VEGGIES, FRUIT & SCIENCE—OH MY!

FAMILY SCIENCE SERIES

Written by Denise Scribner

These age appropriate activities are fun, sometimes wacky, and always mind stretching---taking “family quality time” to a new limit. No special equipment is needed. The activities use common household items and ingredients found in the kitchen or at a local hardware store.

The next time your family is preparing a meal why not try some of these fun activities.

VEGGIES, FRUIT AND SCIENCE, OH MY! ACTIVITIES

Electrifying Fruit

Potato Power

Paper Sack Wonder

Potato Porcupine

Banana Illusion

Invisible Ink

Banana Surprise

Striped Stalk Snack

Bean Necklace

Potato Puncture

Building With Peas

ELECTRIFYING FRUIT

What do you think citrus fruit and potatoes have to do with electricity? As it turns out, you can use this fruit and vegetable to cause an electric charge to flow.

You will need:

  • 2 ripe, juicy lemons
  • 2 ripe, juicy oranges, limes or grapefruit
  • knife
  • 3 strips of copper ¼” x 4” (0.5 cm x 10 cm)
  • 3 strips of zinc ¼” x 4” (0.5 cm x 10 cm)
  • 4 pieces of insulated wire with alligator clips at both ends
  • LED (light-emitting diode)

What to do:

  1. Have an adult cut two lemons in half. Using only half of a lemon, insert the strip of copper in one side of the lemon and the zinc strip in the other side. See exhibit #1. Make sure the metals are inserted into the juicy part and not into the white, pulpy part of the fruit. The tops of these strips are your terminals.
  2. Attach one end of the first wire with an alligator clip to the copper terminal. Attach one end of the second wire with an alligator clip to the zinc terminal. See exhibit #1.
  3. Attach the loose end of the first wire from the copper strip to the long end (positive terminal) of the LED. Attach the loose end of the wire from the zinc strip to the shorter leg of the LED. What happens?
  4. Place copper and zinc strips in two more lemon halves and put them next to the first lemon. Remove the alligator clip on the zinc terminal from the LED and connect it to the second lemon’s copper terminal. Then connect the zinc terminal of the second lemon half to the copper terminal in the third lemon half using wire 3 with alligator clips. Using wire 4 with alligator clips, attach the free (negative) leg of the LED to the zinc strip in the third lemon. See exhibit #2. What happens?
  5. If you wish, you can use other citrus fruits, such as oranges, grapefruits or limes. Which fruit works the best?

HOW IT WORKS

When you connected the wires to the LED and to the metals in the three lemons, the LED lit up. The lemon half with the zinc and copper strips in it is an electrochemical cell. When two or more cells are connected together, we call them a battery. All cells or batteries have a negative electrode or terminal. In your cell, this was the strip of zinc. Cells also have a positive electrode or terminal---in this case, the piece of copper. Zinc loses electrons more easily than copper. The acidic lemon juice acted as the electrolyte, or conducting solution. Electrolytes contain charged particles called ions, which can move between the electrodes. Acids are good electrolytes because they form ions in water solutions. These chemical changes act like an “electric pump” to push the electrons through the wire, so that an electrical current is produced.

The small bubbles seen around the copper are hydrogen gas, separated from the electrolyte. Each

cell alone produced a small amount of voltage, but not enough to light the LED. When you connected the three lemon halves together, you saw that the LED lit. Because you connected the lemons together in a series, you increased the overall voltage, allowing the LED to light. The lemon cell you made produces about 0.7 volts.

POTATO POWER

You will need:

  • Large, fresh raw potato
  • Knife
  • Two 4” (10cm) pieces of insulated copper wire
  • Wire strippers
  • 2 insulated wires with alligator clips at each end
  • 9-volt battery

What to do:

  1. Have an adult or older sibling cut the potato in half.
  2. Use the wire strippers to remove about 1” (2.5 cm) of the plastic insulation from both ends of the pieces of wire without the alligator clips.
  3. Using the wires with alligator clips, attach one of the wires to the positive terminal of the battery and the other wire to the negative terminal of the battery.
  4. Firmly embed the loose ends of the wires without clips in the potato. Make sure there is at least 1” (2.5 cm) distance between the two wires.
  5. Clip the unattached end of the wire from the positive terminal of the battery to a potato wire. Clip the loose end of the wire from the negative terminal of the battery to the second potato wire. Observe what happens.

