Classroom Activities on a Budget

Feeling the pinch from the current economy? Carolina understands. That's why we've put together 8 fun, educational activities that won't wreck your budget.

Living

Activity 1: Photosynthesis

A much-repeated experiment in plant physiology concerns the production of gas 0₂ by Elodea in the presence of light. The usual procedure requires collection of the gas over a relatively long period of time. A different approach to this experiment gives the student a clear idea of the change in volume of gas produced relative to light intensity, and of the rapidity of the response. This simple system allows the student to make immediate observations about the effects of variations of such physical factors as temperature and light intensity.

Materials

• Elodea
• Fine needle
• 0.5% solution of sodium bicarbonate
• Bell jar or beaker (500 cc)
• 200-W lightbulb

Procedure

1. Use a fine needle to pierce in several places the stems of 1 or 2 sprigs of Elodea.
2. Place the sprigs in a 0.5% solution of sodium bicarbonate in a small bell jar or beaker (500 cc).
3. Expose the Elodea to a 200-W bulb. This will elicit a nearly immediate response as demonstrated by streams of bubbles coming from the holes in the stems.

Activity 2: Observing Streaming of Cytoplasm (Cyclosis)

Students can use a number of organisms to easily observe the streaming of cytoplasm, but Elodea, Nitella, and Physarum are most frequently used for this purpose. Do not use a stain in the following procedures, as most stains will kill the cells and prevent cyclosis.

Materials

• Elodea
• Nitella
• Physarum
• Stereomicroscope
• Slide and coverslip

Procedure

Elodea:

1. Choose a bright green leaf from near the growing tip of an Elodea sprig.
2. Place the leaf in a drop of water (top surface of the leaf uppermost) on a slide and add a coverslip.
3. Observe under the microscope at 100% magnification, then 400%.
4. As heat from the substage illuminator warms the slide, chloroplasts (small green spheres) may be seen streaming along the periphery of cells. Although not as suitable, Vallisneria or Cabomba can be substituted for Elodea.

Nitella:

1. The procedure is similar to that for Elodea, except focus on the internodal cells. Chara can be substituted for Nitella.

Physarum:

1. Use a plate culture under a stereomicroscope.
2. Focus on a vein. Streaming of nuclei and granules is easily observed.
3. Streaming will reverse course after several seconds.

Preserved

Activity 3: Cow Eye Dissection

After your students have participated in a dissection lab, extend their learning (and the money you've spent on science materials!) with activities that explore related topics. Carolina's Perfect Solution® Cow Eyes are an economical specimen for learning about anatomy, light, and sight. Here are some suggestions.

• Ask students how the lens of a cow's eye feels. Is it soft or hard? Have students hold the lens up to the light and look through it. Have them write in their science notebooks what they can see.
• Direct students to place the cow eye lens on a newspaper and look through it at the words on the page. Have them write in their science notebooks what they see.
• Have students explore the principles of light. Compare the lens of the cow's eye to other lenses found in the classroom or at home.
• Offer some occupational education by inviting an ophthalmologist or optometrist to your classroom to discuss careers in the optical field.
• Have students research a topic pertaining to blindness or services for the blind in their community. Some students may choose to organize a service project based on their research.

Activity 4: Crayfish

Dissecting doesn't have to be a purely scientific activity. Use your dissection lab to provide math, social science, and reading opportunities! The Crayfish Dissection BioKit® , which features Carolina's Perfect Solution® specimens, offers many chances to extend your students'learning.

Prior to dissection, ask students to measure their crayfish. Put the data on the board and have students do stem-and-leaf plots of the class data. Send students online to find the cultural and economic importance of crayfish, then have them write about a particular aspect that interests them.

For younger students, a wonderful group of books that teaches about crayfish and other organisms is the Clovis Crawfish series by Mary Alice Fontenot. The series includes a number of titles so assign a different title to every group of students. In each book Clovis meets a new organism; have students research the organism in their book and present their information to the class. Another book students may find interesting is Crawdad Creek, a story about the adventures of 2 children who visit a stream. Let students have a "Crayfish Dish Day." They can prepare crayfish dishes for each other to enjoy. Measuring ingredients and portions allows students to practice their math skills. Bring music into your classroom. When crayfish are mentioned, many people think of Cajun country-New Orleans.

Whatever exercises you try, your students are sure to enjoy learning about the crayfish. And while you'll be helping to satisfy their curiosity and the National Science Education Standards, you'll have fun, too.

Physical Science

Activity 5: Magnetic Money

This activity comes from the Science of Money Kit. Float a US currency bill on water and pull it with a magnet. The ink in paper currency is magnetic. Using a strong magnet, currency can be pulled easily across water. The bill's attraction to the magnet is strongest where the bill has more ink.

