Objective Students will gain an understanding of how the properties of a solid material can affect how it interacts with water.

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Willa Greer
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1 OOBLECK! (1 Hour) Addresses NGSS Level of Difficulty: 4 Grade Range: K-2 OVERVIEW Students will examine the behavior of different types of solids when they are dissolved in water and explain those behaviors by examining the properties of the solids. Topic: Oobleck! Real World Science Topics: An exploration of the nature of dissolution and mixing An exploration of molecular nature of various common solids Objective Students will gain an understanding of how the properties of a solid material can affect how it interacts with water. Materials Needed for Each Team of 2-4 students: sand salt sugar water a large bowl corn starch Additional Materials: laundry starch glue Preparation: This could be a messy activity so make sure that the work area is covered in newspaper NGSS Three-Dimensions Science and Engineering Practices Constructing Explanations and Designing Solutions Make observations (firsthand or from media) to construct an evidence-based account for natural phenomena. Disciplinary Core Ideas PS1.A: Structure and Properties of Matter Different kinds of matter exist and many of them can be either solid or liquid, depending on temperature. Matter can be described and classified by its observable properties. Different properties are suited to different purposes. Crosscutting Concepts Energy and Matter Objects may break into smaller pieces and be put together into larger pieces, or change shapes.

2 STEPS FOR OOBLECK! 1. Warm-up Activity: Hold up a small rock the size of a jelly bean. Ask students to describe what the rock is made of. Guide them towards the proper answer by asking what would happen if you cut the rock in half. And then what would happen if you cut one of the halves in half. Would you be able to keep doing that forever? (No). Tell them that rocks, and everything else that you can see or feel, is made up of tiny particles called atoms. Inform them that there are many different types of atoms, and that many of them are attracted to each other, or to atoms of other types. 2. Divide students into groups of 4 and distribute the materials needed for this lab, as well as the handout. 3. Have students look at each of the different solids that will be mixed with water in this activity and record a description in the handout. This should include a description of the color of the material, whether it is liquid or solid, and its texture. 4. Have students first pour the white sand into the water and observe what happens to the sand. Students should note whether the sand dissolves or not on the handout. 5. Next, students should pour sugar into the water and stir it until it is completely dissolved. Have them record their observations of what happens when the sugar particles are dissolved in water. 6. Students should then perform the same action with salt and record their observations. 7. Students should then follow the instructions to create oobleck. To make oobleck you can simply mix one cup of water with 1.75 cups of cornstarch and stir for 5-10 minutes. Ask students to describe their initial impressions of oobleck. Is it more like a liquid or a solid? Have the students slowly put their hand into the oobleck. It should move downward as if it were in a very thick syrup. Have students then slowly remove their hand. Once they have done that have them hit the oobleck. Was it more like a solid or a liquid? Oobleck is a fascinating material, so encourage students to squeeze it, mold it, and otherwise explore its bizarre properties.

3 8. Wrap-Up Activity: Lead a discussion of the properties of the various solids that lead to their observed behaviors when they were dissolved into water. Ask students what they remember about atoms from the introductory discussion at the beginning of the activity. Remind them that atoms are the small particles that make up everything and that these particles are attracted to each other. Tell them that the way the materials behave when they are mixed in water is related to how much the atoms are attracted to water compared to each other. Ask the students which of the materials were most attracted to water and how they know. They should recognize that sugar and salt were, because they dissolved easily in water. Tell that that oobleck is made of long chains of atoms called polymers, and that scientists think that it is the interaction between these chains that causes oobleck to have such strange behaviors. Oobleck Extension Activity There are other non-newtonion fluids that students might be interested in exploring. Have students make glurch by mixing 1 cup of laundry starch, a pinch of salt, and a blob of white glue. Students should compare the physical properties of glurch and oobleck. Have them explore which is more fluid, which is more elastic, and other properties.

