Sticky Situation

Learning Objectives: Students learn that some mixtures can be separated using chemical properties.

GRADE LEVEL SNEAK PEAK inside …

3–8

ACTIVITY

SCIENCE TOPICS Students make and test glue, which they make from mixing milk and vinegar. Atoms and Molecules

Chemical Reactions STUDENT SUPPLIES Industrial Chemistry see next page for more supplies

non-fat powdered milk vinegar PROCESS SKILLS sturdy paper towels or coffee filters baking soda, etc…. Describing and Defining

Measuring ADVANCE PREPARATION

see next page for more details

GROUP SIZE Make milk from milk powder Fill bottles with vinegar, etc…. 2–3 OPTIONAL EXTRAS

DEMONSTRATION

Glue Show and Tell (p. F - 40)

EXTENSIONS Glue Inventions (p. F - 44)

TIME REQUIRED

Advance Preparation Set Up Activity Clean Up

10 minutes 10 minutes 30 minutes 10 minutes

Sticky Situation F - 37 Chemistry in the K–8 Classroom Grades 3–8 2007, OMSI

SUPPLIES

Item Amount Needed non-fat dry milk powder 1 cup per class water 3–6 cups per class vinegar ¼ cup per group baking soda 1 tsp per group pop-top squeeze bottles (e.g., water or sports drink) 2 per group plastic cups 3 per group wooden craft sticks (e.g., popsicle sticks) 1–2 per group plastic spoons 1–2 per group strainers several for class to share scraps of paper 5–8 per group

For Extension or Demonstration supplies, see the corresponding section.

ADVANCE PREPARATION

Supplies Preparation

Milk Solution: ‰ This recipe makes a total of 4 cups of milk solution, or enough for 16 groups. Adjust the recipe if you have more groups than this. ‰ Add 1 cup of non-fat dry milk powder to 3 cups of water. Mix well. ‰ Fill pop-top squeeze bottles with about ¼ cup in each bottle. ‰ Label these bottles “milk.”

Vinegar ‰ Fill pop-top squeeze bottles with about ¼ cup of vinegar. ‰ Label these bottles “vinegar.”

Baking Soda ‰ Fill plastic cups with about 1 teaspoon of baking soda. ‰ Label these cups “baking soda.”

Sticky Situation F - 38 Chemistry in the K–8 Classroom Grades 3–8 2007, OMSI

SETUP

For each group ‰ milk in pop-top squeeze bottle ‰ vinegar in pop-top squeeze bottle ‰ baking soda in plastic cup ‰ 2 empty plastic cups ‰ 1–2 plastic spoons ‰ 1–2 wooden craft sticks ‰ sturdy paper towel or coffee filter ‰ 5–10 scraps of paper

At a central location (or with the teacher) ‰ several strainers for class to share ‰ towels and sponges for clean up

INTRODUCING THE ACTIVITY

Let the students Students will use milk and vinegar to create a glue that can stick speculate before paper together. offering answers to any questions. The What does glue look like? What does it feel like? Or smell like? answers at right are Glue is sticky. Some glue is liquid when you use it, but it dries hard. provided for the teacher. Some dries like a thin skin. Some glues are stronger than others. Some glues have a strong smell. Choose questions that are Are all glues the same? How are they the same? How are they different? appropriate for Glues are not all the same. Examples include: white liquid school your classroom. glue, clear or bluish school glue, yellowish liquid mucilage glue,

solid glue sticks, strong-smelling industrial-strength glue, epoxy that must be mixed, fast-drying superglue, spray glue, hot-glue-gun gel sticks, yellow wood glue, slow-drying book-bonding glue, denture glue, etc.

Why are there so many different kinds of glue? Each glue is designed for a different purpose. Each surface (paper, wood, cloth, glass, plastic, fabric) needs a different kind of glue to stick together. Some glues are permanent (super glue) but some are temporary (Post-it Notes, cereal boxes). Some glues need to be waterproof (denture glue).

