Transpiration is an important concept in both biology and environmental science, especially in terms of role it plays in the water cycle. As water evaporates from the stoma of leaves water is pulled up (due to hydrogen bonding) through the xylem from the roots which have drawn the water from the surrounding soil.
Because transpiration is essentially an invisible process, a potometer is used to measure the rate of water lost to the air. The advantages that sensor technology makes in many investigations in biology and environmental science are that it allows students to see the data in real time while great improving the accuracy and significantly decreasing the time needed to capture data.
Setting up a classic potometer with a Wireless Pressure Sensor is one example of how integrating sensors can improve the data collection process. With the included Leur connectors and tubing, all you need is a plant sample and optional stand with clamps to complete the lab. Students can choose from any plants available, but there are three general guidelines which help ensure success. Students should choose a plant with
a woody stem/branch that will fit snugly into the tubing, making it less prone to crushing and easier to setup.
relatively soft cuticle leaves because they generally have higher rates of transpiration and good stomatal density.
high leaf surface area (either large leaves or lots of leaflets) per stem/branch.
Insert the plant stem into the tubing as shown, making sure there are no bubbles in the tubing and that you have a few centimeters of air between the sensor and water. This can take a few tries to get right, and having a sink or tub to submerse the tubing in will help. The cohesion and adhesion of the water along with a slight positive pressure created when connecting the sensor will keep water out of the sensor even if a stand is not available.
Figure 1. Potometer Setup with Wireless Pressure Sensor
Data collection usually takes 5-10 minutes depending on the plant. For the control run (taken at room temp with ambient light) wait for a change of at least 5.0 kPa before stopping data collection. After the control run is complete, find the rate of transpiration in kPa/min using the curve fit tool and save this into a data table. Save the plants from each trial so the surface area can be calculated and the trial data normalized for comparison.
Figure 2. Sample data from control run at room temperature with ambient lighting
Calculating surface area (SA) can be done using the tried and true method with graph paper, but if you have cameras and computers available students can also use ImageJ— a free image analysis tool from the National Institute of Health. This is a powerful software and the basics are pretty easy to master. The steps for conducing area and size calculations in ImageJ can be found in this blog article or on this video. Although not part of the PASCO software suite, this is another tool that eliminates some repetitive work from the procedure and let students really focus on the data and analysis that support learning.
Figure 3. ImageJ program analyzing leaf SA from control trial.
When the SA is determined, add it to the data table in SPARKvue. A simple calculation provides the adjusted rate in kPa/Min/cm2. In subsequent trials students can investigate the impact of environmental variables such as light intensity, humidity, temperature, and wind— or they can compare different species of plants.
Figure 4. Data analysis table with control and windy trial data
You can download the sample data with the table formatted and calculations created. After students go through the procedure once they can easily iterate this setup to conduct their own inquiry— where the true learning transpires!
We high school physics teachers tend to associate the right-hand rules with electromagnetism. As a student, my first encounter with a right-hand rule was when I was introduced to the magnetic field produced by the electric current in a long, straight wire: if you point the thumb of your right hand in the direction of the conventional current and imagine grasping the wire with your hand, your fingers wrap around the wire in a way that is analogous to the magnetic field that circulates around the wire.
I only later discovered that this same rule can be applied to rotational quantities such as angular velocity and angular momentum. The topic of rotation has become more important in AP physics when the program was updated from the older Physics B program. Strictly speaking, AP Physics 1 does not include the use of the right hand rule for rotation, but I have found that introducing it actually helps solidify student understanding of angular vectors.
Describing the direction of rotation as being clockwise or counterclockwise is helpful only if all parties involved have a common point of view, which is ideally along the axis of rotation. As with left and right, clockwise and counterclockwise depend on your point of view. This is why it is often preferable to describe translational motion in terms of north, south, east, west, up, and down, or with respect to a defined x-y-z coordinate system; directions can be communicated unambiguously, provided that everybody uses the same coordinate system.
It is precisely for this reason that the right hand rule can (and should) be used for rotational motion. Consider the hands of an analog clock. Assuming that the clock is a typical one, it will have hands that turn “clockwise” when viewed from the “usual” point of view, but if the clock had a transparent back and you were to view it from the back you would see the hands turning “counterclockwise!” The observed direction of rotation (clockwise or counterclockwise) depends on the observer’s point of view.
