When I was only 5 years old, I remember watching a cooking show on television.  The chef was
making this delicious looking cream sauce, and at the end he added several pats of butter.  “Butter makes
everything better,” he said, as his concoction blended together perfectly.  Sometime later I sat down at the table with my mom, and a cup of hot apple cider...and I remembered the chef’s assertion about butter.  I can’t quite remember the face my mother made as I attempted to stir butter into my hot cider, but I do remember the result—greasy, yellow orbs floating menacingly in the pale brown liquid.  Apparently, butter doesn’t make EVERYTHING better!

So why could the chef make a perfect sauce with butter, while my apple cider wound up a disaster? 
The difference is caused by solubility.

Solubility is the ability of one material to become fully dissolved in another, usually liquid, material.  When one material is soluble in another, the two materials will blend together such that their individual molecules (their smallest building blocks) will be evenly blended together.  If one material is not soluble in another, this material will remain in globs, and never blend evenly within the other material.  For an example, let’s look at the butter again.  When the chef made his cream sauce, he put the butter into a mixture of heavy cream and other fats, in which the butter is soluble.  This is why the butter melted perfectly into the sauce.  I had put the butter into apple cider, a drink made mostly of water, in which butter is not soluble, causing globs of
butter to simply float around in the cider without dissolving.

So why should butter be soluble in fatty heavy cream, but not in watery apple cider?  The simplest explanation for this is that like tends to dissolve like—that is, fats will dissolve in other fats, but not in water.  Because of this, the fats in butter will blend well with vegetable oil, which is also a fat, but not in water.  Likewise, things that will dissolve in water—such as juice or coffee, which are made mostly of water—will not blend well with fats like butter or oil.  

There is also a more complex explanation for this, which is polarity versus non-polarity.  To understand what makes a molecule polar or non-polar, we have to look at what happens when the atoms (the most basic building blocks) that make this molecule bond with each other.  

When two or more atoms come together to make a molecule, like hydrogen and oxygen bonding to form water, they share their electrons—the extremely small negatively charged particles that make up the outer cloud of the atom.  These atoms may share their electrons equally, but sometimes one atom winds up pulling the electrons closer than the other.  This unequal sharing is what happens with water:  the oxygen molecule is more attractive to the electrons, and therefore the electrons want to be closer to the oxygen when it bonds with hydrogen.  Because the electrons are closer to the oxygen, it has a slight negative charge, while the hydrogen has a slight positive charge.  This slight negative charge to one end of the molecule, and slight positive charge to the other end is called polarity.  Because of this polarity, the water molecule is very good at dissolving other molecules that are polar or carry an electric charge, like sugars or salts.

On the other hand we have non-polarity.  This is what happens when the atoms of a bond share electrons equally, so no one atom holds the electrons closer than any other atom. As an example, let’s look at oil. Oil is made up of fats, or fatty acids, which are long chains of carbon and hydrogen atoms bonded to each
other.  All the carbon atoms in this chain have the same attraction for the electrons, and so all share them equally.  As a result, no one atom has extra charge, and the molecule is non-polar.  Because of this non-polarity, these molecules will dissolve other non-polar molecules, like the ones found in butter.  On the other hand, these molecules will not blend with polar molecules like water.

TRY IT!!


 Here’s what you’ll need:

 1.   Four clear drinking glasses

 2.   Two ¼ cups of vegetable oil

 3.   Two ¼ cups of water (tap water is fine)

 4.   Two teaspoons of sugar

 5.   Two teaspoons of lard or coconut oil

 6.   Four small spoons for mixing

  
Here’s what to do:


 1.   Line up all four of your glasses

 2.   Pour one quarter cup of water into one of the glasses and one quarter cup of oil into another glass.

 3.   Add one teaspoon sugar to the glass with the water, and another teaspoon of sugar into the glass with the oil.

 4.   Mix them both well with two of your spoons, one for each glass, for at least two to five minutes.


What happened to the sugar in the water?  Can you see any grains of sugar now?  Write down what you saw happen.

What happened to the sugar in the oil?  Did it dissolve?  Write down what you saw.