CAUTION: Students should never put lab supplies in their mouths. Even if lab supplies are foods, they may be contaminated by other items in the lab.

Sticky Situation F - 39 Chemistry in the K–8 Classroom Grades 3–8 2007, OMSI

TEACHER DEMONSTRATION

Glue Show and Tell Bring a variety of different kinds of glue to show students. Discuss the properties of each glue and how it is specially designed for its purpose. You can also work with students to create categories for the different glues. Some examples are listed to help you get started.

Non-Toxic Waterproof Weak vs. Strong glue stick super glue Post-it Notes white glue fabric glue stickers clear glue wood glue labels Post-it Notes stickers super glue stamps epoxy rubber cement denture glue

Sticky Situation F - 40 Chemistry in the K–8 Classroom Grades 3–8 2007, OMSI

CLASSROOM ACTIVITY

Have students follow the Scientific Procedure on page F - 47, working in groups of 2–3. Below are suggestions to help the teacher facilitate the activity.

NOTES

This handout

is on p. F - 47.

Running Suggestions

‰ When students mix the milk and vinegar together, they will notice a strong “sour milk” smell. This reaction is similar to the reaction that occurs when bacteria spoils milk, so it makes a similar smell. ‰ Test the experiment yourself with a paper towel or coffee filter. If your filter does not work well (it filters too slowly or it breaks), try other methods. Coffee filters are stronger, but also tend to filter slowly. Paper towels will filter faster but are weaker. ‰ To minimize messes, encourage students to do all their experiments on a cafeteria tray.

You may want to have students answer questions and draw pictures on separate pieces of paper so they will have more space. Ongoing Assessment

‰ Encourage students to make careful observations of what happens to the milk as vinegar is added. ‰ Where do the solid parts come from? (The milk is changing from liquid to solid.) ‰ Is all of the milk changing to a solid? (No, some parts stay liquid.)

Sticky Situation F - 41 Chemistry in the K–8 Classroom Grades 3–8 2007, OMSI Safety and Disposal

‰ All materials may be thrown in the trash when finished. ‰ Refrigerate unused milk solution and use within two weeks.

CAUTION: Students should never put lab supplies in their mouths. Even if lab supplies are foods, they may be contaminated by other items in the lab.

CLASSROOM DISCUSSION

Ask for student The sticky substance students made in this activity is able to glue observations and paper together. Although it may not seem sticky at first, once it explanations. Let the students guide dries, the paper should stay together very well. the discussion and present their What happened when vinegar was added to the milk? hypotheses before It clumped, or became solid (curdled). It smelled bad, like spoiled discussing explanations. milk. A chemical change occurred. The liquid milk separated into solid white curds and clear liquid whey. Choose questions that are What happened when baking soda was added to the curds? appropriate for your Bubbles appeared. The baking soda (a base) reacted with the classroom. vinegar (an acid) to produce a gas (carbon dioxide).

Have you heard the rhyme “Little Miss Muffet sat on her tuffet eating her curds and whey…”? Have you ever eaten curds or whey? Most cheeses are made from the curds of milk. Cottage cheese is the most obvious example. Spoiled milk also forms solid curds. Whey is the liquid part of milk. Low-fat milk and non-fat milk have more whey than whole milk.

What would happen if you change the formula (or recipe) for this glue? For example, what if you use less vinegar in the formula? Let students predict what they think will happen in different scenarios. The glue might be more sticky, less sticky, more liquid or more solid. The glue could dry really fast or dry very slowly.

Record students’ suggestions for use in Extension A. This extension allows students to experiment in creating different glue recipes.

Sticky Situation F - 42 Chemistry in the K–8 Classroom Grades 3–8 2007, OMSI

EXPLANATION

This background information is for teachers. Modify and communicate to students as necessary.

In this activity, students discovered that milk and vinegar react to create a sticky solid. This solid can be used to make paper stick together.

