Science Discovery Classroom Presentation Guide

To view this page ensure that Adobe Flash Player version 9.0.124 or greater is installed.

Please login or register to make a comment!

...Description...... more. less.

famil- iar with it. General information about the Laboratory is presented in the next section. The Science Discovery Laboratory The Science Discovery Laboratory is an open-ended exploration environment consisting of 32 simulations on various topics in the physical, life, and earth sci- ences. Each simulation focuses on a particular phenom- enon (osmosis, for example) or scientific relationship (speed = distance / time, for instance). These simulations allow students to investigate phenomena and relationships in controlled environ- ments. Teachers or students control the interaction and are free to modify variables in ways that best suit their teaching or learning style. The 32 simulations are divided into ten topics, or modules. A list of the 10 topics and the 32 simulations can be found in Table 1. These are selected topics found in most middle school curricula. The Laboratory also supplies various student resources accessible via the resource bar. There are tools for measuring, a glossary, an atlas, and several note- books. One, labeled simply Notebook, is for students to record their observations. The second, labeled Instruc- tion, displays instructions for students to follow in manipulating the simulations. The third, labeled Ques- tion, enables students to read and respond to questions about the simulations. 2 Introduction May 3, 2005 3:57 pm May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 3 Classroom Presentation Lesson Plans Laboratory This section is tailored for use with the Science Discovery Laboratory. No video is used in these lesson plans. It contains lesson plans for 10 classroom presentations based on 10 of the simulations in the Science Discovery Laboratory, one from each topic module. 4 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Static Electricity:Metal Balls and Rods Overview There are two types of charge:positive and negative. The smallest unit of positive charge is found on the pro- ton. The smallest unit of negative charge is found on the electron. Protons and electrons are two of the particles that make up atoms. Like charges repel, and opposite charges attract. If we bring together a positive charge and a negative charge, the two charges will cancel the effect each has on another charge. Objects contain both protons and electrons. In many cases, there are just as many protons as electrons. We say that these objects are electrically neutral. However, if an object has an excess of either protons or electrons, it is electrically charged (either positively or negatively). If the charge is unable to leave the object, it is called static, or unmov- ing, charge. Charged objects attract and repel other charged objects. An object could conceivably get an excess of posi- tive or negative charge by gaining or losing either pro- tons or electrons. However, protons are rarely found by themselves in nature, so it is not possible to add them to an object. Protons are found tightly bound in the nucleus of atoms, and for this reason it is not easy to remove them. Therefore, the only easy way to positively charge an object is to remove electrons, and the only easy way to negatively charge an object is to add elec- trons. Some materials hold their electrons more tightly than others. For example, rubber holds its electrons more firmly than fur. When a rubber rod rubs a piece of fur, electrons transfer from the fur to the rubber rod. The rubber then has an excess of electrons and is nega- tively charged. The fur has a deficiency of electrons and is positively charged. Key Outcomes Students will be able to: " describe the relationship between positively and neg- atively charged particles. " state the law of electrostatics:like charges repel; opposite charges attract. " determine whether an unknown charged object has a negative or a positive charge by using an electroscope. " observe the effects of like and opposite charges on objects. " build an electroscope. Vocabulary " Electroscope " Like charges " Opposite charges " Negative charge " Positive charge " Attract " Repel Materials " a long (4-6 feet) 2 × 4 wooden board " a small glass " an ebony rod, a glass rod, or a balloon " a piece of wool or fur Motivation Static electricity is responsible for lightning, for clothes sticking together in the dryer, and for the shock people receive sometimes by touching a doorknob after walk- ing across a carpet. This lesson plan explores the causes and effects of static electricity and offers some experi- ments to demonstrate its effects. May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 5 Static Electricity:Metal Balls and Rods Classroom Presentation Have you ever been shocked after walking across a car- pet and touching a doorknob? Have you ever lost a sock inside the clothes dryer? Have you ever seen lighting? All of these occurrences are caused by the same thing 4 static electricity. We are going to explore the causes and effects of static electricity and perform some experi- ments to demonstrate its effects. To demonstrate the power of static charge, we will move a large board with- out touching it. Instructions for Doing the Demonstration in the Classroom The following demonstration can be used to show the power of an induced charge caused by the buildup of static electricity. The balanced wooden board can be made to rotate on the watch glass by moving a charged object (rod or balloon) near the board. 1.Balance a 4- to 6-foot-long wooden 2 × 4 on an upside-down watch glass. 2.Charge an ebony rod, a glass rod, or a balloon. 3.Hold the rod or balloon near the outer end of the board. Do not touch the board with the rod or bal- loon. 4.The board will rotate in the direction of the charged object because electrons in the wooden board are free to move toward or away from the charged object. An induced charge is caused by the move- ment of electrons toward an object with a positive charge or away from an object with a negative charge, thus leaving a positively charged area on the object where the electrons have left. Why did the board move? By rubbing the balloon, we deposited a negative charge on the balloon. This charge attracted the protons in the board, causing the board to move. Let 9s use the Science Discovery Labora- tory to explore the effects charged objects have on other charged objects and on neutral objects. Instructions for Doing the Experiment in the Laboratory Before using the simulation during a presentation the presenter should review the online Instructions and become familiar with the functions available in this simulation. Enter the Science Discovery Laboratory, click the Static Electricity lab, click the Metal Ball and Rods simulation. This experiment examines the effects of positively and negatively charged rods on neutral and charged metal balls. It might be useful to create a table to record observations either in the notebook or on the black- board, or students may want to create their own tables. See the sample table below. 1.Select the positive rod by moving the cursor on it and clicking. The red rod is positively charged. The blue rod is negatively charged. 