Cohesion

Hi everyone! Today my subject is  cohesion. 

Cohesion: The phenomenon that occurs when individual molecules are so strongly attached to each other that the tend to stay together, even when exposed to tension.

Watch the video, then I will talk about it.

So in the video I had a shallow bowl of water, and two threads, I put a needle across the threads then carefully lifted it onto the water. When I laid them across the water, the threads sank, but the needle floated on the water! We have all done the 'will it float?' test, and we all know that a needle is heavy enough to sink. So why did it float? Because of hydrogen boding and water molecules polarity, which we have talked about before, the water wants to stick together. Even though the needle was putting tension or pressure on the water, the molecules has enough tension of their own to fight back.

I also put a drop of dish soap in the water, and when I did, the needle sank! What happened? The active ingredient in dish soap is called sodium stearate, it has long molecules that are attracted to the water molecules. Those sodium stearate molecules were able to get between the water molecules enough, that the waters cohesion was weakened, and the needle could sink.

What happened in this experiment is called surface tension. It is a part of cohesion, but as the name suggests, it only refers to the tension on the surface of liquids. Have you ever wondered how plants could suck up water? They have little tube called xylem that, thanks to cohesion, can carry the water up the plant!

I don't know about you, but I think God might have known what he was doing when He made water.

Until next time!

For more information on Cohesion and Surface Tension, see Dr. Jay L. Wiles book Exploring Creation with Physical Science module 4, pages 97-99.

Hydrogen Bonding

          Hi everyone! Well, the school year is back and it is time to start studying science some more! Today we are going to look at Hydrogen Bonding. What is it? How does it work? And why is it important? Check out the video below, then go behind the scene with my report!

          Ok, now I know it may have been hard to see, but here is what happened. I took a glass of melted butter, and a glass of water, liquid forms of both. Then I dropped in a piece of the same stuff, only in solid form! When I put the solid butter in the liquid butter, it sank to the bottom, right? But when I put the solid water (ice) in the liquid water, it floated!
          First, lets remember that water molecules are made from 1 oxygen atom, and 2 hydrogen atoms (H2O). They form together via a chemical bond that happens when they share electrons. As we learned in my science post (Water as a Solvent), water molecules are polar molecules, because the electrons are uneven. So the hydrogen atoms have less then their share of electrons so when they get close to other water molecules they try to take electrons from the other oxygen molecules who have more then their fair share of electrons. But there are not enough electrons to form chemical bonds, so they form hydrogen bonds, which are similar, but very weak. See my example below.

See how the hydrogen atoms turn so they can connect with other oxygen atoms? Chemical bonds take atoms and link them together to make molecules, and hydrogen bonds take molecules and link them together. There you are; hydrogen bonds.
        When water is frozen, the molecules cannot form hydrogen bonds, so it is not held together as well. So when I put the ice in the glass of water, it floated because the water bond was strong enough to hold up the ice. But butter is just the opposite, it is stronger when it is cold, and when you heat it the molecules pull apart. So when I dropped the solid butter in the liquid butter, it was able to push its way through the weaker hot butter, and sink to the bottom.
        Now, lets take a look at what this bond does, lets start with looking at some other similar compounds. There are many chemical compounds that are very similar to water from a scientific view point, take hydrogen selenide, (H2Se). It has two hydrogen molecules, just like water, but instead of an oxygen atom, it has a selenium atom. This chemical formula is a gas at room temperature, and its boiling point is -41.25*C as opposed to waters' 100*C. The key difference? H2Se has no oxygen to form hydrogen bonds, therefor it won't hold together! The same goes for H2S and H2Te. All are very similar to water, but they are gases instead of liquids. Isopropyl alcohol (common rubbing alcohol) is very similar to water, its' chemical formula is C3H8O. See how it has hydrogen and oxygen? That is why it can stay liquid as well, the bond just is not as strong as in water.
        So we know what hydrogen bonds are, and we know how they work, but why does it matter? Think about it. If water could not form hydrogen bonds, then it would become a gas, and we could not drink it, or use it at all! Think about a lake are a pond in winter. When the water freezes it floats to the top, then it insulates the rest of the water, so that not all the water freezes, and the things living in the pond don't die! If it were not for hydrogen bonds, water would not be as it is, plants could not grow, would die, and the earth would be unable to support life! This small simple matter is so vital for our very survival! Yet somehow God sees fit to bestow us the blessing of life and hydrogen bonding. What a great God he is.

Well, I hope you learned something interesting. I next time you go to drink a tall glass of ice water, think about those little molecules, working to keep us hydrated!

Have a great September!
-Kat

To learn more about hydrogen bonding see Dr. Jay L Wiles' book Exploring Creation with Physical Science, module 4 pages 93-97. And check out all the cool chemical formulas at wikipedia.org.