Instead of using clockwise and counterclockwise, we can describe the direction of rotation with a right hand rule: if you curl the fingers of your right hand around with the direction of the rotational motion, your thumb will point in the direction of rotation, which will be along the axis of rotation. Applying this to the above we find that when viewing a clock from the front, the rotation of the hands is three dimensionally into the clock (away from the observer), and when viewing a clock from the back side, the rotation of the hands is three dimensionally out of the clock (toward the observer). If two people view a transparent clock at the same time but one observes it from the front while the other observes it from the back (i.e. the clock is between the two people who are facing each other), they will disagree on which way the hands turn (clockwise or counterclockwise) but will agree on this direction if both use the right hand rule convention to describe the direction of the rotational motion – both observers will agree that it is directed toward the person viewing the back side of the clock.
When first learning about the right hand rule, students are often initially confused, with many students failing to grasp why such a rule is even useful in the first place. Before introducing the right hand rule I like to begin by holding an object such as a meter stick while standing at the front of the classroom. I then rotate the meter stick through its center so that the students claim that it is rotating “clockwise” when asked. Being careful to keep the rotational motion as constant as possible, I then walk to the back of the room. It’s important that the students see that at no point did I stop the rotation of the meter stick – it is still turning the same way as before, and yet at some point each student finds that they must turn around in order to continue to see it. Many students are astonished to see that the meter stick is now rotating counter clockwise from their (now reversed) point of view. This helps establish the need for a better way to describe rotation.
I then introduce the right hand rule and go through a couple of examples. Traditionally, this would have been the end of it, but last year I was able to take advantage of my newly acquired PASCO Smart Cart, which has a wireless 3-axis gyroscope (i.e. rotational sensor). The coordinate system is fixed with respect to the cart, and is printed on the cart itself, but I like to make this more visible by attaching cardboard cutout vectors onto the cart which make the axes more visible to the students while I hold the cart up for them to see. I then set up a projected display of the angular velocity of the cart along each axis simultaneously. I then ask the students how I must turn the cart in order to get a desired rotation of my choosing (i.e. ±x, ±y, and ±z).
I really like how the carts, along with the live display of the 3 angular velocity components make the admittedly abstract right hand rule so much more concrete. Seeing the display agree with our predictions makes it so much more real and is much, much better than me merely saying “trust me.” I have found that introducing and using this right hand rule with rotation has made using this same rule much more natural when using it to later relate the direction of current flow and the magnetic field.
Reposted from the NSTA Blog, original article can be found here.
The PASCO Wireless Spectrometer
Simply put, constructivism is a theory of knowledge that argues that humans generate knowledge and meaning from an interaction between their experiences and their ideas. So it follows that nothing is can be more constructivist than exploring the theoretical with real-time tools that measure the invisible. And the PASCO Wireless Spectrometeris just such a tool.
One of the most amazing things about the PASCO Wireless Spectrometer is that it does exactly what you would want it to do; show you the invisible with ease, simplicity, and leave behind a useful digital paper trail of graphs and charts. Although the main purpose of the PASCO Wireless Spectrometer was “specifically designed for introductory spectroscopy experiments” it actually goes farther than that. Much farther. Much much farther!
This trio of teachers, two from China and one from Mongolia have limited English speaking skills, but instantly understood the iPad app and PASCO Wireless Spectrometer. Seems that light is also a universal language.
The physics and electronics behind the PASCO Wireless Spectrometer are straight forward. The output is clear and obvious. And the mobility aspect is unprecedented. In other words, it does what it should how it should. Amazing enough on its own, but in true paradigm shifting fashion the PASCO Wireless Spectrometer presents the invisible world of visible light in the magical cartoon chart we’ve seen only in static textbooks for most of our lives. It’s as if the dinosaur skeletons in dusty museums suddenly came alive and reacted to the world.
