Controlled Experiment When Becky visited the Brooklyn Botanic Garden with her class she was impressed by the tall sunflowers she observed growing in the Children’s Garden. She did some research on sunflowers and decided that she wanted to investigate which growing conditions would support the growth of the tallest sunflowers. Becky read about organic farming and she became interested in the use of compost and other organic fertilizers for growing crops. She decided she wanted to test the effect of organic matter, compost in particular, on the growth of sunflowers. To test the effects of increasing amounts of compost, she decided to plant some seeds in compost alone, some in the perlite alone, and some in mixtures of the two that contained different amounts of compost and perlite. The 3 mixtures she created were: 75% compost/25% perlite; 50% compost/50% perlite; and 25% compost/75% perlite. This resulted in her planning for 5 different sets of pots. Becky used 3 pots for each soil mixture and 3 pots each for compost and perlite alone. In each of the 15 pots, she planted 3 seeds. Investigation Design Title: The effect of compost on sunflower plant growth. Research Question: How does the amount of compost (organic material) in a soil mixture affect the height of sunflowers planted from seed? Hypothesis: If sunflower seeds are planted in a soil mixture that contains mostly compost defined as 75% compost and 25% perlite then they will grow into taller plants than those seeds planted in the other soil mixtures because the organic materials in compost will provide the plants with nutrients that are beneficial to growth and the perlite will retain water and provide air spaces for the roots to grow. Independent Variable: Amount of compost added to soil mixture (%) Change in independent variable: 100 % Compost 75 % Compost 25 % Perlite 50 % Compost 50 % Perlite 25 % Compost 75 % Perlite 100% Perlite Number of repeated trials: 3 pots 3 seeds per pot 3 pots 3 seeds per pot 3 pots 3 seeds per pot 3 pots 3 seeds per pot 3 pots 3 seeds per pot Dependent Variable: Height of stem (centimeters) Constant Variables: Number of hours of light, amount of water and frequency of watering, type of pots, type of sunflower seeds, number of seeds per pot, temperature, humidity THE EFFECTS OF COMPOST ON THE GROWTH OF SUNFLOWERS 100% compost 75% compost-25% perlite 50% compost-50% perlite 25% compost-75% perlite 100% perlite Final Average Height (cm) 7.9 10.3 11.2 9.1 3.4 Comparing Height of Sunflowers in Different Soil Media (cm) 12 10 Height (cm) 8 6 4 Final Average Height (cm) 2 0 Soil Media N, P, K and pH SOIL TEST RESULTS Nitrogen Level Phosphorus Level Potassium Level pH Level Medium Type Trial 1 Trial 2 Trial 1 Trial 2 Trial 1 Trial 2 Trial 1 Trial 2 Wiggle Worm VH H M L VH M 4 4 Perlite L L L L M H 6 6 VH=Very High H=High M=Medium L=Low I=Inconclusive Percolation Test Results Volume of water that percolated through (mL) Wiggle Worm Trial 1 Trial 2 100% compost 75% compost 25% perlite 50% compost 50% perlite 25% compost 75% perlite 100% perlite 92 82.5 84 82 80 78.5 82 74 85 72.5 Conclusion: My observations show that the sunflower plants in the 50% vermicompost-50% perlite mixture were the tallest. My hypothesis that more compost, defined as a mixture of 75% vermicompost-25% perlite, would provide more nutrients for the sunflower plants and cause them to grow tallest while allowing for some root aeration, was not supported by the data. The 50% vermicompost-50% perlite mixture were the tallest, with an average height of 11.2 cm. The 75% vermicompost-25% perlite mixture yielded the second tallest plant height with an average of 10.3 cm. The shortest plants were grown in 100% perlite with an average height of 3.4 cm. They were 7.8 centimeters shorter than the tallest plants grown in the 50/50 mixture. The second shortest plants were grown in 100% vermicompost with an average height of 7.9 cm. They were 3.3 cm shorter than the tallest plants grown in the 50/50 mixture. According to the background research, sunflower plants need nutrients in order to grow, specifically nitrogen, potassium and phosphorus. Sunflower plants require nitrogen “to form basic proteins, chlorophyll, and enzymes for plant cells. Potassium is used by plants to produce sugars, starches, proteins and enzymes. Plants also use potassium to regulate their usage of water” (Braswell, 2008). Phosphorus is an essential building block of a plants’ DNA. It is used by plants for cell development and growth. (Raven, 1999) Soil test results showed that the compost contains a high level of nitrogen, a low level of potassium and trace amounts of phosphorus. It confirms that the organic material contains essential nutrients which are important for plants. Plants