Compound Story

Have your students write some "science fiction".  

Each student chooses a compound (see below for some ideas) about which to write a story.  While not a report, the story should include scientific information about the compound and include the compound's empirical and structural formulas. 

Encourage your students to be creative in their writing and get into character - they could tell the story from the compound's point of view.  They could "be" one of the elements within the compound.  They could be reporting on a big news story involving the compound. 


If students are having a hard time getting started, they may want to look up their compound to find out what it's used for and where it's found - what they learn may be the start of a story. 

To make sure students don't get too carried away with the fiction aspect and forget the science part, you might wish to require them to use 12 (or whatever number you deem suitable) science terms.  Some possibilities:

• metal
• nonmetal
• solid
• liquid
• gas 
• chemical change
• physical change
• compound
• mixture
• periodic table
• family(ies)
• atomic number
• atomic mass
• stable
• unstable
• positive
• negative
• neutral
• valence electrons
• valence number
• empirical formula
• structural formula
• subscripts
• octet rule
• arms
• giver
• taker
• bonds
• share
• scientific name
• react
• reaction
• atom
• molecule

A list of compounds, to get you started:

• methane
• ethane
• propane
• butane
• octane
• acetylene
• benzene
• toluene
• carbon tetrachloride
• methanol
• ethanol
• propanol
• butanol
• carbon monoxide
• carbon dioxide
• calcium bicarbonate
• calcium oxide
• hydrochloric acid
• carbonic acid
• nitric acid
• water
• hydrogen peroxide
• hydrogen sulfide
• sulfuric acid
• ammonia
• nitric oxide
• nitrous oxide
• sodium chloride
• sodium nitrate
• sodium bicarbonate
• sodium hydroxide
• ozone
• silicon dioxide
• fructose
• sucrose
• potassium chloride
• citric acid
• vitamin C
• silver fluoride
• sodium fluoride
• silver chloride

Dissecting a Diaper

Mystified by the amount of water a single diaper can hold? 

If you've got a few extra diapers laying around after last week's experiment, consider dissecting one and to learn what's inside. 

You'll need a diaper, a pair of scissors, and a zip-top bag.  You may also find it convenient to work over a black piece of paper.

Begin by cutting a slit in the diaper.

Pull the "stuffing" out of the diaper and place it in the bag. 

At this point, you may feel some small granules, and notice white powder gathering on your piece of black paper.  These are sodium polyacrylate crystals - the magical component of disposable diapers. 

You can gather additional crystals by sealing the bag and shaking it for a minute or two. 

While shaking, the crystals should separate from the cotton and settle at the bottom for the bag. 

Once you've isolated the crystals, you can experiment with them (though you won't have very many from a single diaper).  See how much water they absorb.  Or try one of the water-absorbing crystal tricks mentioned here. 

Again, it could be interesting to compare the crystals found in different brands of diapers - are they all the same size, do they come in the same quantity? 

A good scientific exploration to learn more about the world around us, and also an introduction to polymer chemistry!

Moles: Challenge!

After discussing what a mole is (6.02x10^23 things), challenge students to bring in a mole of something.

Some examples to get you started...

A mole is...
...58 g of salt
...18 g of water


This is a good activity to do for Mole Day (celebrated October 23 - sorry to be late in sharing, you'll have to save it for next year!).

I would leave this as an extra credit opportunity for my students, as it's really beyond some of them. But, if you work with older or higher level students, go ahead and make them all do it!

Fun Products: Water-Absorbing Crystals

In preparation for some Halloween fun, you might want to consider getting your hands on some water-absorbing crystals.  They come in a variety of names and can be found in all sorts of locations.  In short, you're looking for a small crystal that can absorb large quantities of water. 

Sodium Polyacrylate is the polymer used in diapers to absorb large quantities of liquids.  You can get it from Educational Innovations, among other sources.  It's great for "disappearing" water magic tricks.  You have a small amount of the powder in a cup.  Pour in some water and a minute or so later, turn the cup upside down and nothing comes out.  (For your performance, you'll want to use an opaque cup, but I wanted to let you "in" on the action).

