Materials: Two wooden blocks, a heavy elastic band, scissors.
Procedure: Take two wooden blocks (same or different sizes) and connect them by wrapping the elastic band around them. Explain that this represents two molecules (blocks) being held together by a chemical bond (elastic band). The blocks may have names or symbols, such as ADP and P printed on them. Using the scissors, cut the elastic. The elastic will fly away from the blocks, showing the release of energy. The blocks now represent the two separate molecules.
DEMONSTRATION 2: Energy stored in foods
Objective: To show that foods contain stored chemical energy that can be transformed to other
types of energy.
Materials: A nut (Brazil nut, cashew, almond, walnut, peanut, etc.), a cork with a pin sticking out of it, a match.
Procedure: Stick the nut onto the end of the pin. Light it with a match. It should ignite quite easily, especially if the nut is high in fat. The nut will burn, giving off energy noticeable as heat and light.
DEMONSTRATION 3: Skin cooling by evaporation
Objective: To show that the evaporation of liquid from skin cools the skin.
Materials: Cotton balls, isopropyl alcohol, water.
Procedure: Using cotton balls, rub the back of one of a student's hands with alcohol and the back of the other with water. After a few seconds, have the student note which hand feels cooler. The one rubbed with alcohol will feel cooler because alcohol evaporates faster than does water. Heat from the skin provides the energy for the evaporation of liquids such as perspiration. When the heat is used this way, it is removed and the body becomes cooler.
DEMONSTRATION 4: Chemical composition of carbohydrates
Objective: To show that the chemical composition of carbohydrates is carbon, hydrogen, and
oxygen.
Materials: Sucrose, 250 ml. or larger beaker, concentrated sulfuric acid.
Procedure: Fill beaker about 1/4 full of sucrose. Add enough concentrated sulfuric acid to cover the sucrose. After a few moments, the acid will react with the sucrose, causing the generation of steam (water vapor = hydrogen and oxygen). A carbon residue will form and rise in the beaker. It can also be pointed out that the heat generated (feel the beaker carefully) is energy from the bonds that held the sugar molecules together.
DEMONSTRATION 5: Transpiration
Objective: To show that plants give off water in transpiration.
Materials: Potted plant, clear plastic bag, elastic band, aluminum foil or melted paraffin.
Procedure: Water plant before class. During presentation, place plastic bag over plant and secure to pot with elastic band. Allow to remain for 24 hours. Water vapor given off will be evident as condensation inside bag. To prevent water from evaporating from soil surface, the soil can be covered with aluminum foil or melted paraffin.
DEMONSTRATION 6: Use of ATP in cells
Objective: To show by analogy that energy needs to be available in small amounts in order to be
used by cells.
Materials: Dollar bill, 100 pennies, gumball machine with gum.
Procedure: Display gumball machine and dollar bill. Ask students if the dollar bill can be used to get the gum balls. Substitute pennies for the dollar bill and show how the gum balls can be obtained using the pennies. Explain that the dollar bill represents a large amount of energy that cannot be used by the cell (gumball machine) to do its work. By breaking the energy into smaller amounts (pennies) the work (releasing the gum balls) can be easily accomplished. This can be related to the generation of ATP molecules from glucose by respiration.
DEMONSTRATION 7: Action of a catalyst
Objective: To demonstrate the action of a catalyst.
Materials: Sugar cube, matches, cigarette ashes.
Procedure: Try to light a sugar cube with a match. It won't burn. Rub the corner of the cube in some cigarette ashes. Try lighting it again. It will ignite quickly. The ashes act as a catalyst. The burning will occur without the catalyst but the catalyst speeds up the process.
DEMONSTRATION 8: Effects of increased surface area
Objective: To show that the speed of a process is increased with an
increase of surface area.
Materials: Granulated sugar (sucrose), 2 spoons, sugar cube, 2 beakers (250 ml or larger), water.
Procedure: Simultaneously add the sugar cube to one beaker of water and spoonful of sugar to the other. (Make certain that the volume of granulated sugar is equivalent in volume to the sugar cube.) Stir. Note that the granulated sugar dissolves much more quickly. Explain that the granulated sugar exposes much more surface to the dissolving action of the water than does the sugar cube. Relate this to the need for foods to be mechanically broken down in order for digestion to occur optimally.
DEMONSTRATION 9: Earth's limited resources
Objective: To show the finiteness of the earth in regard to space that will
support human life.
Materials: Large apple, knife.
Procedure: Hold up the apple. Explain that it represents earth. Cut the apple in two. Point out the peel. This represents the biosphere the thickness of the earth's crust that will support life. Cut the peel from 2/3 of one of the halves. This represents the total amount of space that is habitable by humans.
DEMONSTRATION 10: Effects of mutations
Objective: To demonstrate by analogy the triplet code of DNA and how
mutations can affect it.
