ELEMENTARY SCIENCE PROGRAM MATH, SCIENCE & TECHNOLOGY EDUCATION. A Collection of Learning Experiences on LOOKING AT LIQUIDS

Transcription

1 ELEMENTARY SCIENCE PROGRAM MATH, SCIENCE & TECHNOLOGY EDUCATION A Collection of Learning Experiences on LOOKING AT LIQUIDS CATTARAUGUS-ALLEGANY BOCES GRADES 5/6

2 TABLE OF CONTENTS Unit Overview... 2 Format & Background Information Learning Experience 1 - Getting Started Learning Experience 2 - Oobleck What Is It? Learning Experience 3 - States of Matter Learning Experience 4 - Comparing Drops and Heaps Learning Experience 5 - More Drops and Heaps Learning Experience 6 - The Paper Clip Game Learning Experience 7 - Breaking the Surface Tension Learning Experience 8 - Density of Liquids Learning Experience 9 - Density Beyond Liquids Looking at Liquids Student Assessment And Answer Key More Ideas Inquiry & Process Skills Glossary Teacher References Major Science Concepts

3 Unit Overview LOOKING AT LIQUIDS GRADES 5/6 Students will investigate the properties of various liquids (e.g. adhesion, cohesion, heaping, surface tension, mass, density) throughout the course of this unit. Special emphasis will be placed on observing, manipulating, communicating, collecting data, and predicting. As the students gain experience, they will develop understanding of the properties of liquids. Scheduling This unit may take from nine to eleven weeks to complete depending upon the goals of the teacher and interests of the students. Use of the section included in this manual called More Ideas may extend the time span of this kit. Materials to be obtained locally: Please make one student activity book for each student. chart paper transparency markers pencils notebooks overhead projector scissors folders transparency calculators newspapers plastic bags (optional) paper towels water felt tip markers metric rulers freezer Empty soapy water bottles: To make the soapy water fill the bottles with water and add 3-4 drops of liquid soap to the water and shake the bottle to mix them together. Empty water bottles: Fill these bottles with water for the learning experiences in this unit. Extra bottles of alcohol, glycerol, cooking oil, and a funnel have been provided for refilling 2 oz. dropper bottles. Caution Remind students to wash their hands after handling any of the materials in the kit. About the Format Each learning experience is numbered and titled. Under each title is the objective for the learning experience. Each learning experience page has two columns. The column on the left side of the page lists materials, preparation, basic skills processes, evaluation strategy, and vocabulary. The evaluation strategy is for the teacher to use when judging the students understanding of the learning experience. The right column begins with a "Focus Question" which is typed in italicized print. The purpose of the "Focus Question" is to guide the teacher's instruction toward the main idea of the learning experience. The "Focus Question" is not to be answered by the students. This learning experience includes direction for students, illustrations, and discussion questions. These discussion questions can be used as a basis for class interaction. A Student Assessment has been included in the Teacher s Manual and the Student Activity Manual. If you do not want the students to have the assessment beforehand, 2

4 remove it from the Student Activity Manual before printing a class set of the student manuals. Background Information Matter makes up the world around us. It is generally stated that there are three states of matter: solid, liquid, and gas. Plasma, a form of matter consisting of electrically charged particles under high temperature, is sometimes refered to as the fourth state of matter. All matter has mass and takes up space, regardless of its state. Each state of matter, however, does have characteristics of its own. SOLID LIQUID GAS SHAPE Definite Shape No definite shape No definite shape SPACE Takes up definite Takes up a definite Takes up no definite amount of space amount of space amount of space SPEED OF Moves very Moves faster than Moves very fast MOVING slow a solid PARTICLES Substances change their state due to changes in their energy. We measure change in energy by measuring temperature. Moving molecules have kinetic energy called heat. The more energy the molecules have available to them the faster they move. The less energy that is available to the molecules, the slower they move. The faster the molecules move, the farther apart they get. If the molecules are spaced wide apart and are moving quickly, the substance is a gas. If energy is taken away, the molecules slow down and move closer together. If the molecules are tightly packed together, the substance is a solid. Even though the molecules of a solid are close together and arranged in a pattern, the molecules are still moving (vibrating), but they do not change their position so a solid keeps its shape. The molecules of liquids are not as tightly packed together as those of solids or as loosely as those of gases. Therefore, liquid has no definite shape, and it takes the shape of the container it is in. Liquids do have a definite volume or take up a definite amount of space. Liquids move in a current or stream, and they can be described by their resistance to flow or viscosity. The temperature at which a substance changes from a solid to a liquid is its melting point. The temperature at which a substance changes from a liquid to a gas is its boiling point. 3