The School Year is Coming!

Hey everyone! Hope you all has a great summer!

Just a little heads up to let you all know that

a. I have NOT abandoned this blog

and

b. I will be starting school soon, therefor posting soon.

Have a great week!

Kat

Water as a Solvent

In this experiment we will see how water can be a solvent. As you watch the video see which of the solutes are dissolved in the water.

Solvent - A liquid substance capable of dissolving other substances.

Solute - A substance that is dissolved in a solvent.

So what happened? First we need to understand that water is made of polar molecules.

Polar Molecule - A molecule that has a slight positive and negative charge due to an imbalance in the way electrons are shared.

Atoms are made from protons, neutrons, and electrons. Protons have a positive electrical charge, electrons have negative electrical charge, and neutrons have no electrical charge. Atoms form together by sharing their electrons, forming what is called a chemical bond.

When different kinds of atoms form together they become molecules. Polar Molecules are formed when one kind of atom is stronger then the other, and just like kids "sharing" a toy, whichever atom is stronger will end up with more electrons. In the case of water there are two hydrogen atom (H2) and 1 oxygen atom (O) per water molecule.

As it turns out, the oxygen atom is stronger then the hydrogen atoms, therefor the oxygen atom gets more of the electrons causing the oxygen atom to have a very slight negative charge, and the hydrogen atoms to have a slight positive charge. So water is made of polar molecules.

Polar molecules have a net electrical charge, and that charge wants to find other charges to interact with. There are two different categories of substances that contain an electrical charge. The first, as you know, is polar molecules. The second is ionic molecules.

When an atom loses or gains electrons, we say it has become an ion. And because of the imbalance of electrons, the ions have a net electrical charge. Ionic molecules are made up of ions. As an example, salt is made up of sodium ions, and chloride ions. You get sodium ions when a sodium atom loses an electron, and you get chloride ions when a chloride atom gains an electron.

When an ionic compound (something made from ionic molecules) is mixed with water, the electrical charges in the two substances attract each other. The water molecules surround the ions in the solute and pull them so far apart that the solute is no longer visible to the naked eye, but it is still there.

If you look at this picture you can see the water molecules separating the sodium ions, and the chloride ions. The positive charge in the hydrogen atoms is attracted to the negative charge of the chloride ions. And the negative charge in the oxygen atoms is attracted to the positive charge in the sodium ion. Pretty much the same thing happens when you dissolve a polar molecule in water. So water can disolve polar molecules, and ionic molecules. But as we saw in the expiriment, there are some things that water will not dissolve, namely non-polar molecules.

So if water, or other polar substances will not dissolve non-polar solutes, will anything? The answer is yes! Think about it... why can't water dissolve non-polar substances? Because non-polar substances have no electrical charge. So it stands to reason that non-polar solvents will dissolve non-polar solutes! For example, gasoline is a non-poler solvent. In our experiment we saw that sand and oil were non-polar solutes. So gasoline will potentially dissolve sand and oil!

How cool is that?

Well I hope you enjoyed my essay on Water as a Solvent. To learn more see Exploring Creation with Physical Science by Dr. Jay L. Wile, Module 4, pages 90-93. And next time you go to mix something in your water, think about whether or not it is a polar molecule or non-polar molecule!

Air Pressure

Now that was cool, but what happened? First off, earths air supply is known as our atmosphere.

Atmosphere - the mass of air surrounding a planet

So the air surrounding earth is earths atmosphere. Now air has mass so it weighs something, and the atmosphere is constantly pressing down on the earth. Our atmoshpere weighs aproxamently 6 billion tons! At sea level 1 square inch can weigh 14.7 pounds! So why don't we feel all that weight? Because the air is pushing us on all sides, its like tying two ropes to a rock and pulling with equel strength from both sides, the rock won't move. So we don't feel the air pressure, but it is still there.
So lets start...

we have 1 candle

1 shallow glass bowl

and 1/2 cup blue water.

I put my blue water in my bowl,

it fill it a about 2/3 of an inch deep.

I put the candle in the center of the water.

Lit the candle.

and placed 1 pint jelly jar on top.

Now air is made up of 78% nitrogen, 21% oxygen, and 1 % other gases.

When fire burns it uses up the oxygen in the air, if it is a sealed enviroment it will use up all the oxygen and then die out.

The flame begins to fade as the oxygen is used.
But when the oxygen molecules are used the air cannot exert as much pressure.
So the pressure on the outside of the jar is stronger or 'heavier' then the air on the inside.

So the air on the outside begins to push the water down and it goes up into the jar because the air pressure on the inside is no longer sufficient to equel out the water.

For more information on air pressure read Exploring Creation with Physical Science by Dr.Jay L. Wile. (Module 3, pages 57-61)