2.Drag the rod toward the metal ball without touch- ing the ball, and record your observations in the table. (The metal ball moves toward the positively charged rod.) 3.Click again, and the rod will return to its original position. Blue Negative rod Red Positive rod Observations Neutral metal ball Negatively charged metal ball 6 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Static Electricity:Metal Balls and Rods 4.Select the negative rod. Move it toward the metal ball without touching the ball, and record your observations in the table. (The ball moves towards the negatively charged rod.) Question: Do the rods have the same effect on the metal ball? Answer: Yes. Both rods attract the metal ball. 5.Touch the ball with the negative rod, and record your observations in the table. (The ball is repelled by the rod after contact, and the rod goes back to its original position.) Question: Why was the metal ball repelled by the rod after being touched? Answer: When the rod touched the metal ball, the ball became charged by contact with the charged rod. Since the rod and the ball had the same charge, and since like charges repel each other, the ball moved away from the rod. 6.Select the positive rod. Move the rod toward the ball without touching the ball, and observe what happens. (The ball is attracted to the positive rod.) Question: After the ball was touched by the negatively charged rod, what effect did the positively charged rod have on the ball? Answer: Oppositely charged particles attract each other, so the ball moved toward the rod. Question: How did the ball become charged after being touched by the negatively charged rod? Answer: The negative charges on the negatively charged rod repel one another. When the negative rod touched the neutral ball, some of the electrons from the rod moved to the ball. Since these electrons, which carry a negative charge, were added to the ball, the ball became negatively charged. Question: How do like charges interact? Answer: Like charges repel. Question: How do opposite charges interact? Answer: Opposite charges attract. Question: Why was the neutral ball attracted to both the neg- atively charged and positively charged rods? Answer: Metal has many electrons that are loosely attached and so can move around the metal easily. When the positively charged rod is brought near the metal ball, the electrons in the ball are attracted to the side of the ball near the positively charged rod. Since opposite charges attract, the ball is attracted to the rod. When the negatively charged rod is brought near the neutral ball, the electrons are repelled and move to the side of the ball away from the rod. This leaves the positively charged protons near the negatively charged rod. Again, since oppo- site charges attract, the ball is attracted to the rod. In both cases, the charged rods induced a charge on the neutral ball. The positively charged rod induced a negative charge on the near side of the ball, and the negatively charged rod induced a positive charge on the near side of the ball. May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 7 Light and Lenses:Changing Focal Length Overview A light ray bends as it enters glass and bends again as it leaves glass. The bending of light is called refraction and is due to the difference in the speed of light in air versus in glass. Glass in the right shape can bend parallel rays of light so that they cross at a single point. A lens is a piece of glass that bends light in this way. Typically, there are two types of lens:converging (convex) and diverging (concave). A converging lens is thicker in the middle than at its outer edges. A converg- ing lens bends parallel light rays so that they converge at a focal point after they exit the lens. Diverging lenses are thicker on the outer edges than in the center. Diverging lenses bend light waves away from one another. Light exiting a diverging lens appears to origi- nate from a point in front of the lens. The focal point for any lens is the point at which parallel rays of light cross or appear to cross after they pass through the lens. In order for light rays to be par- allel, the source of the rays has to be extremely far away from the lens. If a light source is moved toward a con- verging lens so that the rays are not parallel, an image will be formed that is not at the true focal point but rather at a point farther from the lens. The closer the object is moved to the converging lens, the farther from the lens the image is formed. There is a simple formula, called the lens maker 9s formula, that relates the focal length, the distance between the object and the lens, and the distance between the lens and the image. Knowing any two of these distances allows you to figure out the third using this formula. The lens maker 9s formula is 1 /focal length = 1 /object distance + 1 /image distance A converging lens can produce an image that is larger than the object (magnifying the image) if the object is moved closer to the lens than the focal length. Images that can be projected on a screen by con- verging light rays are called real images. They are real because the light rays actually form the image on the screen. If an image cannot be projected on a screen, as in the case of diverging images, the image is called a vir- tual image. Images that appear to be behind the plane of a mirror are examples of virtual images. Key Outcomes Students will be able to: " explain the difference between a convergent lens and a divergent lens. " measure the focal point of a convergent lens. " relate the curvature of a convergent lens to its focal length. " use a combination of lenses to construct a telescope. Vocabulary " Convergent " Divergent " Focal point " Focal length " Object length 8 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Light and Lenses:Changing Focal Length " Image length " Upright " Inverted " Enlarged " Reduced " Virtual image " Real image Motivation Eyeglasses are lenses. The eye itself has a lens. How do these lenses help us see? The motivation for this lesson is to discover what happens when light passes through convergent (convex) and divergent (concave) lenses by conducting a classroom project and experimenting with actual lenses to form various types of images. Classroom Presentation Question: What happens when light passes through a lens? Possible answers: " The light rays bend. " The light rays are focused at a point. " The light rays spread out. Question: Why do people wear glasses with lenses? Possible answers: " People wear lenses to focus light rays on the ret- ina so objects can be seen clearly. " People wear glasses to improve their eyesight. " People wear glasses when the lenses in their eyes don 9t work properly. The lens of the eye and an eyeglass lens focus light on the back of the eye. The image focused on the back of the eyes is the image we see. The distance between the lens and the focal point is called the focal length. Different lenses have different focal lengths. If an eye 9s lens cannot focus an image on the back of the eye, an eyeglass lens can be used to change the focal length so that the images focuses on the back of the eye. Question: How can we find out the focal length of a lens? To answer this question, we will perform an exper- iment in the Science Discovery Laboratory. Record the data in the online Notebook or on the blackboard. Instructions for Doing the Experiment in the Laboratory Before using the simulation during a presentation, the presenter should review the online Instructions and become familiar with the functions available in this simulation. 1.Select one of the lenses with the cursor, and click it. Move the lens in front of the light, and click. The path of the light rays through the lens will be shown. 2.The lens can be moved to different locations in front of the light by moving the cursor. The lens can be made stationary by clicking the cursor. 3.Once the lens is stationary, the tape measure can be selected from the Tools menu and used to measure distances. 4.Click the lens again to move the lens to another location in front of the light. 