5 Water Molecules Molecular model of an ice crystal. Liquid water molecules Energy Level Steam water molecules in a gas state Changes in States of Matter Name of Change Changes in State Direction of Heat Example Energy Condensation Gas to Liquid Heat Lost Water vapor condenses on a cold glass Freezing Liquid to Solid Heat Lost Water becomes ice in a freezer Evaporation Liquid to Gas Heat Gained Boiling water evaporates as steam Melting Solid to Liquid Heat Gained Ice melts at room temperature Sublimation Solid to Gas Gas to Solid Heat Gained Heat Loss Dry ice sublimates to form carbon dioxide. No liquid is produced. The properties of liquids are addressed in several learning experiences in this unit. One of these properties is cohesion. Cohesion is the force of attraction between like molecules. Once the molecules that are attracted to each other get together, they tend to stay together. Water molecules are an example of molecules that have strong cohesive forces. Water molecules are strongly attracted to other water molecules. Water forms droplets, or small units of water, when poured or spilled, and when pushed toward each other these water droplets seem to jump together to form larger droplets. Alcohol droplets, however, cohere weakly to other alcohol molecules. Because drops of water are strongly attracted to each other (strong cohesive forces), when two drops of water on waxed paper are led very near each other, they seem to jump together and grab on to each other. Drops of alcohol do not demonstrate this same property. This is because the cohesive forces of alcohol are weak. Glycerol has strong cohesive forces and should have "grabby" drops, but the glycerol is so thick (viscous) that this ability to grab onto another glycerol molecule is impaired. 4

6 Depending on its cohesion, the liquids will form high, round drops or low, flat drops. Cohesion allows the drops to hold onto one another and form its semicircle shape. The drops of water and glycerol are high and round and are often called "hemispheres". Alcohol and soapy water forms the lowest, flattest drops. Adhesion describes the forces of attraction between molecules of different substances. If you drop a pencil into water, the water will adhere to the pencil as it is removed. Glue is a substance that adheres to paper. The previous examples illustrate adhesive properties or adhesion forces of attraction between molecules of different substances. Alcohol drops and oil drops adhere well to waxed paper- much better than water or glycerol. The alcohol leaves a noticeable trail down the waxed paper. Glycerol drops adhere slightly to the waxed paper but its strong cohesive forces keep it together. Drops of water do not adhere to the wax paper. They roll down the waxed paper freely, and it stays in its "drop" shape due to its strong cohesive forces. Heaping A liquid placed in a container (medicine cup) will heap as the liquid reaches the rim. When a liquid is being heaped into a container, there is a point at which just one more drop will cause the liquid to spill over the side. This point depends on three properties of the liquids: the density of the liquid, the viscosity of the liquid (thickness), and the strength of the cohesive forces. If we were to heap water and glycerol, their profiles would be almost identical. They heap the highest. Both liquids show the effects of strong cohesive forces and both have a greater density than alcohol. In addition, glycerol is much thicker or more viscous than the other liquids. Alcohol has very weak cohesive forces and spills over the side before it heaps much above the rim of the cap. This heaping can be compared to the high hemisphere drops of the water and glycerol and the low, flat drops of the alcohol and soapy water. Drop Size Drop size is observed as the liquids are falling from the dropper. Water drops and glycerol drops are about the same size. Alcohol drops are much smaller. Alcohol drops are small because of the cohesive forces in alcohol are weak. The alcohol drops in the dropper let go of each other easily so the drops break into smaller portions. The opposite is the case for the water drops. The cohesion is so strong that it does not break apart into such small parts. It sticks together to form larger drops. Surface Tension All liquids have surface tension. Some liquids have stronger surface tension than others. The surface tension of water results from the cohesive forces of water molecules. A water molecule in the middle of a body of water is subjected to this cohesive force from all sides. A water molecule on the surface of water cannot be pulled by water molecules above it. Therefore, this pull is strengthened in other directions (sides, below), and it is tougher to pull apart the layer that is formed. There is a net inward force since there is no force acting from above the molecule. An elastic "skin" or film is formed on the surface. Surface tension allows water to hold up substances heavier and denser than itself. A paper clip carefully placed on the surface of water will float due to surface tension. An aquatic insect, like the 5

7 water strider, that moves along the surface of the water relies on surface tension to walk on the water. Water molecules surrounded by other water molecules below the surface Water molecules on the surface Effects of Soap on Water Soap added to water reduces the cohesive forces between water molecules, thus greatly reducing the strong surface tension of water. When soapy water drops are made on waxed paper, they will be flatter than plain water drops. Lower cohesion accounts for this. Soapy water washes things better than plain water because soapy water allows an item to wet more thoroughly. For example, with clothing, soapy water flows more easily into the clothes and more deeply into the fabric. Therefore, more dirt mixes with the water and it is rinsed out. Many detergents contain "wetting agents" designed to reduce surface tension and to increase fabric penetration by water. Plain Water (cohesion) Soapy Water (reduced cohesion) Effects of Alcohol on Water When alcohol drops are added to a dish of water, the water seems to boil or shimmer. Students may observe this and say that the water is moving. There are two reasons why this is occurring. One reason is that the alcohol molecules are getting between water molecules and are pulling them apart. The movement is seen along the border of the two liquids. Another reason this apparent movement is happening is due to the high evaporation rate of alcohol. As the alcohol evaporates quickly from the water s surface, the fumes mix with the air along the surface to produce the boiling effect. Mass is a measure of the amount of matter in an object. Mass is measured by comparing the object s mass with a standard mass. Therefore, some sort of a balance scale is needed to measure mass. It is important that students understand that mass does not equal weight. Weight is the measure of gravitational pull on an object. Therefore, weight will vary with gravitational force. If you measure the weight of an object on the Earth and then measure the weight of the same object on the moon, the object would weigh less due to the fact that the force of gravity is different on the moon verses the Earth. However, the mass of the object would be the same on the Earth and on the moon because the amount of matter in the object remains constant. 6

