Carbon Dioxide & Oxygen Gas Sensors - Five activity ideas

Hello. Thank you for joining me today. My name is Cynthia Sargent. In today's video we'll be looking at the Carbon Dioxide and Oxygen Gas Sensors. You can use these for a number of activities in your classroom. Just a basic introduction to the sensors and calibration: The front of each of the sensors has a green calibration button, and you'll want to calibrate using an empty sampling bottle. Each of the sensors comes with a sampling bottle. You can plug the sampling bottle with the sensor, hold down the green calibration button, and when you see the flashing-light behavior change, then you know that your sensor is calibrated. For each of the demonstrations that I'm going to show you today, I've already calibrated the sensors. The first activity that we're going to look at will help your students understand diffusion and gas exchange in the lungs. Let's go ahead and get started. [Room Air vs Exhaled Breath] In this first activity, we're going to look at a simple demonstration that students can do to compare the amount of carbon dioxide and oxygen gas, in parts per million, of a standard sample of room air to the parts per million of those gases that are in their exhaled breath. I have the Carbon Dioxide and Oxygen Gas Sensors connected to what we call a metabolism chamber. It's a little different than the sampling bottle that I used for calibration. It has an opening at the top for one sensor and a second opening at the side, so you can use the two gas sensors at the same time. Right now, my sampling bottle is empty, but I would remind students that it has air, it has those gases commonly found in air, present inside the bottle. On the screen, you can see the initial parts per million, the concentration, of each of those two gases. Now, we're going to compare the room air to exhaled air. I'm going to preserve these initial values by taking a snapshot of the page, and then I'll return to my data collection. I'm going to remove the oxygen sensor from the side of the bottle, take a deep breath and exhale into the bottle, and seal the bottle back up with the oxygen sensor. The meter display gives that visual help to the student for determining is the carbon dioxide more or less compared to the initial sample of air, and is the oxygen more or less? Again, I can take a snapshot to preserve those values and do an easy comparison. Students will probably notice that the carbon-dioxide meter showed an increase in carbon dioxide and the oxygen showed a decrease in oxygen. Taking a snapshot, we can compare those initial and final values. I started with 541 parts per million of carbon dioxide in that sample of room air, and you can see, for my sample of exhaled air, that it went up to 33,132 ppm. Students can see that the difference in concentration is not just a little bit between the air and their lungs, but the difference is significant. They can also do a similar comparison for oxygen, initially starting out at 205,780 ppm. You can see the needle go down, and that concentration of oxygen was less in their exhaled air, only 181,192 ppm. Once students have collected evidence of the differences in concentration of those samples, what I would have students do is write for me a claim about the gas exchange in the lungs, as to whether or not it's passive transport or active transport, and use the numbers that they collected with the sensors as evidence to support their claim. Then I can do a quick poll of the class to see which ones thought passive transport and which ones thought active transport. In SPARKvue 2.0, I made an active assessment item that will show the students whether or not their conclusion of diffusion or active transport was correct. [Exhaled Breath Before & After Exercise] For this activity, we're going to use just the Carbon Dioxide Gas Sensor by itself, and instead of using a sampling bottle or a metabolism chamber, we're just going to use some plastic bags that zip closed. This is convenient because, with the sample bottle, you have to be sure to refresh the air in the bottle between trials. With the plastic bags, you can just use a new plastic bag for each trial, and you don't have to worry about refreshing the air. I would have my Carbon Dioxide Gas Sensor and a straw, and the rest of the bag is sealed up around those items. On the screen, I've set up a bar graph to collect a reading of the amount of carbon dioxide in my exhaled breath, and then I'm going to compare that to after exercise. I would just take a deep breath and breathe into the bag, and then pinch it closed. Then, once the carbon dioxide concentration stabilizes, I'll preserve that value. Then, what students would do is they'd have some nice, comfortable shoes. They'd run around, do some dancing, do some push-ups, make sure that they got five minutes of cardio exercise in, and then they'd put the Carbon Dioxide Gas Sensor and straw into a new bag and collect the amount of carbon dioxide in their exhaled air following that exercise. The students will always see that the amount of carbon dioxide in their exhaled breath after exercise is greater than what it was when they were at rest. [Cellular Respiration] The most common use of the Carbon Dioxide Gas Sensor is for experiments about cellular respiration. You can use a number of different organisms for these experiments. You can use germinating seeds, you can use a solution of yeast, or you can go to the pet store and get crickets or meal worms. Students always find it exciting if the living thing that they're studying actually moves around. For today's video, I'm going to use germinating seeds. I've filled the sample bottle up to the 50 mL mark on the side of the bottle with some germinating seeds. They've been soaked in water for about 24 hours. You can leave them for one or two nights before your students use them. Just make sure that germination is evident in the seeds. You can plug the sample bottle with the Carbon Dioxide Gas Sensor, and then hit play to start collecting your data. The most basic comparison is usually germinating seeds to non-germinating seeds. On my screen here, I've got germinating