HOW IT WORKS:

After a minute or two, you will see something green coming from the wire attached to the positive terminal and bubbles coming from the wire attached to the negative terminal. The current flow caused a chemical reaction. The green color around the positive electrode occurs because the copper in the wire is losing electrons and changing into copper ions. Copper ions have a bluish green color, and they dissolve in the liquid of the potato. The bubbles at the negative electrode are hydrogen gas, formed when electrons go into the water of the potato, causing the water to split apart, releasing hydrogen.

PAPER SACK WONDER

You will need:

  • Unripen or not fully ripen fruit
  • A lunch size paper bag

Place one piece of unripe fruit in the crisper of the refrigerator for a day or two. Place another in a paper bag and close it securely. Put it somewhere out of the way—on top of the shelf or refrigerator. Let it stand for a day or two. Taste both.

After a day or two, the fruit in the refrigerator softens—but it is not very tasty. The fruit in the paper bag softens and sweetens.

HOW IT WORKS

Fruits naturally release ethylene gas which ripens fruit. In the paper bag, ethylene gas released by fruit naturally, is trapped and becomes concentrated. This helps the fruit ripen faster. In the refrigerator, the ethylene gas is shared with the other contents in the crisper.

Bananas work a little different. They also release ethylene gas. On the counter the skin’s green chlorophyll disappears and reveals the yellow peel. The starch of the banana changes to sugar and the pectin, which holds the cells of the banana firm, breaks down making the flesh of the banana soften and easier to digest.

In the refrigerator the fruit doesn’t ripen and the skin blackens. However, once the banana is ripe it is safe to store in the refrigerator, the skin may darken but the fruit inside will remain tasty for several days.

POTATO PORCUPINE

You will need:

  • Potato
  • Spoon and knife
  • Buttons or beads
  • Grass seed
  • Cotton balls
  • Water

Make the body from a well-shaped potato. Scoop out the inside with a knife or spoon, leaving plenty of goof solid potato on the sides and bottom. Make the eyes from beads or buttons and pin them in place. Use bits of wooden matches for feet.

The porcupine bristles are grass seed. Rye is the fastest growing. Plant them on a piece of well-moistened cotton balls placed in the hollow of the potato. Water the cotton a little each day and in a few days plants will sprout into a crop of green bristles. Keep watered, and it will last 1-2 months.

BANANA ILLUSION

You will need:

  • Two bananas of equal size

Hold one banana directly above the other and ask a member of your family:

“Which arc is bigger?”The bottom arc will always look bigger than the top one.

Reverse the arcs to make the other one look bigger.

HOW IT WORKS

This is an optical illusion of comparison. An arc seems much longer if it is placed with an identical segment so that the ends are even on one side. Your brain compares the longer, top edge of the bottom arc to the shorter, bottom edge of the top arc. The illusion is convincing even when the top arc is centered over the bottom arc.

INVISIBLE INK

You will need:

  • citrus fruit juice (lemon, orange, grapefruit)
  • cup
  • paper and pencil
  • cotton swab
  • iron or lamp

It fun to send secret messages to other members of your family. The trick is to write one message, double-spaced, and then insert the secret message between the lines that are not invisible. Once you teach everyone how to make invisible ink the fun will begin.

Place a small amount of any of the citrus juices listed above into a cup.

Write a message you wish everyone to see on the piece of paper. Be sure to leave room for your secret message.

Dip the cotton swab into the cup containing juice and write your message. You may not be able to see what you have written, so concentrate on your penmanship. When the ink is dry, it will be colorless on the paper.

In order to read the secret message, the recipient must warm the paper with an iron or by holding it up to a lighten lamp light bulb that is exposed.

HOW IT WORKS

Fruit juices are part water. Fruit juices also contain carbon compounds that are colorless when dissolved in water. When heated, the carbon compounds break down producing carbon---which you might know as being black. This chemical reaction results in leaving a black stain wherever the fruit juice was applied. Once the secret message is revealed it will not become invisible again.

BANANA SURPRISE

You will need:

  • Ripe banana
  • Thread
  • Needle

Everything these days is coming pre-packed, pre-sliced and ready to eat. Imagine the surprise your family will have when they peel a banana and it is already sliced into pieces. Follow the instructions below to prepare the banana before it is eaten.

Thread a needle with a long piece of thread.

Insert the threaded needle into one of the

ridges on the banana peel and push it through

under the skin to the next ridge.

Pull the needle through, leaving a few inches

of the tail end of the thread sticking out of the banana.

Reinsert the needle into the same hole, and run it

under the skin again to the next ridge. Pull the

needle through again, leaving the thread in both

the first and the second holes.