5.Find the focal length of the lens by moving the lens toward or away from the light until the light rays passing through the lens are parallel. ( NOTE :The light rays going through the diverging lens will not become parallel at any distance.) 6.The scale at the top of the computer screen can be used to measure the focal length distance. For a converging lens, the focal point is the point at which a beam of parallel light, parallel to the prin- cipal axis, converges. May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 9 Light and Lenses:Changing Focal Length 7.Move the lens to any position on the screen as long as the point at which the rays converge can be seen. Click anywhere on the screen so the lens becomes stationary. 8.Determine the distance from the object (light bulb) to the image (the point at which the rays converge). 9.Compute the focal length ( 1 /object + 1 /image = 1 / focal length), and compare it to previous observa- tions. Repeat steps 5 through 8 for the other two converging lenses. Question: Which converging lens bends the rays the most? Answer: The thickest converging lens bends the rays the most. Question: How does the amount that the rays bend compare to the focal length of the lens? Answer: The greater the amount of bend, the shorter the focal length. Question: What is the difference in the way light passes through the convergent and divergent lenses? Answer: Light rays are bent away from a point in a diver- gent lens, and light rays are bent toward a point in a convergent lens. 10 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Motion:Speed, Distance, Time Overview We use three variables to describe an object 9s motion:distance, speed, and time. Given any two of the three variables, the other variable can be found by rearranging the following formula:average speed = total distance / total time. The average speed does not represent the maximum or minimum speed that may have occurred through the distance traveled. Key Outcomes Students will be able to: " use the formula for average speed = total distance / total time. " compute the average speed for different trials in an experiment. " determine an unknown distance by using the formula:total distance = average speed × total time. " operationally define motion in terms of average speed, total distance, and total time. Vocabulary " Motion " Average speed " Total distance " Total time Materials " wheeled toys or balls " meterstick Motivation The motivation for this lesson is to apply the variables of speed, distance, and time to compute the average speed during a race and to determine an unknown dis- tance using average speed. Classroom Presentation The teacher should have two objects such as wheeled toys or balls that can be rolled or pushed. Lay out a marked track of fixed length along which the objects can roll. Push the two objects along the track so that one object rolls faster than the other. Question: What are various aspects of the toys 9 motion that we can measure? Answer: Distance, time, and speed are used to describe an object 9s motion. Question: How was the motion of the two objects the same? How was it different? Possible answers: " The distance the objects traveled was the same. " The time the objects were moving through the distance was different. " The speed of the two objects was different. Question: How can we describe the motion of the objects? Answer: Motion can be described in terms of speed, time, and distance. Let 9s conduct an experiment in the computer simu- May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 11 Motion:Speed, Distance, Time lation lab to discover more about the relationship of speed, distance, and time when describing motion. Our goal in this computer simulation is to plan a space journey and describe motion using distance, speed, and time. Instructions for Doing the Experiment in the Laboratory Before using the simulation during a presentation, the presenter should review the online Instructions and become familiar with the functions available in this simulation. Enter the Science Discovery Laboratory, click the Motion icon, and enter the Speed, Distance, Time sim- ulation. 1.Click the Select Speed button. 2.Type in the desired speed, and press the return key. (The speed must be between 134 km/hr and 99,999 km/hr. (If the speed is too slow, a message will tell you that the journey will take too long.) 3.Click the Go button. 4.The rocket will travel to the planet. 5.The time required to make the journey will appear on the screen. Question: How long will the journey take if you travel at 2,000 km/hr? Type in a speed of 2,000 km/hr, and click Go. Answer: It will take two hours. Make a table comparing speed and time to planet M. Use the following speeds:500 km/hr, 1,000 km/hr, and 2,000 km/hr. Record your data in the online Note- book or on the blackboard. Construct a graph showing the data from your table. Use the graph to predict the time required to travel to planet M at a speed of 1,500 km/hr. Test your predic- tion by entering the speed and clicking the Go button. Question: If we want to arrive sooner (take less time), should we increase or decrease our speed? Answer: To arrive sooner, we must increase speed, so a speed greater than 2,000 km/hr would be needed. Question: Write a formula that shows how speed, distance, and time are used to describe motion. Answer: Average speed = total distance/total time. 12 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Forces:Friction Overview Newton 9s first law of motion states that if an object is in motion, it will travel in a straight line and at a con- stant speed unless a force is exerted on it. One force that acts on almost every object is friction. Friction is a force that opposes motion and causes objects to slow down. Surface friction is due to small bumps and ridges on the surface of two objects sliding against one another. No matter how highly polished two surfaces are, there are always microscopic irregularities. Friction is directly proportional to the force push- ing two surfaces together. For example, gravity pulls a brick against a table with a greater force than gravity pulls a wooden block of the same size. Therefore, the brick experiences greater friction forces as it slides across the table than the block does. The force of friction is larger for an object that is on the verge of sliding than for an object that is sliding. Static friction is the force needed to start an object moving, and sliding friction is the force needed to keep an object moving at a constant speed. The difference between static friction and sliding friction is important when braking your car for an emergency stop. Key Outcomes Students will be able to: " describe friction. " explain how the force of friction depends on the weight of the object or on the force pushing objects together. " explain the difference between static friction and slid- ing friction. " provide examples of situations in which reducing the force of friction is beneficial and when it is necessary to increase the force of friction. " give examples of lubricants and explain their effect on friction. Vocabulary " Friction " Force " Lubricant " Sliding friction " Static friction Motivation The motivation for this lesson is to conduct a classroom experiment to test and observe the effects of friction on different surfaces and to understand how friction helps us in our everyday lives and how it hinders us. Classroom Presentation Question: Why is it more difficult to walk on a frozen pond (or other surface covered with ice) than on the ground? Possible answers: " The ice is slippery. " The ground gives you better traction. " There is less friction between your feet and the ice than between your feet and the ground. Question: Does the reduced friction on ice make it easier or harder to move across it? Answer: It makes it easier to ice-skate but harder to walk. Question: Does the force of friction depend on the surfaces rubbing together? To answer this question, we will perform an exper- iment in the Science Discovery Laboratory. Record the May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 13 Forces:Friction data in the online Notebook or on the blackboard. The goal of this experiment is to determine what factors affect the force of sliding friction by observing the effect of three different triggers on various surfaces. Instructions for Doing the Experiment in the Laboratory Before using the simulation during a presentation, the presenter should review the online Instructions and become familiar with the functions available in this simulation. Three different triggers will be used to move a block on different surfaces. The distance the block moves with each trigger on each surface will be compared to deter- mine the order of the surfaces from greatest to least amount of friction. 