Exploring the Properties of Water - Fourth Grade

Water is pretty amazing. It not only comes in three forms: solid (ice), liquid (water), and gas (water vapor), but it covers most of our Earth--97 percent to be precise!

Water is also extremely important to ALL living things. In some organisms, up to 90% of their body weight comes from water. Up to 60% of the human body is water; the brain is composed of 70% water, while the lungs are nearly 90% water.

Insects called water striders can skate on water because of a unique property called SURFACE TENSION. Surface tension is caused by water molecules sticking together at the surface, creating a kind of "water skin."

And while most liquids contract (get smaller) when they get colder, water is different. Water contracts until it reaches 4 degrees Celsius and then it expands until it is solid. Solid water is less dense than liquid water because of this. If water was like other liquids, then there would be no such thing as an ice berg, the ice in your drink would sink to the bottom of the glass, and ponds would freeze from the bottom up!

Water is constantly being recycled through a process called "The Water Cycle."  Now sing this little ditty to the tune of "She'll Be Comin' 'Round the Mountain."

Water goes around in a cycle, yes it does!

Water goes around in a cycle, yet it does!

It goes up as EVAPORATION

Forms clouds as CONDENSATION

Then comes down as PRECIPITATION

Yes it does!

Urban Nature Club Goes Birding in Prospect Park

Today the Urban Nature Club grabbed their binoculars and headed to Prospect Park to watch birds at the "secret" bird feeders, generously filled by Brooklyn Bird Club President Peter Dorosh. What a great day! We saw chickadees, downy woodpeckers, white-breasted nuthatches, cardinals, juncos, white-throated sparrows and even a red-winged blackbird. We also spotted many empty birds' nests in the now leafless trees. (Oh yes, winter is a great time to go bird nest hunting!)

SCIENCE IS ALWAYS CHANGING!

Big news. Scientists found a tooth in Israel that may have belonged to an ancestor of modern humans, scientifically known as Homo sapiens. The accepted scientific theory is that Homo sapiens originated in Africa 200,000 years ago and migrated out of the continent. Scientists say that if this tooth is definitively linked to modern human's ancestors, it would mean that modern man in fact originated in what is now Israel 400,000 years ago, which would change the whole picture of evolution. Further research is needed to see if this pans out. Anyone out there want to be a archaeologist or paleontologist?

SNOW DAY!

Prospect Park

I hope all my PS 230 students are getting outside to enjoy the snow. Ms. Seitz sure is! Decorate your street with a snowman, have a friendly snowball fight or go sledding in Prospect Park. Remember to dress in layers and wear warm, water-proof boots. Now, go have some fun!

I'm sure many of you have gone to the Pavilion Theatre. Well this is what it looked like on snow day. Notice they had to take down the letters from the marquee because it was so windy.

Prospect Park sledding hill by the Picnic House

Ms. Seitz all bundled up in front of her snowy house

SCIENCE QUESTION - HOW DOES SNOW FORM?

Snow begins in the atmosphere as water condenses into a tiny droplet. As more and more water vapor condenses onto its surface, the droplet grows. Cold air then freezes this water into an ice crystal.

Each ice crystal has a unique shape that depends on the surrounding air's temperature and water vapor content. If it is below freezing and there is a lot of water vapor in the air, the crystal grows six evenly spaced branches. More and more water vapor collects on these branches and freezes, making the ice crystal increasingly heavy. Eventually, the ice crystal falls from the sky, leaving the cloud of precipitation that it helped to form. As it falls, the crystal continues to grow by picking up more water vapor.


As it descends, the ice crystal can come into contact with warmer air that makes it melt somewhat. This melting acts like a glue, causing crystals to bond together into larger flakes, forming what many people think of as the "classic" fluffy snowflake. If the crystals melt too much and then refreeze as they get closer to Earth's surface, the precipitation falls as sleet instead of snow.

Once on the ground, snow will remain if temperatures are cold enough to keep it from melting. Glaciers that form on mountains, for example, are made up of snow that accumulates on the ground and eventually turns to ice.

What's the Difference Between a Food Chain and a Food Web?

A food chain follows a single path of what eats what. But most animals eat more than one type of organism so they are part of more than one food chain. That's where Food Webs come in. A food web is made up of interconnected food chains. How many food chains are in the above food web? Leave your guess and Ms. Seitz will let you know if you're right!

THE GREAT EGG DROP CHALLENGE

Fifth-graders were recently asked become engineers to create a protective container for a raw egg that would be dropped from 2.5 meters. The only materials they could use were: a Foodtown bag, three straws, six cotton balls, 75cm duct tape, two 75-cm pieces of yarn, a dixie cup. The students have come up with all kinds of designs--some have protected their egg, while others have not.

Why is this important? Well, think of your egg container as a bicycle helmet protecting your brain from a bicycle fall. A good helmet provides padding, which absorbs some of the force and reduces the impact of the force on your head. In other words, increased time applied to the force of impact will protect an object from breaking.  Air bags in cars do the same thing--they create a cushion between the force and you so you won't feel it as hard. Now do you see why it's important to have a well-engineered egg container?

Here are the results so far:

Ms. Robb's class: 3 survivors, 4 tragedies
Ms. Greenspan's class: 6 tragedies
Ms. Water's class: 6 survivors
Ms. Grant's class: 2 survivors, 4 tragedies

CONGRATULATIONS FIFTH-GRADERS!

It was great having you all for science. I wish you happiness, success, health and a plain old good time in middle school as well. Have a wonderful summer! Ms. Seitz