growing in a soil mixture containing some amount of compost will be provided with these nutrients. The nutrient tests revealed that perlite has low levels of nutrients, so the 100% perlite may not have the necessary nutrient levels to support healthy plant growth thus resulting in shorter plants. My percolation test results showed that the perlite retained significant amounts of water, as did the compost. We did not conduct a test to determine the level of oxygen within the soil mixtures. In a future experiment I would like to support my understanding that perlite provides aeration in the soil. I can conclude that either 100% compost or 100% perlite does not support the growth of plants because the 100% compost lacks aeration and the 100% perlite lacks nutrients. Since the 50/50 mixture yielded the tallest plants, I can conclude that this mixture has an optimum amount of nutrients and an optimum amount of aeration in the soil. The other two mixtures, the 75% compost-25% perlite and the 25% compost-75% perlite have adequate amount of nutrients, and adequate aeration in the soil because both of those mixtures produced plants that were tall, however, not the tallest. Design Investigation Ms. Hussain introduced her students to a unit on force and motion by giving them the opportunity to experiment with making and launching their own straw rockets. She challenged the class to create a rocket that could travel a distance of 15 meters in the shortest period of time. John’s team discussed all the ways that they might change the rocket design so that it could cover the distance faster. They made a list that included: change the length of the rocket’s body tube, change the number of fins, change the length of the fins, change the type of paper used to construct the rocket model. The group hypothesized that a rocket with a shorter body tube and larger fins made from photo paper would be more aerodynamic and travel a further distance than a longer, heavier rocket. They believed that a longer and heavier rocket would slow down the flight and wouldn’t fly as far before it dropped out of the sky. The group decided to test one variable at a time, each variable being one aspect of the rocket’s construction they would change. They agreed that in Test #1 they would change the length of the rocket’s body tube. For Test #2 they decided to change the number of fins. In Test #3 they tried various fin lengths and in Test #4 they constructed the model out of different types of paper. Students tested each of these components 5 times. After testing these four variables, the students made a rocket whose length, number of fins, length of fins were the measurements that gave the best results in each of their tests and they used the paper type that built a rocket that traveled the distance of 15 meters in the shortest period of time. They then tested the rocket with this final design to see if they had indeed built a rocket that could reach the 15 meter distance in as short a period of time as possible. Investigation Design Test #1: Changing the length of the rocket’s body tube. Title: The effect of body length on the speed a rocket travels. Research Question: How will body length affect the speed at which a rocket travels? Hypothesis: If the body length of a rocket is shorter it will travel faster than a longer body length for the same design because there will be less drag on a shorter rocket due to its smaller surface area. Independent Variable : Length of the rocket body (centimeters) Change in independent variable: 5 cm 10 cm 15 cm 20 cm 25 cm Number of repeated trials: 5 trials 5 trials 5 trials 5 trials 5 trials Dependent Variable: Time it takes a rocket to travel 15 meters Constant Variables: weather conditions, setting, launcher, fin size, number of fins, type of material used to make rocket After Test #1, the students repeated the steps above but modified the experimental design of the experiments to investigate: Test #2: Changing the number of fins on the rocket. Test #3: Changing the length of fins on the rocket. Test #4: Changing the types of paper used to construct the rocket. Conclusion: A rocket that is comprised of the various components that had the fastest transit time will be travel slower than then rocket that is made only of the body tube. When looking at the data we decided to calculate the speed of the rocket because it was difficult to determine exactly when the rocket crossed the 15-meter mark. By looking at the average speed for each trial we were able to see how manipulating the rocket changed the speed of travel as well as the total distance that it traveled. The components that had the fastest times for their trials were the 15cm body length, 2 fins, the 2 cm length for fins and the fins made