Materials: Chalkboard, chalk (overhead projector could be used).
Procedure: Print the following sentence on the board: THE OLD RED DOG WAS TOO BIG FOR HIS BED. Each word consists of three letters like the triplet code of DNA. If a mutation were to cause a deletion of the D of OLD, the sentence would now read: THE OLR EDD OGW AST OOB IGF ORH ISB ED. Obviously this is nonsense. If it were a DNA molecule, the resulting protein would probably be ineffective. If the mutation caused an inversion of the word DOG, the sentence would now read: THE OLD RED GOD WAS TOO BIG FOR HIS BED. In this case, the sentence still makes sense, but the meaning is completely changed. A protein resulting from such a mutation would have a different amino acid in one position of its sequence which could have profound implications. This analogy could be extended by making other mutations, such as reversing the sentence, inserting a new word or letter, substituting a different word somewhere along the chain, etc.
DEMONSTRATION 11: Absorption capacity
Objective: To show that increasing the surface area of an object increases
its capacity to absorb.
Materials: Piece of cotton cloth and a piece of terry cloth of equal dimensions, dishpan of water, graduated cylinder or other volumetric apparatus.
Procedure: Soak the cotton cloth in the water. Allow any excess water to drip off. Then wring out the cloth into the graduated cylinder and measure the amount of water that was absorbed by the cloth. Repeat with the terry cloth. There will be a considerable difference in the amount of water absorbed. The terry cloth with its many thin threads has a much increased surface area even though the two pieces of cloth have the same linear dimensions. This can be related to the absorption of digested food by intestinal villi, the absorption of water by root hairs, the absorption of oxygen by alveolar capillaries, or the absorption of gases by the spongy layer of the leaf.
DEMONSTRATION 12: Emulsification
Objective: To show how bile emulsifies fats and makes them easier to digest.
Materials: Jar with cover, vegetable oil, colored water, detergent or bile salts.
Procedure: Pour colored water and oil into the jar. Note that they do not mix. Cover the jar and shake it. Note that the oil and water eventually separate. Remove cover and add some detergent or a pinch of bile salts. Cover and shake again. Note that the oil breaks up into tiny droplets and mixes with the water. This is emulsification. Explain that this is what happens in the small intestine and that it increases the surface area of the fat droplets so that they can be more efficiently acted upon by digestive enzymes.
DEMONSTRATION 13: Gene splicing
Objective: To show a simple illustration of how gene splicing is done.
Materials: Construction paper, glue, scissors, stapler with staples.
Procedure: Before class, cut a long thin strip of construction paper and glue or staple it into a loop. When discussing the procedure of gene splicing, cut the loop (plasmid) with the scissors (restriction enzyme). Then with glue or stapler (ligase), attach another strip of construction paper (inserted gene) into the loop.
DEMONSTRATION 14: Characteristics of life
Objective: To demonstrate that some of the characteristics of life can be exhibited by non-living
materials but that the non- living materials or objects do not have all the characteristics of life and
therefore are not alive.
Materials: Candle, match, sugar or salt solution, microscope slide, clean iron object, rusty iron object, copying machine, wind-up toy, Rock 'N Flowers , color-change shirt, stress tester, mood ring, mercury or alcohol thermometer.
Procedure:
Materials: Geranium plant, paper template, container of boiling water, forceps, hot alcohol (ethylor isopropyl), petri dish, iodine-potassium iodide solution.
Procedure: Keep the geranium plant in the darkness for two or three days so that stored food (starch) will be depleted. To one of the larger leaves, tape a paper template with a cutout in it. The cutout can be a design or perhaps the school letter. Some success has been achieved using a sharp black and white photograph negative. Leave the plant in bright light for 48 hours. Remove the template from the leaf and remove the leaf from the plant. Using forceps, dip the leaf in boiling water until it is limp. Then submerge in hot alcohol until all the green color is extracted. Put the clear leaf in the petri dish and cover with iodine-potassium iodide solution. Pour off the solution and observe the leaf. The areas where photosynthesis has taken place (the areas exposed through the template), will appear black because of the starch present. This shows that the areas exposed to the light are the only ones where food was made.
DEMONSTRATION 16: Effect of catalase
Objective: To show the effect of catalase on hydrogen peroxide.
Materials: Hydrogen peroxide, large test tube or graduated cylinder, drop of blood, glowing splint.
Procedure: Pour hydrogen peroxide into the test tube. Add a drop of blood. The hydrogen peroxide will bubble and froth, indicating its breakdown by catalase in the blood. You can test for the presence of liberated oxygen by using a glowing splint.
DEMONSTRATION 17: Dominance and recessiveness
Objective: To show by analogy the difference between dominant/recessive
and codominant.
Materials: 6 small and 4 larger drinking glasses or beakers, water, red food coloring, bleach, yellow food coloring.