seeds in green and the non-germinating in the blue with diamonds. You can see that the germinating seeds had a significant increase or caused a significant increase in the carbon dioxide in the bottle, while the non-germinating seeds did not, That's a good way to bring in the connection of cellular respiration to the energy needs of an organism and their cells. The students will be able to see that the germinating seeds are growing and make the connection that that growth requires energy. You can then send the students into further exploration, looking at the effect of temperature on cellular respiration. The other run of data that I have here, you can compare the green to the blue here, and that's a comparison of germinating seeds at room temperature to germinating seeds that were soaked in an ice bath. You can also investigate respiration with a solution of yeast. Again, you would just put a small amount of solution in the bottle. You can plug that bottle with the CO2 sensor. It is important to not allow the CO2 sensor to get wet, so you want to make sure that the volume of your bottle does not reach the end of the probe there. Students can look at the amount of carbon dioxide produced by yeast, either through respiration or fermentation, when given different sources of energy. You can first give the students sugar and have them see that yeast do utilize sugar for energy by producing carbon dioxide. You can then give them artificial sweetener or some starch pellets, and you can have them investigate what other carbohydrates yeast might use for cellular respiration. [Photosynthesis] You can also use the Carbon Dioxide and Oxygen Gas Sensors to investigate photosynthesis with your students. In this setup, I have our large EcoChamber with a small plant, and you can really put any potted plant that fits into the chamber in a setup similar to what you see here. I have the Carbon Dioxide Gas Sensor and the Oxygen Gas Sensor in the setup, and all of the other openings of the EcoChamber I've sealed with rubber stoppers. You want to provide the plant with a nice, direct light. I'm using a bright compact fluorescent light bulb as the light source. On the screen, you'll see data that I collected over the course of about 35 minutes. You can see, over long term -- about half an hour -- that you get really good data for both carbon dioxide and oxygen. This provides evidence of photosynthesis, helping students understand the equation for photosynthesis and what the reactants and products are. On the y1 axis, I have oxygen concentration, and y1 is the blue line, and you can see the increase in oxygen over time. On the second y-axis, y2, I have carbon dioxide. y2 is the red line, and you can see the decrease in carbon dioxide as, again, evidence of the photosynthesis. On a smaller scale, you can have students use a green leaf or a couple leaves, like spinach, and you can put those into the sampling bottle under direct light. For this smaller-scale experiment that only takes 10 minutes, or even less than 10 minutes, you can plug the sample bottle with the Carbon Dioxide Sensor, and students can investigate the rate at which carbon dioxide is taken in by the plant and get a rate of photosynthesis. [Enzyme Catalysis] In this final segment, we'll look at a demonstration involving the Oxygen Sensor. This demonstration involves the breakdown of hydrogen peroxide catalyzed by catalase, an enzyme found in yeast and many other organisms. You can use yeast or potato or liver as your source of catalase. Yeast is an easy one to obtain, so that's what I'll be using today. Before having your students use the Oxygen Sensor to measure variables such as temperature or pH and their effect on enzymes, you might start off with a demonstration that helps them understand why they're using the Oxygen Sensor. I'm going to take a suspension of yeast and water and add it to a graduated cylinder, to which I've already added about 40 to 50 mL of hydrogen peroxide. I'm going to add some yeast. The catalase enzyme that's present in those yeast cells takes a slow reaction -- the hydrogen peroxide would decompose on its own, just very slowly -- but with the enzyme present, the reaction happens much, much more quickly. I'm going to light a wooden splint, and perform an oxygen test with the gas that was produced. Students should be able to tell you that one of the products produced in the reaction is a gas, and then you can use the flame test to demonstrate that that gas is oxygen. Once they have the understanding that the hydrogen peroxide is being converted into oxygen and water, then they can take this further into experiments of their own. For these experiments, you can use the sampling bottle that comes with the Oxygen Gas Sensor and small volumes of hydrogen peroxide and yeast. They can add hydrogen peroxide to the bottle first, and then add their yeast suspension containing the enzyme catalase, and then give it a quick swirl. Just set the Oxygen Sensor very loosely inside the opening of the bottle. I'm going to start data collection. You'll see a digits display of oxygen concentration in percent. We'll watch the change in oxygen concentration over time for a short while here. Using the Oxygen Gas Sensor, students can quantify the amount of oxygen being produced, but really, with enzymes, what we're interested in is the rate at which that oxygen is being produced as a measure of the activity of the enzymes. I'm going to show you some data that I collected earlier, using this same method of small volumes of yeast and hydrogen peroxide in the sample bottle. I compared room temperature catalase, at about 24 degrees Celsius, in green here, to warm catalase, at 37 degrees Celsius. Students can do this comparison to see how is the enzyme activity different at their body temperature compared to room temperature? There's also data here for boiled catalase, so they can also get evidence of the denaturing of enzymes at extremely high temperatures. I hope you have some ideas now for your classroom and using the Oxygen and Carbon Dioxide Gas Sensors to help teach your students those concepts throughout the year. Thank you for joining me today.