Chemical and Human Resources, Part II

Lynne Martin, Maxfield Science, Math & Technology Magnet School, St. Paul, MN
Kathy Scoggin, Marcy Open School, Minneapolis, MN

Our venture into history coupled activities for both younger and older students in a unit on chemical and physical changes. The younger children pursued an instructional unit on "Mystery Powders." We selected a several scientists appropriate to the unit and told stories about the scientists during the activities.

The older students conducted research to learn about these and other scientists (both personal and professional items of interest). We had them look especially for how they could actually become that scientist through role-playing. They also looked for a lab activity they could do with younger students to illustrate that scientist's work. They made a "big book" of their scientists. Finally, the older children visited the younger students, set up learning stations for them, conducted historical scientific activities with them, and shared their big book -- while playing the role of the scientist throughout the activity.

Possible extension activities include:

Level: Grades K-6

This curriculum module was developed as part of a project sponsored by Sci-Math-MN and The Bakken Museum and Library. Click to see a directory of other modules using history and philosophy of science.

Other Scientists

There are others that you can find out about and research also. To find historical scientists appropriate to the unit content or skills:

Activities for Younger Students Led by Older Students

Set-up involves five stations to observe chemical and physical changes and the idea of elements versus compounds, complementing the earlier activities of the younger students:
  1. Yeast (temperature change and gas production during chemical change)
  2. Red Cabbage Juice (acid-base color indicators of chemical change)
  3. Inflating Balloon (physical change)
  4. Vitamin C (nutrient testing color change for chemical change)
  5. Marshmallow Models: Compounds and Elements (Dalton's atomic models)

STATION #1 -- YEAST
OBSERVATION AND CHEMICAL REACTION

**Remember to talk about observation as a necessary skill in science. Persistence and accuracy are very important also.

Remember that a chemical reaction occurs when we see a temperature change, a solid coming out of a solution, a color change, or gas production. In this case look for gas production in both experiments and a temperature change in the yeast and peroxide combination.

You have two experiments to do with your students:

  1. Have your students put water into each of the three test tubes. Have the one on the left be for cold water, the middle one for warm water, and the one on the right for hot water - from the black tea pot.
  2. Have the students measure 1/2 teaspoon of the yeast and sugar mixture into each of the three test tubes. (Use the funnel for pouring more easily.)
  3. Put a thumb over the top of the test tube and gently wave the liquid back and forth to mix it a little. Set aside while you do the other experiment.
  4. Have the students measure a yellow spoonful of yeast into a white film container. Add a blue spoonful of hydrogen peroxide and watch the reaction. Be sure to pick up the container also and feel the heat as the reaction occurs. A gas (oxygen) is being produced in the bubbles and water is being left behind with the yeast. Hydrogen peroxide is a compound of hydrogen and oxygen.
  5. Look back to the yeast and sugar mixture in the test tubes. Keep watching until you can observe the differences in the reactions that the different temperatures of water cause. Talk with the students about using yeast in a recipe and how you would know what temperature of liquid to try and add to yeast for the best results.

Teacher's Notes for Station #1 -- Yeast

Materials:

Procedures:
Experiment 1:

  1. Mix a equal mixture of sugar and yeast.
  2. Pour 1/2 teaspoon of the mixture into each of three test tubes.
  3. Place the test tubes next to each other (we used 1 test tube holder per group). Organize left to right for cold, warm and hot water - or label.
  4. Pour 1/2 Tbsp. of the appropriate temperature of water into each test tube. Swish gently back and forth to mix a little. Observe and describe then set aside while you do experiment #2.
  5. Go back and observe and describe again and then make hypothesis regarding the use of yeast and appropriate water temperature in baking. **This works best if you have at least 10-15 minutes to let the reaction happen before making final observtions.
Experiment 2:
  1. Place 1/4 teaspoon dry yeast in the film container.
  2. Pour 1/2 teaspoon hydrogen peroxide onto the yeast.
  3. You will see bubbling as the oxygen is released from the hydrogen peroxide mixture (H2O2). Yeast catalyzes the breakdown of hydrogen peroxide into oxygen and water. You will also be able to feel the heat released in the reaction through the sides of the film container.

STATION #2 -- RED CABBAGE JUICE
CHEMICAL REACTION STATION - ACID/BASE INDICATOR

A chemical reaction has occurred when we see temperature change, formation of a precipitate, color change, or gas production. In this case look for color change.

  1. Have the students put about 1/2 inch of the purple indicator liquid in each of three test tubes. Use eyedroppers to do this.
  2. Explain about acids and bases being opposites. Tell them that vinegar is an acid and baking soda is a base.
  3. Using the eyedropper have the student put several drops of vinegar into the test tube on the right. Notice the color change. Compare to the tube in the middle which always stays the same with nothing added to it.
  4. Using their fingers they should put a pinch of baking soda in the test tube on the left. Notice the color change.
  5. Challenge them to figure out a way to change each of the test tubes of liquid back to their original colors. (Help them with ideas if necessary.)