of photo paper. For the body tube length experiment we saw that the length that went the fastest was the 15cm rocket, going an average speed of 12.03 m/sec. When we tested the number of fins, the rocket with 2 fins went the fastest at 11.87 m/sec. The length of the fins also affected the speed of the rocket. The length of the fin that traveled the fastest was the 3 cm fin, going an average of 11.75 m/sec. We also found that the best type of paper to use for the fins was the photo paper, going an average of 11.80 m/sec. When we put all of these characteristics into one rocket, we found the average speed of that rocket to be 11.83 m/sec. Even though that was faster than the average speed for the length of the fins experiment, by .08 m/sec, and the paper type for fins, by .03m/sec, it was still not the fastest. The final design of the rocket traveled .20 m/sec slower than the rocket that only tested the body tube length. Every time something was added or taken away from the rocket, the mass of the rocket was affected. Having a shorter body tube, meant that the rocket had a smaller mass. The force applied to this smaller mass was not enough to make the rocket travel the required distance because the rocket was to light and was more affected by air resistance. There has to be some balance between too light and light so that our rocket can have optimal performance. As we continued our trials we noticed that there was a proportional relationship between the length of the body tube and the speed at which it traveled. The fins were added to the rocket to streamline or stabilize the vehicle. By altering the size and material of the fin we again altered the mass, but by a much smaller amount. As can be seen in the trials, the effect of this change by comparing the average speed of the 15 cm rocket with no fins, which was 12.03 m/sec, to the average speed of the final design of the rocket, which was 11.83 m/sec. The additional mass added to the rocket account for the .2 m/sec difference could. For the challenge that we were given the fins were not needed. It just added additional mass to the rocket that in turn slowed the rocket down. The optimal design for the challenge was just a 15cm body tube with nothing added to it. Field Study (A) An Urban Advantage class visited the Bronx River with their teacher to study living and non-living features of the wetland. After exploring different portions of the river, a group of 8th graders notice a waterfall. They approach their teacher and propose to investigate the relationship between dissolved oxygen levels of the water and the location upstream or downstream from the waterfall for their exit project. The students hypothesize that the oxygen levels downstream from the waterfall generally will have higher levels than upstream from the waterfall, because of the increased stirring of water as it flows over the falls. The students decide to sample four sites along the river: 20ft upstream from the waterfall, 10ft upstream from the waterfall, 10ft downstream from the waterfall, and 20ft downstream from the waterfall. Students decide to test oxygen levels three times at each location. They repeat this testing at the same locations on the river two additional days. Experimental Design of Science Exit Project Title: The effect of location along the Bronx River on oxygen level of the water. Research Question: How does the water fall on the Bronx River affect the water’s oxygen levels? Hypothesis: If water is downstream from a waterfall then the dissolved oxygen will be higher than it is upstream from the waterfall because churning of the water exposes more water to the air, which adds more oxygen. Independent Variable: Locations along the Bronx River (meters from waterfall) Change in independent variable: Number of repeated trials: 20 feet upstream from water fall 10 feet upstream from water fall 3 tests 3 different days 3 tests 3 different days 10 feet downstream from water fall 3 tests 3 different days Dependent variable: Oxygen level of water (milligrams O2 per liter) Constant Variables: Type of test kit; river. 