural components within our cells.

Storage and Safety Guidelines:
Store Slime in an airtight container for about 3 weeks of use. Slime is non-edible. When you are through with it, discard in a trash container. Do not wash down the drain.

More about Slime:

Slime is a polymer. Polymer is a term used to describe anything that consists of repeating identical structural units. It basically is like a long strand of spaghetti and the long chains flow past each other with ease. They can be naturally occurring or man-made (synthetic). Examples of polymers include plastics, starches, sodium polyacrylate, nylon and many more. Slime is also considered to be a non-Newtonian Fluid, basically a fluid that has special properties.

You should answer the following questions when exploring the properties of slime (a.k.a. playing with the cool stuff). Make sure your record your observations and post them in the comment box below. Try and do this before you read the rest of the article.

1. Describe how the slime reacts when you pull it apart with a quick forceful motion?
2. Describe how the slime reacts when you let it drip between your fingers?
3. Can you form a ball? What happens when you drop it on the table?
4. Do other fluids (like water, or ketchup) act the same way?

History of Slime:

Slime as a toy dates back to the 1920′s, when chemist Hermann Staudinger was researching polymers. He was the first one to try and make long cross-linked chains of the molecules instead of circles. This allowed the polymer to be slippery and gooey. By the 1930′s other scientists used his polymer model and synthetic polymers began to be studied and created. But it wasn’t until the 1980′s that slime began to be sold in stores as a toy for children. Ever since then you can’t step into a toy store without seeing the gooey, oozy stuff on the shelves. The slime you find in the store and the slime you can make with this recipe are both non-Newtonian fluids. Did you try to make it and answer the questions about its properties? If so, read on to find out about non-Newtonian fluids.

What does non-Newtonian mean?

All fluids have a property known as viscosity that describes how the fluid flows – commonly thought of as how thick or thin a fluid is. For instance, honey is much more viscous than water. When a fluid’s viscosity is constant it is referred to as a Newtonian fluid. Slime is an example of a fluid whose viscosity is not constant, it changes depending on the stress or forces applied to it. If you pull it apart real hard and apply a large force, it becomes very viscous and will break in half. If you gently pour it, applying little force, it will flow like honey or molasses. This kind of fluid is called a dilatant material or a shear thickening fluid. It becomes more viscous when agitated or compressed.

Another non-Newtonian liquid is ketchup. Ketchup behaves in just the opposite way from Slime. It becomes less viscous when agitated. Liquids like this are called thixotropic. If you leave a bottle of Ketchup on a shelf, it becomes thicker or more viscous. Nearly everyone has experienced this while trying to pour the liquid from a new bottle – it refuses to move. If you shake the bottle or stir it up it becomes less viscous and pours easily. Another example of a non-Newtonian fluid is Oobleck, one of our other great activities.

Is the slime in the store made using this recipe?

Most commercially sold slime is made using polyvinyl alcohol (PVA), a non-toxic substance that gives slime its texture. PVA still needs to be mixed with borax to get the final slime product. The borax is a gelling agent that cross links the PVA molecules together to form the slime. Borax does the same thing with the glue in this recipe. You can find Borax in the laundry detergent aisle in your grocery store. It is an inexpensive laundry booster and has lots of great household uses.

Other sources about slime:

There are some fun books that discuss animals in nature that produce their own slime, science experiments and other fun facts. You can find these and many other books at your local library.

• The Book of Slime by Ellen Jackson
• Lotions, Potions and Slime: Mudpies and More! by Nancy Blakey
• Oobleck, Slime & Dancing Spaghetti: Twenty Terrific at Home Science Experiments Inspired by Favorite Children’s Books by Jennifer Williams

Make sure you try this at home and don’t forget to come back and write a comment about how it went.

What you need:

• Bar of Ivory™ Soap and another brand of soap
• Paper towel
• Microwave oven
• Bowl of water

HAVE AN ADULT HELP WITH THIS EXPERIMENT!

What to do:

1. Drop the bars of soap into the bowl of water. Notice how one floats and one doesn’t.
2. Remove the Ivory soap from the water. Break it in half and notice if there are any air pockets.
3. Place the Ivory soap in the middle of a paper towel and place in a microwave on HIGH for 2 minutes.
4. Observe what happens to the soap! Don’t over cook your soap soufflé! Allow your soap to cool for a minute before touching it.

