Science Tidbits: Density

Background:

Density can be defined as the ratio of an object's mass per unit volume.  In other words. D=m/v!  More speficially, density depends upon two things:

1. The mass of each molecule that makes up the material.
2. The amount of space or volume the material takes up.

For example, a real boulder has a greater density than a styrofoam boulder. Why? The individual styrofoam molecules have a lower mass and are not "packed" tightly together.  Whereas, the individual molecules that compose a rock are higher in density and "packed" more closely together.  As a result, the real boulder has a greater density than a styrofoam boulder.

Another fact to consider is the density of a material remains the same under the same conditions.  For example, the density of aluminum is 2.7 g/cm^3.  Whether you are talking about aluminum foil or aluminum wire, the density remains the same provided the sample is not hollow or contains a mixture of materials.

What if we have an irregular-shaped object? It is not as straightforward to determine the density because it is more difficult to calculate the volume.  There is a way, though!  The volume of odd-shaped objects can be found by using a graduated cylinder and the fact that 1ml = 1cm^3.  Here's an example.

Let's say we want to find the volume of a rock you found while hiking.  Fill a graduated cylinder with water to a set amount, say 50ml.  Then, add your rock.  Be careful not to splash any of the water out!  Now, note the new water level.  Let's say it rose to 61ml.  Then, the volume of the rock could be found by the following method:

Volume of Rock: 61ml - 50ml = 11ml or 11 cm^3

Pretty easy, right?  Let's face it, most objects in nature are irregular inshape.  This provides an easy way for determining volume and, ultimately, calculating density.

Deeper Explorations:

Activity 1: Floating Carrots

Begin by asking your students if they thing a carrot will sink or float if placed into a container of tap water.  tally your responses.  Have someone drop the carrot into the container and observe what happens.  It should sink because the density of the carrot is greater than the density of the tap water.  Now, ask your students what they think would happen if you added salt to the water.  Again, tally your responses.  Begin adding salt in measured amounts.  Eventually, the carrot should float.  Make note of how much salt you added.  At this point, the carrot floats because the density of the salt water is greater than the density of the carrot.  It is very easy at this point to displace enough water to create a buoyant force that flaots the carrrot.

Activity 2:  The Dead Sea- Sink or Float

Visit the Dead Sea (at least virtually) using Google Earth.  Go online and explore this amazing place.  Find out answers to the following:

• How was the Dead Sea formed?
• Why it is easier for people to float here?
• Is it really deadly?

Extreme science is a great place to begin!

Science Tidbits- Everyday Measurements

One of the most important skills in the scientific process is understanding measurement.  It is essential that measurements are accompanied by the proper unit and that the correct measurement is used for the given task.  To kick off our explorations, I asked our children to brainstorm how their lives are affected by measurements.  They used scriblar to record their responses.

Obviously, this just scratches the surface when thinking about the varied ways we encounter measurements in our daily lives.  Hopefully, this will stimulate curiosity about the topic and spark a discussion.  Do we use liters or gallons?  Do we use kilometers or meters?  Metric or standard? Go ahead and try it!

Science Tidbits- What Do Scientists Do?

This week I asked the kids a simple question: What do scientists do?  They responded by saying "Scientists learn about the unknown by observing, collecting data, performing experiments, and building models."  Pretty sophisticated answer!  The discussion continued by having each child  highlight a type of scientist they found interesting.  Check out their responses! 

Highlight: Astrophysicist (Luc- 3rd grade)

Astrophysicists are scientists that study the physics of the universe.  They have strong math and physics skills.  Stephen Hawking is a famous cosmologist and astrophysicist who has creative and brilliant ideas about time travel and black holes.  Astrophysicists are galactic cool and rock the universe!

Cool Sites to Visit:

• Astrophysics for a Ten-Year-Old-Mind
• GSFC Astrophysics Science Division
• GSFC StarChild
• Kids Net Astronomy and Astrophysics
• George’s Secret Key to the Universe
• Kids Astronomy
• NASA Kids

Highlight: Volcanologist (Ellie- 2nd grade)
Volcanologists are scientists who study volcanoes, lava and magma.  They visit active volcanoes to collect rock and lava samples.  They also make predictions about when volcanoes may erupt.  We think people have been studying volcanoes since 7000 B.C.  Wow!