What’s in Milk Milk is a mixture of water, milk sugar (lactose), fats, protein, and small amounts of other nutrients, such as vitamins and minerals. Milk is a special kind of mixture known as an emulsion since it has several components that do not dissolve in one another. The fats and proteins are in tiny droplets that are suspended in the water of the milk. Other emulsions students may be familiar with are mayonnaise and some salad dressings. Students can look on the ingredient labels for items listed with the description “added as an emulsifier” or “added as a stabiliser.” An emulsifier is anything added to make two liquids that won’t dissolve (like oil and vinegar) to stay mixed together.

Separating Milk Protein The major protein in cow’s milk is called casein. Casein, like other proteins, has a three-dimensional shape that determines its behavior, its characteristics, and its properties. If the shape of the protein changes, then the properties of the protein will change. When the shape of a protein is changed, it is called denaturing the protein. Denatured proteins can look and act differently.

One way to denature a protein is through heat. The protein in egg whites (called albumin) turns from a clear liquid to a white solid when it is heated. Another way to denature a protein is by adding an acid. When students add vinegar (an acid) to the milk, the casein in the milk changes its shape and becomes denatured. The denatured milk protein turns from a liquid to a solid. This solid part of milk is also called curds; the liquid part of milk is called whey.

Fresh milk is not acid or a base, it is neutral. As milk ages, bacteria can grow in the milk, and these bacteria start to produce acid. This is why old milk spoils and has solid parts in it.

Students filter out the solid casein to use as glue. The casein still has traces of vinegar on it, so students add baking soda (a base) to neutralize their glue. Vinegar and baking soda react to produce new chemicals, including water and carbon dioxide gas. The bubbles students see is the carbon dioxide gas, the same as we exhale from our lungs and that makes up the bubbles in soft drinks.

For more information about acids, bases, and the pH scale, see the activity Of Cabbages and Kings.

Sticky Situation F - 43 Chemistry in the K–8 Classroom Grades 3–8 2007, OMSI Polymer Chemistry Proteins are long molecules made of smaller repeating units and are a kind of polymer. Other naturally occuring polymers are DNA and starch. In this activity, students used this polymer as a glue. Regular white glue is also a polymer called polyvinyl alcohol. Industrial chemists often create new polymers in the development of glues, plastics and fabrics.

EXTENSIONS

Extension A: Glue Inventions Students experiment with different ingredients and different ratios of ingredients to invent new glues. They test their new glue solutions and compare them to store glue.

Extra Supplies ‰ different kinds of milk (whole milk, low-fat milk, non-fat milk, soy milk) ‰ different kinds of acid solutions (vinegar, lemon juice, soda) ‰ measuring spoons ‰ various scraps of different kinds of paper (construction paper, tissue paper, cardboard)

Extra Instructions ‰ Students can follow the same procedure as the main activity, just substitute different solutions for the milk and vinegar. ‰ Students can change the recipe in the main activity and measure different amounts of milk and vinegar. ‰ Make certain that students write down their recipes. ‰ Students should test their glues on paper and compare the usefulness of their glue to traditional glues.

Explanation What students are doing in this extension is similar to what chemists do in any industry when they are trying to create something new. Often, chemists start with a recipe that works for one purpose and adjust that recipe to adapt it for a new purpose.

Sticky Situation F - 44 Chemistry in the K–8 Classroom Grades 3–8 2007, OMSI

CROSS-CURRICULAR CONNECTIONS

TECHNOLOGY Pasteurization What is pasteurization? Who discovered it? How has it impacted society? Before refrigeration, milk was a common carrier of tuberculosis bacteria. Have students read about the history of tuberculosis or interview senior citizens about tuberculosis in their generation or their parents’ generation.

ART Collage Have the students use their glue to make collages with different colors and textures of paper. They can also make collages using pictures from magazines.