1.Select a surface by clicking one of the five surfaces displayed. 2.Move the surface selected to the box labeled cSur- face, d and click it to set it in place. 3.Click the block, and move it into position. Click again to set it in place. 4.Select one of the three triggers, and click it in place. Click the Ready button. 5.Click the trigger, and watch the block slide. 6.Select the ruler from Tools. Use the ruler to deter- mine how far the block moved. 7.Record the trigger, surface, and distance in a data table. 8.Click Restart. 9.Repeat the above procedures until all surfaces have been tested with each of the three triggers. 10.Record all data in your data table. Data Table Trigger Surface Distance StrongBrick2.0 cm. MediumBrick1.5 cm. WeakBrick1.0 cm. Display the trials in the Notebook (or on the board) to the class, and have the students compare the results from the trials to find a qualitative relationship. Question: List the surfaces in order from greatest amount of friction to least amount of friction. Answer: The surfaces in order from greatest amount of fric- tion to least amount of friction are brick, leather, wood, steel, and ice. Question repeat: How do the different surfaces affect the sliding block? Answer: Some surfaces, like brick, create more friction and slow the block down quickly. Other surfaces, like ice, create very little friction and slow the block down slowly. Question: Which surfaces would be good for making a side- walk? Which surfaces would be bad for a sidewalk? StrongIce14.25 cm. MediumIce11.5 cm. WeakIce8.0 cm. StrongWood4.5 cm. MediumWood3.25 cm. WeakWood1.75 cm. StrongSteel6.25 cm. MediumSteel4.75 cm. WeakSteel3.0 cm. StrongLeather3.5 cm. MediumLeather2.5 cm. WeakLeather1.5 cm. Data Table Trigger Surface Distance 14 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Forces:Friction Answer: Brick would be good, since it creates a lot of fric- tion. People can walk on brick without much fear of slipping. Ice would be a bad surface, since it creates very little friction. People walking on a sidewalk made of ice would probably slip and fall. May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 15 Waves:Measuring Light Overview Light is a wave. We can describe waves in terms of wave- length, frequency, and speed. When we deal with sound waves, frequency and wavelength determine the pitch of the sound we hear. When we deal with light, fre- quency and wavelength determine the color we see. While studying light, Sir Isaac Newton noticed that white light was made up of many different colors. This is easy to see if we hold a prism in a beam of sunlight. The prism separates the white sunlight into the rain- bow of colors that makes up white light. The order in which the colors are arranged is always the same:Red, Orange, Yellow, Green, Blue, Indigo, and Violet ( cROY G. BIV d). The prism bends the sunlight as it passes through the glass. The reason we can see the different colors as the light leaves the prism is that the glass bends each color to a different extent. Red light, which has the longest wavelength, bends the least. Violet light, which has the shortest wavelength, bends the most. Visible light is only a small part of what we now call electromagnetic radiation. The lowest frequencies (longest wavelengths) of electromagnetic radiation are called radio waves. Higher frequencies are called microwaves. Still higher frequencies are called infrared waves, which we feel as heat. Next comes the visible light that we can see. Fre- quencies higher than visible light include ultraviolet light and x-rays. Key Outcomes Students will be able to: " identify the composition of visible light. " recall the colors of the spectrum in order from longest to shortest wavelength. " observe the spectra from different sources of light. " observe and draw the electromagnetic spectrum of visible light. Vocabulary " Electromagnetic spectrum " Electromagnetic radiation " Prism " Spectroscope " Wavelength " Frequency Motivation The motivation for this lesson is to conduct a classroom experiment in which students observe the spectra that come from different sources of light, draw the spectra, and compare them. Classroom Presentation Question: What happens when sunlight passes through drop- lets of water after a rainstorm? Answer: A rainbow is formed. Question: What happens to the light as it passes through the water droplets? Answer: The light is separated into its colored components. Question: What color is the light before it enters the water droplets? Answer: The light is white. Question: What conclusion can we draw about white light from this information? 16 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Waves:Measuring Light Answer: White light is made of all the colors in visible light. Question: What do we call a piece of glass that acts like the water droplets and separates light into its colored components? Answer: We call a cut piece of glass that separates light into its colored spectrum a prism. Question: What colors make up white light? Answer: Red, orange, yellow, green, blue, indigo, and violet make up white light. Not every source of light gives off white light like the sun. Using instruments like prisms, we can find out exactly what colors of light are given off by different light sources. Such instruments are called spectrome- ters, and they measure each color by the wavelength of that color. Let 9s use the Science Discovery Laboratory to use a spectrometer to look at light from a light bulb. Instructions for Doing the Experiment in the Laboratory Before using the simulation during a presentation, the presenter should review the online Instructions and become familiar with the functions available in this simulation. 1.Click the right arrow to increase the wavelength and observe the colors of visible light. 2.Click the left arrow to decrease the wavelength and observe the colors of visible light. 3.Demonstrate each color and its corresponding wavelength. Question: When the color is purple (violet), what is the wave- length in nanometers (nm)? NOTE :The color vio- let is referred to as purple in the Science Discovery Laboratory. Answer: 425 nm Question: When the color is blue, what is the wavelength in nanometers (nm)? Answer: 475 nm Question: When the color is green, what is the wavelength in nanometers (nm)? Answer: 525 nm Question: When the color is yellow, what is the wavelength in nanometers (nm)? Answer: 575 nm Question: When the color is orange, what is the wavelength in nanometers (nm)? Answer: 600 nm Question: When the color is red, what is the wavelength in nanometers (nm)? Answer: 660 nm Question: Which color has the shortest wavelength? Answer: purple (violet) May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 17 Waves:Measuring Light Question: Which color has the longest wavelength? Answer: red Question: Which color has the lowest frequency? Answer: red Question: Which color has the highest frequency? Answer: purple (violet) Question: This light bulb emits white light, which includes all the colors of the rainbow. Would you expect to see all the colors if the bulb did not emit white light? Answer: If the bulb emitted light other than white light, some of the colors would be missing when the light passed through the spectrometer. 