20 feet downstream from water fall 3 tests 3 different days Data: 20 ft Water Temp Upstream Trial 1 (Ave.) 10 C 4 ppm 35% Sat. Trial 2 (Ave.) 10 C 5 ppm 44% Sat. Trial 3 (Ave.) 12 C 4 ppm 37% Sat. 10 Ft Upstream 5 ppm 44% Sat. 4 ppm 35% Sat. 4 ppm 37% Sat. 10 ft Downstream 8 ppm 71% Sat. 7 ppm 61% Sat. 8 ppm 74% Sat. 20 ft Downstream 8 ppm 71% Sat. 8 ppm 71% Sat. 6 ppm 56% Sat. Total Average 4.3 ppm 38.7% Sat. 7.7 ppm 68.7% Sat. 7.3 ppm 66% Sat. 4.3 ppm 38.7% Sat. Conclusion: The oxygen levels downstream of the waterfall, are higher than upstream, as demonstrated by the data above with the two average measurements upstream from the falls being 38.7% saturated and downstream from the falls being 68.7% and 66.0% saturated. This is consistent with the concept that the churning of the waterfall exposes more water to the air, thus increasing the ability of the water to absorb atmospheric gases. Field Study (B) While on a class trip to the zoo, a group of students noticed the sea lions were bobbing up out of the water. They began wondering if that was their common type of activity throughout the day or if it was related to something else such as feeding schedule. They felt like this bobbing behavior was related to the sea lions anticipating and looking for their food. The students conducted some background research on sea lion behavior and thought that they should conduct some initial observation of the sea lions at the Zoo. The students created an initial ethogram for Bronx Zoo Z. californianus. This tool helped better inform the behavior choices and definitions of “activities” within their study. Then, on three separate days, the students planned to observe the sea lions’ activity 70 minutes before feeding time and again 10 minutes before feeding time. They would observe the sea lions for 10 full minutes using instantaneous sampling every minute. The behavior would be marked “NB” for not bobbing (not bringing their head out of the water and looking around) or “B” for bobbing (bringing their head out of the water and looking around). The students predicted that the sea lions would be bobbing more as feeding time approached, as the sea lions were looking for their food. Investigation Design Title: The effect of proximity of feeding time on the bobbing behavior of sea lions. Research Question: How does proximity to feeding time affect the bobbing behavior of sea lions? Hypothesis: If sea lions are closer to their feeding time then their bobbing level will be greater than at other times because the animals are anticipating getting food. Independent Variable: Number of minutes prior to feeding time Change in independent variable: Number of repeated trials: 70 minutes before feeding time 10 minutes before feeding time 3 different days, 10 minutes per day 3 different days, 10 minutes per day Dependent Variable: Bobbing behavior of the sea lions (not bobbing or bobbing as described above). Constant Variables: location, species of animals, number of animals, time of day, season, intervals (every 1 minute for 10 minutes). Data: The students also used the following system to record their bobbing activity: NB (Not Bobbing): majority (more than 50% of the sea lions in the exhibit) were not bobbing. B (Bobbing): majority (more than 50% of the sea lions in the exhibit) were bobbing. 28-May Morning 70 Mins Prior 10 Mins Prior 1 NB NB 2 NB NB 3 NB B 4 NB B 5 NB B 6 NB B 7 NB B 8 NB B 9 NB B 10 NB B Afternoon 70 Mins Prior 10 Mins Prior NB B NB B NB B NB NB NB B NB B NB B NB B NB B NB B 29-May Morning 70 Mins Prior 10 Mins Prior 1 NB NB 2 NB NB 3 NB B 4 NB B 5 NB B 6 NB B 7 NB B 8 NB B 9 NB B 10 NB B 70 Mins Prior NB NB NB NB NB NB NB NB NB NB Afternoon 10 Mins Prior B NB NB NB B B B B B B 1-Jun Morning Afternoon 70 Mins Prior 10 Mins Prior 70 Mins Prior 10 Mins Prior 1 NB B NB B 2 NB B NB B 3 NB B NB B 4 NB B NB B 5 NB B NB B 6 NB B NB B 7 NB B NB B 8 NB B NB B 9 NB B NB B 10 NB B NB B Conclusion: Sea lions at the Bronx Zoo change their behavior as their regular feeding time approaches. As observed on each of three dates, within 10 minutes before both morning and afternoon feeding times, the sea lions exhibited bobbing behavior. This behavior was not exhibited 70-60 minutes before feeding time. Therefore sea lions in captivity seem to anticipate feeding time and alter their behavior as that feeding time approaches. Is this a response to a stimulus or do the sea lions have a sense of time? We are not sure. Further investigation might reveal which of these may be triggering the change in behavior. Secondary Research An Urban Advantage teacher had just completed a plate boundaries unit in which she introduced the IRIS website which lets students search for earthquake data, map, graph and download it. After researching plate boundaries of different types, a group of 8th graders approach their teacher and propose to investigate the relationship between type of plate boundary and magnitude of earthquakes for their exit project. The students hypothesize that earthquakes occurring at transform boundaries generally will be of greater magnitude than earthquakes that occur at ridges (divergent plate boundaries), because when plates are sliding past each other they would seem to store more mechanical energy than plates that are simply diverging. The students determine the time frame for their study; they include only earthquakes for a 20 year period (from January 1, 1989 to