Teacher's notes for Station #2 -- Acid-base Indicators

You will need:
  1. Soak torn up cabbage leaves - 3 or 4 leaves is plenty - in hot water ( pour boiling water over) in the bucket for up to 1 hour. This will be your indicator solution.
  2. Divide your indicator equally among 3 test tubes ( or cups). Label one cup as your 'control'. Place this cup in the center of the three and do not add anything to your control. Add a small amount of vinegar (a few drops) to one of the tubes of indicator and swirl. Compare the color of this indicator to the color of your control.
  3. Now add a small amount of baking soda (a pinch) to the other tube of indicator and swirl. Compare the color in this tube to your control.
  4. If either of your indicators changed color, (and they should have !) challenge the students to figure out what to add to it to make it turn back to the color of the control.

STATION #3 -- INFLATING BALLOON
PHYSICAL CHANGE STATION

  1. Explain that a physical change occurs when something changes from one form to another form. Discuss water: it can be a solid, a liquid, or a gas. Ask the students to think of examples of water in each of these forms.
  2. Have students place about 1/3 of an inch of water in the test tube.
  3. Cover the test tube with a balloon.
  4. Carefully hold the test tube over the lit candle until the balloon begins to inflate.
  5. Talk about why this happened. Have them try to tell you first (The water molecules heated up and began to bounce around and take up more space than they had before.)

Teacher's notes for Physcial Change Station #3

Materials: Procedure: The children place about 1/3 of an inch of water in the test tube. Cover the test tube with a balloon. Hold the test tube over the lit candle until the balloon begins to inflate.

STATION #4 -- TESTING FOR VITAMIN C
CHEMICAL REACTION AND THE BIG BOOK OF SCIENTISTS

**Remember to talk about a chemical reaction as happening when we see a temperature change, a color change, gas production, or the formation of a precipitate (a solid from a solution).

  1. Have students measure about an inch of the starch and iodine indicator solution in the test tube (pour from the measuring cup to do this easily).
  2. Add drops of the Vitamin C solution one at a time - with the eyedroppers - until you get the color to change.
  3. Discuss the color change as the evidence of a chemical reaction.
  4. Share the book. The 'scientists' need to be the page turners so that the least amount of wear and tear happens.

Teacher's notes for Chemical Reaction Station #4 (Testing for Vitamin C)

Materials:

Procedure:

  1. First make a stock starch solution using 1/2 teaspooon cornstarch and 1 cup water in a saucepan. Warm over low heat until the cornstarch is completely dissolved. Pour into a jar, label and cover. This will keep for a few days in the refrigerator.
  2. To make the test solution put 1 teaspoon of the stock starch solution into a jar with 1 cup of water and 4 drops of iodine. Label. This will be blue-black due to the reaction of starch with iodine.
  3. Test the test solution using the vitamin C. Dissolve several vitamin C tablets in 1 cup of water ( I used about 7 1000 mg tablets.) Put 1 or 2 tablespoons of the starch plus iodine test solution into a test tube. Add 1 drop of the vitamin C solution. The mixture should become colorless as the vitamin C reacts with the iodine. -- if not add more drops of the vitamin C solution as needed.
  4. **You can also test food samples such as tomato juice, orange juice, pickle juice, lemonade powder, Tang, etc.

STATION #5 -- MARSHMALLOW MODELS
ELEMENTS AND COMPOUNDS

  1. Have students glue on one color of small marshmallows to the first section of the chart to represent element A. No more than 5 marshmallows are needed.
  2. Glue two large white marshmallows to the second section to represent element B.
  3. In the third section glue two large white marshmallows and four small (the same color as was used in the first section) - but they should not touch at all.
  4. In the last section glue two large white marshmallows and then glue two small colored - same color as before - right next to the big ones to represent a compound.
  5. Talk over the theory with the group and then glue the white sheets which explain Dalton's Atomic theory on to the back of their sheets.
*Have everyone write their names on their sheets please.

Teacher's notes for Station #5

Dalton's atomic theory included the following ideas:
  1. All elements are composed of tiny indivisible particles called atoms.
  2. Atoms of the same element are identical. The atoms of any one element are different from those of any other element.
  3. Atoms of different elements can combine with one another in simple whole number ratios to form compounds.
  4. Chemical reactions occur when atoms are separated, joined, or rearranged. However, atoms of one element are not changed into atoms of another by a chemical reaction.

Materials:

Procedure: Marshmallows are glued onto the columns to represent the various atoms:
  1. one color of small marshmallows as element A
  2. large white marshmallows as element B
  3. a mixture of the small (same color as in the first column) and large white in the third column - make sure they do not touch
  4. compounds in the fourth column -- illustrated by two small colored marshmallows connected to one large
The atomic theory sheets were copied for each student and glued on to the reverse side of the chart to be discussed.
Link to activities for younger students.