Friday, December 31, 2010

A Hole in the Water

This is a very cool demonstration!  Make sure you only use a spoonful or two of water - I tried to do this repeatedly, but with too much water, and was getting very frustrated by the lack of results.  When I broke down and followed the directions, it worked beautifully.  I had to do it 3 times in a row just to marvel at it!  

Place a spoonful of water onto a plate.  Add a drop of food coloring and swirl to mix.

When the water has settled, add a few drops of rubbing alcohol to the center of the water.

Watch the water pull away from the alcohol - the alcohol has less surface tension than the water.  The water molecules want to stick together (literally), so they pull away from the alcohol, leaving a hole in the middle.

Watch the edge of the water.  It literally quivers as it tries to stick together.  So cool!

Thursday, December 30, 2010

Atoms: Tasty Atomic Models

If you teach your students about the Thomson, Rutherford, Bohr and Heisenberg/Schrodinger models of the atom , you need to use this activity.  It's from Roseann McCarthy at Ocean Township High School, New Jersey and it's super fantastic.

Put your students in groups of four. 

Give each group a bag containing:
--A chocolate chip cookie
--A Tootsie Roll pop (or a Blow Pop)
--A Gobstopper
--A Ferrero Rocher chocolate

The students examine the candies/cookies and discuss which item best illustrates each model of the atom and why.

I like to have students explain why the item is a good model as well as provide a reason why it is not perfect and brainstorm ideas for other objects that would work to represent each atomic model.

Thomson - Chocolate Chip Cookie
Thomson described the atom as having negative charges scattered throughout it, like the cookie has chocolate chips scattered throughout it. 

Rutherford - Tootsie Roll Pop
Rutherford first proposed the idea of a nucleus.  The Tootsie Roll pop has a dense Tootsie Roll center, or nucleus.

Bohr - Gobstopper
Bohr placed electrons in energy levels, or layers outside the nucleus.  Gobstoppers change colors as the oustide dissolves because there are many layers of color.

Heisenberg/Schrodinger - Ferrero Rocher
The Heisenber/Schrodinger model places electrons scattered outside the nuclues - they care in a predictable space but no exact location can be identified.  The Rocher candy has a hazelnut center (nucleus).  In addition, there are chopped hazelnuts in chocolate surrounding the center - those pieces of nut are found in a specific region, but we can't pinpoint exactly where each piece of nut will be.

In case you aren't familiar with the Ferrero Rocher candies, here's a picture of one, cut through the middle:

At the end of the activity, I allow the groups to divide the items as they see fit.  Sometimes serious negotiations take place, but I've never has it turn into an argument (if it looks like it might, all you have to do is threaten to dispose of all the items for them).

A few more ideas/extensions:
--You can add Dalton's orginal atom as a sour ball or other piece of hard candy that's the same throughout.
--You might want to have a knife available, in case a group needs to cut one of the items open.  Keep it in your possession and you can do the cutting as directed by the group.
--If you can't bring candy into your classroom, take pictures of the candies and let the students work them out that way.  By using materials familiar to the students, they will develop a greater understanding of the models.  Going through the Ferrero Rocher model really helped me understand electron clouds better. 

Wednesday, December 29, 2010

Comparing Amino Acids & DNA

A quick review...
DNA provides instructions for the assembly of amino acids into protein.

Similar proteins have a similar amino acid sequence.  And if the amino acid sequence is similar, the DNA is similar.

Scientists believe that similar DNA sequences indicate a common origin.

Hemoglobin (a protein in red blood cells) is one protein that has been studied in humans, gorillas, and horses.

Each group will be given 10 different colors of beads (each one representing a different amino acid - see list below).

Students use the beads to create the partial amino acid sequence for human, gorilla and horse hemoglobin (see below).

For assembly purposes, I give the students an index card with three pipe cleaners attached.  It keeps it all in one place, and it makes it easy for the students to compare the sequences at the end.

After students have completed the amino acid sequences, I use my keys to quickly check their work.
They then count and record the differences in the amino acid sequence.

From there, you can discuss...
--what determines the order of amino acids?
--where do we get our DNA from?
--where did our parents get their DNA from?
--random chnages in DNA occur over time, the mroe time passes, the more changes there will be.

At the end of the activity, students remove thier beads and return them to their appropriate bag.