4 OOBLECK! BACKGROUND INFORMATION Why do some solids dissolve in water and others do not? How does polarity effect the dissolution of salt in water? Whether a solid dissolves in water or not is determined by its molecular structure. When the molecules of a substance are more attracted to water than to other atoms within the molecule then the molecule will dissolve in water. The hydrogen and oxygen within water are bonded very tightly together, but because of the way they are arranged in the water molecule, the water molecule is polar. This means that is has a slightly negative charge on one end, and a slightly positive charge on the other end. This behaves somewhat like a magnet with the positively charged end attracting negatively charged ions and vice versa. Ions are charged particles. Table salt is an ionic compound that is made of sodium and chloride molecules that are bonded together in a crystalline lattice. If you could look at the atoms in a salt crystal you could see that they are spread out at regular intervals. Under normal circumstances sodium has one too few electrons, and chlorine has one too many. This gives sodium a positive charge and chlorine a negative charge. Like a magnet they are attracted. But when they are put into water the sodium ions are more attracted to the negatively charged end of the water molecule than they are to the chlorine ions. Similarly the chlorine ions are more attracted to the negatively charged side of the water molecules. This causes the salt particles to break up. A glass of salt water is actually a glass of water with sodium and chlorine ions scattered throughout. What about sand and sugar? Sand and sugar are covalently bonded. In covalent bonds the atoms share electrons, and are usually much more closely bound to each other. The silicon and oxygen atoms that make up most of the sand particles are attracted to each other much more than they are to the water, so they do not dissolve. Sugar does dissolve, but unlike salt, it does not break down into its constituent elements. A sugar particle is made up of a variety of molecules, some of which, like water, are polar. These polar molecules are more attracted to water than they are to each other. However, the carbon, oxygen and hydrogen that make up the sugar molecules stay firmly bonded to each other, even when dissolved in water. If you could look at dissolved sugar under an extremely powerful magnifying glass you would not see a sea of individual ions like dissolved salt. You would instead see a number of multiatomic sugar molecules.

5 OOBLECK! BACKGROUND INFORMATION What about oobleck? Oobleck is a mixture of corn starch and water. These mix to form a colloid which is a type of mixture where very small particles are suspended with in a liquid. This may sound a lot like the solution of sugar or salt, but in a colloid there are still particles much larger than single molecules, although they may not be visible even under a standard microscope. Oobleck itself is a non-newtonion fluid, which means that it doesn t behave like normal fluids do. Oobleck behaves like a solid when it is stressed by pressure or fast movement. On the other hand if you simply pour it out of the bowl it will flow like a very thick liquid. Scientists are still unsure what causes oobleck to have such strange properties. (salt/sugar) (oobleck) The difference between colloids and dissolved solids can be seen in the diagram. In dissolved solids like sugar and salt the solids break down into individual molecules or ions (black). In colloids some of the molecules remain bonded to each other forming larger particles (white chains). The particles may still be too small to see with the naked eye. Key Vocabulary: Atom: the smallest particle of an element that retains its unique properties Molecule: a group of atoms that are bonded together and have unique properties

6 TEACHER HANDOUT FOR OOBLECK! Name Date Describe the four solids that will be mixed with water in this lab. Sand- [this is hard and white] Sugar- [this is also hard and white, but is it more square shaped] Salt- [this is similar to the other two] Cornstarch- [this is more powdery than the first three] What happened when you mixed sand with water? [The sand did not dissolve. Once I stopped stirring the sand it simply settled into a pile on the bottom of the bowl] What happened when you mixed water with sugar? [The sugar completely dissolved into the water. I can not tell the difference between regular water and sugar water.] What happened when you mixed water with salt? [The salt completely dissolved into the water. I can not tell the difference between regular water and salt water.] Describe the properties of oobleck. Oobleck is very thick, like pancake batter. If you run your hand through it slowly you hand will eventually go all of the way down. If you move you hand quickly, the oobleck seems to turn into a solid. This is strange.]

7 STUDENT HANDOUT FOR OOBLECK! Name Date Describe the four solids that will be mixed with water in this lab. Sand Sugar Salt Cornstarch What happened when you mixed sand with water? What happened when you mixed water with sugar? What happened when you mixed water with salt? Describe the properties of oobleck.

Virtual Library Lesson: Oobleck, Gloop, and Glurch

Virtual Library Lesson: Oobleck, Gloop, and Glurch Oobleck, Gloop, and Glurch Lesson Overview Throughout this lesson, students will use inquiry skills to identify states of matter, describe physical properties, and modify the recipe to change physical