Continue threading the banana until the needle comes out of the first hole you made. The thread now circles the banana under the skin. Gently pull the two ends of the thread, slicing the banana on the INSIDE.

Repeat the threading instructions to make more cuts inside the banana. You may want to make up to 3 or 4 for the best results. Wait a few moments, then give the banana to a member of your family after waving your hand over the banana commanding it to be sliced “magically.”

HOW IT WORKS

Juices that flow from the banana reseal the small hole made when you inserted the needle. This makes the holes almost invisible. By pulling the thread through the same holes you created, you have eliminated the evidence that anything has been done to the banana.

It is recommended that the “pre-sliced” banana be eaten within a day after you have completed the instructions. This way the banana will be fresh and tasty.

STRIPED STALK SNACK

Plant stems have an important job---which is to carry water from the roots to the leaves of the plant. Try this fun activity to see how it happens with celery.

You will need:

  • Two Celery stalks with leaves
  • Water
  • Food coloring
  • Two glasses
  • Vegetable peeler
  • Knife
  • Peanut butter or cream cheese (your choice)

Fill each glass with water and place a few drops of food coloring into each one. Remember, make each glass a different color. For instance—glass #1 is red and glass#2 is blue.

Cut the leaves off one stalk of celery and place it into glass #1. Place another stalk of celery (with leaves still on) in glass #2. Check the glasses every 10 minutes or so to see what is happening.

When the water has moved all the way up the stem (in about one hour), remove the celery stalks from the glasses. Use the vegetable peeler to shave away the outer surface of the celery.

Under adult supervision, use the knife to cut off each end of the celery stalk in glass #1. What do you see?

Which celery stalk had the water reach the top of the stem faster? Why? Does it have to do something with the leaves (which do the work of the plant known as photosynthesis). Which parts of the stem have the most food coloring? Be sure to record your findings in your science log notebook.

After you are finished looking at the celery, rinse the stalks and spread peanut butter or cream cheese down the middle. This makes a healthy and tasty snack with a little extra colorful decoration thrown in. You can make several striped tubes to serve more peanut butter or creamed cheese snacks by repeating the experiment with several stalks of celery in each glass of colored water.

HOW IT WORKS

The long narrow tubes in the celery stem are called xylem. They are hard to see in the plant stem since they are the same color as the stem itself. The xylem carries water to the top of the plant by capillary action. Capillary action carries water from the soil up through the roots of plants and trees. The liquid rises through the xylem hollow tubes that are tiny enough to produce the required capillary force. The food coloring added to the water stains the inside membrane of these hollow tubes, making them visible.

DOING MORE

See if you can find the xylem in other vegetables likes white radishes, carrots, or scallions. Use red or blue food coloring so you can see it in the vegetables.

Two Tone Flowers: Fill two glasses with water. Color the water in one glass with red food coloring and the other with blue food coloring. Carefully split the stem of the white carnation. Place half of the stem in one glass, the other half in the other glass. After a few hours you will find that you have a two-colored blossom.

BEAN NECKLACE

This craft will take a little preparation time but it has great results.

You will need:

  • Various kinds of dried beans (enough for a necklace)
  • 1 or more colors of food coloring
  • several small bowls and spoons
  • a strainer
  • paper towels
  • plastic bag
  • needle and thread

Coloring the beans:

Fill each bowl halfway with ¼ cup of water and place a few drops of food coloring into the water. Use a separate cup for each color.

Add beans to each bowl of colored water. The colored water should cover them. If needed, add more water. Soak the beans for about 3 hours.

After three hours, pour the bowlful of water and beans into a strainer held over the sink. Rinse the beans and spread them out on several layers of paper towel.

Let the beans dry for about two hours. Put the beans into a plastic bag for storage until you are ready to thread them.

Making the necklace:

Measure a piece of thread by placing it around your neck and allowing it to drop down to the length desired. Do not cut the thread. Hold the thread at the length desired then double back on itself. Now cut the thread. You have twice as much as you need.

Thread a needle, pulling it halfway through the needle’s eye and knotting it at the end. Now you have a double thread (which is stronger than just a single thread). Then string the beans onto the thread making a necklace. Be creative with your colors and type of beans when stringing the necklace. Tie off the thread

HOW IT WORKS

Beans absorb water so that the tiny new plant inside can start to grow. The food coloring in the water stains the fiber inside and the skin covering the bean turning it a different color. Since you dried the bean and did not plant it into the ground, the bean will not sprout.