Ghost Crystals (also available from Educational Innovations) are lots of fun. This are much larger crystals than the sodium polyacrylate.  After you've enlarged your crystals, very carefully tie a thread around a single crystal.  Fill a water bottle with water and submerge the crystal, on its leash, in the water.  Leave the thread hanging over the side of the water bottle and screw on the cap.  Tell your students you've brought your ghost pet to visit for Halloween day.  They'll look and look, but all they'll see is a leash suspended in the middle of the water! 

It's also fun to trick your student with some "chunky" water.  A clear container filled with the enlarged crystals and a small amount of water will look just like a glass of water.  Fill a pitcher with the polymers and offer to pour a student a glass of water - instead of a stream of water, chunks will come out of the pitcher.

Other places to find water-absorbing polymer crystals:
Steve Spangler's Water Jelly Crystals look to be of a similar size to the ghost crystals, if you prefer to shop there. 

I've seen similar products (I'm not sure of their exact chemical make-up, but they function in the same way) at:
Toy stores (random locations within the store)
Garden centers (as an additive to retain moisture in soil)
Craft Stores (usually in the floral area)
Science supply catalogs

Lots of fun for Halloween or April Fool's Day, but also useful when studying polymer chemistry!

Periodic Table: Sticker Atoms

Each year, aAfter my students had learned about atomic structure and were beginning their periodic table investigation, they each chose an element to research a bit.  Every year I varied the product they produced a bit - variations on the element models and an element block (watch for more information on that one coming soon). 

One year, in addition to making their block, I had them create a sticker picture of their element. 

Each student was given a piece of black paper, blue dot stickers for protons, green dot stickers for neutrons, tiny smiley face stickers for electrons and a white colored pencil. 

Making the picture was not particularly challenging - though some interesting questions did arise about electron orbitals for students who were doing transition metals. 

The reason for making the picture wasn't in the interest of challenging the students, but instead to create a giant periodic table.  I laminated each of the individual pictures and then assembled them using clear packing tape. 

This periodic table does a nice job of showing the enlarging nuclei and increasing electron orbitals.  And by taking part in making the table, the students were much more invested in the process and obtained greater understanding of how their element fit in the periodic table.

FYI:

I had three classes of students and each student had to choose a unique element.  Each class was informed of the parameters during class time and element choosing "opened" at the end of the school day - so each student had equal opportunity to have the first choice.

In addition, I had a few students who helped make pictures for some of the elements that weren't chosen, so we had a more complete periodic table - at least for the first several periods. 

Public Service Announcement: Dihydrogen Monoxide: UPDATE!

April Fools*!!

Dihydrogen monoxide is another name for water - dihydrogen means 2 hydrogen atoms and monoxide means 1 oxygen atom - H2O!

Share the information from the Coalition to Ban Dihydrogen Monoxide with your students and see if you can get them going - some of them will jump right on board!  (You probably work with some people who would join the crusade as well)

It's another lesson in making sure you think and evaluate as you read and listen - everything stated in the "article" is true, but I don't think anyone really wants to ban water. 

I've also used this activity with students learning about the rules of compound nomenclature and it has the same effect, whether it's April Fool's Day or not.


*Yes, I know April Fool's Day isn't until tomorrow, but if I waited until tomorrow to share this gem, you would have to wait a whole year before sharing with your students and that just didn't seem right.

Acid/Base Chemistry: Mystery Solutions Lab

 I really enjoy this lab - it's like a big chemistry logic problem. 

This lab is one of the activities found at Science CAP (part of the ide@s website).  You'll need to visit the website to download and print the file, but I'll give you a brief synopsis. 

Before class, you prepare 12 sets of 4 dropper bottles (A, B, C, D).  The 4 bottles in each set contain an acid (vinegar), a base (ammonia), water and phenolphthalein.  Which substance goes in which bottle varies with each set - the provided materials include a chart so you know how to fill the bottles. 