18 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Sound:Doppler Shift Overview As an object emitting a sound of constant pitch approaches or leaves a stationary listener, the apparent pitch changes. The pitch of an approaching object is higher, and the pitch of a retreating object is lower, than the pitch actually emitted from the object. This change in pitch can be explained by the wave nature of sound. Sound waves are compression waves. The number of compressions per second determines the sound 9s pitch, or frequency. The compressions move out from the source of the sound in all directions at a constant speed. In the figure below, it is clear that relative to a station- ary observer, if the sound source is moving, the com- pressions in the direction of motion are spaced closer together and the compressions in the opposite direction are spread farther apart. It is as if the sound source were emitting more compressions per second in front of it and fewer compressions per second behind it. This is exactly how a stationary listener hears the moving sound source:a higher pitch when standing ahead of the moving source, and a lower pitch when standing behind the moving source. Key Outcomes Students will be able to: " describe Doppler shift as pitch change generated by a moving object. " experience the Doppler shift. Doppler effect (or shift) " explain the Doppler shift as it relates to frequency of waves. Vocabulary " Compression waves " Doppler shift " Frequency " Pitch Motivation The motivation for this lesson is to make a device that demonstrates the Doppler effect and to use it to observe the Doppler effect firsthand. Classroom Presentation Question: Have you ever stood near a railroad track when a train approaches and then passes? What did you observed about the sound made by the passing train? Have you ever listened to a car approach you or drive away with its horn blaring? How would you describe the change in the sound of the horn as the car draws nearer and then farther away? Possible Answers: " There is a change in the pitch of the sound. " The sound of the train or horn seems higher pitched as the vehicle approaches. " The sound seems lower pitched as the vehicle moves away. Question: What other examples of this change in pitch have you observed? May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 19 Sound:Doppler Shift Possible Answers: " Fire engine sirens. " Police sirens. " Ambulance sirens. " Insects flying past the ear. " A barber 9s electric razor moved quickly past your ear. " Any other object that is moving toward or away from you and producing sound. Question: What do we call this change in pitch? Answer: The Doppler effect. To better understand what the Doppler effect is, let 9s use the Science Discovery Laboratory. Instructions for Doing the Experiment in the Laboratory Before using the simulation during a presentation, the presenter should review the online Instructions and become familiar with the functions available in this simulation. Explain that sound is a wave, and that the Doppler effect is due to the wave nature of sound. Explain that since we cannot see sound waves, we will look at water waves to see what happens when a sound is Doppler- shifted. The water bug in the top box makes circular ripples as it walks across the water. These ripples are water waves, and they behave in the same way that sound waves do. By watching the waves made by the water bug, we can see how sound waves would behave. 1.Click the Tread button to observe the bug treading water in one place. 2.Use the ruler to compare the water waves created by the bug in front and in back. Record your obser- vations in the online Notebook or on the black- board. 3.Click the Swim button to observe the bug swim- ming forward in the water. 4.Use the ruler to compare the water waves created by the swimming bug in front and in back. Record your observations in the online Notebook or on the blackboard. Question: How are the waves different when the bug moves from when it stays in place? Answer: When the bug is staying in place, the waves are evenly spread out both in front and behind (just under 1.5 cm between waves). When the bug is moving, the waves are closer together in front of the bug (1 cm between waves) and more spread out behind the bug (just under 2 cm between waves). These waves move out from the bug. A person could count the waves as they passed. Waves are often classi- fied by how many waves pass per second. The number of waves passing a point per second is called the wave 9s frequency. Question: Where do the waves have the greatest frequency--in front of the stationary bug, behind the stationary bug, in front of the moving bug, or behind the mov- ing bug? Answer: Since the waves are closest together in front of the moving bug, more waves would pass a stationary point per second there. The number of waves per second is the frequency. Question: Where do the waves have the lowest frequency, in front of the stationary bug, behind the stationary bug, in front of the moving bug, or behind the mov- ing bug? Answer: Since the waves are farthest apart behind the mov- ing bug, fewer waves would pass a stationary point per second there. The number of waves per second is the frequency. 20 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Sound:Doppler Shift Question: Why does the frequency of the waves in front of and behind the bug change when the bug is moving? Answer: In front of the moving bug, the bug and the waves are moving in the same direction. The bug follows the wave it just emitted and is closer to that wave when it emits the next wave than it would be if the bug stayed in one place. Behind the moving bug, the bug and the wave are moving in opposite directions. The bug is moving away from a wave it just emitted and is farther away from that wave when it emits the next wave than it would be if the bug stayed in one place. Let 9s compare the behavior of water waves with sound waves. In the box with the car, sound waves are represented with black lines. Observe how the sound waves behave when the car is stationary and when it moves. 5.Click the Idle button to observe the sound waves emitted by the car when it 9s not moving. Record your observations in the online Notebook or on the blackboard. 