Cool Sites to Visit:

• How to Become a Volcanologist?
• Discovery Kids: Volcano Explorer
• Weather Wiz Kids: Volcanoes
• National Geographic Kids: Volcanoes
• Facts About Volcanoes
• neoK12: Volcanoes
• National Geographic: Forces of Nature- Volcanoes

Highlight: Marine Biologist (Abby-5th grade)
Marine Biology is the study of organisms in the ocean.  These scientists study a wide variety of life ranging from the prodigious blue whale to microscopic plankton.  I find the cetaceans the most interesting.  This group of marine mammals  includes  the many species of toothed and baleen whales.  From the blue whale measuring over 30m to the Hector’s dolphin measuring only 1.25m, marine biologists agree these are amazing, social animals to observe!  

Cool Sites to Visit:

• The Marine Mammal Center
• National Geographic: Blue Whale Interactive
• NOAA Online Games and Activities
  • Spotlight: Whale Migration Game
  • The Kid's Times

• ReefEd- Great Barrier Reef Resources
• National Geographic Kids Creature Feature
• Winter's Tail
• Explore the Marine Sanctuaries
• Jonathan Bird's Blue World TV
• Kids Do Ecology: Marine Mammals



Exploring Surface Behaviors on a Virtual Whale Watching Expedition!

Want to go whale watching? In this fun activity students will go on a virtual whale watching expedition where they explore surface behaviors of these gentle giants.

Activity

• As a class, view the introduction to surface behaviors online at Maui Whale Watching Tours.
• Discuss what behviors students think are the most common.
• Pass out the tally sheets to each student.
• View the video together and have class tally surface behaviors. 

• Upon completion, graph results online at Create-a-Graph sponsored by NCES Kids.

Blubber Fun!

Marine mammals spend all or most of their time in ocean water.  What keeps them warm?  If you were swimming in the warm waters off the coast of the Bahamas, it might seem a crazy question to ask.  However, at some point, your body would get cold!  What if you were to dive into the icy waters of the Arctic Ocean?  The cold waters would be almost unbearable for most humans.  So how do whales, dolphins, seals and other marine mammals keep from being cold?  One simple word: BLUBBER!

For these mammals, body temperature must remain between 95-100.4 degrees Fahrenheit (35-38 degrees Celsius).  Blubber is a thick layer of fat cells beneath the surface of the skin that preserves heat and keeps body temperatures in the ideal range.  It's the perfect insulator!  This layer of fat is very thick!  For example, a dolphin has a layer of blubber around .7” and the fat layer for sperm whales is between 1-2ft thick.  In addition to serving as an insulator, blubber is also used to store fat, as an energy source and for buoyancy. 

Scientists have recently discovered a downside to this layer of insulation.  Blubber also stores and/or absorbs harmful chemicals and toxins that are polluting the earth's waters.  These toxic chemicals are feared to be passed from parents to offspring.  Whale blubber is documented to have higher levels of mercury, PCB’s and pesticides! 

Activity

Materials: white model magic, buckets, and ice water

Procedure:

• Brainstorm ways humans stay warm.  Now, lead a discussion about how they think marine mammals survive in their ocean habitats. 
• Discuss with students what they think will happen if they plunge their finger into a bucket of ice water.  Record results.
• If you have a brave student, you can let them test the frigid water before continuing on with the activity.
• Now discuss with students what they think will happen if a finger covered in"blubber" is plunged into a bucket of ice water.  Record your results.
• Distribute balls of model magic to each student.  Ask them to flatten each ball using the heel of their hand.  Now, have them wrap their index finger completely.
• Once covered, students will take turns plunging their "blubber finger" into the icy water.  
• Ask students to form an opinion about how blubber works and add to a class wallwisher.  Each student should form a response.

Conclusions: All marine mammmals, like other mammals, are warm-blooded.  Their body temperature remains constant and does not adjust to changes in the surrounding temperature.  Blubber provides the perfect layer of insulation to keep them warm.  It's their built in "snuggy"!

To make this super fun, you could record the demonstratin with a Flip camera and post on a class wiki or create a slideshow using Google Docs.  In addition, you could easily post student responses there.  Be creative have fun learning!