Current Conditions: Assessing air quality
As Abram Katz reports in the June 21, 2000 New Haven Register, “This summer may not swelter, but New Haven will be hot”. He reports cities make their own microclimates, creating ozone and smog. This year, he notes, Connecticut has had more than 8 days of unhealthful airand the summer has yet to begin! The solution, according to a NASA scientist Dale Quattrochi: “Plant the right kind of trees in the right spaces”.
The United States releases 7000,000 metric tons of air pollutants each day. These include carbon dioxide, oxides of nitrogen and sulfur, and chlorofluorocarbons. Oxides of sulfur and nitrogen are among the worst air pollutants. Coal burning power plants, metal smelters and factories emit most sulfur dioxides. Motor vehicles, power plants that burn gas and oil, and nitrogen-rich fertilizers produce nitrogen oxides
During a thermal inversion weather conditions trap a layer of cool, dense air under a layer of warm air. If the trapped air contains pollutants, winds cannot disperse them, and they may accumulate to dangerous levels. Cities create their own thermal inversions because of a heat island effect. Heat reflected between buildings warms up the air which rises. As air flows upwards and outwards, it cools and begins to sink carrying air pollutants down near the ground. Thermal inversions have been a key factor in some of the worst air pollution disasters, because they intensify an atmospheric condition called smog, the pollutant most visible to students.
Urban areas also have large numbers of people living in a relatively small area. There is also usually more automobile driving, paved areas and industrial activity. These activities release tons of pollutants into relatively small volumes of air each day. The automobile is the chief source of primary air pollutants. Auto exhaustunburned fuelcontains Hydrocarbons, Carbon Monoxide and Nitrogen oxides. At present in the United States motor vehicles are responsible for up to half of the ozone-forming volatile organic compounds and nitrogen oxides. Motor vehicles release more than 50 percent of the hazardous air pollutants. Motor vehicles release up to 90 percent of the carbon monoxide found in urban air.
Furthermore, cities have more cars emitting pollutants, moreso at rush hour. Auto pollutants are emitted close to the ground, at just about breathing level. Traffic lights and slow moving traffic are the worst polluters as well. Stop-and-go driving produces more auto exhaust than open highway driving. Since morning rush hour traffic occurs usually when breezes are light and radiation inversions form, air pollution levels can be very high, especially at busy intersections or along highways. And the city of New Haven is particularly at risk as the city itself is congested and located right next to one of the most congested highways in the country--Interstate 95!
Experiment: The physical properties of air
A property describes objects and helps us identify an object, through its appearance or behavior. A physical property identifies an object by its shape, form, size, and color: appearance. A chemical property identifies an object by its behavior, particularly when it interacts with other objects. Chemical properties include the ability to form compounds with other substances and change.
Physically speaking, air is a mixture of gasses. Nitrogen (N2) and oxygen (O) make up 99% of the troposphere. The balance is composed of traces of argon, carbon dioxide and other gasses. Air is transparent, colorless, and tasteless and odorless. It has weight and takes up space. Because air posses these physical qualities, it is considered matter. Matter is anything that has weight and takes up space.
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Materials Project 1: Air takes up space
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2 soda bottles
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2 small funnels
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glass beaker filled with water
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modeling clay
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Project 1: Air takes up space procedures
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Set the funnels in open ends of the bottles
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Seal one of the funnels around the edges with clay Make sure the seal is tight and no air can get in or out of the bottle except through the funnel
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Pour water through the funnel and into the bottle that is not sealed
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Observe how much water goes in the unsealed bottle
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Pour water into the bottle that is sealed
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Observe how much water goes into the sealed bottle
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Explain: were there differences in the amount of water that went into each bottle? Why? What matter existed in the bottles?