Procedure: Fill two small glasses with water colored a deep red with food coloring. Fill two more small glasses with plain water. Point out three apparently empty larger glasses. (In the third of these, there should be 1 ml of bleach, put there before class). Tell the students that the red and clear waters represent genes. Now pour some of the red solution from each of the two glasses (parent genes) into the first large glass (F1 generation). The solution is still red, showing that the phenotype for two homozygous genes is the same as that of the parents. Repeat for the two glasses of clear water, showing that the phenotypes are still the same as that of the parents. Now pour simultaneously from both the red and clear glasses into the third glass (with the bleach). The resulting solution (heterozygous) will be clear showing the trait of only one parent. Ask the class which gene was dominant. Answer: The clear water. The second experiment involves two small glasses, one with red water and the other with yellow water. When the two are poured together into an empty larger glass, the result is an orange-colored solution. This represents codominance or blending inheritance in the F1 generation. Neither of the two genes (colors) was dominant over the other.
DEMONSTRATION 18: Temperature and diffusion
Objective: To show that diffusion is a result of molecular motion and that its rate is a function of
its temperature.
Materials: Overhead projector, two petri dish bases, permanent marker, near-freezing water, near-boiling water, powdered dye (methylene blue, etc.) scoopulas or spoons.
Procedure: Label the petri dish bases HOT and COLD with the marker. Place them on the overhead projector. Add near-freezing water to the one labeled COLD and near-boiling water to the one labeled HOT. At the same time, drop a small quantity of powdered dye into the center of each dish. The dye in the cold water will diffuse very slowly while that in the hot dish will diffuse rapidly.
DEMONSTRATION 19: Dominant and recessive genes
Objective: To show by analogy how a recessive gene is present in a heterozygote even though
only the dominant gene is expressed.
Materials: Sodium chloride solution, potassium chloride solution, flame test (nichrome) wire or inoculating needle, cobalt glass square, bunsen burner flame, 3 beakers.
Procedure: Do a standard flame test for sodium by dipping the test wire into the sodium chloride solution and placing it in the flame. It will give the flame a yellow color. Repeat the test for potassium, using the potassium chloride. The flame will be violet. Now mix some of the sodium chloride solution with some of the potassium chloride solution in the third beaker. Do another flame test. The color will be yellow, making the solution appear to contain only sodium. Now repeat the test, but this time view the flame by putting a piece of cobalt glass in front of the flame. The violet color (recessive gene) can still be seen, even though only the yellow color (dominant gene) can be seen under normal conditions.
DEMONSTRATION 20: Dependence on sight
Objective: To show how much we depend on our sense of sight to give us information on our
position in space.
Materials: Blindfold (optional).
Procedure: Time how long a student can stand on one foot with arms outstretched and eyes open. Then blindfold him or have him close his eyes and repeat the procedure. Most likely the student will be able to stand quite awhile with eyes open but a relatively short time with eyes closed. This can provide an interesting motivation for discussion of the role played by our eyes in our sense of balance.
DEMONSTRATION 21: Fooling the sense of position
Objective: To show how our sensation of position and motion can be fooled when sight cannot
be used.
Materials: Sturdy plank, 2 books or bricks, blindfold, 4 people to act as helpers.
Procedure: This demonstration is based on a party stunt called the "Airplane Ride." Support the plank (airplane) with a book or brick at each end. Blindfold the subject and have her step to the center of the plank. Have two helpers stand on either side of her and the plank. Place the subject's hands on the shoulders of the two helpers. Tell the subject that you are doing this to steady her when the airplane takes off. Now have the other two helpers lift the plank at each end. They should not lift it more than a few centimeters off the floor. While they are holding the plank off the floor, the two helpers on the sides gradually lower themselves into a crouching position. The subject on the plank will believe that she has actually risen high in the air. The only sense she has functioning to give her position information is her sense of touch. It is interesting to repeat this demonstration with other students who have witnessed what has happened. If they close their eyes it is not necessary to blindfold them. The illusion is so powerful that it works regardless of what they have seen. Many will open their eyes to see if they are really being lifted.
DEMONSTRATION 22: What is a million?
Objective: To show the concept of one million.
Materials: Word processor or typewriter, paper, photocopier.
Procedure: Type $ signs to fill a piece of paper. Count the number of $ and calculate how many pages it will take to make a million $. Photocopy the page the calculated number of times. (You will likely have to type the last page separately as it probably won't be a full page.) Whenever you need to refer to numbers in the magnitude of millions, you can pull out your "million dollars." Students often have difficulty understanding what million, billion, trillion, etc., mean. This type of demonstration is useful when referring to such items as the number of species of living organisms, the number of cells in the body, or the number of bacteria that can result from one bacterium dividing every 20 minutes for 24 hours. When discussing pollution statistics, often the numbers given are in parts per million. To make this idea clearer, you can highlight the required number of dollar signs and show the students just how small the concentration is. You can reinforce the concept by telling them that one part per million is the same as one minute in two years, one inch in 16 miles, a 1 gram needle in a ton of hay, or one penny in $10,000.