Based on these observations, is sugar polar or non-polar?  (Remember, polar things dissolve in water, while non-polar things dissolve in oil.)


Now for our next experiment:

 1.   Using your other two spoons, smear one teaspoon of lard or coconut oil onto the inside bottom and sides of each of the remaining two drinking glasses.

 2.   Add one quarter cup of oil to one of the glasses, and one quarter cup of water to the other glass.  
 
 3.   Stir both glasses well for at least five minutes.  Sometimes the lard or coconut oil is hard to dissolve, so be sure to mix for enough time!

 
What happened to the lard in the water?  Did it dissolve?  Is any still clinging to the bottom of the glass? Write down what you saw happen.
 
What happened to the lard in the oil?  Is there any still clinging to the glass?  Write down what you saw.
 
Based on these observations, is lard polar or non-polar?  (Remember, polar things dissolve in water, while non-polar things dissolve in oil.)

 
 
MAKE UP YOUR OWN EXPERIMENT!


What else can you test in oil and water?  Try other things you find in your kitchen, like salt, milk, juice, or baking soda.  Write down everything you test, and what you observe!

REMEMBER: Some things you might test are complex mixtures of things that are polar AND things that are non-polar, so they not completely dissolve in either water or oil.

Although we don’t think about it very much, air is something very important.  We need to breathe it to stay alive, it is part of what creates our weather here on Earth, and it allows birds and air planes to fly.  Because air is everywhere around us and above us, and we can move and see through it so easily, we tend to think of air as being “light”.  But is this really true?  Is air light, or does it have weight like any other object?

First, we need to discuss, what exactly is air?  Air is a mixture of different gaseous elements (that is, building blocks) which, because of Earth’s gravity, surround the planet like a blanket.  These gasses are also referred to as Earth’s “atmosphere”, which extends from the surface of the Earth to halfway to the moon (over 440 miles). 

Next, we need to discuss what weight is.  When we say an object “weighs” a certain amount, it means the Earth’s gravity is pulling down on it with a certain force.  For instance, if we say a bag of flour weighs 5 pounds, this means that the Earth is pulling that bag of flour towards itself with a force of 5 pounds.  Therefore, anything under the influence of the Earth’s gravity (that is, anything the Earth is pulling down on) is going to have some weight.

But wait...if gravity is keeping the atmosphere—the air—in place, that means Earth is pulling down on it!  If Earth is pulling on it, the way it does other objects, that means it has weight like other objects!  So we can now say yes, air has some weight!  But how much does air actually weigh?  That depends on how high up we go. 

As we measure the weight of the air (also called the atmospheric pressure) farther away from the Earth’s surface, gravity pulls the air down with less and less force, so air actually weighs less the farther away we are from Earth.  Often we use the Earth’s “sea level” (that is, the average weight of the ocean) as a standard for elevation, and at sea level the air will weigh 1.2 kg/m3, or about 2.6 pounds per cubic meter.  That means that if you could make a square box that was about three feet long on every side, the air inside that box would weigh about 2.6 pounds at sea level.  It also means that if you had a column of air as high as the Empire State Building in New York City (443.2 meters high), it would weigh over 1,000 pounds!

So now we know that air is actually pretty heavy.  But back to our original question, is anything lighter than air?  The answer is yes!  Since air is made up of certain elements (mostly nitrogen and oxygen), any gaseous elements or molecules that are lighter than these elements—such as helium, hydrogen, or methane—will be “lighter than air”.  This is why when you fill a balloon with helium, it floats!

TRY THIS!!

To prove to your friends that air has weight, try this experiment!

Here’s what you need:

1.      Two latex balloons

2.      A pencil or a wooden dowel

3.      Three pieces of string or thread, one about two feet long, and the other two six inches each

4.      Strong tape, such as duct tape

First, blow up one of the balloons.  Get a parent or teacher to help you if you have trouble!

Next, tie the pencil or dowel to the two-foot piece of string such that it balances straight across—one end should not be higher than the other.  Fasten the other end to the top of a door with strong tape, such that it hangs suspended in the doorway.  Get a parent or teacher to help you with this, too!