Visible light, or the light our human eyes sense and convert to electrical impulses to our brains, only encompass a tiny fraction of the electromagnetic spectrum. Wavelengths between 390-700 nanometers, or from the short blue/violet waves to the longer orange/red ones with green and yellow in the middle. Infrared waves are just a little too long for us to see, and ultraviolet ones are a little too short. Even longer are radio waves, and even shorter are x-rays. The PASCO Wireless Spectrometer has a range of 380 to 950 nanometers meaning it can “see” a little into the ultraviolet and a lot into the infrared.
An ultraviolet light spikes the graph just outside the shortest wavelength we can see with our eyes.
Where this all comes together is that when the PASCO Wireless Spectrometer and various light sources are manipulated with our hands, the extended visible spectrum becomes something we can explore with the same cognitive dexterity as the microscope affords us in biology. When used in the classroom for demonstrations and explorations, the PASCO Wireless Spectrometer literally lets “humans generate knowledge and meaning from an interaction between their experiences and their ideas.” So yes, the PASCO Wireless Spectrometer is the epitome of constructivist theory into educational practice.
Although Isaac Newton is credited with discovering the inner workings of visible light back in the latter 1600s, the basic concept behind a rainbow was suggested by Roger Bacon 400 years earlier who in turn drew upon the works of Claudius Ptolemy a millennium before, and even Aristotle another 300 years before that.
As a quick digression here, the Newtonian physics behind the PASCO Wireless Spectrometer has roots much more than five times deeper into the past than Mr. Newton’s distance in time is from us right now. Sorry to go all Einstein on you, but the individual colors of visible light that Newton coaxed out of sunlight with only a glass triangle, and then reassembled with nothing more than a companion prism was like yesterday. Yet the attempts to explain the phenomena were first floated last week.
And now to think that within the palm of a student’s hand and the screen of their iPad is a gift of knowledge as great as the discovery itself. A stretch? Perhaps, but unless a scientific concept can be truly understood to the point one can make personal meaning out of the discovery, memorized facts are little more than coins used to buy grades.
Technically speaking, the PASCO Wireless Spectrometer is a battery operated spectrometer that uses Bluetooth wireless or a USB wire in order to communicate with a computing device running the necessary software. With its own built-in LED-boosted tungsten light source and three nanometer resolution, the PASCO Wireless Spectrometer provides an exceptional tool for traditional experimentation with pl
enty of room left over to inspect rarely explored specimens of light scattered throughout our lives.
The operation of PASCO’s unassuming black brick puts the power of spectrometry into the hands of grade school students and Ph.D. candidates alike. While maybe not the most durable block in the scientific toy box, the PASCO Wireless Spectrometer does offer a level of simplicity (when desired) as easy to use as glass prism and sunlight. Of course you can do much more with the PASCO Wireless Spectrometer, but you don’t have to in order to get your money’s worth. This spectrometer does so much so well so easily that it literally rewrites lesson plans just by walking into the classroom.
On a higher level, the PASCO Wireless Spectrometer can be used in chemical experiments of intensity, absorbance, transmittance and fluorescence all while using a device that, according to PASCO, has light pass through the solution and a diffraction grating and then a CCD array detects the light for collection and analysis. Sounds simple enough just like a digital prism should. Except this one gives about nine hours of service per battery charge.
In the off chance that the battery fails, it is user-replaceable. in the off chance the light burns out, it is user-replaceable. And in the likely chance that liquid from a cuvette spills into the holder, a drain hole limits the damage, and cleaning the holder is user-serviceable with a cotton swab and deionized water.
A portable studio light is used to provide a background of predictable photons in order to explore the absorbance properties of various types of matter including sunglasses, polarizers, fabric, and theater lighting filters.
The PASCO Wireless Spectrometer must interface with a computer or tablet. Both Mac and Windows are supported as is iOS and Android.
PASCO also suggests using the Wireless Spectrometer for the following popular labs:
Absorbance and transmittance spectra
Beer’s Law: concentration and absorbance
Photosynthesis with DPIP
Absorption spectra of plant pigments
Concentration of proteins in solution
Rate of enzyme-catalyzed reactions
Growth of cell cultures
Light intensity across the visible spectrum
Emission spectra of light sources
Match known spectra with references
And PASCO also provides several sample labs for plug-and-play directly into the chemistry classroom. But the really exciting plug-and-play option is the accessory fiber optic probe. With no more effort than sliding a faux cuvette into the receiving slot on the spectrometer, a meter-long fiber cord moves a directional sensor out into the wild where it can capture photons from all kinds critters. Some of my favorite animals include UV lights, filtered lightbulbs, various school lighting sources, sunlight though sunglasses, polarizers, and pretty much any LED flashlight I can find, especially the really good ones.