RESOURCES

Web – http://solutions.3m.com/en_US/ The Minnesota Mining and Manufacturing (3M) Company started out making sandpaper and now makes every type of tape, label, glue, and sticker imaginable. If you are having trouble thinking of different kinds of adhesives, take a look at their product line.

Web – http://www.3m.com/intl/uk/3mstreetwiseuk/teachers_landing_page.htm The 3M Company has a curriculum about safety that is free for teachers. Use this link to request teaching materials.

Cleeland, Holly, Glue & Go Costumes for Kids: Super-Duper Designs with Everyday Materials Using just a glue gun and easy-to-find materials (fabric, cardboard boxes, plastic cups, foam core), you can make unique costumes. Book includes full-color photographs.

Wolf, Allan, Haiku Stickies: 100 Haiku to Write & Leave Behind A pad of partial haiku poems is included with this book. Each poem has blank spaces for children to fill in; earlier in the pad, they’ll need to add only a word or two, while the later haiku will have kids writing nearly from scratch.

VOCABULARY

acid: a compound with an excess of available hydrogen ions; often sour in taste

albumin: protein found in egg whites

base: a chemical compound that takes up hydrogen ions; often bitter in taste

Sticky Situation F - 45 Chemistry in the K–8 Classroom Grades 3–8 2007, OMSI casein: protein found in cow milk curds: the solid part of milk denature: to cause a protein to change its shape; when a protein changes its shape and therefore loses its properties dissolve: when the molecules of one substance separate and become completely surrounded by the molecules of another substance emulsifier: something added to two liquids that normally won’t dissolve to keep them uniformly mixed emulsion: a suspension of tiny droplets of one liquid in a second liquid; the two liquids do not normally dissolve in one another neutral: a chemical that is neither acid nor base; typically has a pH of 7 polymer: a large molecule made up of many repeated molecules whey: the liquid part of milk

Sticky Situation F - 46 Chemistry in the K–8 Classroom Grades 3–8 2007, OMSI Sticky Situation SCIENTIFIC PROCEDURE

1. Add 3 spoonfuls of milk into the plastic cup. • Describe the milk. What does it look like? What does it smell like?

2. Add 3 spoonfuls of vinegar into the cup with the milk.

3. Mix the milk and vinegar together with a wooden stick. • What is happening to the milk?

• What does it look like? What does it smell like?

4. Place a paper towel or coffee filter inside a strainer. Put an empty plastic cup under the strainer.

5. Carefully pour your mixture into the strainer. Wait for the liquid to filter through the strainer and into the cup.

6. Gently lift the paper towel or coffee filter out of the strainer. • Describe the solid you collected. What does it look like? How does it feel?

7. Sprinkle a pinch of baking soda onto the solid. • What happens?

8. Use the glue you made to stick paper together. Leave the paper alone until the glue is dry.

9. Clean up your area. • Follow your teacher’s directions.

SUPPLY WORKSHEET

This worksheet is also available online at www.omsi.edu/k8chemistry.

Sticky Situation Recommended group size: 2–3

Number of Students: Number of Groups:

Supplies Amount Needed Supplies Supplies on Hand Needed non-fat dry milk powder 1 cup per class water 3–6 cups per class vinegar ¼ cup per group baking soda 1 tsp per group pop-top squeeze bottles 2 per group (e.g., water or sports drink) plastic cups 3 per group wooden craft sticks (e.g., popsicle 1–2 per group sticks) plastic spoons 1–2 per group strainers several for class to share scraps of paper 5–8 per group Extension A different kinds of milk (whole milk, ¼ cup each milk per group low-fat milk, non-fat milk, soy milk) different kinds of acid solutions ¼ cup each acid per group (vinegar, lemon juice, soda) Teacher Demonstration Glue Show and Tell variety of different glues 1 or more each kind

Sticky Situation F - 48 Chemistry in the K–8 Classroom Grades 3–8 2007, OMSI