DEMONSTRATION 23: Enzyme action
Objective: To show the action of an enzyme.
Materials: Chocolate-covered cherries.
Procedure: To start your discussion on enzymes, distribute to each of your students a chocolate-covered cherry. Ask them how the liquid centers of the candies got there. When the candies are made the white sugary material is a solid which is coated by dipping into melted chocolate. The white candy consists of a concentrated semi-solid sucrose solution to which has been added the enzyme invertase as it was processed. After the chocolate coating has been added, the enzyme and the moisture from the sucrose solution allow for the hydrolysis of the sucrose. During the time when the chocolates are being packaged, shipped, stored, and sold, the enzyme completes the digestion of the sucrose to fructose and glucose. Fructose, being much more water-soluble than sucrose, dissolves in the moisture, creating a thick sugar syrup.
DEMONSTRATION 24: Synthesis and hydrolysis
Objective: To illustrate by analogy the meanings of dehydration synthesis
and hydrolysis.
Materials: Sawdust, water.
Procedure: Take a handful of wet sawdust. Show students that the sawdust is made up of individual particles. Now compress the pile in your hands, squeezing the water out (dehydration synthesis). The sawdust particles will adhere to each other to form a new configuration (polymer). Now add water to the lump of sawdust and the lump will fall apart. This, of course, is a much oversimplified demonstration but it helps students who haven't studied chemistry understand the concepts of synthesis and hydrolysis.
DEMONSTRATION 25: Gene splicing
Objective: To demonstrate by analogy the process of gene splicing.
Materials: Several lengths of 16 mm film, scissors, tape.
Procedure: Take a long piece of film which you have previously taped into a loop. Now take another length of film and cut a "scene" from it. Cut open the loop and, using tape, splice the new scene into it. Make the analogy that films and tapes are made by splicing scenes together just as a gene sequence (new scene) is spliced into an existing plasmid or chromosome (original loop), using restriction enzymes (scissors) and ligases (tape).
DEMONSTRATION 26: Cell fractionation using a tomato
Objective: To show by analogy how cells are broken down to liberate cellular
components.
Materials: Tomato, blender, centrifuge, centrifuge tubes.
Procedure: One of the common methods to study cell structure and function is cell fractionation. Through this process the cell is broken, liberating its organelles and substances of the protoplasm. Using a tomato to exemplify a cell, cellular components can be demonstrated. First, fractionate the tomato in a blender for 10 to 20 seconds. Then pour the blended tomato into a tube and centrifuge for 20 to 30 seconds to separate the components. If the centrifuge process is fast enough the following layers will be seen (from bottom to top): (1) Seeds representing the nuclei (heaviest); (2) thicker layer of dense, red material representing the organelles (mitochondria, lysosomes, ER, etc.); (3) more fibrous red material representing plasma membrane; (4) somewhat clear with fibrous material suspended in it representing cytoplasmic fluids; (5) pinkish fibrous, foamy material representing inclusions of the cytoplasm (proteins, lipids, carbohydrates, RNA).
DEMONSTRATION 27: Cell permeability
Objective: To illustrate that certain materials can move in and out of the cell without damage to
the cell membrane and without expenditure of energy.
Materials: Zip-loc bag and sharp pencil.
Procedure: Fill the bag 3/4 full of water and close. Then, using a twisting motion, push a sharp pencil into the bag straight through to the other side. The nature of the bag material is such that it seals around the pencil, not allowing any of the water to leak out. This can lead to detailed discussions on the nature of the cell membrane, fluidity of the membrane, and the process of entry.
DEMONSTRATION 28: Starch goop now it's running, now it's not
Objective: To illustrate changes of states of matter and properties of certain
organic materials.
Materials: Starch, water, beaker.
Procedure: Instead of using hot gelatin to show a change in viscosity as it cools, a quicker method is to use starch and water. Obtain a small amount of starch in a beaker and add a small amount of water to it. Work the mixture with your fingers. If it is too "runny," add more starch and knead it. It is in the palm of your hand, and as you work it, the mixture will become hardened due to the driving of the water into the medium. When you stop working it, it will begin to flow since the water comes "out of hiding." You can continue to use this material for a long time. After a time, the material dries out so that more water must be added. In biological systems the fluids are in a constant state of flux, both in materials and consistency. Solids, liquids, gases, gels and colloids are frequently applied to identify these states.
DEMONSTRATION 29: Fossil hunting
Objective: To simulate a dig for fossils and other artifacts and to reconstruct
the findings.
Materials: Several different colors of jello, animal crackers, pan or glass dish.