Although the screen output from the PASCO Wireless Spectrometer’s software is a graphical representation of a physical property, it takes almost no mental gymnastics to understand the changes to the graph once your mind is oriented to the display. The color-coded background and gesture-ready scaling provides an exceptionally smooth relationship with the data to the point all the hardware and software disappear leaving only the experiment and the results. And in my book, that kind of invisibility is the true measure of success with a teaching product.
When teaching the next generation about the important discoveries of the past generations, we have an obligation to use the most powerful educational tools possible. The PASCO Wireless Spectrometer is truly 100% pure constructivism-in-a-box. It turns experiences and ideas into personal meaning. Battery included and no wires necessary.
Coming Fall 2019! Free Upgrade for Capstone 1.x users!
Updated with new tools! Designed specifically to collect, display and analyze data in physics and engineering labs.
What’s New in Capstone 2
Reinforce circuit concepts and tackle student misconceptions using circuit visualization. Combine real-world circuits with simulations, animation, and live measurements.
With the Circuits Emulation tool in Capstone 2, you can:
Construct and modify circuits
Show conventional current and electron flow animation
Animate circuits with live sensor data
Drag components out from the components list. Rotate components, and connect pieces together by drawing wires.
This is how science is actually done.
You never take only one run in science. You take multiple runs, and calculate averages. Next, you vary a parameter while holding the other constant; again, taking more runs and calculating averages. Most software data tables don’t actually allow this to be done easily.
The Capstone Trails table was created for how data is collected in the science lab, and allows for the kind of analysis students need to perform.
Organize your data to easily define physical relationships.
Plot derived values
Using the simple pendulum lab as an example, students will time a simple pendulum under various conditions. They will vary the mass, length, and starting angle. The Capstone Trials Table allows you to vary and keep track of experimental parameters between trials, and runs taken in each trial. You can also keep track of statistics for averaged runs and experimental error.
Helps students develop computational thinking skills
Physics educators want more experimental control and programming access to all PASCO interfaces and sensors. Students need tools to develop creative programming and problem-solving skills in science. Blockly coding has been built into Capstone 2, giving teachers and students the tools they need to develop these skills.
Graph Pop-Up Tools
Now, whenever tools are activated, the most common actions will be easily accessible on the graph. The pop-up tools allow for easy access to tool features and options.
PASCO Capstone allows users to quickly layout custom pages, automatically recognizes sensors when connected, has a powerful set of analysis tools and much, much more.
PASCO Capstone was built from the ground up to be the most powerful and flexible option for physics and engineering applications.
Can be used with all current and legacy PASCO USB interfaces.
Works with all PASCO sensors — ScienceWorkshop, PASPORT, and Wireless.
Completely customizable lab pages
Multiple displays including graphs, tables, oscilloscope, bar meters, FFT and more
Capstone includes a very powerful video analysis feature which can be used for comprehensive analysis of moving objects as well as to improve understanding. Short video clips from your smartphone can be easily imported and analysed with a range of tools. The movement of objects with a high contrast to a uniform background can be automatically tracked by the software.
A ball will be thrown in a parabolic arc and various tools will be used to analyze the motion. Note that the vertical and horizontal axes have been marked and a distance of 4.00 m has been measured. This will enable the software to translate from pixels to m:
As part of the analysis, the position of the ball in each frame is marked and the result is as shown below:
It is now possible to have the software generate various graphs such as position vs time and velocity vs time.
A graph of vertical position vs time is as shown below:
A graph of horizontal position vs time yields the following:
A graph of the vertical component of velocity vs time yields the following result:
Capstone also includes tools that improve understanding. For example, in the screen below, the vertical and horizontal components of velocity are shown for the ball as it flies through the air.
To make the display less cluttered and less confusing it is possible to mark the vectors at an interval other than every frame. Below the vectors are shown every third frame:
It is also possible to have a single vertical vector and a single horizontal vector appear and move with the ball as it goes through the air.