6.Click the Gas button to observe the sound waves emitted by the moving car. Record your observa- tions in the online Notebook or on the blackboard. Question: How are the waves different when the car moves from when it is staying in place? Answer: When the car stays in place, the sound waves are evenly spread out both in front and behind (just under 1.5 cm between waves). When the car is mov- ing, the sound waves are closer together in front of the bug (1 cm between waves) and more spread out behind the car (just under 2 cm between waves). These sound waves move out from the car. A person standing at the side of the road with the appropriate equipment could count the sound waves as they passed. Sound waves, like water waves, are classified by how many waves pass a point per second. The number of waves passing a point per second is called the wave 9s fre- quency. Question: Where do the sound waves have the greatest fre- quency--in front of the stationary car, behind the stationary car, in front of the moving car, or behind the moving car? Answer: Since the sound waves are closest together in front of the moving car, more waves would pass a station- ary point per second there. The number of waves per second is the frequency. Question: Where do the sound waves have the lowest fre- quency, in front of the stationary car, behind the stationary car, in front of the moving car, or behind the moving car? Answer: Since the sound waves are farthest apart behind the moving car, fewer waves would pass a stationary point per second there. The number of waves per second is the frequency. The frequency of a sound wave determines the pitch of the sound. The higher the frequency, the higher the pitch of the sound. Question: When the car is moving, where would you stand in order to hear the lowest pitch and where would you stand in order to hear the highest pitch? Answer: You would stand behind the car to hear the lowest pitch and in front of the car to hear the highest pitch. This change in pitch is called the Doppler effect. Question: Why does the pitch of the sound waves in front of and behind the car change when the car is moving? Answer: In front of the moving car, the car and the sound May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 21 Sound:Doppler Shift waves are moving in the same direction. The car fol- lows the wave it just emitted and is closer to that wave when it emits the next wave than it would be if the car stayed in one place. Since the waves are closer together, someone at the side of the road would count more waves per second. This higher frequency means the sound has a higher pitch. Behind the moving car, the car and the sound wave are moving in opposite directions. The car is mov- ing away from the wave it just emitted and is far- ther away from that wave when it emits the next wave than it would be if the car stayed in one place. Since the waves are farther apart, someone at the side of the road would count fewer waves per sec- ond. This lower frequency means the sound has a lower pitch. 22 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Circuits:Insulators and Conductors Overview Electrical current is the movement of charged particles through a closed circuit, or loop. In solids, it is typically the negatively charged electrons that move. Many met- als, for example, are made of atoms in which the nuclei hold some of their outer electrons very loosely. This makes it possible for an electric field to pull these elec- trons from atom to atom around the loop. Materials in which electrons can move easily are called conductors of electricity. In other materials, the atomic nucleus holds almost all the electrons tightly. Since there are few elec- trons to flow around the circuit, there is little electrical current in these materials. These materials are called insulators. Nearly all metals are good conductors, and most nonmetals are insulators. Gold, silver, platinum, and copper are some of the best conductors. Conductors are used as wire for transporting electricity to places where it is needed. Insulators are used to coat wires to protect us from shocks and to keep electricity in the wires. The electric field that causes electrons to flow in conductors is the same field created by static charges. An excess of electrons at one end of the circuit forces the electrons in the wire around the loop. An excess of pos- itive charges attracts electrons around the loop. The dif- ference between the number of excess charges at one end and the number of excess charges at the other end of a circuit determines the force with which the elec- trons are pushed or pulled around the loop. We measure this force in volts. The larger the voltage, the stronger the push or pull on the electrons. The number of electrons per second that the volt- age pushes around the circuit is the electrical current and is measured in amperes. An ampere is the number of charged particles that pass through a point in one second. The amount of current that flows through a cir- cuit depends not only on the voltage but also on the resistance of the conductor. For example, it takes less force to push sand through a pipe that has been greased on the inside than it does to push the same amount of sand through that same pipe when it hasn 9t been greased. The grease lowers the resistance to the moving sand and so allows the sand to be pushed through with a smaller force. Georg Simon Ohm discovered the rela- tionship between current, voltage, and resistance. The relationship is called Ohm 9s law. Voltage = current × resistance Key Outcomes Students will be able to: " describe what is meant by electric current. " identify which materials are good conductors and operationally define conductors as materials that have many electrons that are free to move. " identify which materials are good insulators and oper- ationally define insulators as materials that have few electrons that are free to move. Vocabulary " Charge " Electroscope " Conductor " Insulator " Electric current " Electric field " Voltage " Atom " Nucleus " Ampere " Resistance " Electron May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 23 Circuits:Insulators and Conductors Materials " 30- to 100-cm piece of garden hose with an inner diameter about the diameter of a marble " enough small marbles to fill the entire length of the hose (The marbles should fit snugly into the hose.) Motivation Our lives in modern society depend on electricity. Cir- cuits bring electricity to our homes for lights, stoves, televisions, heaters, computers, and telephones. Con- trolling the resistance of different parts of silicon chips allows us to make integrated circuits that are the brains of our computers. Electrical circuits help run cars, planes, and most of our other transportation systems. Understanding how circuits work allows us to under- stand the objects we see around us. Classroom Presentation How does electricity flow through materials? Let 9s con- duct a simple demonstration that will help us under- stand how. Push the marbles into the hose so that the entire hose is filled with a line of marbles. Explain that the hose is filled with a line of marbles, and ask students what will happen if another marble is added to one end of the hose. Hold the two ends of the hose, and have a student push another marble into one end (it may take some effort). A marble will fall out of the other end. In this model, the hose represents a conductive wire and the marbles represent the electrons in that conduc- tor. The energy provided by the person forcing the mar- ble into the hose represents energy provided by a battery. Question: Is it the marble that was added to the hose that came out the other side? (This can be tested, if nec- essary, with a differently colored marble.) Answer: No. Question: As a model of a simple electric circuit (refer to the one set up) what do the marbles, hose, and student represent? Answer: The marbles represent electrons, the hose repre- sents a conductor, and the student represents a bat- tery. Question: Predict how the results would change if the marbles were glued into the hose. Answer: The marbles would not move at all. This represents a very poor conductor, also known as an insulator. Question: What makes a material a conductor or an insula- tor? Answer: A conductor has free electrons that are available to move, but the electrons in an insulator are so tightly bound that they are unavailable to move freely. Question: Are electrons used up in an electrical circuit? Answer: The electrons are not used up in an electrical cir- cuit. The same number of electrons that leave a bat- tery return to it. Question: Does a battery supply the electrons that move in an electric circuit? Answer: No, the battery provides the energy to push the electrons that are already freely available in the conductor that makes up the circuit. Now let 9s conduct an experiment in the Science Discovery Laboratory to find out more about insulators and conductors. 