The Amino Acid Sequences:
Human: gly lys val asp val asp glu val gly gly glu lys leu his val asp pro glu asp phe arg leu

Gorilla: gly lys val asp val asp glu val gly gly glu lys leu his val asp pro glu asp phe leu leu

Horse: asp lys val asp glu glu glu val gly gly glu lys leu his val asp pro glu asp phe arg leu

This activity comes from a wonderfully creative and talented teacher who presented it in a workshop at the New Jersey Science Teachers Association Convention.  Unfortunately, I don't have her name written down.  If you know her, or are her, please contact me and I will give her all the credit in the world for this great activity!

Tuesday, December 28, 2010

Solar System: The Planets to Scale

Textbooks are notorious for completely out-of-whack drawings of the planets in our solar system.  They're about as out-of-whack as the solar system models made by 3rd graders - you know the ones, made from styrofoam balls.  The craft stores only sell about 3 sizes of styrofoam balls, so Jupiter ends about being about twice as big as Mercury and Pluto. And the sun is maybe a little bigger than Jupiter...

Remember these pictures?  They're a good place to start your discussion of planet size. 

But, why not add some props to make the lesson even more fun and memorable.

For each planet (and the sun) I'll give you the object I used, the planet's actual diameter and the scaled diameter (so you can take your ruler with you to the produce department in search of the perfect melon to represent Saturn). 

The Sun:
1,400,000 km --> 140 cm
1/2 plastic tablecloth

4,900 km --> 0.49 cm

12,100 km --> 1.21 cm
(in the pictures, I used a Gobstopper for both Venus and Earth because my marshmallow was missing)

12,800 km --> 1.28 cm

6,800 km --> 0.68 cm
split pea
143,000 km --> 14.3 cm
small (size 3) soccer ball

120,000 km --> 12.0 cm

51,800 km --> 5.18 cm

49,500 km --> 4.95 cm
small apple

2,300 km --> 0.23 cm

I like to begin the demonstration by showing students the sun and then having them guess how big Earth would be at that scale; everyone holds up their hands to show me how big it would be.  They always think it's way bigger than it is! 

After revealing the Earth, we then go back to Mercury and work our way through all the planets in the same way. 

It's a good way to begin a discussion of Pluto's classification, as Pluto looks absolutely puny after those gas giants. 

Monday, December 27, 2010

Graphing & Extrapolating: How Many Licks Does it Take?

Last week, we started to find out How Many Licks Does it Take to Get to the Center of a Tootsie Roll Pop.  Last time largely focused on data collection, which is a great skill, but doesn't answer the question at hand. 

Since we weren't able to complete enough licks to get our answer, we need to graph the data and then extrapolate to find the answer.  You can do this by hand or using Excel. 

Here are the instructions for creating the graph on Excel*
Open a new excel worksheet

Label column A "Number of Licks"

Label column B "Mass"

Fill in number of licks, continuing by 10s until you reach 200 (yes, go to 200 even if you didn't get anywhere near that many licks done).

Fill in corresponding masses

Highlight the numerical data (don't include the column titles in your highlighting)

Go to Insert, then Chart

Click on XY Scatter, then click Next

Click Next

Enter a chart title (name of lab), the x-axis label (Number of Licks), and the y-axis label (Mass (g))

Click Next

Select the option to place the chart as a new sheet

Click Finish

Click on one of the points on the graph - all the points should be highlighted

Go to Chart, then Add trendline

Click Okay

Click on the legend and delete it

Double click on the numbers on the y-axis.

Click on Scale

Change Minimum to 0

Double click on the background of the graph

Set area to none

Print the graph

Draw a horizontal line at the value you had for the stick and wrapper

At the point where the line you drew hits the line on the graph, draw a vertical line to the x-axis.

Estimate the value for where the line hits the axis - that is the number of licks it would take to get to the center of a Tootsie Roll Pop

*I wrote these instructions using an older version of Excel, which is still what I have access to. If you use a newer version and find that some of the terminology needs to be changed, please let me know.  Also, please let me know if something is unclear or you just aren't sure about something and I'll do my best to help.

Thursday, December 23, 2010

Action/Reaction: Spring Scale Demonstration

Spring Scales (Complete Set)

For this demonstration, you'll need 2 student volunteers and 2 identical spring scales. 

Hand each student a spring scale.  They'll hold the loop end with one finger.  Hook the opposite ends of the spring scales together.

Instruct one of the students to pull his/her spring scale with 10 N of force (or whatever number is appropriate for the spring scales you are using; something in the middle of the scale) and the other student to pull with 0 N of force (or 5 N or any number as long as it's different from the first student). 

Then let them try to do it.

When they can't get it to work, I usually step in and try to "help".  I have the one student pull the spring scale so it reads 10N.  Once that one's set, I tell the other student to then pull his spring scale to the predetermined number. As they're doing this, they'll notice that both spring scales are always at the same number, no matter what they do.

