Oceanic Acidification & Seashells

Birds and their eggs aren't the only animals for whom an increasingly acidic environment would cause great harm.  This simple activity demonstrates the effect of acid on shellfish.

You'll need a couple of shells (large or small, any variety, but for the sake of comparison, it's good to have two of the same), two cups or beakers, vinegar and water.

Place each shell in a cup/beaker.

Cover one shell with water.  You might want to use salt water, as these organisms live in the ocean, but I didn't think of that as I was setting things up. You could also do three shells at a time - one in vinegar, one in water and one in salt water.

Cover the other shell with vinegar. 

You'll notice that the shell in the vinegar immediately begins to form bubbles and fizz.  The vinegar is breaking down the calcium carbonate that composes the shell. 

Within 24 hours, you'll notice the shell that was in vinegar has holes in it.  If there was still a creature living in the shell, this could obviously be detrimental.

Vinegar, while a weak acid, is quite a bit stronger than acidified ocean water.  The stronger acid speeds up the process, making it visible within a short period of time - perfect for students to grasp an understanding of the process.  Shells in an acid ocean environment would be subject to the same chemistry, it would just take place at a slower rate.  

You can learn more about the chemistry taking place, as well as ocean acidification here.  

You may wish to continue to leave the shell in the vinegar for an extended time to observe further.  If so, it may be necessary to replace or replenish the vinegar.  (I used a small enough amount of vinegar that the chemical reaction came to a halt within a day or so).

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Summer Science Camp: Chemistry Demonstrations

If you're running your science camp in a full science lab, and you're comfortable with chemistry, consider putting on a chemistry "magic" show for your campers. 

While this doesn't have the same hands-on, active participation as most science camp activities, the students loved it!  They oohed and aahed and were captivated the entire time. 

Grab your science supply catalogs and look for the chemistry demonstrations (I've gotten them from Flinn Scientific, Ward's Natural Science and Nasco) - they have kits that contain the chemicals (and often anything else you might need, minus the glassware) you need for each demonstration.  Look for demonstrations that involve color changes or some other wow-factor.  It's fun shopping, but if you're not careful, you could blow your whole camp budget on this one session - choose wisely and realistically.

Make sure you follow all safety precautions - wear your goggles and lab coat and make all the students wear goggles as well. 

When you're "performing." show the students the solutions you'll be mixing together and ask them for predictions as to what will happen.  Make sure you react appropriately amazed and awed by the reactions, as they occur!

I don't expect the students to learn a whole lot from this session (they're elementary students and there's no way they'd understand the chemistry), instead I use it as an opportunity to build their enthusiasm for science and just have a little fun (it is summer, after all!).

End of School: Playing with Polymers

Tracy from The Science Spot has come through once again with a fantastic unit, Playing with Polymers, in which students make four different polymers - Gloop, Boogers, Goobers, and Super Slime.

Tracy does this as part of curriculum, as part of a study on petrochemicals.  I did it at the end of the school year, and the one drawback to doing it then is that this activity does require quite a few supplies and pieces of equipment.  But, the students LOVE it - I'll take the mess if I can have engaged students right up until school's out! 

And, Tracy does make it fairly painless for the teacher; she includes lists of materials (in quantities for 100 students), recipes, set-up instructions and so on.  If you keep the materials well-organized and labeled, things will go smoothly.  And your students will love you!

Acid/Base Chemistry: The Cabbage Caper

Still have some red cabbage juice indicator in the freezer?  Pull it out for this fantastic investigative lesson, utilizing knowledge of acid/base indicators. 

The story begins....

Click here for the full story, with all the suspect information. 

When you've read the full story, you'll learn that each of the suspects was using a particular solution.  The students test each of those solutions with red cabbage juice and with turmeric (found in the spice section of the grocery store) to determine which solution, and therefore which suspect, was responsible for the green and orange stains and the murder of Mr. Worthington. 

The suspects' solutions:

• Water
• Salt Water
• Battery Acid (you can use any kind of weak acid)
• Lemon Juice
• Vinegar
• Lye (baking soda dissolved in water will serve the purposes of the lab)
• Ammonia Water (you could use window cleaner)

If you have spot plates, students could set up their tests in one of those - put each suspect's solution in two wells, then add a few drops of cabbage juice to one of those wells and a few grains of turmeric to the other.  If not, use test tubes or small beakers, just make sure to wash them well between each test (you wouldn't want an innocent person to be accused of murder!). 

To conclude the lab, have students summarize the tests they performed and the results of their tests in a statement for the court.

One more note, the color change in turmeric is subtle - it remains yellow in an acid but turns orange in a base.

Today, homicide division has asked you, a reputable chemist, to personally accompany Detectives Sippowicz and Martinex on a murder case. Mr. Robert Worthington, a prominent citizen of our fine community, has been murdered.