A related demonstration is to pull flakes of Total cereal floating on water. Total contains iron filings in order to meet the US recommended daily allowance (RDA) requirement for iron (8 mg for men, 18 mg for women). Elemental iron is used because some iron salts cause foods to go rancid, while others are not readily absorbed by the body. Stomach acid converts iron to ferrous ions, which the body needs, primarily in hemoglobin. Note: Regular metal alloy magnets work, but not as well as neodymium magnets.

Materials

• Neodymium magnet
• Stirring bar retriever
• Plastic cup lid
• Large transparent plastic container
• Paper currency
• Water, 3 L
• Funnel, 6 in

Hazards

Large concentrations of airborne ammonia-based glass cleaner may irritate people's sinuses.

Preparation

1. Lay the display board flat on a level surface. Draw arrows on the back of the board to indicate the upright position.
2. Using the brush, paint the letters using phenolphthalein. When the solution dries, paint over the letters.

Procedure

1. Spray the board with glass cleaner to reveal the hidden words. (It may take several sprays.)
2. Come back to the sign at the end of the day. By this time, if not sooner, the words will have faded.

Activity 6: Magic Sign

Acid-base indicators are weak organic acids that change color when neutralized. Some plants (such as red cabbage) contain acid-base indicators that can be extracted from the plant's leaves. Indicators are widely used in titrations to determine end points.

In this activity a blank display board is painted with the acid-base indicator phenolphthalein, which is colorless at acidic and neutral pH values but red at basic pH values. The glass cleaner spray is a solution of ammonia, a base. The base reacts with the indicator, changing its color. Words (painted with the phenolphthalein) quickly fade as the ammonia evaporates from the board and as carbonic acid, formed from carbon dioxide and water in the air, neutralizes the ammonia. Note: Do not use solutions of sodium hydroxide to colorize the letters, as these solutions can irritate nasal membranes.

Materials

• Display board
• Phenolphthalein, 1% in ethanol
• 1 inch paint brush
• Glass cleaner with ammonia (such as Windex®)

Preparation

1. Pour water into the container.
2. Attach the magnet to the end of the stirring bar retriever.

Procedure

1. Fold a bill in half lengthwise twice.
2. Place the folded bill on the cup lid and float the lid on water. Pull the bill with the magnet.

Disposal

Pour the water back into its original container using the funnel.

Activity 7: Money Laundering

Water is an amazing liquid. Not only is it the main solvent of cellular protoplasm, it also helps to moderate climates by being able to absorb large quantities of heat and then slowly release it over a period of time. The high heat capacity of water is the reason why coastal climates are more moderate than climates farther inland. Water's specific heat capacity (the amount of heat needed to raise 1 gram, 1° C) is 1.0 cal/gram°C. On the other hand, quartz sand has a much lower specific heat capacity of only 0.2 cal/gram°C. This means that it takes 5 times as much energy to heat one gram of water as it does for one gram of sand. That is why, by midmorning on a warm sunny day, it is difficult to walk on beach sand while the ocean with its higher heat capacity still feels relatively cool.

The following inquiry demonstration is a great way to illustrate water's high heat capacity and to introduce this concept to your students.

Materials

• US 1-, 5-, 10-, or 20-dollar bill, donated by a student
• Beaker, 250 mL
• Graduated cylinder, 100 mL
• Ethyl alcohol, denatured, 60 mL
• Water, 40 mL
• Crucible tongs
• Match or Bunsen burner with gas lighter

Procedure

1. Ask a student to "lend" you a one-dollar bill (or a higher denomination).
2. Tell your class that the money has germs so you want to sterilize it.
3. Pour 40 mL of water into a 100-mL graduated cylinder.
4. Continue filling the cylinder with denatured ethyl alcohol to the 100-mL mark.
5. Pour the solution into the 250-mL beaker.
6. Submerge the bill completely in the solution and tell the class that you are "money laundering".
7. Remove the bill, unfold it, and tell the class you are going to have to quickly dry it.
8. Hold the bill by the corner with crucible tongs and ignite the bill with a burning match or Bunsen burner.
9. Much to the surprise of the students, the bill will ignite but will not be consumed.
10. Have students brainstorm as to why the bill did not burn from the flames. Answer: The 40% water in the solution absorbed the heat and kept the bill from burning. The bill should be moist from the remaining water. You can pat it try with a paper towel. This demo is even more dramatic with a 5-, 10-, or 20-dollar bill!

Activity 8: Boiling Water in a Paper Cup

Materials

• Paper cup, unwaxed
• Ring stand with iron ring and wire gauze
• Bunsen burner with gas lighter
• Water source

Procedure

1. Fill paper cup a little over halfway with water.
2. Place paper cup on wire gauze and heat with burner.
3. The top of the cup will burn down to the water level and stop.
4. Have students explain why the paper cup does not burn below the water level. Answer: The water in the cup absorbs the heat due to its high heat capacity and keeps the cup from reaching its ignition temperature of 233 °C. Note: Do not try this with a Styrofoam® cup. Styrofoam® is a good insulator and will not allow the water to absorb the heat.