Saturday, December 10, 2011

Cave Chandeliers Explained

Have you ever walked into a cave and were amazed at what you saw?
Oh My!
Okay, maybe not this! More like this:

These things in caves that look like spikes or chandeliers (whether coming up from the ground or down from the ceiling) are called speleothems. Speleothems are found in two forms: stalactites and stalagmites.

You may wonder: "How are these even created?" Well, as usual, science has an answer for this!

These chandeliers first start because there is a cave or cavern in the ground, or a big open space where they can grow. Just like the crystals we talked about last time. When it rains the water travels through cracks in the rock. This water reacts with the rock (normally soluble limestone) and creates calcium bicarbonate or other chemical solutions. When the solution drips through that cracks and into the cave it comes into contact with the air in the cave and solidifies. This creates the stalactite.

Stalactites will often drip solution onto the ground creating a stalagmite. The best way to remember the difference is through their spelling.
C- Ceiling G- Ground
Sometimes stalactites and stalagmites grow close enough to touch. Stalactites are also sometime called "soda straws" because when they first form they are long thin formations that look like straws. When speleothems form they grow in layers. Each layer is slightly different than the others because the way water reacts with the minerals and contaminates in the rock.

Cave Chandeliers

In our last experiment, Candy Crystals, we talked about where crystals came from.  This experiment is another type of crystal formation that we thought about.  On the week of Thanksgiving break, we decided to demonstrate another formation of crystals using this experiment. What is it? Well it demonstrates the idea of stalactite and stalagmite.

Lab materials you will need:

  • Epsom salts
  • 2 small jars, (Many I've seen have used mason jars, we decided to go with baby food jars.)
  • string (Use cotton yarn/string it works the best)
  • scissors
  • 2 washers
  • spoon
  • ruler
  • paper
  • water
  • tray or flat container

[Step One]
Fill both jars  two-thirds (2/3) of the way with Epsom salts.

[Step Two]
Fill the jars halfway with hot water.

[Step Three]
Stir the mixture.  Saturate the water with Epsom.  When the water cools down, add Epsom 1/4 of the way.  Then, add a little more water until the jar is 3/4 full.  The added Epsom salt should not dissolve in the water.  Mix the solution enough times to see whether or not it will dissolve. 

[Step Four]
Cut a piece of string, 24 inches (60 cm).   Then, tie a washer to each end of the string.
Soak the string in Epsom Salt solution. This does not need to soak long, but soaking allows the crystals to grow. This is considered the seed crystal.

[Step Five]
Place one washer in each of the jars.  Let the washers rest on top of the undissolved crystals. (Our jars are pictured half full here, but since have had water added for better results.)

[Step Six]
Place a piece of paper between the jars.

[Step Seven]
Position the jars so that the string hangs between them with the lowest part of the loop about 1 inch (2.5cm) above the paper.

Now allow the jars to stand undisturbed and out of any draft for one week. Water will drip from the center of the loop onto the paper.  A hard, white crust will form on the string and grow downward as the time passes.  A mound of white crystals will build up on the paper beneath the string.

Make sure to place this experiment in a container, such as a pan or baking sheet; the water will penetrate through the paper and spread all over the counter.

There will be an additional blog explaining Cave Chandeliers.

Friday, December 2, 2011

Icy Ovens Explained

In the last post we did an experiment involving ice cubes. We briefly explained how the same idea behind the movement of the ice cubes is also the concept for a convection oven. But this idea is astronomically larger than that (like earth or sun or galaxy sized). The idea of convection is an environmental and geological one.

According to the 3rd edition of the Glossary of Geology, convection has 4 different meanings. The definitions for economic geology, meteorology, oceanography and tectonics are slightly different however the underlying idea is the mass movement of something caused by a change in heat or density.

Convection currents are the driving force of tectonic movement.
In most schools students learn about plate tectonics. (I think my school touched on them in 7th grade.) However, we've noticed that most students learn very little about tectonics (and geology in general.) They learn that tectonics make mountains and earthquakes, but how are those created? Simply? Convection!
Convection is the movement of the heat in the Earth.  Convection causes the tectonic plates to shift. When they move we get tectonic activity and this causes a bunch of things to happen. Earthquakes, volcanoes, expanding oceans, mountain building. You name it, tectonics probably has a hand in it.

Convection is also found as a force in stars. To think about this concept we will use the closest start to Earth for studying...

The Sun!

Just like the earth the sun is made of different layers. We've all heard about the Earth's core (or seen the terrible movie called Core. Now that we've talked about geodes that movie makes less sense.) but we don't often chat about the core of the Sun. The sun is very important to life on Earth. We are at the perfect distance for heat to sustain life and with our magnetosphere blocking UV waves we get pretty auroras.

How exactly does convection work in the sun? Well, in the layer of the sun called the photosphere, convection occurs and moves the heat from the core. The photosphere is the lower layer of the sun's atmosphere and is where the brightness of the sun comes from. The core is where nuclear fusion takes place, this fusion causes enormous amounts of heat. This heat circles through the photosphere through convection currents.

It's simply amazing how much heat can do. It keeps our Earth moving and keeps sediments occurring. A professor at our schools likes to say "Without tectonics there would be no serious sedimentation." And this includes ocean currents, waves, rivers and all other forms of sedimentation.

Now, how cool is that?

Icy Ovens

I take it you have heard of the convection oven. A convenient cooking tool that makes sure the whole oven is warm. The best way to make perfect cookies!
Mmmm, gingerbread cookies! How festive!
We know you all like cookies.