Materials Project 2: Air has mass
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yardstick
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3 15” long strings
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2 balloons
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sharp pin
Project 2: Air has mass procedures
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Blow up 2 balloons to just about the same size
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Tie the ends so no air can escape
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Attach one 15” string to each balloon
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Tie the balloons to each end of a yardstick
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Tie the third string to the center of the yardstick with a loose knot
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While holding the yardstick up by the third string, use a sharp pin to puncture one of the balloons.
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What happens? What property explains the different mass of the balloons?
Experiment: Test for the presence of carbon dioxide
Baking soda consists of the chemical compound sodium bicarbonate (NaHCO3). Compounds containing carbonate (CO3) react with acids such as vinegar (acetic acid) to produce carbon dioxide gas (CO2).
Limewater Ca(OH)2 is used to test for the presence of carbon dioxide gas because it reacts with carbon dioxide to form the compound calcium carbonate (CaCO3). The equation for this reaction follows: CO2 + Ca(OH)2 ( CaCO3 +H2O
Materials:
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Glass soda bottle
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63 ml water
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scissors
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ruler
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tissue
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5 ml baking soda
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baby-food jar with lid
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limewater
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63 ml vinegar
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modeling clay
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flexible drinking straw
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1. Pour water and vinegar into the bottle
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2. Cut a 7.6 cm strip of tissue
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3. Spread the baking soda across the tissue
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4. Roll the tissue around the baking soda. Secure the packet by twisting the ends of the tissue
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5. Fill the baby food jar three-fourths full with limewater
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6. Mold a walnut size piece of clay around the end of the straw. Do not cover the hole
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7. Drop the packet of baking soda into the bottle.
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8. Quickly plug the mouth of the bottle with the clay around the straw. The short end of the straw should be inside the bottle.
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9. Hold the jar of limewater near the bottle so the other end of the straw is beneath the surface of the limewater.
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10. When the bubbling ceases, observe the limewater
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11. Secure the lid on the jar and allow the jar to stand overnight.
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12. Observe the contents of the jar
Why? The chemical reaction:
NaHCO3 + HC2 H3O2 NaC2H3O2 + H2O + CO2
Sodium bicarbonate + acetic acid yields sodium acetate + water + carbon dioxide
Experiment: Exhaust Effect on living things [PROSECUTION EVIDENCE 1]
Materials:
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Bio bag (see Internet Resources: www.scotthubbard.com)
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6 small planters
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seeds: bean & dill germinate and grow quickly
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water
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graduated cylinder
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metric ruler
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light source
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emmissions from a car (preferably older)
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1. Plant three seeds in each of the six pots
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2. Water all of the seeds 25 ml
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3. Fill a biobag with car exhaust (use careadult supervision required)
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4. Place three of the planters in the biobag and seal; put near light source
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5. Place the other three planters near the same light source; this is your control set
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6. Repeat procedures 2 through 4 every three days
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7. Observe planters and record plant growth when you water and reset plants in
Research [PROSECUTION EVIDENCE 2]
Investigate air quality in your area (in Connecticut, see State of Connecticut Department of Environmental Protection) for a town-by-town air quality index. Graph air quality and temperature daily for a month. Make a note of anything that could affect air quality: highway accidents, town events drawing many visitors, local construction. (See HYPERLINK http://dep.state.ct.us/updates/oz/aqi.asp http://dep.state.ct.us/updates/oz/aqi.asp and/or http://www.epa.gov/airnow/ http://www.epa.gov/airnow/)
Research [PROSECUTION EVIDENCE 3]
Ask students: If a car differs in size, make, and model, then the amount of pollution emitted from it will also vary. Research if different cars emit different amounts of pollution. Gather data on the amount of carbon monoxide, hydrocarbons, and nitrogen oxide since these emissions have restrictions on them set by the EPA. Go to the Emissions Testing Center to retrieve field information on this subject. Use sources from the internet, books and the Department of Emissions testing as well. Include as references any Annual Statewide Report as well as books such as, Lawrence White’s The Regulation of Air Pollutant Emissions from Motor Vehicles (AEI Studies, 1992). Use Internet sources, including EPA’s “Your Car and Clean Air” (1988)
(http://www.epa.gov/orcdizux/18-youdo.htm"http://www.epa.gov/orcdizux/18-youdo.htm)
Survey a busy intersection. Record the model and number of vehicles that pass through the intersection. Estimate auto emissions for a day, week, month
Survey [PROSECUTION EVIDENCE 4]
Survey classmates to see if students or others in their family have asthma. Ask those with asthma to keep track of how well they feel each day for three weeks. Ask them to record if they feel any difficulty in breathing at all, as well as any attacks. Ask them to rate their breathing on a scale of 1 to 5: 1 being the most difficulty breathing, including any attack; 5 represents “best” days, where breathing is not labored at all. Record EPA air quality information and temperature. (See Prosecution Evidence 2). Set up a data table which includes the date, temperature, percentage of Asthmatic students who have difficulty breathing, (Respond 1, 2 or 3 when surveyed), and air quality information. Is there any correlation between labored breathing and /or Asthma attacks during poor air quality days? Is there any correlation with temperature? Determine if students with Asthma in your area have difficulty breathing when it is hot or during poor air quality days.