It's that whole "For every action there is an equal and opposite reaction" thing. If a student pulls on one scale with 10N of force, the other scale pulls with 10N of force (equal force), but in the opposite direction. 

It's a really simple demonstration, but it really exemplifies the "equal" part of Newton's third law. 

Wednesday, December 22, 2010

Body Systems: Respiratory System: Model Lung

Creating a model lung is pretty simple.  You can find directions all over the internet, including right here!

Start with a plastic bottle, any size will do.  (Pictured here is a water bottle, but 2 liter bottles work as well).

Cut the bottom off the bottle.  If you're having students make their own lung, you may want to do this for them, and if the students are young, you may want to tape over the cut edge so no one gets cut.

Place a balloon in the neck of the bottle, and stretch the opening of the balloon over the opening of the bottle  (see the blue balloon in the above photo).
Cut the narrow part off of a second balloon.  Stretch the remaining balloon over the bottom of the bottle.

That's it.  

Now to use it.... 
The blue balloon represents a lung.  The red balloon is the diaphragm.  

When you breathe in, the diaphragm contracts (pull the diaphragm balloon down).  This lowers the air pressure in the chest cavity (because there's more room) and air fills the lungs.

When you exhale, the diaphragm relaxes (release the balloon, you can even push up on it a little).  The air pressure in the chest cavity increases and air flows out of the lungs.  

Tuesday, December 21, 2010

Comparing Crystals

Note: I'm including this activity, even though I continue to struggle to get it to work myself.  I like the idea, and know that crystals can be grown from each of the following solutions, even if I can't grow them.  I can grow great Borax and Alum crystals.  The rest of them... not so good.  If anyone has any advice, please pass it my way. 

When leading a study of minerals, you'll talk about the repeating crystal structure of minearls.  Unfortunately, most mineral samples (especially those found in the classroom) don't provide students with the opportunity to see those crystals and the different shapes they can be. 

Consider making up a set of crystal sticks so students can see some of the different shapes crystals can take on.

Here's how you do it:
Make a super-saturated solution* of any of these solids in water:
--Table salt
--Rock salt
--Epsom salts
--Baking soda

Place a length of pipe cleaner into the solution and let sit overnight (or longer, depending on the solution). 

In the morning remove the pipe cleaners and allow them to dry.  Make sure you keep the nametags with the crystals, so you know which is which.

*To make a super-saturated solution:
Begin with boiling water in a jar.  Stir in as much of your solid as you can, until no more will dissolve and it starts to settle to the bottom of the jar.  You'll need a different amount of each solid to get the job done.

Monday, December 20, 2010

Measurement: How Many Licks Does it Take?

Remember the old Tootsie Roll Pop commercial...

This lab addresses that very important question, How Many Licks Does it Take to Get to the Center of a Tootsie Roll Pop? 

There are quite a few scientific skills that go with this lab...
...scientific method
...measuring mass
...collecting data
...graphing data
...extrapolating based on data gathered

For today, we'll focus on the first three things listed.  We'll come back to the graphing and extrapolating next week.

Before we begin, there are a few assumptions being made in this lab
  1. The center of the pop is the stick.
  2. The pop is made of a uniform material.
How many licks does it take to get to the center of a Tootsie Roll Pop?

If I lick the pop _____ times, then I will reach the center.

  1. Measure the mass of the pop and wrapper.  Record.
  2. Lick the pop 10 times.
  3. Measure the mass of the pop and wrapper.  Record.
  4. Repeat steps 2 and 3 five more times (or as many as class time allows). 
  5. Finish the pop.
  6. Measure the mass of the stick and wrapper.  Record.
Graph the data.
You can have the students graph the data by hand and then draw in a best fit line to determine how many licks it would take.  Or you could have the students use Excel to graph the data. 

Teacher Notes:
**Make sure you define a lick before you start.  They can't be "dainty" or they'll never gather enough data and their graph will be unusable.  Define a lick as putting the pop in their mouth, twirl it around once and removing it. 

Tune back in next Monday for step-by-step instructions for creating graph (including the best fit line/trend line) in Excel. 

I know, you aren't sure you can wait a whole week for such exciting information.  Try to contain yourself.  And, while you're waiting, go find yourself a Tootsie Roll pop and start licking... :)

Friday, December 17, 2010

GIANT Microbes

MINI Giant Microbes (Mini Microbe - Miniature in Size - 2-3 Inches) Common Cold (Rhinovirus)FLU GIANT MICROBE PLUSHSORE THROAT GIANT MICROBE PLUSHSTOMACH ACHE GIANT MICROBE PLUSH

Add a bit of whimsy to your study of viruses and bacteria!  I picked up these Giant Microbes quite a few years ago now.  I think they were pretty new then - they've since increased the collection by quite a bit. 