To explain the idea of convection (the process that makes perfect cookies) we are going to do an experiment with ice cubes!

- A rectangular tub about 10 inches deep
- Desk Lamp (with lightbulb)
- Ice Cube Tray
- Blue and Red Food Coloring


What To Do:
(Pre-Lab Set Up) - Fill an Ice Cube Tray with water; add a few drops of blue dye to each container
1. First fill the tub with about 8 inches of water.

2. Place both the tub and the lamp on a flat surface. Position the lamp over one half of the tub. Let the light sit on over the tub for 10-20 minutes.

3.) Put the ice cubes in the side of the tub opposite the lamp.

4.) Place a few drops of red food coloring on the side with the lamp.

5.) Watch the initial reaction. The food color should not mix at this point because they are different temperatures. (However some of the dye may mix, that happened with us.)

6.) After about 20 (maybe more) minutes the water should be a purple and the ice cubes melted. This is because heat from the lamp has moved throughout the container (convection!) and the food coloring has mixed.

Suggestions: When making the blue ice cubes make the water very dark blue. The dye freezes at a different rate than the water. also it will help when viewing the mixing of colors.

Monday, November 14, 2011

Crystal Candy Explained

The last experiment we did was "Crystal Candy," and you may find yourself asking
Caroll, how does this relate to science? What kind of lesson can I put with this?
Have no fear! I am here to explain.

What did the lab explain?
This lab is meant to explain the idea of crystal growth. In this experiment you can watch the crystals growing. (You don't want to sit and stare at the cup though... remember 'a watched pot never boils.')
This is as fun as watching paint dry...
After the cup has been left and the sugar has recrystallized you will see the faces, or sides, of the sugar crystals.

Why does this happen?
How do the sugar crystals form? Well, when you heat the sugar water you allow for more sugar to be added. If you had a cup of room temperature water and added two cups of sugar only some of it would dissolve and most of the sugar would sit in the bottom of the cup. However if you heat the water the sugar will dissolve. This is because heating the solution makes the molecules move faster and allows the sugar to dissolve into the water. This causes a supersaturated solution of sugar and water.

Crystals cannot form without something to grow on. In our experiment the skewer is our crystal holder. In nature it can be a rock or even another crystal. Crystal growth depends on solution (or chemical) type, time, temperature and the space available. A sugar solution is not going to produce quartz crystals. All minerals have their own chemical makeup and a crystal's growth and structure display this. Some minerals have specific shapes that they grow in. Sugar crystals grow very quickly but minerals like quartz, chert, and calcite take a long time to grow.
Calcite Left; Quartz Right
How fast crystals grow is also dependent on the temperature in which they are growing. Often, it is easier for a crystal to grow in hotter temperatures than cooler ones. What limits the size of crystals though? If you noticed in this experiment the sugar was growing on the skewer but it could not grow outside of the cup. This is the same in nature, a crystal cannot grow outside of the space available for it. A really good example of this is the geode. A geode is a small, durable rock that is often hollow on the inside. In this hollow area crystals can often be found. If the crystals growing in the space reach the center from all sides the crystal must stop growing.
Quartz Geode
This is what happens when you leave it sit too long.

Saturday, November 12, 2011

Crystal Candy

Have you ever seen a crystal and wondered "Where did that come from?" I know I have. This weekend Rachel and I put together an experiment (one that is old, tried and true) that helps demonstrate the idea of crystal growth.

Of all the old-fashioned candy, rock candy is one of the most popular. It is uncommon to find someone who has never tried rock candy.

This lab uses:
Wooden Skewer
Tall, thin glass
1 Cup Water
2.5 Cups Sugar

Step One: Attach the clothespin to the skewer and hang across the top of the cup. Have the end of the skewer about 1 inch from the bottom of the cup.

Step Two: Bring the water to a rolling boil. This means, boil the water so there are tons of little bubbles! (Keep the stove on, you will have it boiling the whole time.)

Step Three: Add 1/4 of the sugar to the boiling water. Stir in the sugar so it dissolves.

Step Four: Slowly add the rest of the sugar, 1/4 cup at a time. Continuously stir so the sugar dissolves. Add the sugar until you no longer have any or the sugar stops dissolving. This may take a while.

Step Five: Take the sugar solution off the heat and allow to cool. (You have now created a supersaturated sugar solution!)

Step Six: Dip the end of the wooden skewer in the sugar solution, then roll the end in some sugar. This creates a 'seed' for the sugar crystals to grow on.

Step Seven: If you want colored rock candy add in food coloring. You want the liquid to be dark enough that it will have a color after the crystals form.

Step Eight: Pour the sugar in the cup.

Step Nine: Put the skewer on the clothespins in the cup. Make sure the skewer is not touching the bottom or the sides of the cup.

Step Ten: Allow the crystals to grow! Update: Let your crystals sit until they start forming around the skewer. The first time we made ours they instantly started growing and in 4 hours were done. However the second time we tried they did not crystallize for a few days. This difference can be caused by the amount of sugar used or the time the solution is let sit and cool before being poured into the cup.
When you take the skewer out of the cup, give it a few minutes to dry. Then enjoy your beautiful crystals!
Lab variables to try: flavoring and other colors

*An explanation of this lab will be put up after this. In that post there will be picture of our rock candy. We accidentally left ours for a day and the whole cup crystalized!*