8 Density is the measure of the compactness of a material. It is the ratio of mass to volume for any material. It is usually measured in grams per cubic centimeter (g/cm³) and tells how much matter is packed into a given space. Density is not a simple comparison of the heaviness or lightness of materials. It is instead, a comparison of the heaviness or lightness of the same volume (mass per unit volume). The larger the amount of the substance that is packed into a certain volume or space, the more dense the substance is. The density of a material is determined by the masses of the atoms in the material and the amount of space between the atoms. Gases have a low density not only because the atom making up the gases have a small mass, but also because there is a large amount of space between the atoms. The heavy metals like gold, lead, and uranium are very dense because the atoms they are composed of are massive and spaced closely together. Water has a density of one gram per cubic centimeter (1 g/ cm³) at 3.98 degrees Celsius and water is the standard for comparing the density of materials. Materials with a density greater than one gram per cubic centimeter are denser than water and will sink in water; materials with a density that is less than one gram per cubic centimeter will float in water. Lead has a density of 11.3 grams per cubic centimeter (11.3 g/cm³). This tells us it is more than eleven times as dense as water. It also means that a hundred grams of lead would have eleven times less volume than a hundred grams of water (atoms in lead are much more closely packed together so they take up less space.) Oil floats on the surface of water because it is less dense than water. Glycerol sinks in water because it is more dense than water. Displacement In order for an object to be submerged in a liquid, the object must push aside or displace some of the liquid it is contained in. This is called displacement. Volume of an object can be determined by displacement. Let s say that 10 ml of liquid is placed in a graduated cylinder. If an object is dropped into the cylinder, the water level appears to go up, even though no more water was added to the cylinder. This is due to the fact that the object has displaced or pushed aside some of the liquid when it was put into the container. If the object is submerged, it will displace the object s volume. Therefore, if there was 10 ml of liquid before the object was placed in the fluid and the measurement of the liquid in the cylinder is 14 ml after the object is placed in the fluid then subtracting 14 ml from 10 ml would equal how much space the object took up in the cylinder. Since the definition of volume is the amount of space taken up by an object it can be concluded that the volume of the object placed in the fluid is 4 ml. 7

9 Learning Experience 1: Getting Started Objective: Students will discuss their background knowledge of liquids and contribute ideas to a "How to Succeed" chart. Materials: For the class: Chart paper* Felt tip makers* Notebooks* Folders* *provided by teacher Preparation: Each student should obtain a notebook and a folder with pockets to hold the activity sheets for this unit. Create a KWHL chart to post in the classroom. Basic Skills Development: Reading Writing Discussing Listening Brainstorming Evaluation Strategy: Students will contribute ideas to complete a KWHL chart and a How to Succeed chart for use during this unit. Vocabulary: Learn succeed observe strategy What do we know about liquids? How can making a list on How to Succeed help you during our study of Looking At Liquids? Using the KWHL Strategy, students will explore their knowledge about liquids and then expand on it throughout the unit. Brainstorm what all the students already know about the liquids they will be studying. Record their ideas on a class-size KWHL chart. Ask students to think about these liquids and decide what is it about these liquids they would like to know more about concerning liquids and record their ideas under the want to know column. Now that the students have decided what they want to know, they need to think about how they are going to find out the answers to the questions they have. After the hands-on activities, maintaining journals, and discussions, students can then record information into the what we learned and still want to learn column. This process can also be done in cooperative groups where students gather information in small groups and then share their ideas with the class. Explain to students that the learning experiences in this unit has them working with various materials. They will be sharing materials with a partner. They will be completing several activity sheets that go along with the learning experiences. Brainstorm with students what they should be ready to do to complete this unit successfully. Use the How To Succeed information on page 9 as a guide. Create a classroom chart and post it in the classroom so students are reminded of these responsibilities. 8

10 Learning Experience 1 continued Page 2 KWHL Strategy What we know What we want to know How are we going to find out What we learned and still want to learn HOW TO SUCCEED 1. Make sure you have all the necessary materials ready for each learning experience. 2. Keep your materials and work area clean and your notebook neat and organized. 3. Cooperate with your partner. Each person should participate in these learning experiences. 4. Read the questions and directions carefully. Ask for help if you do not understand what you are to do. 5. Observe and measure accurately and write down your observations. 6. Use your time wisely. 7. Be careful. Use the equipment correctly. 8. Stick to your job. Do not give up. 9. Try new ways to do the learning experiences. Discuss your observations and ideas with your classmates. 9