Each team of students takes one set of bottles and a spot plate.  Using their knowledge of acids, bases and indicators, the students combine the substances (one drop at a time) in varying combinations to determine the identity of each substance. 

This activity can prove to be a bit challenging for some students, but encourage them to keep working to solve the problem and resist the urge to give away too much information.  Encourage students to review what they know about the substances:

--phenolphthalein turns pink in a base

--phenolphthalein stays colorless in an acid

--water does not change whether a substance is acidic or basic

In case you haven't figured it out yet, I highly value hands-on experiences for students.  Virtual is great and provides opportunities that students may not otherwise be able to have, but if both the hands-on activity and a virtual version were available, I'd choose hands-on each time. 

Now that you know my feelings on such things, I wanted to let you know there is a virtual version of this lab available.  I could see myself using the virtual version to introduce students to the activity and demonstrate how they'll be proceeding when they get to their lab stations. 

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. 

Chemistry: What’s a Molecule?

Hold up a piece of paper.

Rip it. Is it still paper?

Rip it. Is it still paper?

Repeat, over and over.

Is there any time it won’t still be paper? Just before that point, you’ve reached a molecule.

Molecules: Shapes of Molecules

Determining the shape of molecules can be a tricky business.

For example,
Carbon dioxide (O=C=O) has a central atom (C) with two atoms bonded to it and it has a linear shape.

Water (H-O-H) has a central atom (O) with two atoms bonded to it, but it has a bent shape.


Here’s a demonstration to help you students visualize molecular shapes. And catch your students attention!

Use balloons to represent the number of “things” around a central atom.

As mentioned before, carbon dioxide has two atoms around the central atom, so we tie two inflated balloons together, and voila! The linear molecule is formed:


How about carbon tetrachloride (CCl4) or another molecule that has four atoms surrounding the central atom? Tie four balloons together (I make two pairs of balloons and twist them together) and you’ve got the tetrahedral shape!



Now, back to that tricky water example….

If you draw the electron dot diagram for water, you’ll notice that there are not just two atoms around the central atom, there are also two electron pairs hanging out there. Those need to be accounted for as “things” around the central atom.

So… The oxygen atom in water has four “things” around it that need to be represented with our balloons. Just like with the carbon tetrachloride, I make two pairs of balloons, only this time, I make each pair out of a different color (one color represents the atoms, one color represents the electron pairs).

Twist the two balloon pairs together, and…


Let’s say the green balloons represent the hydrogen atoms…take a look, the green balloons are bent down into a bent shape. The yellow balloons are pushing them down, just as the electron pairs push the hydrogen atoms down!


Cool stuff!

Try it yourself and see what happens if you have 3, 5 or 6 “things” surrounding a central atom.

*********
This activity was presented by C. Lee in a workshop entitled “The End of Boring Biology and Confusing Chemistry” at the 2006 New Jersey Science Teachers Association Convention

Ideal Gas Law with a Balloon

The ideal gas law is basically a combination of a bunch of scientific laws relating to gases. It's stated as:

PV = nRT

P = pressure
V = volume
n = number of moles* of the gas
R = a constant (no need to worry about its value for our purposes)
T = temperature

In order to keep any equation balanced, if you change one thing in the equation, something else will change to compensate.

Here are some examples:

If you increase the number of moles of the gas, the volume it takes up will increase.
If you increase the pressure on the gas, the volume will decrease.
If you increase the temperature of the gas, the volume it takes up will incrase.


A balloon does a lovely job of containing a gas. Use one to demonstrate these properties of gases.
-Increase the number of moles of gas in the balloon (by blowing it up) --> the volume increases.

-Increase the pressure on the gas (by squeezing the balloon) --> the volume decreases.
-Decrease the temperature of the gas (by placing the balloon in a refrigerator) --> the volume decreases.


*A mole is simply a unit of measurement, like a dozen or a pair. In this case, it's a really big number: 6.02x10^23 but we use it the same way. A mole of atoms would be 6.02x10^23 atoms, a mole of people would be 6.02x10^23 people, a mole of eggs would be 6.02x10^23 eggs.