Another activity that you may want to perform is found in HANDS-ON SCIENCE by Dorothea Allen. This activity allows the student to see how burning puts pollutants into the atmosphere and how they travel, once in the atmosphere, by using a covered 10 gallon glass aquarium tank and burning wood chips.
Plants to the Rescue: Oxygen production & Air purification
“How long can an average person survive in an airtight room that's packed with plants, assuming there is plenty of food and water?” Environmental engineers have been working on this very question since the 1950s in hopes of one day sustaining life on Mars. Survival in an airtight podwhich requires 500 to 650 liters of oxygen per person dailydepends largely on the kinds of plants you choose as roommates. Cram a well-lit room with philodendrons or other slow-growing houseplants, and you'll be gasping for air within a month. But stock the same room with corn, beans, or other fast-sprouting vegetables, and you could spend a natural lifetime there. Plants take in carbon dioxide and emit oxygen during photosynthesis, and varieties that grow faster generate more oxygen; about 600 grams of new leaves, stem, or stalk produce the minimum 500 liters you need daily. Farm-variety vegetables grow six new grams every day under ideal conditions, so 100 seedlings would do the trick, notes former NASA engineer Bill Wolverton,
As photosynthesis consumes carbon dioxide and releases oxygen, it helps counteract the effect of combustion of fossil fuels. The burning of fossil fuels releases carbon dioxide as well as hydrocarbons, nitrogen oxides, and other trace materials that pollute the atmosphere and contribute to long-term health and environmental problems. Can the principles of photosynthetic solar energy harvesting be used in some way to produce non-polluting fuels or energy sources?
Photosynthesis Defined
Plants use chlorophyll to trap energy from the sun. They use this energy to combine carbon dioxide from the air and water from the soil to make food. This food making process is photosynthesis. Without photosynthesis, the replenishment of the Earth's fundamental food supply would halt, and the planet would become devoid of oxygen. During photosynthesis energy is used to convert carbon dioxide, water, and minerals from the environment into organic compounds and gaseous oxygen--the food we eat and the air we breathe. The process is an almost exclusive property of the plant kingdom.
Photosynthesis is the process of turning the energy of sunlight into chemical energy from the raw products of CO2 and H2O. Recall the chemical equation is:
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6 H2O & 6 CO2 ((light(( (CH2O)n & 6 O2.
Although numerous intermediary reactions are involved, the overall photosynthetic reaction is simple. Carbon dioxide combines with the hydrogen from water yielding a carbohydrate, the 6-carbon sugar (hexose) glucose, and oxygen. Ask students to balance the equation:
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_____CO2 + _____H2O ----> C6H12O6 + _____O2
(Hint: How many carbons are needed to make the carbohydrate?).