11 Learning Experience 2: Oobleck-What is it? Objective: Students will determine the properties of the Oobleck and decide whether Oobleck is a solid or a liquid and support their decision with evidence from their observation. Materials: For each student: 9 oz. clear plastic tumbler (plastic bags* could also be used) For the class: 3 boxes of cornstarch Food coloring Large wooden dowel Large bucket Measuring cup Water* Newspaper* Paper towels* Chart paper* Felt tip markers* *provided by the teacher Preparation: Read background information on the states of matter on pages 3 and 4. Mix Oobleck ahead of class and decide how it will be distributed to students. Cover all work areas with newspaper. Leave room on the chart created in this learning experience for a brainstorm on gases which is done in Learning Experience #3. Basic Skills Development: Discussing Observing Describing Evaluation Strategy: Students will determine whether Oobleck is a solid or a liquid and support their position. Vocabulary: solid liquid gas Is Oobleck a solid or a liquid? Oobleck is a substance that is a mystery. Scientists have not decided if it is a liquid or a solid. It is a strange substance that flows like a liquid but resists pressure like a solid. This learning experience provides students the opportunity to make observations and arrive at conclusions supported by data. Oobleck recipe (for 30 students): 3 boxes of cornstarch, 2 1/3-3 cups of water, 20 drops of food coloring. The Oobleck recipe is to be mixed in the large bucket provided. Oobleck should be mixed with the large dowel provided. The mixture should flow when tipped but feel solid when your hit it or rub your hand across it. Approximately ½ cup of the substance is then to be transferred to the clear plastic tumblers for students to touch and explore the substance. Left over Oobleck can be set aside until it is dry and then thrown into the trash. DO NOT POUR OOBLECK IN THE SINK. IT WILL CLOG DRAINS. Brainstorm with students the differences between solids and liquids. Use the chart on page 3 of this guide to help with this brainstorm. Once students have a clear concept of the differences between the two states of matter, explain that we are going to look at a substance that could be one or another, and they will need to decide what it is. The book Bartholomew and the Oobleck by Dr. Seuss may be found in your school library and could be read to students before the Oobleck is distributed. As a follow-up to the learning experience, students can write persuasive pieces of 10

12 Learning Experience 2 continued Page 2 writing supporting their opinions of Oobleck as a liquid or a solid. Students could also participate in a debate defending their opinion of Oobleck as a solid or liquid. Discussion Questions: Can the Oobleck bend, break, roll, etc? Do you think it is it a solid or a liquid and why? What do you think Oobleck is made of? What would happen if we added more water to the Oobleck? More cornstarch? What do you think would happen if we heated the Oobleck or froze the Oobleck? What do you think would happen if we let the Oobleck sit out overnight? 11

13 Learning Experience 3: States of Matter Objective: Students will explain the differences between the three states of matter and how matter changes from one state to the other. Materials: For each student: Looking at Liquids Student Activity Book Pencil* Scissors* For the class: Thermometer 2 clear plastic jars Food coloring 9 oz. clear plastic tumbler Candle Measuring cup Box of matches Aluminum pan Chart from Learning Experience #2 Water* Transparency chart pg. 4* Overhead projector* Paper towels* Freezer* 3 different transparency markers* *provided by teacher Preparation: Read background information on states of matter on pages 3 and 4. Have the chart that was started in Learning Experience #2 available so it can be completed. Prepare the two clear plastic jars. Fill one jar with warm water and fill the other jar halfway with warm water. Add a few drops of food coloring to both jars. Place both jars in the freezer overnight. Have a cup of warm water also on hand for this learning experience. Basic Skills Development: Discussing Recording data Predicting Observing Brainstorming How can we compare the three states of matter? In Learning Experience #2, students brainstormed the differences between solids and liquids. In this learning experience, students are to continue their brainstorm by comparing gases to solids and liquids. After the chart is completed, review with the students the ideas they have generated. Students are going to create a graphic organizer to record specific information about the three states of matter. A diagram of the graphic organizer is found on the activity sheet for Learning Experience #3 in the Looking at Liquids Student Activity Book. Directions for the graphic organizer: Hold the paper horizontally and fold the paper at the line that says fold. Fold Cut Cut Cut the left side of the paper into three equal strips. If you are holding the paper so the fold is on the left side, you will notice that the half of the paper that has been cut act like flaps. If you pull the flaps to the side, you will notice that it only reveals part of the other half of the paper. 12

14 Learning Experience 3 continued Page 2 Evaluation Strategy: Students will identify and compare the three states of matter. Students will explain how the transfer of energy is necessary for matter to change from one state to another Vocabulary: solid liquid gas evaporation condensation molecule Instruct students to write solid, liquid, and gas on each flap. SOLID LIQUID GAS Picture of molecules Shape- Space- Feel- Shape- Space- Feel- Shape- Space- Feel- Students will note in their graphic organizer specific information about each state of matter. Discuss with students the information on the chart that they brainstormed about each state of matter. Circle or highlight anything on the chart that refers to the shape of a solid. As a class, come to the conclusion that a solid does have a definite shape. Continue looking at the chart for items that refer to the space and feel of a solid. Circle information about space in one color and circle the information about feel in another color. Complete the same information same for liquids and gases. Use the chart on page 3 of this guide to help focus this discussion. 13