December 31, 2008), and have identified one ridge and one transform fault off the Pacific South American coast that they will compare for their project. Using the IRIS web site, they set the search parameters to the settings described above, download the data, then calculate and compare average Richter magnitudes for all the quakes at the transform boundary vs. the divergent boundary (ridge). Investigation Design Title: The effect of plate boundary type on magnitude of earthquakes. Research Question: How will the type of plate boundary affect the magnitude of earthquakes occurring along that plate boundary? Hypothesis: If an earthquake occurs at a transform plate boundary then its magnitude will be greater than if it occurs at a divergent plate boundary because when plates are sliding past each other (transform) they store more mechanical energy than plates that are simply diverging. Independent Variable: Type of plate boundary Change in independent variable: Transform plate boundary Divergent plate boundary Number of repeated trials: Number of earthquakes recorded at 1 boundary in 20 years Number of earthquakes recorded at 1 boundary in 20 years Dependent Variable: Magnitude of earthquakes (on the Richter Scale) Constant Variables: Twenty years’ earthquakes per boundary type; all values taken from one database, oceanic crust on both sides of each boundary. Plate boundaries are adjacent to each other to reduce variation in other variables. Data: Transform Divergent Date Magnitude Date 10/24/07 4.4 5/16/07 5/7/07 Magnitude 3/22/08 5.6 4.7 7/28/07 4.4 5.4 12/12/04 4.9 6/15/05 5.6 9/19/04 4.2 3/12/05 4.6 3/29/04 4.3 1/9/03 4.9 12/31/03 3.7 12/23/02 4.3 6/3/03 4 8/4/02 5.6 6/3/03 4.4 7/18/02 5.3 5/31/03 4.3 4/6/02 4.6 5/20/03 4.9 3/11/02 5.2 3/18/02 4.8 2/22/02 4.4 3/15/02 3.9 1/29/02 4 1/25/02 3.9 7/28/01 4.2 10/23/01 4.6 6/30/01 4.4 9/10/01 4.8 5/26/01 4.7 5/25/01 4.1 2/19/01 5.1 4/20/01 4.6 12/31/00 4.5 12/23/00 4.3 8/1/99 3.7 2/6/00 4.7 7/12/99 4 5/9/99 4.6 3/20/99 4.9 5/19/98 5.1 3/9/99 4.5 8/26/97 4 12/24/98 4.4 3/18/97 4.2 11/6/98 4.5 10/5/96 5.2 1/19/98 4.6 1/22/91 4.7 10/25/97 4.1 9/13/89 4.9 3/5/96 4.2 11/17/95 5.3 8/25/93 5.6 7/1/93 5.2 11/20/91 5.3 2/13/01 5.2 2/21/89 5.3 Average earthquake magnitude at a transform plate boundary: 4.7 (for 33 earthquakes) Average earthquake magnitude at a divergent plate boundary: 4.5 (for 26 earthquakes). Conclusion: Our hypothesis that plates that are moving past each other (transform boundary) store more mechanical energy than those moving away from each other (divergent boundary) and therefore result in larger earthquakes is not strongly supported by our observations. Our observations show a mixed result, at a divergent plate boundary (ridge) we found an average magnitude of 4.5 on the Richter Scale for 26 earthquakes and an average of 4.7 on the Richter Scale for 33 earthquakes recorded on a near by transform plate boundary over the same period of time. It should also be noted that the largest earthquakes recorded at each plate boundary type had magnitudes of 5.6. We conducted some research on line and ran across these two references: “The crust may first bend and then, when the stress exceeds the strength of the rocks, [they] break and "snap" to a new position. In the process of breaking, vibrations called "seismic waves" are generated.” (http://pubs.usgs.gov/gip/earthq1/how.html 6/12/09 Maintained by John Watson and Kathie Watson
Last modified 10-23-97 (jmw)) “… When two blocks of rock or two plates are rubbing against each other, they stick a little. They don't just slide smoothly; the rocks catch on each other. The rocks are still pushing against each other, but not moving. After a while, the rocks break because of all the pressure that's built up. When the rocks break, the earthquake occurs.” (http://www.geo.mtu.edu/UPSeis/why.html, 6/12/09, This site is currently maintained by: Kevin Endsley kaendsle@mt u.edu and Carol Asiala <cj asiala@mtu.edu> For Dr. Wayne Penningt on, Dept. of Geological Engineering and Sciences, Michi gan Technological Uni versit y) Perhaps another way of looking at this situation is that at both of our chosen transform and divergent boundaries we are looking at a boundary between two oceanic plates with the same type of rock. Perhaps the more important factor related to the magnitude of an earthquake is not the speed at which, and the way the plates are moving, but the materials that the plates are made of and the strength of those rocks. Since properties like hardness are the same for all samples of a mineral, then perhaps the strength of samples of the same rock are the same, and they break at the same point releasing similar amounts of energy in an earthquake no matter how fast they reach that point of stored energy.