Tie the empty balloon to one end of the pencil or dowel using one of the six inch pieces of string, and tie the air-filled balloon to the other end of the pencil or dowel using the other piece of string.  Watch what happens!

REMEMBER:  If the air has weight, the balloon with the air will be heavier than the balloon without air.  As such, it will pull down on the end of the dowel or pencil which it is tied to.

What happened when you tied the full balloon and empty balloon to the pencil?  Write down what you saw.

Take a look at a picture of the inside of a cave (click here to see some wonderful pictures online).  Do you see all those pointy formations on the roofs and floors that look a bit like icicles in winter?  Believe it or not, those are not ice!  The ones hanging down from the roofs are called stalactites, and the ones sticking up from the floors are called stalagmites.  What are stalactites and stalagmites, and how do they form?

Most commonly, stalactites (also called 'dripstones') and stalagmites are found inside limestone caves (a cave is just a large, open space that is underground).  They form when water seeps through the rocks above, picking up minerals along the way, and finally seeping through the cracks in the cave's ceiling where it drips down onto the floor. 

As the mineral-laden water drips from the ceiling to the floor, it leaves some of those minerals behind. 

Slowly, drop by drop, the dripping water deposits enough minerals for this icicle-like shape to form, both on the ceiling of the cave and on the floor, where the drops land. 

This is a very, very slow process--a typical stalactite will grow only 0.0051 inches per year!  That's only about the width of a human hair!  You can just imagine how old those big stalactites and stalagmites in the pictures you saw must be!

TRY MAKING YOUR OWN STALACTITE AND STALAGMITE!

Here's what you need:

1 cup Epsom salts

2 small cups (about 6 oz each)

1 piece of cotton string, 12 inches long

2 metal washers or small bolts

1 piece of cardboard, 6 inches by 10 inches

some water from your kitchen sink

a ruler


Here's what to do:

1. Pour half of the Epsom salts into each cup.
2. Add just enough water to cover the salts in each cup, and stir each for about 30 seconds (don't
   worry, not all the salts will dissolve).
3. Soak the string in water, and squeeze out the excess.
4. Tie one washer to each end of the string, and put each end into one of the cups.
5. Place the cups on the cardboard, far enough apart that the middle of the string hangs about 1 inch
   from the cardboard.
6. Place the cardboard and cups somewhere where they will be left alone, such as on a shelf in your room, or on the counter in your kitchen (ask your parents' permission first!). 
7. Watch the middle of the string, just where it gets closest to the cardboard.  You should see the water start to slowly drip from the string to the cardboard.
8. Observe the cups and string every day at the same time for at least 7 days.  Each time write down what you see.  Very carefully use your ruler to measure how long the stalactite is each day.  BE CAREFUL NOT TO TOUCH IT, OR IT MAY BREAK!
9. Allow the cups and string to sit longer, another 7 days if possible, and continue writing down what you see each day.  Be sure the cups still have some water in them, and add some water if needed.

This is what your experiment should look like: two cups with Epsom salts and water, a piece of string with a washer at each end hanging between the glasses, all on top of a piece of cardboard.

How long was your stalactite after 7 days?  After 14 days?  How much did it grow each day?  You can calculate the average growth per day by taking the length after 14 days, subtracting the length at 7 days, and dividing by 7, like this:

Did your stalactite grow fast or slow, compared to average?


MAKE UP YOUR OWN EXPERIMENT!

How else could you get a stalactite to form?  Remember, a stalactite is just a formation made by the deposition of some solid by dripping water. 

Another type of stalactite is an icicle, which is just a stalactite made from frozen water!  If it's cold outside, try to make an icicle by using a paper cup of water with a tiny hole in the bottom.  Make a few holes in the sides of the cup, just under the rim, and tie the ends of a single piece of string to each hole.  You can make the tiny hole in the bottom of the cup using a needle or a pin (get your parents' help!).  Hang the cup over a branch outside, and fill it with warm water.  Wait and see what happens!

Vinegar and baking soda are things you probably see in your own home.  But did you know you can use
them to blow up a balloon? When you put vinegar and baking soda together, you get a chemical
reaction, and this chemical reaction produces carbon dioxide gas. 