This process is necessary to sustain nearly all forms of life. The whole process is begun by light reacting with pigments in the leaf causing the splitting of water molecules. Three products are produced in this reaction. Electrons from the hydrogen molecules and remaining H+ ions are used to form two separate energy storage molecules. The air we breathe is from the remaining oxygen portion of H2O.
Not all plants produce the same amount of oxygen, however. Some plants are more efficient “air purifiers” than others. Part of the photosynthetic process, the dark reaction, is also called the Calvin Cycle. With one cycle of this reaction 3 carbon atoms are fixed or placed in a sugar molecule. This pathway is called C-3 photosynthesis. This is the way that most dicots or broadleaf plants make sugars during the dark reaction. C-3 photosynthesis has a disadvantage though. Oxygen competes with CO2 for a binding site during the dark reaction. Sometimes sugars are not formed, but energy is still expended to complete the cycle. This is called photorespiration.
Another dark reaction pathway is called C-4 photosynthesis because 4 carbons are fixed or placed in a sugar molecule each time the cycle is completed. The dark reaction of C-4 photosynthesis occurs inside of specialized parts of leaf cells in the leaf called the bundle sheath, which exclude the presence of O2. Because there is no oxygen present photorespiration does not occur. The C-4 photosynthetic pathway is what occurs in most monocots or grasses. This is a more efficient pathway and allows grasses to grow faster than broadleaf plants.
Use the Encarta Encyclopedia contents page for the Photosynthesis article and the animation on photosynthesis. Using the animation, guide students through the steps of the process. This video is an excellent resource for helping students understand photosynthesis. Show them the photograph of chloroplasts in the Onion Root Cells photo and mention the importance of chloroplasts in the process. For additional information and materials, see Plants, Milliken Publishing Company, St Louis, MO, 1986. The unit includes excellent overhead transparencies/graphics.
Experiment: How do we know plants produce oxygen? [DEFENSE EXHIBIT 1]
Materials:
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Large bowl
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Water
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Glass jar
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Plantselodea, an aquatic plant available at most pet stores, is ideal
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1. Fill a bowl with water and add some elodea
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2. Place the jar upside down in a bowl
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3. Tilt the jar to let the air out of it
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4. Push the weeds ½ way into the jar, then rest the jar on top of the stems
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5. Leave the bowl in bright light for several hours (or overnight)
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6. Observe the jardeduce: What are the bubbles?
Do all plants produce oxygen? [DEFENSE EXHIBIT 2]
Complete the above experiment, How do you know plants produce oxygen? Using as many aquatic plant types as can be collected; try to get at least one for each student.
Additional materials:
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Triple-beam balance
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Tracing paper and pencil
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Guide to identify plants (http://plants.usda.gov/plants http://plants.usda.gov/plants, http://aquat1.ifas.ufl.edu/,)
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Cm ruler
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1. Observe all the plants. Lay them out one by one so all students can observe each.
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2. Each students predicts which plant they think will produce the most oxygen. The least? Ask students to explain why they formulated these hypothesis.
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3. Provide each student with one plant type
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4. Working in teams, students trace their leaf and estimate volume
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5. Students calculate mass using a triple beam balance
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6. Each student completes “How do you know plants produce oxygen?” using his/her plant. Each student counts the number of bubbles after 40, 80, 120 and 160 minutes.
*note: I have 42-minute classes. On day one, we observe all the plants, calculate volume and mass (advanced students calculate density). On day two and three we set up the experiment with a recording chart in front of each plant station. Working in teams of two, period 1 sets up 10 plants for periods 2, 3 & 5 to record and observe. On day three, period 2 sets up for periods 3, 5 & 6 to observe and record.
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7. Which plant created the most bubbles/produced the most oxygen? Was there any relationship between size of the plant and oxygen produced? What other factors might affect how much oxygen was produced?
