Diagraming a sentance for Essentials

Joseph, Collin, Stephanie and their siblings enjoyed a day at the National Museum of the Navy!

Jack pulled the damper while Grace and Griffin tried to push. Collin had the right idea, supervisor in the cool shades!

Robert, Stephanie, Christopher and Amy helped with the ooooh awwwws in Justanian's family presentation.

Mike held up signs displaying the acts against colonies.

Justin and Jill, the English Parliment.

If ever I'm in a war I hope to have Jack, Travis, Joseph and Benjamin on my side. We'll all hide together and pray for peace.

Annabelle and her mom act out the First Great Awakening.

There is a rare history sentence that is complete without a
dramatic fall. Robert is always willing to throw himself into history.

WEEK 12: Surface Tension.
This ended our series on flotation/buoyance/density/volume. The children tried to make a needle float, which you can't do by just placing it on top of the water. However, if you place it on a small piece of paper towel, the paper towel and needle will float, but then the towel will soak up water and sink, leaving just the needle. The needle defies all we've been learning about densities, buoyancy and volume, because there's another property: surface tension. Surface tension describes the attraction between the surface water molecules which causes the surface of a liquid to act like a thin skin stretched across it.

We saw that water can actually rise above the rim of a cup if we put small objects one at a time into a full cup.

Applications: don't touch the tent! Surface tension will bridge the holes in the fabric of a tent when it rains, but if you touch it, you will break the surface tension, enabling the rain to drip into the tent.

Clinical test for jaundice uses surface tension of urine. Normal urine has a surface tension of about 66 dynes/cm but if bile is present (a test for jaundice), it drops to about 55. In the Hay test, powdered sulfur is sprinkled on the urine surface. It will float on normal urine, but sink if the S.T. is lowered by the bile.

We also used food coloring on top of water to "see" surface tension being broken by an object touching the water surface.

Then we added the concept of a surfectant. Here's what we did:

1. Pour enough milk in a dinner plate to completely cover the bottom. Allow the milk to settle.

2. Add one drop of each of the four colors of food coloring - red, yellow, blue, and green - to the milk. Keep the drops close together in the center of the plate of milk.

3. Find a clean cotton swab for the next part of the experiment. Predict what will happen when you touch the tip of the cotton swab to the center of the milk. It's important not to stir the mix. Just touch it with the tip of the cotton swab. Go ahead and try it.

4. Now place a drop of liquid dish soap on the other end of the cotton swab. Place the soapy end of the cotton swab back in the middle of the milk and hold it there for 10 to 15 seconds. You'll see an amazing color show.

5. Add another drop of soap to the tip of the cotton swab and try it again. Experiment with placing the cotton swab at different places in the milk. Notice that the colors in the milk continue to move even when the cotton swab is removed. What makes the food coloring in the milk move?

How does it work?

Since milk is mostly water, it has surface tension like water. The drops of food coloring floating on the surface tend to stay put. Liquid soap wrecks the surface tension by breaking the cohesive bonds between water molecules and allowing the colors to zing throughout the milk. We call things that mess up the surface tension of water SURFECTANTS.

There's another reason the colors explode the way they do. Milk is mostly water but it also contains vitamins, minerals, proteins, and tiny droplets of fat suspended in solution. Fats and proteins are sensitive to changes in the surrounding solution (the milk).

When you add soap, the weak chemical bonds that hold the proteins in solution are alteredn The molecules of protein and fat bend, roll, twist, and contort in all directions. The food coloring molecules are bumped and shoved everywhere, providing an easy way to observe all the invisible activity.

At the same time, soap molecules combine to form a micelle, or cluster of soap molecules. These micelles distribute the fat in the milk. This rapidly mixing fat and soap causes swirling and churning where a micelle meets a fat droplet. When the micelles and fat droplets have dispersed throughout the milk the motion stops.

If you want to so more at home:

Hypothesize what would happen if you repeated the experiment using water in place of milk. Will you get the same eruption of color? Why or why not? What kind of milk produces the best swirling of color: skim, 1%, 2%, or whole milk? Why?

Application: why detergent pollution is bad – soap breaks bond between oil and water – that’s why we use soap to clean dishes, but birds depend on this. If water fowl come into contact with soap, they lose their waterproofing, water soaks them, they get heavier and sink.

Why we should wash our hands with soap: our hands have oils that can't be broken down by just water - we need a surfectant - soap - to break down the oils that may be trapping dirt and germs, which leads us to...

I'm not sure which absolute monarch Robert is
but he is definitely enjoying being absolute in his power.

Henry the VII of England and Phillip the II of Spain pose in Stacy's class.

We dissected cow eyeballs today!

Douglas!

Stephanie!

Douglas was concerned that if he homeschooled he'd never meet new friends. Poor, Douglas, no friends for him.


Grace absolutely loves Caleb -- most of us do.



Zonked!

Dry Ice

Today's science terms and concepts:

There are 4 states of matter (Tutors, this will be in our Science grammar next semester): Solid, Liquid, Gas, and Plasma. Plasma is a really complex subject so I just told the children that stars (including our sun) is made of plasma and that is probably enough for them to know now.

Water at standard atmospheric pressure (normal pressure) which is "1 ATM" goes from solid (ice) to liquid (water) to gas (steam) as we increase temperature. However, if we increase or decrease pressure, it may behave differently. We can see how it behaves by seeing water's phase diagram. At 1 ATM, water goes from liquid to solid at 32 degrees F or 0 degrees C. It goes from liquid to gas at 212 degrees F or 100 degrees C (shouldn't we just convert to Celcius?! Much easier to remember!).

However, all materials have their own phase diagrams. Carbon Dioxide, at 1 ATM, or standard pressure, goes directly from solid (Dry Ice) to gas at around -110 degrees F. So any temperature above -110 degrees, it will become a gas. That is why dry ice is so good for putting in the fridge during power outages (should never be put in a working fridge) and mailing perishables. You won't be left with a wet mess after it melts.

At higher pressure, Carbon Dioxide will go from solid to liquid to gas. That is why soda manufacturers have to introduce high pressure in order to liquefy Carbon Dioxide to add to the rest of the junk that's in soda :).

The process for ice becoming water is melting.
The process for water becoming steam is boiling.

However, the process when you skip the liquid stage and go from solid directly to gas is sublimation. Even if they don't remember the word, they get the concept that different materials behave differently.

Dry ice precautions:

Dry ice isn't dangerous per se but it is so cold that it will kill your skin cells with very short contact, so should never be touched without thick gloves.

The gas is not dangerous but large amounts of it can asphyxiate.

Dry ice should not be put in a closed container. The gases will build up and if they can't escape, will explode the container it is in. This is just about true for any gas buildup.

Dry ice can be put in drinks to make an interesting show, but no one should drink the actual ice so it's safest to wait until all the ice is gone. And each time children should be reminded not to eat or drink science experiments without permission, no matter what they think.

Harris Teeter in Reston (near the Home Depot) has a dry ice fridge. Otherwise, it's a little difficult to find. And it usually sells out during power outages and Halloween.