15 Learning Experience 3 continued Page 3 After the information on space, shape, and feel of each state of matter has been recorded, students are to draw what the molecules of water as a solid, liquid, and gas would look like in the column titled Picture of Molecules. Students are to use the following diagram to represent a water molecule. Hydrogen Hydrogen Oxygen Water molecule (H20) Use the background information on pages 3 and 4 of this guide to help focus students on what their pictures would look like. The molecules of the solid are tightly packed together and barely move around (vibrate). Molecules of liquid move around more quickly and are not as packed together. Connect this with the fact that liquid (water) does not have a definite shape but a solid (ice) does. Gas molecules are moving very quickly and are spread far apart. Again, no definite shape. Gases also have no definite shape and take up no definite space because the molecules are spread so far apart and are moving so quickly. Session 2: In preparation for this session of Learning Experience #3, one of the clear plastic jars was to be filled with colored water and placed in the freezer. Another capped plastic jar was to be filled halfway with colored water and placed in the freezer. Also, have a plastic tumbler filled with warm water available. Now that students have a concept of how the states of matter are different, begin a discussion with students of how the states of matter change from one state to the other. To begin, you may want to brainstorm with students a list of things that change (ex. leaf colors, animal growth, seasons, etc.). Show students that you have water in two of its states solid (ice) in two clear jars and liquid (water) in a clear plastic 9 oz tumbler. Discussion Questions: How did the solid (ice) get to the state it is in? (water in its liquid state was frozen heat loss) Take the temperature of the jars containing ice and the warm water and record them on the chalkboard. Refer to these temperatures when discussing both melting and condensation. The warmer temperature causes the ice to melt however, the cooler temperature causes the condensation to form. Students are to predict what will happen if the warm water is poured into the container half filled with ice. As a teacher demonstration, pour in the warm water in the jar half filled with 14

16 Learning Experience 3 continued Page 4 ice and observe. Students should begin to see the ice melting due to the warm water. The color from the ice will begin to mix into the warm water to further illustrate this concept. Discuss the results and why they are occurring. The melting of the ice shows the solid has gained heat and it is turning back into a liquid. The jar can be passed around the class so students can get a closer look. Turn the attention to the jar filled with ice. Students should be noticing beads of water forming on the outside of this jar. Students should predict where this water is coming from. If students wipe water on the outside of the jar, they will not see any food coloring which should indicate to them that it is not coming from the inside of the jar. (The condensation forming on the outside of the jar is due to cooling of the water vapor in the air. The cooling of the water vapor (gas), due to heat loss turns into a liquid. These liquid drops are the beads of water found on the outside of the jar. The jar may be passed around the room so students can take a closer look at what is happening.) Depending upon the time of year this learning experience is done, the amount of condensation on the outside of the jar will vary. If it is completed in the winter months, the air is very dry, therefore, less water vapor is in the air so there will be less condensation on the jar. Students will have to look closely for it. However, if it is done on a day with more humidity in the air, more condensation will form on the jar. This concept can be a basis for further discussion. Students may begin to think of the condensation that forms on a mirror in the bathroom after someone takes a hot shower. The water vapor in the air is great, therefore, there is quite a bit of condensation that forms on the mirror. As the jars are being passed around, students could also breathe on the jars and see the condensation form. The water vapor that is in our breath cools near the ice filled jar and turns into water drops on the jar. Students, as a class, can create a chart similar to the one on page 4 of this guide to help the students see how the heat transfer changes matter from one state to another. The discussion of sublimation may be more difficult if students are not familiar with dry ice. An overview of the sublimation may be all that is needed. Discussion Questions: What other materials have you seen change from one state to another? Are there any items that you can think of that you re not sure what state of matter they are? (Example clay, malleable solid) What do you see on the outside of the jar? Where did these drops come from? If students are saying the water came from the inside of the jar, wipe the water off with a paper towel to show no coloring from the water.) Have you ever seen condensation form in a real life situation? Discussion Question: In what real life situations is evaporation helpful? (ex. drying clothes outside) 15

17 Learning Experience 3 continued Page 5 When trying to show students the concept of evaporation, place a thin layer of water on the bottom of the aluminum pan. Hold the pan over a lighted candle and observe as the water boils. Students should begin to see the steam. It is similar to what they see when water boils on a stove. Students should respond to the fact that the steam coming off of the boiling water is an indication of the evaporation occurring. It is due to the heat gain from the flame. Discussion Questions: How does evaporation occur in nature? What is the heat source? In what real life situation is evaporation helpful? (drying clothes, hair, etc.) Can you think of any way that evaporation would be harmful? How would we get this water vapor that just evaporated back into a liquid state? (remove heat condensation) 16