According to David Hershey at the MAD Scientist Network:
There are two phenomena that take place in the process of photosynthesis. One is the splitting of water (to obtain electrons and release oxygen) in the so-called 'light reactions' and the other is the fixation of carbon dioxide into an organic compound in 'dark reactions'. Both of these changes are used to measure photosynthetic rates. And both require some specialized equipment.
Measurement of oxygen evolution is probably the easiest method. It can be performed using an oxygen electrode or, in the case of aquatic algae, Winkler titration. Winkler titration relies on chemical changes to measure oxygen content in water after photosynthesis takes place upon exposure to light. Oxygen electrodes measure oxygen concentration in air or water and are quick, efficient and accurate. Since most researchers are interested in the amount of carbon fixed more so than oxygen released, the oxygen-based rate is converted to carbon fixed by the ratio known as the photosynthetic quotient. (This is often assumed to be 1:1,but actually varies a bit). Both techniques require a "dark" control sample to account for respiration.
Both of these techniques measure net photosynthetic rates. That means that respiration is already factored into the results. In other words, when one measures oxygen evolution on a whole plant or cell, respiration, which consumes oxygen is also taking place and affects the measured oxygen evolution. Thus the need for a dark control sample.
There are some simple techniques for measuring productivity (rather than photosynthesis). In these cases the results of photosynthesis and growth are measured. Of course plants depend on photosynthesis for growth so there is a relationship. Some of these techniques are quite simple. They measure the mass of plant material. Weighing before and after treatment can do this. Aquatic botanists also relate the length of the blade of seagrass or seaweed to growth as well. Both methods give reliable results BUT the changes in mass (or blade length) must be large enough to measure. This means short-term experiments are not appropriate.
Factors affecting photosynthesis
To produce food for itself a plant requires energy from sunlight, carbon dioxide from the air and water from the soil. If any of these ingredients is lacking, photosynthesis, or food production, will stop. If any factor is removed for a long period of time, the plant will die. Photosynthesis literally means "to put together with light."
Photosynthesis is dependent on light. Generally speaking, as sunlight increases in intensity photosynthesis increases. This results in greater food production. Many garden crops, such as tomatoes, respond best to maximum sunlight.
Water plays an important role in photosynthesis in several ways. First, it maintains a plant's firmness of plant tissue. Firmness pressure in a cell can be compared to air in an inflated balloon. Water pressure or turgor is needed in plant cells to maintain shape and ensure cell growth. Second, water is split into hydrogen and oxygen by the energy of the sun that has been absorbed by the chlorophyll in the plant leaves. The oxygen is released into the atmosphere and the hydrogen is used in manufacturing carbohydrates. Third, water dissolves minerals from the soil and transports them up from the roots and throughout the plant, where they serve as raw materials in the growth of new plant tissues. The soil surrounding a plant should be moist, not too wet or too dry. Water is pulled through the plant by evaporation of water through the leaves (transpiration).
Photosynthesis also requires carbon dioxide (CO2) which enters the plant through the stomata. Carbon and oxygen are used in the manufacture of carbohydrates. Carbon dioxide in the air is 350 parts per million (ppm) or 0.035% at sea level and is plentiful enough so that it is not a limiting in plant growth.
Leaves have the important function of manufacturing food for the plant using water, carbon dioxide and light. The single layer of cells that forms the upper outside surface of a cell is the upper epidermis. The lower epidermis has many minute openings that permit photosynthesis. The middle section contains layers of tissues that are rich in chlorophyll. Leaves are food producers. In photosynthesis, leaves use chlorophyll to convert water, carbon dioxide and light energy into sugar and oxygen. Photosynthesis occurs in green leaves and stems inside the chloroplasts in the cells. Carbon dioxide enters through the stomata. Oxygen is a byproduct of photosynthesis. It exits leaves through the stomata. Transpiration, the release of water vapor from a plant, occurs through the stomata.
Experiment: Investigate factors affecting photosynthesis: “The floating Leaf Disc"
This experiment is consistent with the Connecticut Academic Performance Task (CAPT) standards and includes a report outline consistent with the standards.