24 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Circuits:Insulators and Conductors Instructions for Doing the Experiment in the Laboratory Before using the simulation during a presentation, the presenter should review the online Instructions and become familiar with the functions available in this simulation. 1.Select one of the items from the box of materials by clicking the item:copper wire, safety pin, cotton ball, glass, plastic, puddle of water, staple, potato chip, balloon, or paper clip. 2.Move the object to the empty space in the circuit, and click to set it in place. If the item is a conductor of electricity, the white dots representing electrons will flow and the light bulb will light up (turn yel- low). If the item is an insulator, the white dots will not flow and the light bulb will not light up. 3.To remove the item from the circuit, click the item, move it back to the box of materials, and click to set it in place. 4.Repeat this process until you have selected each item in the box of materials. Ask students to make two lists:one for conductors and one for insulators. Question: Which items completed the circuit? Answer: The copper wire, safety pin, puddle of water, staple, and paper clip completed the circuit. Question: Are these items conductors or insulators? Answer: Conductors. Question: Which items are insulators? Answer: The cotton ball, glass, plastic, potato chip, and bal- loon are insulators. Question: What properties do most of the conductors have in common? Answer: The conductors are metals with the exception of water. Pure water is not a conductor of electricity a 4it is only when ions are present in a solution that water can conduct electricity. All conductors have elec- trons that are free to flow. Question: What properties do most of the insulators have in common? Answer: The insulators are nonmetals and do not have elec- trons that are free to flow. May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 25 Simple Machines:Inclined Plane Overview Inclined planes help us lift objects. They do this by decreasing the force we need to lift an object to a certain height compared to the force we need to use to lift the object straight up. However, using an inclined plane to lift an object requires that we exert this smaller force over a longer distance. Inclined planes do not change the amount of work necessary to raise a load to a given height. Work is defined as follows:work = force × dis- tance. Key Outcomes Students will be able to: " describe an inclined plane. " explain the effect of inclined planes on the force and distance necessary to raise a load. " understand that inclined planes do not change the amount of work required to lift an object. " understand that work = force × distance. Vocabulary " Inclined plane " Load " Work " Joule Motivation The motivation for this lesson is to design a wheelchair ramp, taking into consideration the space available to build the ramp and the financial costs involved. Classroom Presentation Question: Why do people use ramps? Ask the class for sugges- tions. Possible Answers: " Ramps, or inclined planes, allow us to raise loads using smaller forces than if we were lifting the load straight up. " In the case of a wheelchair, it would not be possi- ble for people to roll their wheelchair up a ver- tical face, so a ramp actually allows them to move where they wouldn 9t otherwise be able to. " Ramps help us raise loads. " Ramps make it easy to lift loads. Question: How do inclined planes change the job of lifting loads to higher places? To answer the question, we will perform a simple experiment in the Scinece Discovery Laboratory. To enter the Science Discovery Laboratory, click Simple Machines, and then click the Inclined Plane simulation. Instructions for Doing the Experiment in the Laboratory Before using the simulation during a presentation, the presenter should review the online Instructions and become familiar with the functions available in this simulation. Explain that for an inclined plane to help us as much as possible in moving a load, we must exert the smallest force we can to move a load along an inclined plane. In the simulation, each time we find a force that moves the load, we will check to see whether it is the smallest force that will move the load. (The smallest 26 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Simple Machines:Inclined Plane force must be used for the work = force × distance cal- culations to be correct.) 1.Note that the inclined plane is 5 meters long. Click the block to place it on the inclined plane. Point out the different controls that appear at the top of the screen. One displays the length of the inclined plane, another displays the weight of the block, a third displays the force exerted on the block, and the fourth displays the angle of the force exerted on the block. Note that the force applied to the block will be 3,000 newtons. Click Move to see whether 3,000 newtons will move the load up the inclined plane. (It won 9t.) 2.Click Reset to move the block off the inclined plane. 3.Click the bottom of the inclined plane and move it to the left until the inclined plane is 8 meters long. Click again to set the inclined plane in place. 4.Click the block and then click Move to see whether 3,000 newtons will move the load up an 8-meter inclined plane. (It will.) 5.Click Reset and click the block. 6.To find out whether 3,000 newtons is the smallest force that will move the block up an 8-meter inclined plane, click the down arrow on the Force box to change the force to 2,999 newtons. Click Move to see whether this will move the load. (It won 9t.) Since 2,999 newtons does not move the load, 3,000 newtons is the smallest force that will move the load up this inclined plane. Record the size of the force and the distance the load moved (the length of the inclined plane) in the Notebook or on the board. 7.Click Reset. 8.Change the length of the inclined plane in the man- ner explained above to 4 meters. 9.Click the block. Click Move to see whether 2,999 newtons will move the load up the inclined plane. (It won 9t.) 10.Click Reset, and click the block. 11.To change the force, click the number in the Force box. Type in 6,000 and then press the return key. 12.Click Move to see whether 6,000 newtons will move the load up a 4-meter inclined plane. (It will.) 13.Click Reset, and click the block. 14.Click the down arrow on the Force box to change the force to 5,999 newtons. Click Move to see whether this will move the load. (It won 9t.) Since 5,999 new- tons does not move the load, 6,000 newtons is the smallest force that will move the load up this inclined plane. In the Notebook or on the board, record the size of the force and the distance the load moved. 15.Click Reset. 16.Make the inclined plane 3 meters long. 17.Test whether 5,999 newtons will move the load up the inclined plane. (It won 9t.) 18.Click Reset, and click the block. 19.Change the force in the Force box to 8,000 newtons. 20.Test whether 8,000 newtons will move the load up a 4-meter inclined plane. (It will.) 21.Click Reset, and click the block. 