On the way to the Worthington mansion, you learn that Mr. Worthington was stabbed, in his own kitchen, with his own carving knife. The maid, according to the police report, had found the cook standing over the body. The police officer on the scene had, therefore, arrested the cook on suspicion of murder. The cook, being a good friend of Sippowicz, had immediately called him, seeking his help. Sippowicz claims that the cook could not have done it since Mr. Worthington paid his cook more than any other employer in the city. His death will mean a substantial reduction in the cook’s salary, he claims. Besides, she is a very gentle person. She would never even raise a hand to kill a fly.

When you arrive on the scene, Mr. Worthington is still lying on the kitchen floor with the carving knife still protruding from his chest. As you examine the knife, you notice a STRANGE GREEN STAIN on the handle. Nearby are some ODD ORANGE STAINS. These are unusual because they are not blood stains. Fingerprints are covered up by the stains, making them unavailable for evidence. As Martinez questions the cook, you and Sippowicz set out to question the rest of the staff. One hour later, you, Martinez and Sippowicz meet to discuss the suspects.

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. 

Acid/Base Chemistry: Goldenrod Paper Indicator

If you can get your hands on some true goldenrod paper, you'll have yourself an indicator paper.

Goldenrod paper turns bright red in the presence of a base. 

The red color can be returned to the goldenrod color with an acid.

Dissolve some baking soda in water or use ammonia to paint and vinegar to erase. 

I know a high school science teacher who, on Halloween, would pretend to cut himself, "wash" his hand (with ammonia) and fling his hand at a sheet of this paper hanging on the board.  Totally freaked his students out!  He lists several other demonstrations using this paper on his website. 

Now, not all goldenrod paper is true goldenrod (i.e. it doesn't contain the real dye/extract), so you'll want to test yours out before passing it along to your students.  Astrobrights Galaxy Gold paper does work, so look for it at office supply stores if you're having a hard time finding paper that works.

Homemade Indicator Papers

If you've made some cabbage juice indicator and are looking for another way to save it for longer use, try making your own indicator papers.

Cut paper (I used coffee filters) into strips about 1/2" wide and a 2-3" long.

Submerge the strips in cabbage juice until they are fully soaked.

Remove the strips and place them in a warm spot to dry.

Store the dried strips in a resealable bag.

To use, place a drop of the liquid to be tested on the paper.  If it's a base, it will turn pink.  If it's a base, it will turn green.  And if it's neutral, there will be no color change.

The color change isn't as drastic as you'd see with litmus paper, but it's there. 

Cabbage Juice Indicator

Red cabbage juice is a great indicator - it turns pink in an acid, green in a base, and stays blue in a neutral substance.  And while it takes a little time to make, it's a whole lot cheaper than other indicators. 

To make some: 
Chop up a head of red cabbage and place it in a large pan.  Cover the cabbage with water.  Simmer for about 20 minutes (your house will smell like cabbage).

Let the contents cool before you remove the cabbage.  Store the water (now cabbage juice) in a jar*.

To test your cabbage juice:
Set up three glasses:
Pour a little vinegar in the first, some baking soda dissolved in water in the second, and tap water in the third.

Add a few drops of cabbage juice to each glass and observe.

*You can freeze the cabbage juice for longer storage.  Pour it into ice cube trays and freeze.  Then place the cubes in a freezer bag or box.  Pull out individual cubes as you need them.

Acid/Base Chemistry: pH of Household Substances

Gather a large collection of household substances; cleaning products, health and beauty products, beverages, etc. (See below for a more detailed list).

To perform this experiment in a classroom, place a small amount of each substance into a small beaker. Label the substance, either with a label on the beaker or an index card next to the beaker. Place a stirring rod (or comparable tool) in each beaker.

Students will touch the stirring rod to a piece of pH paper. They will then consult the key that comes with the pH paper to determine the substance's pH (I have laminated several of the keys and try to tape one to the end of each lab table, so there's always one nearby and all students are crowded around one or two small pieces of paper).

By touching the stirring rod to the paper (as opposed to dipping the paper into the substance) students will be able to test 3 or 4 substances on each piece of pH paper.

After testing each substance and recording the pH, students can create a pH scale of household items.

Have your students look for patterns... foods, skin care products, cleaning products, etc.

What are the commonly used numbers on the pH scale? Are there any numbers that weren't used at all?

What results surprised your students?

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Some substances you might* want your students to test:
ammonia
lemon juice
toilet bowl cleaner
Coke
coffee
liquid soap
rubbing alcohol
shampoo**
orange juice
glass cleaner
lotion**
bleach
Borax**
milk
Simple Green
grapefruit juice
vinegar
cranberry juice
tea (regular and herbal)
aspirin**
tub/tile cleaner
Brasso
7-Up
plant acidifier (MirAcid)**
soap scum remover
Drano**
oven cleaner
saline solution (for contacts)
Rolaids/Tums**

*Always use your best judgement and keep your school's policies in mind.
**Dissolve in water.