18 Learning Experience 4: Comparing Drops and Heaps Objective: Students will compare the drops and heaps of various liquids and determine how and why they are similar or different. Materials: For each pair of students: 2 Looking at Liquids Student Activity Books Dropper bottle of water Dropper bottle of cooking oil Dropper bottle of glycerol Dropper bottle of alcohol Dropper bottle of soapy water 2 pieces of wax paper (approx. 20cm. x 30cm.) 2 pieces of aluminum foil (approx. 20cm. x 30cm.) C-whip container 2 cardboard trays For the class: Bottle liquid soap Water* Chart paper* Felt tip markers* Newspapers* *provided by teacher Preparation: Read background information on cohesion and adhesion on pages 4 and 5. Have each student use their cardboard tray to set liquids on. Dropper bottles labeled water and soapy water will need to be filled. See instructions for soapy water on page 2. Work area should be flat; if necessary, covered with newspaper. Students should be able to observe the drops of the liquid from the top and from the side (profile). Students can store all materials in their C-whip containers for future learning experiences. Basic Skills Development: Recording data Discussing Following Directions Observing Describing Interpreting Data How can we compare drops of different liquids? Student pairs should investigate to find the answers to the questions on the activity sheet for Learning Experience #4 in the Looking at Liquids Student Activity Book. Discuss the outcomes. (A list or chart of similarities and differences between the liquids may help students recognize some of the properties of the liquids.) Have students repeat Learning Experience #4 with aluminum foil instead of the wax paper. Make a comparison chart comparing the liquids on wax paper and aluminum foil. Liquids water oil glycerol alcohol soapy water Drops, Heaps and Adhesion waxed paper aluminum foil Discussion Questions: What do you notice about the water drops in comparison to the alcohol drops? To the glycerol drops? What did you notice about the drops of water as you added more drops to it? Which liquid seemed to stick to the wax paper as it rolled down it? Which liquid did not appear to stick to the wax paper at all? What are the differences between the results you had with the wax paper and with the aluminum foil? 17

19 Learning Experience 4 continued Page 2 Evaluation Strategy: Students will identify the similarities and differences between the drops and heaps of various liquids. Vocabulary: profile cohesion adhesion alcohol glycerol viscous 18

20 Learning Experience 5: More Drops and Heaps Objective: Students will observe and describe how the forces in liquids affect the heaping and drop size of the liquids. Materials: For each pair of students: 2 Looking at Liquids Student Activity Books 2 medicine cups Dropper bottle of soapy water Dropper bottle of water 2 cardboard trays Piece of waxed paper (approx. 20cm x 30cm) For the class: Bottle liquid soap Water* Newspapers* *provided by teacher Preparation: Read background information on drop size, heaping, and effects of soap on water on pages 5 and 6. Keep medicine cups clean and soap free for each learning experience. Have each student use their cardboard tray to set liquids on. Basic Skills Development: Discussing Describing Interpreting Data Counting Measuring Following Directions Predicting Evaluation Strategy: Students will determine that there is a relationship between drop size and heaping ability and the cohesion and adhesion of liquids and explain that relationship. Vocabulary: adhesion cohesion heaping ability hemisphere How can you find out if all drops are the same size? Student pairs should investigate to find the answers to the questions on the activity sheet for Learning Experience #5 in the Looking at Liquids Student Activity Book. Discuss the outcomes. Help the students make generalizations about the size of drops, different surfaces, and heaping. Connect with students in the discussion the relationship between these properties and the cohesion and adhesion of these liquids. Discussion Questions: Why do the water drops heap higher than the soapy water drops? Does cohesion play into the reason of why the water drops are larger than the soapy water drops? How? Explain how drop size relates to the number of drops it took to fill the medicine cup to the 5 ml. mark. How do you think alcohol and glycerol would have acted in this learning experience? What are the reasons behind your predictions? (As a teacher demonstration, heaping the glycerol and alcohol in a medicine cup may also help students see the relationship between heaping ability and drop size. 19

21 Learning Experience 6: The Paper Clip Game Objective: Students will investigate the surface tension of water and explain what causes it to occur. Materials: For each pair of students: 2 Looking at Liquids Student Activity Books 9 oz clear plastic tumbler 2 paper clips (unused and clean) Dropper bottle of soapy water 2 cardboard trays For the class: Water* Newspapers* *provided by teacher Preparation: Read background information on surface tension and the effects of soap on water on pages 5 and 6. A demonstration of how to float the paper clip may be necessary. Some students will find other ways to float the paper clip than the one illustrated. Have each student use their cardboard tray to set liquids on. Students should save the 9 oz clear plastic tumbler from this activity to be used in their Knex balance in Learning Experience #8. Basic Skills Development: Reading Discussing Writing Observing Describing Following Directions Evaluation Strategy: Students will describe how surface tension allows a paper clip to float on the surface of the water. Vocabulary: surface tension molecules cohesion How can you float a paper clip? Have student pairs fill their clean plastic tumbler half full of water. Students will attempt to float a paper clip by creating a cradle with one of the paper clips and placing the other paper clip on the cradle. The cradle is then lowered slowly into the water. Once the clip is floating, the cradle is to be removed. This may take several tries to get the paper clip to float. Students need to be sure that the paper clip is lying flat as it is placed on the water. Students are to also be careful not to bump their desks as they are trying this learning experience. Student pairs are to find the answers to the questions on the activity sheet for Learning Experience #6 in the Looking at Liquids Student Activity Book. Discuss the outcomes. As a class, agree upon a working definition of surface tension. This definition can be posted in the room for reference when completing Learning Experience #7. Discussion Questions: Why is the paper clip able to float on the water? What happens if one drop of soapy water is added to the water floating the paper clip? What does the drop of soapy water do to the water to make the paper clip sink? 20