A chemical reaction happens when one set of substances (called the reactants) transforms into different substances (called the products). When scientists talk or write about chemical reactions, they usually write them like this:

Chemical reactions happen everywhere, all around us.  When you digest your food, your body performs chemical reactions to turn your food into energy.  When you sit beside a campfire and enjoy its warmth, you are being warmed by a chemical reaction.  Sometimes these chemical reactions happen slowly, but sometimes they are fast and violent.  One type of chemical reaction happens between acids and bases.
           
An acid is a substance that releases hydrogen ions (usually written as H+) when mixed in solution (that is, when it is in liquid form, like when you mix it in water).  Hydrogen is just one of the building blocks that make up lots of different substances, but with acids this hydrogen ion wants to separate from
the rest of the building blocks, and go into the water.  This means that when you mix an acid in water, it will push part of itself –the hydrogen—into the water, like this:

This released H+ is what makes this substance an acid.  One acid you may be familiar with is citric acid, which we find in lemon juice.  If you’ve ever tasted lemon juice, you know what an acid tastes
like...very sour!  
           
A base can be thought of as the opposite of an acid.  Often, it is a substance that, if mixed in water, can take the hydrogen (H+) ions back out of solution.  So, while the acid is putting H+into the solution, the base is taking them away:

Acid-H + Base  -------------------> Acid- + Base-H  

The hydrogen ions jump from the acid to the base, and in the process other things are made. For this experiment, we are using acetic acid (vinegar) and sodium bicarbonate (baking soda).  This reaction will
look like this:

Don’t let this scare you!  This just means that two different substances come together, and when they do they produce some new substances.  One of them is a gas, which will come out as bubbles or foam. This means when vinegar and baking soda are combined, some new things will be made, and one of them is carbon dioxide gas.  

The vinegar (acid) and the baking soda (base) are like two towers made up of
bricks:

When we mix them together, the baking soda takes one of the bricks--the H+--from the vinegar:

But now, the baking soda tower is not stable, so it falls apart!  After it has fallen apart, what it turns into is water and carbon dioxide gas!

These are the products of the reaction!  The vinegar has lost H+, and becomes acetate, which pairs with
the sodium from the baking soda (the sodium is just floating around in the watery liquid, but it likes to hang out with acetate!).  This carbon dioxide will escape into the air as bubbles or foam, and it is this gas you can use to blow up a balloon!


TRY IT!!
 
1.     Measure 1 teaspoon of baking soda into a balloon.

2.     Add 4 tablespoons of vinegar into a small soda bottle.

3.     Carefully stretch the mouth of the balloon over the opening of the bottle.

4.     Lift the balloon, and shake the baking soda into the bottle so that it mixes with the vinegar in the bottle.

5.     Watch as the CO2 gas produced by the chemical reaction between the acetic acid in the vinegar and the sodium bicarbonate (baking soda) blows up the balloon!

6.     When the balloon stops growing, measure how wide the balloon is with a ruler or a tape measure.

QUESTIONS:

How large did the balloon get?


What happens if you double the amount of baking soda and vinegar?  (That is, try adding 2
teaspoons of baking soda in the balloon and 8 tablespoons of vinegar in the bottle.) Will the balloon be twice as big?  Write down what you think will happen.

Try the same experiment again, adding 2 teaspoons of baking soda to the balloon and 8 tablespoons of vinegar to the bottle. 


How big does the balloon get when you double the amount of baking soda and vinegar?

Were you right about how big the balloon would get?

What happens if you change the amount of baking soda, or the amount of vinegar? 



TRY THIS:
  Add one teaspoon of baking soda to 8 tablespoons of vinegar. How big does the
balloon get?

Add two teaspoons of baking soda to 4 tablespoons of
vinegar.  How big does the balloon get now?

CHALLENGE YOUR FRIENDS!!

Who can make their balloon blow up biggest?  Challenge your friends to a contest, and see who can make the biggest balloon.  Try different amounts of vinegar and baking soda. What combination of vinegar and baking soda produce the largest balloon?