What’s the science?
Ivory soap floats because it has air pumped into it while it is being made. It also contains water, both in the form of water vapor trapped in air bubbles and water in the soap matrix itself. The heating of the water that is inside the soap causes the expanding effect. As the water vaporizes, air bubbles are formed. The heat causes trapped air to expand and the soap to soften and become pliable.

This is an example of Charles’ Law which states that as the temperature of a gas increases so does its volume. When the soap is heated, the molecules of air move faster and move farther apart from each other. This causes the soap to puff up and expand.

• Apples (bigger is better)
• Knife (a butter knife will wok just fine)
• Potato peeler
• A few tablespoons of lemon juice
• 1/2 cup of salt
• 4 cups of water
• String

Start with a nice big apple that has the stem still attached. You will eventually hang the head to dry from the stem so keep it attached. If your apple is missing a stem you can thread a wire through the core and use a large button to support the bottom of the head. Remove the skin from the apple with the potato peeler or knife. You can leave a little at the top and bottom. A freshly peeled apple will begin to brown as the oxygen in the air begins to oxidize the surface of the fruit. We can slow this down by coating or dunking the fruit in a mixture of lemon juice and salt.

One of the hardest parts of carving a shrunken head to where to start? I’ll show you how I carve my heads, then you can use this as a starting point for your own creations. Step one is to create the ears. Turn your apple so you have plenty of working material on the sides. Start by marking off a big square on the side. Now remove the fruit around the outside of the square to reveal a sort of blocky looking ear.

Shape up the ear by cutting the corners back and boring an ear canal. Remember, we are going to shrink this head so carve the features BIG. Small details will be lost after shrinking so go for really BIG features. Once you have one ear completed, turn you head around and make another one on the other side. If you want the ear to really look good when dry, carve a little indent around the base where it attaches to the head. When dry the ear will have a bit more depth.

Now to start the face outline the forehead and nose with a few simple lines. Once you have this in place bring your knife in from the sides to create an eye socket. You may want to cut the lines around the nose a bit deeper than the forehead line. Be careful when making the eye sockets that you don’t pop off the nose! Use a pencil or chopstick to create a hole for the eye in the socket. Once the apple is dry you can push in a whole clove or pepper corn here for an eyeball.

Under the nose carve a little space to separate the nose from the lips. If you nose is really big, you might be able to drill in two nostril holes that will show up when dry. If you nose is small don’t bother. Often you won’t have enought material for a big set of lips since the bottom of the apple usually tapers down. If you have enough, make them big and make sure to make an upper and lower lip. Cut a deep slit between them so as they dry they will become separate lips. Another option for the mouth is to just make a deep cut and when things are all dried out you can add some dry rice for teeth!

Now you are ready for the salt water soaking. Ideally you want to soak your head for 24 hours in the salt water. This will help draw water out of the apple to help with shrinking. If you’re impatient, just give it a short soak and then hang it up to dry. Ideally you want a nice dry location for your head. I would avoid trying to dry the head in a moist bathroom! You can speed up the drying process a bit by placing the apple in the oven at a really low temp (~150 degrees) for an hour or two before setting aside to dry. After about 1-2 weeks your head should be ready. Be sure to check on your head periodically and if any mold is growing you can remove it with a cotton swab.

If you really want to dress up your head, you can add whole cloves for eyes, maybe rice for teeth, some yarn or fake hair on top might look nice. Add coloring to your head with charcoal or use food coloring as a paint. If you have an old Halloween wig around you can use some of that hair to make it look more spooky. It’s up to you! While I’ve never tried it, I’ve heard you can use a craft sealer, wood sealer or shellac to seal and preserve your head. Make a few heads and experiment to see what works for you.

That’s it! Use your imagination, have fun and let us know how it works for you!

What can I feed my crab?
Pretty much anything because they are omnivores and scavengers. Here is a small list of what they will eat.

• popcorn
• cheerios
• shrimp
• sardines
• turkey
• chicken
• salmon
• fish flakes
• spirulina
• oatmeal
• granola
• nuts (almonds, pecans, walnuts, pistachios, peanuts, cashews)
• peanut butter
• wood
• leaves
• scrambled eggs
• organic baby food
• freeze dried shrimp
• naturally dried red seaweed algae
• chickpeas (a.k.a. garbanzo beans)
• dulse (seaweed)
• alaria (seaweed)
• hamburger
• coconut
• strawberry
• banana
• dried brine shrimp

What CAN’T I feed my crab?

