IndexApparatus:Variables:Independent variable:Dependent variable:Controlled variable:Risk assessment: how can it be avoided? glass could break; In this experiment we were testing the rate of photosynthesis in elodea. For a plant to photosynthesize, it needs carbon dioxide, water, and sunlight, a factor in photosynthesis. In order to measure the rate of photosynthesis, we needed to measure the products made, glucose and oxygen. Since oxygen is a visible product, we counted the oxygen bubbles that formed when we moved the light source. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay Hypothesis: Plants need light for photosynthesis. In this experiment, the intensity of the light is changed by changing the distance of the light source closer or further away from the Elodea, so in theory, as the intensity becomes stronger due to the proximity of the light source to the Elodea, the rate of photosynthesis should increase and therefore the number of oxygen bubbles will also increase. From further away the light intensity will be less, and therefore light will be a limiting factor, however when we increase the light intensity by bringing the light source closer to the Elodea, this means that light cannot be the limiting factor of photosynthesis. Since light is no longer the limiting factor in photosynthesis, it will photosynthesize at a high rate until another variable becomes a limiting factor. Apparatus: Elodea Lamp Beaker Test tube Water meter Ruler Stopwatch Funnel Method: First, fill the glass with water and place the Elodea inside . Place the funnel over the inverted elodea and place the test tube over the funnel. Place the meter ruler and lamp 50cm away from Elodea. It records the accumulated data over five minutes and counts the bubbles that rise to the surface. Repeat the operation with 40 cm, 30 cm, 20 cm and 10 cm. Record the data. For the experiment to be correct, repeat the experiment three times to get an average from the data, if you have time. Variables: Independent variable: Light intensity Dependent variable: Photosynthesis rate Number of oxygen bubbles produced Controlled variable: The time at which the oxygen bubbles are counted must be the same (5 min) The distance between Elodea and the lamp The temperature of the 'waterThe mass of ElodeaThe volume of waterRisk assessment: how can it be avoided?The Elodea could fall to the floor and water could escape; Keep water and Elodea away from the edges of the table and make sure it is away from anything it could damage, such as books or electrical sockets. Glass equipment may break; Use plastic utensils or handle all equipment safely and with caution; I believe my hypothesis was valid based on my results, excluding the 20cm measurement. I believe that the higher the light intensity, the rate of photosynthesis increases as it would no longer be a limiting factor of photosynthesis and therefore the plant would photosynthesize at a higher rate as shown in my results. My investigation demonstrated evidence to support my hypothesis. Evaluation: Overall, there was an increasing trend, however at 20cm there was an anomaly as it did not follow the pattern displayed by the other results. However, this could be due to several factors, the system could be tired or there could have been another limiting factor, for example temperature or carbon dioxide. One of the variables we couldn't control was the size of the oxygen bubbles or the age of the plant.