It is also possible to show the acceleration vector as shown below:
The fact that a few vectors do not point directly down is likely due to minor errors made when marking the position of the ball in various frames with a mouse.
Your students will be amazed at how the PASCO strobe light instantly and dramatically freezes the motion of a vibrating string – appearing as if it’s stopped in time.
By slightly adjusting the strobe’s frequency, the string’s frozen wave will appear as if it is moving slowly forwards or backwards. This wave freezing demonstration approaches absolute zero on the ‘cool’ factor scale!
It was the shot heard across Canada. There were a lot of factors that made Kawhi’s buzzer beating basket so remarkable. Aside from there being no time left on the clock and the weight of a sport’s nation on his shoulders, Kawhi had to overcome the backward momentum that is inherent in a ‘fadeaway’. The purpose of a fadeway is to create space between the shooter and defender(s), which was a necessity for Kawhi as there were several seriously tall 76ers trying to screen his shot.
Over-coming the fadeway’s backwards momentum is no easy feat as it requires players to quickly calibrate in their minds the additional force that is required to successfully sink a basket, which for most mere mortals is not intuitive. The shot is so challenging that only a handful of NBA basketball players have been able to reliably make this shot; and we’re talking the great players such as Michael Jordan, Lebron James, Kobe Bryant and of course Kawhi Leonard.
The video below provides an extreme example of backwards momentum with a soccer ball shot from the back of a truck
Investigating Kawhi Leonard’s shot in the lab
In addition to backwards momentum there were many additional physical factors at play such as the angle of the shot and gravity. Investigating all these forces in a single activity would not be practical. Fortunately most of these forces can be isolated and explored in the lab using PASCO sensors, software and/or equipment.
Exploring The fadeaway’s negative momentum using PASCO
PASCO offers an intriguing and affordable solution to model the dramatic effect of a fadeaway’s negative momentum on projectile distance. PASCO’s mini launcher will consistently launch projectile balls the same horizontal distance for a set angle, assuming that the launcher is stationary. If however, the launcher is placed on PASCO’s frictionless cart, the force of pulling the trigger will cause the cart to move backwards at a velocity that can be measured using the motion sensor. Students will be surprised to see that even though the cart travels just a few centimeters, the overall projectile distance is significantly reduced. This can be a very simple demonstration or an in-depth quantitative analysis that factors in the projectiles initial angle and velocity, the time of flight and even the k-constant of the spring.
Other Forces Affecting a Basketball Shot
Momentum and Explosions
When a basketball player takes a jump shot (as with a fadeway), the player and the ball could be viewed as 2-object linear system if you ignore other outside forces such as gravity. What’s interesting, and perhaps not apparent to many students, is that the basketball will exert an equivalent force to the player as the player is exerting on the basketball (Newton’s 3rd Law). Of course because of the very significant inertia (mass) difference between the two objects, the basketball will accelerate at a much fast rate than the player. The player however will experience some acceleration in the opposite direction to that of the basketball.
Using Smart Carts to explore Momentum and Explosions (Free Lab)
The Wireless Smart Carts are equipped with an exploding plunger. Multiple 250g bars can be added to one cart to skew the masses. The velocities of both carts are measured using the cart’s internal position sensors enabling students to determine that momentum is conserved in a linear exploding system.
The player’s force on the basketball will be equal to the opposing force of the basketball onto the player. Of course most students will consider this a ridiculous proposition until they prove this for themselves.
Using Smart Carts to explore Newton’s Third Law
There are several ways the carts can be used. The simplest activity is for two students to have a tug-of-war using the internal force sensors of two Smart Carts and an elastic band as depicted in the image. The equal but opposite forces will be confirmed, however in relation to a basketball player taking a shot, it has some shortcomings as the forces are pulling as oppose to pushing.
An equally simple activity, and one more relevant to the basketball shot scenario, is to collide two Smart Carts (with magnetic bumpers attached to their force sensors). As both carts have equivalent masses, students may not be surprised to see the impact forces are identical. However, what will probably surprise your students, are the force measurements that occur during a collision when one cart is weighed down with one or more 250g masses. Using their intuition, most students will speculate that one of the carts will experience a much greater force than the other. Of course, Newton’s 3rd Law will triumph and the forces will be identical.