Procedure: When studying evolution or fossils, jello and animal crackers can be used to simulate the preservation of various animals by cataclysmic events of the earth. Pour one color jello into a pan or glass dish, and when it has solidified put several animal crackers or other foodstuffs in the shape of various animals on the top. Then pour another color of jello that has been cooled over the crackers and the first layer. This process can be repeated for another layer or so. The layers can be thick or thin and can have other artifacts in them.
DEMONSTRATION 30: AIDS transmission
Objective: To show how quickly AIDS can be spread.
Materials: Test tubes, silver nitrate, salt water, fresh water.
Procedure: In advance, speak to two students privately so that the other class members have no knowledge of this set-up. Instruct one student that he/she will have the HIV virus in the fluid and that the other student selected will not engage in any fluid exchange activity. As the entire class is assembled, explain this activity as one to illustrate how easily the HIV virus can spread. This is done by giving each student a test tube half-filled with water, making sure to secretly give the student you selected to have the virus a test tube half-filled with salt water. The students are then instructed that the fluid represents the sexual secretions, and that they can mix the fluids with whomever they wish. After 5 to 15 minutes (depending upon time frame), stop the exchange activity. Then, all the test tubes are tested by dropping a drop or two of silver nitrate in each one. Those who have exchanged fluid with the "infected" person, either directly or indirectly, will clearly show the white precipitate and be labeled as a positive for HIV. Those who have not, and clearly the student who has selected to abstain, won't have any of the salt mixture and thus no precipitate. Once the positive and negatives are identified, then ask the "infected" student to identify him/herself. The immediate question the students ask is why did that person knowingly spread the virus. This leads to some very interesting discussions of why and how.
DEMONSTRATION 31: Chocolate chip mining
Objective: To demonstrate by analogy the effects of mining of the earth's resources, the
distribution of resources and land restoration.
Materials: Chocolate chip cookies, forceps.
Procedure: A chocolate chip cookie can be used to illustrate the earth's natural resources from coal to diamonds and the problems involved in land reclamation. To illustrate resource distribution, a cookie is dissected and its number of chips counted. Repeat with several other cookies and compare the numbers of each. Some cookies should have more chips and some less (make reference to the oil reserves of the Near East and the Commonwealth of Independent States formerly the Soviet Union and the coal in the U.S.). Land restoration problems can be demonstrated by trying to reconstruct the dissected cookies to their original condition. This works well in groups to see who can make the best extractions and restorations.
DEMONSTRATION 32: Right or left eye
Objective: To illustrate the favoring of one eye over the other.
Materials: Piece of plain white paper.
Procedure: Roll the paper into a tube, and holding it at arm's length, look at a person through the tube. The person being viewed will see the dominant eye.
DEMONSTRATION 33: Overturn in lakes or oceanic circulation
Objective: To illustrate the principle of spring and fall overturn due to the cold, dense water or
oceanic circulation.
Materials: Blue-eyed ice cubes, dish or small aquarium, room temperature water.
Procedure: Put the blue-dyed ice cubes in a dish that has clear, room temperature water. The cold, blue water will fall straight down and go along the bottom, pushing the warmer water to the top.
DEMONSTRATION 34: Enzyme discoveries
Objective: To show the action of an enzyme.
Materials: Jello, fresh pineapple, blender (preferably), graduated cylinders, marbles.
Procedure: Blend some of the fresh pineapple. Mix up the jello and add the pineapple to the jello. In one cylinder add only the jello and in the other put the jello-pineapple mix. Put in the refrigerator for five minutes or so. Then simultaneously drop a marble in each of the cylinders and check the speed of each marble. This should be done several times so that it is clearly seen that the plain jello started to solidify (since the marble dropped slowly).
DEMONSTRATION 35: Bobbin' raisins
Objective: To demonstrate surface interaction of the water and air.
Materials: Raisins, carbonated beverage, beaker.
Procedure: When raisins are placed in a carbonated beverage, such as 7-Up, the raisins will periodically rise to the surface on the bubbles and then fall. This is fascinating, and initiates many questions about gases and pressures.
DEMONSTRATION 36: Reproduction trick
Objective: To illustrate the rapid rate of reproduction in tapeworms and
sponges.
Materials: Milk carton to which a secret partition has been installed, cut pieces to represent little tapeworms or sponges, one big adult tapeworm or sponge.
Procedure: Attach the secret partition to the inside of the milk carton so that it is not detected. In one side put the little tapeworms or sponges. Take an adult tapeworm, in front of the class, and tear off one of its segments (or tear the sponge), and place in the other compartment. Magically shake the milk carton, flip the partition so that only the little ones come out and invert the milk carton, shaking out the young.
DEMONSTRATION 37: Transpiration and water transport
Objective: To show how evaporation of water from leaves pulls water upward
in a plant stem.
Materials: Geranium, 30 cm piece of glass tubing, 4 cm piece of rubber tubing, large container of water, scissors, ringstand, ringstand clamp, glass marking pencil, metric ruler.