• Aloe vera (interferes with potassium absorption)
• Dill
• Garlic
• Geranium
• Ivy (of any kind)
• Onion
• Peppermint
• Pine, cedar wood or needles
• Rosemary
• Thyme
• Citrus (leaves and branches are to be avoided because they are part of the evergreen family. The fruit is fine.)

What type of shells do I give my crabs?
It is recommended that you offer you’re hermit crabs natural unpainted shells to choose from. The painted shells can chip and the paint is unhealthy for the hermit crabs.

Where can I buy shells?
You can buy your shells from a pet store or you can buy shells from a craft store. If you buy your shells in a craft store you should boil the shells before you put them in the tank for the crabs. The shells should boil rapidly in de-chlorinated water for 10 minutes to kill any bacteria that may be in the shells. Make sure the shells are completely cool before you put them in the tank.

How can I tell if my crab is getting ready to molt?
The pre-molt symptoms (PMS) are:

• Digging
• Consuming large amounts salt or fresh water
• Soaking in the salt or fresh water dish
• Cloudy eyes
• Ashy looking exoskeleton
• Lethargic (inactive)
• Spilling water to dampen the sand

How do I take care of a molting crab?
Normally when hermit crabs molt they will bury themselves deep within the sand. You should never dig up your crab. You should leave the crab under the sand until it is ready to come back to the surface after it has molted. On rare occasions a crab will attempt to molt on the surface of the sand. If this happens it is recommended that you isolate the crab from the other crabs in the tank. This is because other crabs may bother or even try to eat another crab that is molting. You can cut a 2-liter bottle in half and put it over the crab. Make sure that you include water and food for the isolated crab. You can also move the crab to a second tank until it has finished molting. The crab will shed its exoskeleton and then eat it. The old exoskeleton contains nutrients that helps the new exoskeleton to harden. The crab will then return to normal activities like climbing and walking around the tank.

How long does it take for my crab to molt?
The length of time depends on the size of your crab. Small crabs will take a couple of weeks while large crabs will take up to three months.

How much sand do I need for my crab?
The amount of sand depends on the size of your crab. The sand depth can range from 2 inches for small crabs (1/2 inch or less in length) to 10 inches for very large crabs (three inches in length).

What is that sound?
Hermit crabs actually make noises. They sound like a cross between a cricket chirping, a frog croaking, and a squeaky hinge on a door. It is unclear how the crab makes this noise, some think that there are two plates of exoskeleton inside the crab that rub together. Hermit crabs make this noise when they are agitated. So if you hear your hermit crab sing it isn’t happy!

Below is some information about Hermit Crabs that our workshop participants should find useful and some photos from today.

What has ten legs, lives in a mobile home with a purple door, and needs a weekly bath but never uses soap? It’s a Coenobita clypeatus (sen-uh-BID-uh klih-pee-AY-tus), also known as a land hermit crab, a purple pincher, a tree hermit crab, or a red legged hermit crab! Whew! What a lot of names for one small animal.

There are several families of hermit crabs. Those that live in the ocean are marine hermit crabs. Hermit crabs that live on land are terrestrial, or land hermit crabs.

Coenobita clypeatus is a particular species of land hermit crab. When you look closely at one of these interesting creatures, you can see why it is sometimes called the purple pincher. The largest claw, the cheliped (KEE-luh-ped), is usually a very deep purple. Likewise, if you look at the legs, you can understand why it is also called the red-legged hermit crab. These colors are more evident on some crabs than others. And, although they don’t live in trees, land hermit crabs can climb trees and almost anything else they can grip with their claws!

Where are they found?
There are over 80 species of land hermit crabs found around the world. Usually they live where it is warm, often near the ocean. The purple pincher is found from southern Florida to Bermuda and the West Indies, and farther south to Venezuela, South America. It is the only land hermit crab native to the shores of the Western Atlantic Ocean. Adult land hermit crabs rarely live right on the beach. They prefer dry ground, close to a fresh water source. They will sometimes move inland 15 kilometers (over nine miles) from the ocean.