22.Change the force to 7,999 newtons. Test whether this will move the load. (It won 9t). Since 7,999 newtons does not move the load, 8,000 newtons is the smallest force that will move the load up this inclined plane. In the Notebook or on the board, record the size of the force and the distance the load moved. Display the three trials in the Notebook or on the board to the class, and have the students answer the fol- lowing questions: Question: How do inclined planes change the job of lifting loads to higher places? Answer: Inclined planes change the size of the force neces- sary to raise an object and the distance the object must be moved to reach the desired height. Question: How does a change in force relate to a change in dis- tance when using an inclined plane? Have the students compare the results from the three trials to find a qualitative relationship. May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 27 Simple Machines:Inclined Plane Answer: As a longer inclined plane is used, the force needed to lift the load becomes smaller. Question: Why does the size of the force decrease as the dis- tance increases? (Answer this question while look- ing at the data from the lab experiment.) Answer: When we lift loads, either with or without simple machines, we are doing work. Work is defined as fol- lows: Work = force × distance where the force is in the direction that the object moves. Have the students calculate the work done in each trial. Note that the work done is the same in each trial. Inclined planes do not change the amount of work it takes to do a job. Therefore, if the work stays the same and if the force needed to lift a load decreases, then the distance over which that force is applied must increase, so that force times distance still equals the same amount of work. 28 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Cells:Diffusion and Osmosis Overview Living cells are able to maintain concentrations of cer- tain chemicals inside that are different from the levels of those chemicals outside. The cell membrane makes this possible by acting as a barrier. However, cells do need some chemicals to move in and out through the cell membrane. Two related processes help cells move chemicals around within the cell and in and out of the cell. These processes are diffusion and osmosis. Neither process requires the cell to expend energy. Diffusion is the process of a substance moving from an area of greater crowding to one of less crowding until that substance is evenly spread throughout the area. The amount of crowding of a particular kind of mole- cule in a given area is called its concentration. The dif- fusion of water across a semipermeable membrane such as the cell membrane is called osmosis. Key Outcomes Students will be able to: " explain that molecules move from areas of higher con- centration to areas of lower concentration. " explain models of how molecules enter and leave cells by diffusion and osmosis. Vocabulary " Concentration " Diffusion " Hypertonic " Hypotonic " Isotonic " Osmosis " Osmotic pressure " Semipermeable membrane " Solute " Solution " Solvent " Water displacement Materials " overhead projector " petri dish " water " dye Motivation The motivation for this lesson is to enable students to construct a model of how the cell membrane functions with respect to osmosis. Students can then perform the experiment in the extension to compare their model with the function of a real cell membrane. Classroom Presentation A demonstration would greatly facilitate this discus- sion. A simple demonstration is to place a petri dish on an overhead projector. Fill the dish with colored water. Add a drop of clear water to the dyed water. The stu- dents can watch the clear water diffuse into the dyed water. Question: What is a solution? Answer: A solution is a mixture in which one substance, called the solute, breaks up into individual mole- cules or ions and spreads evenly through another substance called the solvent. In a dye solution, the dye is the solute and water is the solvent. May 3, 2005 3:47 pm Classroom Presentation Lesson PlansLaboratory 29 Cells:Diffusion and Osmosis Question: What happens when a drop of water is placed in a dish of dye solution? Possible answers: " The water and dye mixed together. " The molecules of water and dye solution were in constant and random motion and mingled until perfectly blended. " The dye diffused into the water drop and the water drop diffused into the dye. Question: What is diffusion? Answer: Diffusion is moving of molecules from a region of higher concentration to a region of lower concen- tration. There is no dye in the drop of water, so the dye is more highly concentrated in the dye solution around the drop of water. The water is more highly concen- trated in the drop because there are no dye molecules present in the drop. So the dye diffuses into the water while at the same time, the water diffuses into the sur- rounding dye solution. Question: What is osmosis and how does it relate to diffusion? Possible answers: " Osmosis is the process through which water passes in and out of plant and animal cells. n Osmosis allows plants to absorb water and reg- ulates the exchange of water between an ani- mal 9s cells and its body fluids. Osmosis occurs as the water diffuses across the semipermeable membrane of the cell. All cells have a cell membrane that is the outer boundary of the cell. This membrane lets some molecules through--water, for example 4and does not allow other molecules to pass 4many chemicals that might be dissolved in water, for example. Diffusion happens naturally, so a cell does not have to exert any energy to move water in or out of itself if the water moves by diffusing across the cell membrane, in other words, by osmosis. Cells do not usually exist in pure water. Almost all cells live in an environment that is itself a solution. Ocean water is a salt-water solution. Animal cells are usually surrounded by some sort of fluid like blood which is mostly water with other molecules dissolved in it. Even freshwater lakes and rivers are not pure water. They often contain dissolved minerals and other nutri- ents. To understand how osmosis affects cells that live in solutions, let 9s investigate osmosis across a semiperme- able membrane using three different solutions and a tank of sugar-water. Instructions for Doing the Experiment in the Laboratory Before using the simulation during a presentation, the presenter should review the online Instructions and become familiar with the functions available in this simulation. Enter the Science Discovery Laboratory. Mark Cells. Once at the Cells simulation selection screen, mark Diffusion and Osmosis. Explain that the top three bags on the left are made of semipermeable membranes and are filled with solu- tions of sugar-water of three different concentrations. The first bag is filled with a 1% sugar-water solution. That means for every molecule of sugar, there are 99 molecules of water. The second bag is filled with a 10% sugar-water solution, which means that for every mole- cule of sugar, there are 9 molecules of water. The third bag is filled with a 25% sugar-water solution. This means that for every molecule of sugar, there are 3 mol- ecules of water. Question: In which bag is the water most concentrated? Answer: Water is most concentrated in the 1% solution bag. In the 1% solution bag, almost every molecule 499 out of 100 4is water. 30 Classroom Presentation Lesson PlansLaboratory May 3, 2005 3:47 pm Cells:Diffusion and Osmosis Question: In which bag is the sugar most concentrated? Answer: Sugar is most concentrated in the 25% solution bag. In the 25% solution bag, one of every four mol- ecules is sugar. Explain that the tank on the right is filled with a 10% sugar-water solution. We can consider each of the bags of solution as cells. Like cells, these bags are made of chemicals such as water and sugar surrounded by a semipermeable membrane.

less