Procedure: Cut off a portion of a geranium plant that includes the stem and several leaves. Put the stem into a large container of water, being careful not to get the leaves wet. With scissors under water, cut off a 1 or 2 cm piece of the stem at an angle. Place the rubber tubing over one end of the glass tubing. Immerse the rubber tubing end into the container of water and suck the water into the tube until it is about 3/4 full. Hold a finger over the end of the glass tubing while fitting the cut stem of the plant into the rubber tubing. (It will probably take two people to do this.) If the rubber doesn't fit tightly over the stem, tie a string or rubber band around the tubing, but be careful not to crush the stem. Now invert the whole assembly and secure in the ringstand clamp. With a glass-marking pencil, mark the water level and note the time. After an hour or so, note the time and mark the level again. Measure the distance between the two marks. You can calculate the volume of water transpired by using the formula, volume = r2h, where r is the inside radius of the glass tubing and h is the distance that the water has moved. The rate of transpiration can be calculated with the formula, rate = v/t, where v is the volume and t is the time.
DEMONSTRATION 38: Antigen antibody simulation
Objective: To show a simulation of an in vitro antigen-antibody reaction.
Materials: Petri dish, agar, cork borer, silver nitrate solution, sodium chloride solution.
Procedure: Pour molten agar into petri dish and allow to harden. With cork borer, cut two holes (wells) in the agar. Fill one well with silver nitrate solution and the other with sodium chloride solution. The two solutions will diffuse toward each other. When they meet, a cloudy line will result. This line represents the reaction of the antigen and antibody with each other. The closer the two wells are placed, the faster will be the reaction.
DEMONSTRATION 39: Temperature, concentration and diffusion
Objective: To show the effect of temperature and concentration on the rate of
diffusion.
Materials: Potassium permanganate crystals, 6, 250 ml beakers, water, ice cubes, hot plate or bunsen burner, clock or stopwatch.
Procedure: Fill each beaker with water. Place two or three ice cubes in beakers 3 and 4. Heat the water in beakers 5 and 6 to boiling. Add a constant amount of potassium permanganate to beakers 1, 3, and 5. Add twice as much potassium permanganate to beakers 2, 4, and 6. Do not stir or jar the beakers. Time the amount of time it takes for the purple crystals to diffuse completely throughout the water. It should be clear that the greater the temperature and concentration, the faster the diffusion.
DEMONSTRATION 40: Diffusion and tonicity
Objective: To illustrate the actions of hypotonic and hypertonic solutions.
Materials: Egg, large beaker, vinegar, Karo corn syrup, 100 ml graduated cylinder, distilled water.
Procedure: Put 200 ml of vinegar into the beaker. Add the egg. Wait 24 hours. The vinegar will dissolve the egg shell and, being hypotonic to the egg, will diffuse into the egg through the membrane. This will cause the egg to swell. Measure the amount of vinegar left to show that some has entered the egg. Put the egg into 200 ml of Karo syrup and wait 24 hours. The egg will shrivel in the hypertonic solution. Measure the liquid to show that some has left the egg. Now place the egg into 200 ml of distilled water and wait another 24 hours. It will all swell up again as the hypotonic water diffuses into the egg. Measuring the remaining water will show that some has gone into the egg.
DEMONSTRATION 41: Hypotonic and hypertonic solutions
Objective: To show the effects of hypotonic and hypertonic solutions on raw
vegetables.
Materials: Slices of raw potato, celery, carrots, cucumbers, turnips, beets, etc., culture bowls or other containers, distilled water, 10% sodium chloride solution.
Procedure: Put slices of the vegetables into containers of water and salt water. Allow to remain for several hours or overnight. Compare the pieces of vegetable from the two liquids. The vegetables in the distilled water (hypotonic) will be crisp and rigid while those in the salt water (hypertonic) will be soggy and limp. Students can be asked to explain, in terms of water concentration, why water passes into or out of the cells.
DEMONSTRATION 42: Tonicity
Objective: To illustrate the effects of hypotonic, hypertonic, and isotonic solutions on cell
models.
Materials: 3 15 cm pieces of dialysis tubing, string, 0.9% saline, distilled water, 10% saline, 3 beakers.
Procedure: Soak the three pieces of dialysis tubing in water. Tie one end of each piece. Fill each piece of tubing with 0.9% saline solution and tie the other end of the tubing. These three setups represent cells. Place the three filled pieces of tubing into the three beakers. Fill one beaker with 0.9% saline (isotonic); one with distilled water (hypotonic); and one with 10% saline (hypertonic). Allow to stand for 24 hours. Then compare the three tubes. Ask students why the size and stiffness of each tube varies. Discuss the concepts of hypertonicity, isotonicity, and hypotonicity.
DEMONSTRATION 43: Effects of smell on taste
Objective: To show that the sense of taste is dependent on the sense of smell.