What do they eat?
Hermit Crabs are omnivorous (ahm-NIV-or-us) scavengers. They eat just about anything, plant or animal. Some of their favorite foods are coffee grounds, rotten fruit, and decaying meat. Hermit crabs help keep the areas they live in free from dead animal carcasses and decaying vegetation. When they live close to human beings, land hermit crabs will eat from garbage dumps and drink water from leaking faucets or animal pens.

A Hermit Crab’s Home
Hermit Crabs use shells to protect their abdomens. They carry shells with them wherever they go. The shell not only protects the soft abdomen of the hermit crab, but also gives the crab a means of carrying a supply of water with them to keep their gills moist. Hermit crabs are unable grow their own shells, so they use shells from dead sea or land snails.

The Hermit Crab Anatomy
Hermit crabs have several parts that make up their body. They have segmented (divided) body parts and an exoskeleton (a hard covering on the outside of the body, rather than an internal skeleton like we have); it is identified as an arthropod (AR-thruh-pahd). Spiders and insects are also arthropods. Because it breathes with gills, and has two pair of antennae (an-TEN-ee) in front of its mouth, it is also a crustacean (krus-TA-shun), a large class of arthropods that live in, or frequently goes into, water.

Instead of having a backbone or skeleton inside its body like you do, a hermit crab has an exoskeleton made of chitin (KY-tin). When we grow, our skeletons grow with us. But a crab’s exoskeleton does not grow as the crab grows. When a crab grows too large for its exoskeleton, the exoskeleton splits open, and the crab crawls out. This is called molting. After molting, a crab’s body is very soft. It takes up to ten days for the new exoskeleton to harden.

Hermit crabs have compound eyes. This means that a hermit crab’s eye is made up of many independent light sensitive units. Instead of seeing one image like you do, a crab sees multiples of the one image.  This allows the hermit crab to detect fast movements and see in a very wide angle.

More information on Hermit Crabs

• How to Care for your Hermit Crab
• Some common questions about Hermit Crabs
• Ask questions or talk with other crab owners in the Hermit Crab discussion fourm

• Box of Toothpicks
• Bag of Gumdrops

What to do:

1. Use gumdrops to connect 5 toothpicks in a ring. This is your base.
2. Use 2 toothpicks and 1 gumdrop to make a triangle on one side of the base.
3. Repeat all the way around the base until you have 5 triangles.
4. Use toothpicks to connect the gumdrops at the tops of the triangles. Now how many triangles do you have?
5. Push 1 toothpick into each of the top gumdrops.
6. Use one last gumdrop to connect these toothpicks at the top.

What’s the science?
Engineers often use triangles when they design buildings. Did you notice that your dome is made up of lots of triangles? That’s because triangles are stable shapes. That means they don’t bend, twist, or collapse easily when you push on them. A square is not as stable as a triangle. Test it. Make a square and a triangle out of toothpicks and gumdrops.  Press down on one corner of each shape. How do the two shapes compare? Does one bend, twist or collapse more easily than the other?

What will happen if . . .

• you make a base with six sides instead of five sides?
• you build squares rather than triangles on top of the base?

Choose one thing to change (that’s the variable), and predict what you think will happen, then test it.

What you need:

• Chocolate chip cookies
• Toothpicks
• Paper plates

Before you start:
The earth’s crust is made up of soil, rocks and minerals. Rocks are made up of a combination of different minerals. Rocks are also mined to find minerals. Taking care of the earth is very important. When we mine for precious stones and minerals, we do not want to harm the earth around the rocks. In this activity, you will be a miner for precious gems. Your cookie is the earth and the chips are gemstones.

What to do:

1. Place a chocolate chip cookie on a paper plate.
2. Use a toothpick like a real pick to mine the chocolate chips out of the cookie.
3. See how many chips you can poke out of the cookie and still keep it in one piece. Be careful not to break the cookie. How many chips were you able to mine?
4. After you’ve finished mining your cookie, you can eat it.

What’s the Science?
Mining is the extraction of minerals or rocks from the earth. The minerals that are recovered from the earth through mining include silver, copper, salt, petroleum, gold, and lead. Some of the rocks include coal, diamonds, granite, marble, and emeralds. These materials can be used to make many different things. Some examples include coal, which is used as a fuel, copper which is used in electrical conductors, and lead which is used in making car batteries.