22 Learning Experience 7: Breaking the Surface Tension Objective: Students will observe and describe how soap effects the surface tension of water. Materials: For each pair of students: Spool of thread Dropper bottle of soapy water Dropper bottle of alcohol 3 petri dishes Newspapers* Water* Scissors* *provided by teacher For the class: Dropper bottle of food coloring Container of baby powder Preparation: Read background information on surface tension, the effects of soap on water, and the effect of alcohol on water on pages 5 and 6. Petri dishes must be clean and free of soap. Basic Skills Development: Discussing Predicting Following Directions Observing Describing Evaluation Strategy: Students will explain how soapy water and alcohol effect the surface tension of water. Vocabulary: surface tension What does soapy water or alcohol do to the surface tension of water? Student pairs should fill two petri dishes full of water and one petri dish with only a thin layer of water in it. Have students cut a 15cm. 20cm. piece of thread. Take one piece of thread and tie the ends together to form a loop. Cut off the extra thread near the knot. In the first petri dish full of water, ask students to carefully place the thread loop on the surface of the water. Petri Petri dish dish Thread Water Ask half of the class to place a drop of soapy water into the center of the floating loop of thread, and ask the other half of the class to place a drop of soapy water outside the loop. Discuss the results. In the second petri dish full of water, tell students you will come around to their groups and sprinkle baby powder lightly over the surface. Ask students to observe the powder on the surface carefully because with the powder they can clearly see the skin effect of the surface tension. Have students predict what will happen if a drop of soapy water is placed on the edge of the dish and in the middle of the dish. 21

23 Learning Experience 7 continued Page 2 Place a drop of soapy water on the side of the petri dish first. The students should notice the powder move to the other side of the petri dish. Then drop the soapy water in the center of the petri dish with the powder. Discuss the results. If there is some baby powder still on the surface of the water in the second petri dish, students may want to add a few drops of alcohol to it and observe what happens. The third petri dish should only have a thin layer of water in it. Tell students you will come around and add a drop of food coloring to the water. Make sure the colored water is spread as thinly as possible, but still covering the bottom of the petri dish. Students should place a drop of alcohol in the center of the layer of water and observe. Discuss the results. Discussion Questions: What is holding the thread and powder on the surface of the water? What happens to the surface tension of water when soap is added? What happens to the thin layer of colored water when a drop of alcohol is placed in the center of the water? How does the alcohol s reaction with water compare to the soapy water s reaction? Groups should think back to their working definition of surface tension from Learning Experience #6 and refine it after observing the activities in Learning Experience #7. Groups should share their definitions of surface tension with the class. The class definition of surface tension can then be revised. 22

24 Learning Experience 8: Density of Liquids Objective: Students will find the density of water, oil, and glycerol using the equation: Density = Mass/Volume and explain the relationship between the density of the liquids and the order in which the liquids layer. Materials: For each pair of students: 2 Looking at Liquids Student Activity Books K nex balance (to be assembled by students) Direction card for Knex balance 2 9 oz clear plastic tumblers Pkg. of gram masses 3 medicine cups Dropper bottle of glycerol Dropper bottle of cooking oil Dropper bottle of water 2 plastic eyedroppers Piece of modeling clay Calculator* Chart paper* Felt tip markers* Water* *provided by teacher Preparation: Read background information on density on page 7. Assembly of the Knex balance is necessary for this learning experience. A direction card for assembly of the balance for each pair of students is included in the kit. One Knex balance that has already assembled has also been included as a model for students constructing their own balance. Students should keep the balance they have assembled for Learning Experience #9. A review for the students on how the balance works may be necessary. Discuss where the fulcrum is located and that the use of modeling clay maybe needed to help level the balance. Place the modeling clay on only one end of the balance. Which liquid has the greater density: oil, water, or glycerol? Density is defined as the mass of an object per unit volume. Ask students to explain what they think density is in their own words. Once students have attempted this, discuss their thoughts and ideas as a class. Write any information that they come up that is correct on a piece of chart paper. Use the background information on density on pages 6 and 7 to help you. Show students the formula for density. (Density = Mass/Volume) Using the background information on pages 6 and 7 of this teacher s guide, discuss with students the meaning of this formula and how the ideas they came up with relate to this formula. Students should complete the activity sheet for Learning Experience #8 in the Looking at Liquids Student Activity Book. Students will find the densities of the liquids and see how density relates to why liquids layer as they do. Discussion Question: Use the findings and questions on the activity sheet as the basis of discussion. (These are approximate densities) Mass Volume Density Glycerol ml 1.13 Cooking Oil ml.73 Water ml 1.0 Water Cooking oil Glycerol 23

