KEY CONCEPTS AND PROCESS SKILLS. 1. Creating models is one way to understand and communicate scientific information.

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1 Inside a Pump to 1 50-minute session ACTIVITY OVERVIEW L A B O R ATO R Y SUMMARY In this activity, mechanical pumps serve as potential models for the human heart. In order to understand the working of the valves of the heart, students analyze the pumping action of two different bulbs, a siphon bulb and a pressure bulb, and relate the pumping action to the presence or absence of a valve in the heart. KEY CONCEPTS AND PROCESS SKILLS 1. Creating models is one way to understand and communicate scientific information. 2. Human body systems are composed of organs. The structure of an organ is adapted to perform specific functions within one or more systems. 3. Blood is pumped around the human body by the heart. 4. Valves control the direction of flow and allow liquid to move under pressure in both a pressure bulb and the human heart. KEY VOCABULARY function structure model Teacher s Guide B-123

2 Activity 21 Inside a Pump MATERIALS AND ADVANCE PREPARATION For the teacher 1 Transparency 18.1, Diagram of Blood Flow 1 Transparency 21.1, Cross-sections of the Bulbs 1 Transparency 21.2, Inside the Bulbs * 1 overhead projector * 1 apple and knife (optional) For the class 4 siphon bulbs with tubing * sponges * mops * paper towels For each group of four students 1 pressure bulb 2 45-cm (18-inch) lengths of clear plastic tubing 2 plastic bins (or buckets) * supply of water *Not supplied in kit Teacher s Note: Some teachers have found it more effective to combine Activities 21 and 22 into a single activity. Decide how you will approach these activities given your classroom structure and the materials available. The kit provides four siphon bulbs to be shared by the class. This means that, in a class of 32, two groups of four students each will have to share the siphon bulb. If you require additional materials, consider borrowing materials from another teacher or purchasing additional bulbs at a hardware store or a marine supplier. Be sure to practice using the siphon and pressure bulbs prior to conducting the activity so you can assist students as necessary. To control potential spills, fill one plastic bin 3 4 full of water for each group of four students in advance. Also have sponges, mops, and paper towels available to clean up any spills. Or you could conduct this activity outdoors. If you decide to slice open a siphon bulb and a pressure bulb, be sure to purchase an additional pressure bulb for activities that appear later in the unit. B-124 Science and Life Issues

3 Inside a Pump Activity 21 TEACHING SUMMARY Getting Started 1. The class reviews concepts from Activity 18 and 19. Doing the Activity 2. Introduce mechanical pumps as potential models for the heart. 3. Student groups experiment with the pumps. Follow-Up 4. Students apply the concept of a cross-section (Analysis Question 1). 5. Discuss the role of valves inside the pressure bulb. BACKGROUND INFORMATION Mechanical Pumps Siphon bulbs are used to siphon water out of fish tanks or residual fuel from boat engines (which do not have drain holes). Once the fluid begins flowing, it continues to flow. Using a siphon bulb eliminates the risk of swallowing toxic chemicals. Pressure bulbs are used to prime outboard motors on boats. Squeezing the bulb will move fuel from the fuel tank to the motor. Once the motor has started, it draws fuel on its own. A continuously operating pressure pump maintains pressure and can pump fluid against the force of gravity, unlike a siphon bulb. Valves in the heart enable the heart to function similarly to a pressure pump. Teacher s Guide B-125

4 Inside a Pump Activity 21 TEACHING SUGGESTIONS GETTING STARTED 1. The class reviews concepts from Activity 18 and 19. Begin by reminding students of their work on the circulatory system in Activity 18, The Circulation Game. Use Transparency 18.1, Diagram of Blood Flow, to review the movement of blood through the body. Focus on the function of the heart by asking, What functions of the heart were explored in Activity 18, The Circulation Game? What functions of the heart were explored in Activity 19, Heart-ily Fit? Point out that in both activities, the heart functioned to pump blood around the human body. The blood supplied oxygen and removed wastes from tissues in different parts of the body. Ask students, In The Circulation Game model, did your blood travel in more than one direction? Remind students that the blood, though traveling to different organs, moved in only one direction. DOING THE ACTIVITY 2. Introduce mechanical pumps as potential models for the heart. Show students the two kinds of bulbs and ask, Where have you seen or used such pumps? Students may have seen adults using siphon bulbs to transfer liquid. At this time, do not refer to the specific differences between the bulbs. Instead, explain that they will investigate how these bulbs work and which bulb is better at pumping water. Reinforce the Safety note on page B-57 in the Student Book by reminding students never to put anything into their mouths in science class unless instructed to do so. Discuss the danger of using the mouth to siphon liquids. Before students begin the activity, have them remove backpacks, etc. from the floor. Show them where the mops and sponges are located and caution them to be careful when walking around the classroom during this activity. There is bound to be inadvertent squirting of water as students explore the pumps and the floors will get slippery. This is an exploratory lab so provide only minimal instructions. Allow students maximum time to explore the pumps. 3. Student groups experiment with the pumps. Provide student groups with laboratory materials and have them complete the activity. To minimize spills members of the group who are not actually pumping can help keep tubing from slipping out of the bins. Students quickly discover that water flows only one way through the pressure bulbs. On some pressure bulbs, an arrow on the side of the bulb indicates the direction the water will flow. Some groups may have trouble starting a pump using the siphon bulb. Encourage these groups to experiment with holding the bulb at different levels in relation to the level of the water in the bin. Some students may discover that the siphon bulbs Teacher s Guide B-127