Materials: Blindfold, glass of water, Life Savers candy (cherry, lemon, lime, orange) lemon extract, orange extract, almond extract, forceps.
Procedure: Break candy into small pieces. Blindfold a student volunteer. Ask him to hold his nose. Using forceps, place a piece of candy in his hand. Ask him to put it onto his tongue and suck on it but not chew it. Ask him to identify the flavor. Repeat several times, having him rinse his mouth between trials. Select the flavors of candy randomly. Now ask him to stop holding his nose. Repeat the experiment, but this time hold opened bottles of various extracts under his nose while he tastes the candy in the different trials. (Almond extract has a cherry odor.) The results usually show that students make many mistakes in identifying the candy flavors with the nose closed and that the sense of taste can be fooled by using different scents.
DEMONSTRATION 44: Smell fatigue
Objective: To show how smell receptors get fatigued.
Materials: Blindfold, vanilla extract, almond extract.
Procedure: Blindfold a student volunteer and ask her to hold one nostril closed. Hold an open bottle of vanilla extract under the open nostril. Ask the student to tell you when she thinks you have removed the bottle. After a few minutes, the volunteer's smell receptors for vanilla will have become fatigued and she will say that the bottle has been removed. At this point, hold the bottle of almond extract under her nose. She will be able to smell the new scent. Ask her to unplug the closed nostril. Hold the vanilla extract under that nostril. She will smell the vanilla because the smell receptors in that nostril have not been fatigued.
DEMONSTRATION 45: Autosomal recessive genes
Objective: To illustrate the risk of autosomal recessive genes for dangerous
or lethal conditions.
Materials: Four shoe boxes with holes cut into the sides, three mouse traps, four pieces of cloth.
Procedure: Display the four shoe boxes with holes which have been covered with cloth to prevent students from seeing the contents. Explain that one box is empty, two contain unset mouse traps, and one contains a set trap. These represent the four possible genotypes (AA, Aa, Aa, aa) produced by a couple, each of whom carries a recessive gene (Aa). Ask each student to mentally choose a box. Explain that there is a 1/4 chance that the chosen box will have a set trap (aa). Ask how many would choose to have a pregnancy with this risk. From those who would take the risk, tell them you are going to select a student to put a finger through the hole in one of the boxes. This will usually result in tension as the risk becomes more realistic. Reduce tension by asking for a volunteer. Don't actually allow a student to stick a finger into a box, but allow him/her to substitute a pencil. When the occasional pencil breaks, the risk is shown more powerfully. Students seeing this demonstration will have a better idea of the reality of the risk when two carriers marry.
DEMONSTRATION 46: Need for a thumb
Objective: To show the importance of the opposable thumb for human
activities.
Materials: Masking tape, various other objects.
Procedure: Wrap tape around the hands, securely holding the thumbs in place. Now with the thumbs no longer usable, have the student try various common activities. Suggested activities that should be very difficult to do without using the thumb include the following: tying a shoe, opening and closing a door, threading a needle, zipping a zipper, buttoning and unbuttoning a button, writing, opening a screw-cap jar, opening a pop-top can, unlocking a combination or key-operated padlock, using a fork or spoon, cutting something with a knife or scissors, applying makeup, lipstick, or nail polish, combing hair, shaving, and wrapping a package.
DEMONSTRATION 47: Sensation of temperature
Objective: To show how temperature receptors in the skin can be fatigued.
Materials: Large containers containing ice water, room- temperature water, and hot water.
Procedure: Place the hand of a student volunteer into the container of ice water. Place the hand of another volunteer into the hot water. Allow the hands to remain for 30 seconds. Now lift the two hands out of the containers and place both into the container of room-temperature water. Ask the students to tell you what temperature they feel in the second container. The first will say that the water is warm and the second will say it is cool. Everyone can see that it is the same water. This can lead into a discussion of fatigue in sense receptors and conclusions as to why two people coming into the same room often perceive the temperature to be different, or how we "adjust" to the temperature in a bathtub or hot tub.
DEMONSTRATION 48: Spill the peas
Objective: To illustrate how substances diffuse from an area of higher concentration to an area of
lower concentration.
Materials: Container of dried peas, index card.
Procedure: Fill a jar or other transparent container with dried peas. Hold an index card over the open mouth of the container so the peas will not fall out as you turn the container over and set it upside down on the demonstration table. Point out that the peas in the container are in high concentration. Lift the container from the table. The peas will rapidly run out in all directions. Relate what the students have seen to the way that molecules diffuse from an area of higher concentration to an area of lower concentration.
DEMONSTRATION 49: Chromosome numbers in body cells and gametes
Objective: To show the meanings of haploid and diploid numbers of
chromosomes.
Materials: Two shoe boxes, several pairs of socks, several single unmatched socks.