What goes up must come down. This is true of course for all earth bound objects (including basketballs) due to the ever present force of gravity. Without gravity the trajectory of a basketball player’s shot would be straight to the ceiling of the arena, where most of the fans would be viewing the game.
Exploring the accelerating force of gravity using the Motion sensor
PASCO offers several technologies and techniques for measuring gravity including the Wireless Smart Gate and Picket Fence and the new Freefall apparatus. Both of these techniques are accurate and precise means to measure gravity. A third technique and one more appropriate for relating to a basketball shot is to measure the position of a vertically tossed ball and then have the software derive an acceleration graph from this data. Statistics, including the Mean of the acceleration plot can be calculated by the software for the period when the ball was in freefall as shown in the graph.
Originally posted on PASCO’s Blog. Blog is written by Bruce Taterka a teacher at West Morris Mendham High School in New Jersey
PASCO’s Wireless CO2 Sensor provides a powerful opportunity for students to explore the effects of photosynthesis and respiration in their local environment. This blog will describe how students can use a “Pretzel Barrel CO2 Chamber” to design experiments to measure rates of photosynthesis and respiration in a wide variety of settings and circumstances.
Soil plays an important role in the carbon cycle and global climate because it acts as a carbon sink, sequestering CO2 from the atmosphere in the form of organic matter. The upper layers of soil contain organic matter that is actively decomposed by the soil community: microbes, insects, worms and other animals.
While respiration by soil organisms decomposes organic matter and releases CO2, the plant community is photosynthesizing and taking in CO2 from the atmosphere. So in this part of the earth’s carbon cycle, CO2 is moving in two directions – into the atmosphere from soil, and out of the atmosphere into plants. We refer to this transfer of carbon as “CO2 flux.” With PASCO’s Wireless CO2 Sensor, students can explore the carbon cycle, plant and soil biology and climate change by measuring CO2 flux.
The rate of CO2 flux depends on a wide variety of factors. For soil, the rate of CO2 production may be affected by:
The content and type of organic matter in the soil
For the plant community, the rate of CO2 production may be affected by:
Type and density of plants
Carbon flux will vary with the weather, throughout the day, and throughout the year as the seasons change. Measuring CO2 flux provides an excellent jumping-off point for engaging in NGSS practices regarding the earth’s carbon cycle.
Figure 1. Collect data, and construct explanations. Integrating a range of analytical results can form the basis for creating a model of the earth’s carbon cycle and designing solutions to problems such as climate change and food production.
Students can define their own research questions and problems, analyze the results, and generate designs to conduct a variety of controlled experiments using the chamber. Most experiments will identify the CO2 concentration inside the chamber as the dependent variable and will test the effect of an independent variable of students’ choice.
On land students can compare CO2 flux on soil, lawn, forest, sunny vs. shady areas, and in a wide variety of other situations. In general, when the chamber is on bare soil or leaf litter, the CO2 concentration inside the chamber will be expected to increase, usually within a short time period such as 5 or 10 minutes. Figure 1. For longer investigations the sensor can be placed in logging mode (storing data to internal memory) and left for ~24hrs before the batteries will be depleted.
The chamber can be placed over plants that can fit inside it, in which case CO2 concentration inside the chamber should decrease, although it may be counteracted by respiration. The chamber can even be used on water by wrapping a piece of foam insulation around it, allowing it to float.
In any type of environment, students can design their own studies to investigate the effect of different variables on CO2 flux.
How to make a Pretzel Barrel CO2 Chamber
The chamber is made of a plastic pretzel container available in supermarkets.
Draw a straight line around the container, then cut it in half using a razor knife to form two large plastic chambers open at the bottom and closed on top.
You have two options here. You can cut a hole in the top for a CO2 sensor using an electric drill or a razor knife. The hole should allow the CO2 sensor to fit snugly, keeping the container airtight; the hole can be adjusted with tape if necessary to create a tight seal around the sensor. Alternatively, the sensor can be placed inside the container since it’s wireless!
The chamber is now ready to be used by placing it on top of soil and measuring CO2 flux.
For aquatic environments, wrap a piece of foam pipe insulation around it.