25 Learning Experience 8 continued Page 2 Moving the modeling clay toward or away from the end of the balance, it is easier to find the right amount to level the balance. Fulcrum may also help in leveling the balance. Students will need to know how to compare decimals (<, >) in order to make predictions on how the liquids will layer. Basic Skills Development: Interpreting Data Gathering Data Inferring Discussing Following Directions Predicting Measuring Students will find that there is only one way these liquids will layer due to their densities. If students question why density is represented on the chart in units of g/cm³ and we are dividing grams (g) by milliliters (ml), explain that 1 ml is equal to 1 cm³. Density is usually shown in units of g/cm³ instead of g/ml. Learning experience #9 addresses this issue and shows students why 1 ml = 1 cm³. Evaluation Strategy: Students will find the density of three liquids and compare the actual densities to how the liquids layer. Vocabulary: density contaminate decant mass volume balance fulcrum horizontal level modeling clay 24

26 Learning Experience 9: Density Beyond Liquids Objective: Students will find the density of various objects using the equation Density = Mass/Volume. Students will find the volume of various objects by using a ruler or by using displacement. Materials: For each pair of students: 2 Looking at Liquids Student Activity Books Small square block of wood Large square block of wood 8d nail White marble Gradulated cylinder K nex balance Centimeter cube Metric ruler* Calculator* Water* Chart paper* Felt tip markers* *provided by teacher Preparation: Read background information on density and displacement on page 7. Review with students how they found the density of the liquids in Learning Experience #8. Students should disassemble the K nex balance once they have completed this learning experience. Basic Skills Development: Gathering Data Interpreting Data Discussing Following Directions Measuring Observing Evaluation Strategy: Students will find the densities of a variety of objects by finding the object s mass and volume and using the equation Density = Mass/Volume. How do you find the density of an object? Discuss with students the meaning of volume of an object. The volume of an object indicates how much space the object occupies. If the object is rectangular or square in nature, a ruler can be used to measure the length, width, and height of an object. Volume = length x width x height Give each pair of students a ruler and a 1 cm cube. Ask each student to measure the length, width, and height of the cube. Write these numbers on chart paper and give the equation for volume. As a class, find the volume of the cube. Volume = length/1 cm x width/1 cm x height/1 cm = 1 cm³ A second way to find the volume of an object is to measure the amount of fluid it displaces when it is submerged. If an object is placed in water, some of the water had to move out of the way to make room for the object. The volume of the water that was moved out of the way or displaced is equal to the volume of the object. Give each pair of students a graduated cylinder with 10 ml of water in it. If the object is placed in the 10 ml of water, the water level will move up. The measurement of that water level minus the 10 ml equals the volume of that object. Ask each pair of students to place their 25

27 Learning Experience 9 continued Page 2 Vocabulary: mass volume density displacement submerge 1 cm3 cube in their 10 ml of water. Students are to read the water level with the cube in it. It should read 11 ml. 11 ml 10 ml = 1 ml Remember: an object must be completely submerged in water before an accurate reading for volume can be done. If necessary, students may need to push the cube underwater until it is submerged. Discussion Questions: How does the volume of the block compare with the rise in water level? *(1 cm³ = 1 ml) Which method of finding volume would you use if you were trying to find the volume of a rock? Why? Which method of finding volume would you use if you were trying to find the volume of a block of wood? Why? Students should complete the activity sheet for Learning Experience #9. Discuss the results. (Student answers are approximate). Answers: 1. Volume of the: Marble 1 ml - displacement Nail 1 ml - displacement Small Square Block of Wood 2.5 x 2.5 x 2.5 = cm³-l x w x h Large Square Block of Wood 5 x 5 x 5 = 125 cm³ l x w x h 2. Mass of the: Marble 3 g Nail 8 g Small Square Block of Wood 14 g Large Square Block of Wood 104 g 26

28 Learning Experience 9 continued Page 3 3. Density (approximate) of the : Marble 3 g/cm³ Nail 8 g/cm³ Small Square Block of Wood.896 g/cm³ Large Square Block of Wood.832 g/cm³ 4. The marble should sink in glycerol. The marble has a greater density than glycerol. 5. The block of wood should float in water. The wood s density is less than water. 6. The blocks of wood should have similar densities. Due to the natural growth process of wood, the densities may be slightly different. Students should understand that size does not change the density of an objects made from the same material. 7. B has the greater density. B has the same mass as A, however due to the fact it is smaller in volume, B has more matter squeezed into a smaller space. Therefore, the density is greater. 27

29 Name: Looking at Liquids Student Assessment Date: Directions: Read the question carefully and answer based on your knowledge about looking at liquids. Circle the correct answer Fill in the table below by answering the questions in the left hand column. Does this phase of matter have a definite shape? Does this phase of matter have a definite volume? Are the particles in this phase moving slow or fast? Rank these using slow, faster, and fastest. 10. Substances change their state due to changes in their a. phase c. energy b. viscosity d. pattern 11. Moving molecules have kinetic energy called a. heat c. temperature b. phase d. viscosity Solid Liquid Gas 12. When energy is taken away from a substance, the molecules in that substance a. move farther apart c. speed up b. move closer together d. change size 13. Liquids sometimes resist flowing, which is also called a. vibration c. temperature b. kinetic d. viscosity 14. When water turns to solid ice, it is called a. freezing c. condensation b. evaporation d. melting 15. When ice turns to water at room temperature, it is called a. freezing c. condensation b. evaporation d. melting 28