Procedure: In one box place six pairs of socks of distinctly different colors or patterns. The socks do not have to be the same sizes or styles. Mix the socks up. Label the box, "body cell nucleus." In the other box, place six single socks of the same colors or patterns as in the first box. Label this box, "sex cell nucleus." When discussing diploid and haploid chromosome numbers, open the boxes and remove the socks. Show that the body cell nucleus box contains six matched sets which represent the diploid (2N) state. The sex cell nucleus has six unmatched socks (one of each pair) representing the haploid (N) state. Many other items besides socks could be used in this demonstration. Some suggestions are wood blocks, poppit beads, earrings, gloves, pencils, coins, and cut pieces of colored sponges.
DEMONSTRATION 50: Pain receptors
Objective: To show that pain receptors are not located in the epidermis.
Materials: Thin sewing needles or insect pins, alcohol swabs.
Procedure: (Note: It is suggested that the teacher perform this demonstration on himself/herself rather than on one of the students.) Sterilize the needle and the skin of a finger by wiping with an alcohol swab and allowing to dry. Carefully slide the needle through the skin of the finger by sliding it just under the epidermis. Students can see that the needle is actually under the epidermis, but that there is not pain involved. They should be able to conclude that the pain receptors (free nerve endings) are in the dermis layer below the epidermis. The demonstration can be made more spectacular by inserting several needles into various fingers. The thicker epidermis on the fingers makes this an easy place to do the demonstration. This demonstration also shows that there are no capillaries in the epidermis as there is no bleeding when the pins are inserted.
DEMONSTRATION 51: How do our ears fool us?
Objective: To demonstrate that without the sense of sight, we cannot always determine the
direction of a sound.
Materials: Blindfold, electric buzzer or bell on the end of a long stick, 6 volt DC power supply.
Procedure: Before doing this demonstration, construct the apparatus by attaching a buzzer to one end of a large stick (at least 1 meter in length). The push-button to control the buzzer should be at the opposite end of the stick and wired to the buzzer. A long cord should lead from the push-button to the power supply. Blindfold a student and seat him in a chair in front of the class. Tell him that, when he hears the sound from the buzzer, he should point in the exact direction from which he hears the sound. The class members can keep score of right or wrong answers. Place the buzzer at various positions around the student and press the push-button for about one second. Note where the student points. About half the time, he will point in the wrong direction, sometimes completely opposite to the sound source. For instance, if the buzzer is sounded under the chair, the student will almost always point above his head, and very often the subject has difficulty telling whether the sound is in front of or behind him, particularly when the buzz is close to the floor. This demonstration can show dramatically that the ears alone cannot be relied on to determine the source of a sound.
DEMONSTRATION 52: Innate behavior
Objective: To demonstrate a type of innate (unlearned) behavior.
Materials: Knife, large onion.
Procedure: With the knife, slowly peel and cut the onion. As the students observe, many will begin to produce tears. At this point, discuss the concepts of stimulus and response. Ask the students why they produced tears. Could they control it? Why not? Discuss why this is innate behavior and not learned behavior.
DEMONSTRATION 53: Learned behavior
Objective: To demonstrate several types of learned behavior.
Materials: Hand bell, paper square puzzles, overhead transparencies of 10 nonsense syllables, 10 common words, and a 10-word sentence, overhead transparencies of 2, 4-line verses, items for creating distractions.
Procedure:
Materials: Two pieces of fairly thick paper, cellophane tape, large book.
Procedure: Loosely crumple one of the pieces of paper and set the book on it. The crumpled paper will collapse under the weight of the book. Roll the second sheet of paper into a cylinder and secure with tape. Stand the cylinder on end and place the book on top of it. The cylindrical shape will support the book in the same way that the long leg bones (femur, tibia) support the body.
DEMONSTRATION 55: Overdose
Objective: To show a model of what an overdose of a substance is like to the
body.
Materials: Funnel, ringstand with ring (or tripod), water, large beaker or basin.
Procedure: Place the funnel into the ring or tripod. Put the beaker under the setup. Pour water into the funnel fast enough so that the amount entering the funnel is the same as the amount leaving. This corresponds to a proper dose of a drug, food, water, etc. Now pour water into the funnel more rapidly than it flows out. Eventually water will spill over the top. This corresponds to an overdose.
DEMONSTRATION 56: Plant cell size and wall thickness
Purpose: To show that some plant tissues consist of small, thick-walled cells while others consist
of large, thin-walled cells.
Materials: Large carrot, sharp knife.
Procedure: Cut the carrot into thin slices. Distribute a slice to each student. Ask the students to hold the slices up to the light. They should see that there are an inner and an outer ring. The inner ring is opaque while the outer ring is somewhat translucent. The inner ring (vascular tissue-xylem and phloem) consists of small thick-walled cells, whereas the outer ring (storage tissue-cortex) is made up of large, thin-walled cells.