5 Activity 21 Inside a Pump can be made to work if they position the empty bin below the bin filled with water and then block the open tubing end with one finger, while they release the bulb. This creates reduced pressure in the tube. When they release the bulb, water will rush in from the unblocked end. When they then release the finger blocking the end of the hose, water will flow out. Once started, the water will continue to flow. It is not necessary to continue squeezing the bulb. Eventually, all students are likely to realize that the siphon bulb cannot pump water efficiently and in a single direction the way a pressure bulb can. Teacher s Note: Be sure to save one pump set-up for review during the Follow Up. FOLLOW UP 4. Students apply the concept of a cross-section (Analysis Question 1). Introduce the concept of a cross-section as a way to show what an opaque three-dimensional object looks like inside. Give an example such as an apple, and ask, What does the cross-section of an apple look like? Be sure students understand that it will depend on the direction and the location of the slice through the apple. You may wish to demonstrate this with an apple. Then hold up one of the pressure bulbs and ask, What would the outline of a cross-section of the bulb look like if it were sliced through the middle in the long direction? (This is shown on Transparency 21.1, Cross-sections of the Bulbs, as well as on page B-59 in the Student Book, but do not refer to these illustrations at this time.) After eliciting student ideas, refer students to Analysis Question 1. Begin assisting students to work in groups to answer this question. After students have had a chance to respond to the question, have them share their drawings of what might be inside the bulbs, based on their observations. You can use Transparency 21.1 for them to present their ideas to the class. Encourage students to compare ideas and discuss which of the various ideas is most likely to be correct. If possible, lead students to the idea that valves inside the pressure bulb make it a one-way pump. If the class is having difficulty with this idea, use Transparency 21.2, Inside the Bulbs, to present the complete bulb cross-sections. 5. Discuss the role of valves inside the pressure bulb. Use Transparency 21.2 to discuss the role of valves. Ask, What were the differences in how water flowed through the two different pumps? Students are likely to realize that the siphon bulb allowed water to flow in either direction; the pressure bulb kept water flowing in one direction. Ask, What prevented water from flowing in both directions inside the pressure bulb? Point out that the spring and ball (or whatever terms students used to describe the structures inside of the pressure bulb) acted as valves. Ask students, Do you expect valves in your heart to look similar to or different from valves in the pressure bulb? Inform students that they will continue to investigate this question in the next two activities. Use Analysis Question 3 to summarize this activity, perhaps at the beginning of the next class period. B-128 Science and Life Issues

6 Inside a Pump Activity 21 SUGGESTED ANSWERS TO ANALYSIS QUESTIONS 1. If you cut lengthwise through each bulb, the outer walls of the bulbs will look like the diagrams below. These are called lengthwise cross-sections. A cross-section gives a view inside a sliced object. Pressure bulb (or both) directions. In the case of the pressure bulb, water exits from the side containing the valve, or in this case, the ball that acts as the valve. c. What made one pump work better than the other? The valves kept the water flowing in one direction, thus allowing the water to continue to flow against gravity. 2. Which type of bulb is better at pumping water? Why? The pressure bulb is better at pumping water. Many students may figure out that the ball inside the pressure bulb maintains pressure and Siphon bulb a. What do you think is inside each bulb? Draw a cross-section of both the siphon bulb and the pressure bulb, as shown above. Complete the cross-section by drawing and labeling what you think is inside each bulb. See Transparency Many students are likely to realize that there is something inside the pressure bulb. A trap door or flap is a common description. Some students may look inside and identify it as a small ball. The siphon bulb does not have any internal structures. b. On your drawings of the bulb cross-sections, add arrows showing which way water flows inside the bulb. Because the siphon bulb does not contain any valves, an arrow can be shown going in either this is why it works better than the siphon bulb. The pressure bulb allows the whole bin to be completely emptied, regardless of the relative heights of the bins. Since it builds up pressure, it can continue pumping the water with each squeeze of the bulb. The siphon bulb, which relies on gravity, is useful only in starting the flow of water through the hose. If squeezed, it breaks the flow. It cannot maintain continuous pumping against gravity, and if used like a pressure bulb, it will squeeze water out in both directions. 3. Your heart pumps blood around your body. Would you expect it to work more like the siphon bulb or the pressure bulb? Explain. The heart works like a pressure bulb. In Activity 18, The Circulation Game, students learned that blood flows around the body in only one direction. If the heart worked like the siphon bulb, then every time the heart contracted, blood would flow out from every opening. This would result in blood flowing in more than one direction. When the heart relaxed, blood could flow back in from every opening. Teacher s Guide B-129

7 Cross-Section of the Bulbs Pressure Bulb Siphon Bulb 2006 The Regents of the University of California Science and Life Issues Transparency 21.1 B-131

8 Inside the Bulbs spring (acts as a valve) ball (acts as a valve) 2006 The Regents of the University of California Science and Life Issues Transparency 21.2 B-133