I went with microbes common to schools (from left to right): common cold, flu, sore throat, and stomach ache.  There are all variety of microbes including those making news in recent years: Swine flu, Bird flu, Mad Cow Disease, Multiple-Resistant Staph, etc.  And there are also some cells (which might be worth adding to my collection): red blood cell, white blood cell, platelet, neuron, brain cell.  You really just need to check out the whole collection...

The microbes come with a small information card, including the name of the actual virus/bacterium/fungi. 

My students get a kick out of them, and they do come in handy when talking about virus/baceteria shapes.

Seriously, go now and take a look! 

Thursday, December 16, 2010

Glue Stick Magnifying Glass

Did you know a clear glue stick (for a hot glue gun) can be used as a magnifying glass?  The way the light bounces around the cylinder and refracts because of the change in material causes the glue stick to act as a lens.  Lay it over some small type and see how much larger it appears. 

Some other objects that can be used in the same way:
--a glass stirring rod
--a test tube filled with water (sealed with a stopper)

Wednesday, December 15, 2010

Soda, Tea and Your Teeth

Soak an egg* in Coke or tea overnight.

Show your students a plain egg and the egg soaked in the Coke/tea - that's what the Coke/tea does to your teeth over time.

Then, use different brands of toothpaste and toothbrushes to try to clean the eggs.

 *You may want to hard boil the egg, in the name of reducing the mess which will occur if students get a bit carried away with their brushing.

FYI I used a brown egg, which makes the stain appear extra dark, and makes it harder to tell when you've brushed it off.  For students, I would use white eggs, but for the purpose of taking pictures for this blog, I used what was on hand. 

Tuesday, December 14, 2010

Catch a Raindrop

Mix 2 parts of flour with 1 part of salt. 

Fill a shallow pan with about half an inch of the mixture. 

On a rainy day, hold the pan outside for a few seconds.  (Or you could let water drip from your hand into the pan, but going out in the rain is more fun).

Let it sit, undisturbed for a few hours (or until the next day).

Use a fork to carefully remove the wet spots.  Set them on a plate to dry.

After they're dry, examine their shape and size.  Why do they look like balls and not like a "raindrop" shape?

You may want to try this on a variety of days - a day when it's barely raining, a day when you have a steady shower, and if you dare, a day when you have a downpour.  What similarities and differences do you observe between the raindrops collected on each of these days?

Older students could measure each of the drops they collected and then analyze the data; graph it, determine the mean, median, and/or mode. 

Monday, December 13, 2010

Exploring Water with a Pipette

Small children, kindergarten and 1st grade students (and even some preschoolers) can be taught to use a pipette.  This activity is a great way to have those young students learn about water, use a pipette and have some fun.  Older students will enjoy the activity as well (rooms full of teachers will enjoy it too). 

Provide each student with the following set-up:
A paper towel with a piece of wax paper on top of the towel.  A small cup of water and a pipette next to the wax paper. 

Begin by showing students the pipette, naming the bulb and stem. 

Walk students through the process of using a pipette:
--Squeeze the bulb
--Place the stem in the water
--Release the bulb
--Remove the stem from the water
--Squeeze the bulb a small amount to release a drop of water. 

Guide the students through the following exercises:
--Make a single drop on the wax paper.
--Use the pipette to pick up the drop of water.
--Move the drop of water around the piece of wax paper.
--Make 2 or 3 drops of water on the wax paper and push the drops together.
--Split the drop of water into smaller drops.
--Make a picture using drops of water (a face, for example).

Without even trying, the students will learn a lot about the nature of water by observing the shape of the drops, watching the drops come together, and struggling to separate the drop into smaller drops. 

With older students, you'll discuss adhesion, cohesion and surface tension, maybe even mentioning Hydrogen bonds. 

With younger students you'll discuss what you saw happening and the general idea that the water likes to stick to itself. 

If your students are on a roll with this activity, here are a few extentions you can use:
  1. Have the students make drops of oil and/or rubbing alcohol on the wax paper.  Guide them through the same exercises and above and see if these liquids behave in the same manner as water.
  2. Have students make their drops of water on other materials: paper towels, aluminum foil, plastic wrap.  How does the water behave on each of the surfaces? 

Activity from Linda Burroughs, The College of New Jersey, presented at the 2010 New Jersey Science Teachers Association Convention