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SCIENTIFIC METHOD I PURPOSE (PROBLEM) Should state what you are studying; it is the question to be answered via the experiment. The purpose encompasses the variables within the experiment. Three variables are found in every experiment: 1. Manipulated (independent) variable – the variable that is being deliberately changed in the experiment. 2. Responding (dependent) variable – the variable that you are measuring in the experiment. 3. Controlled variable(s) – variables that are held constant or kept the same. Ex….. What is the effect of water on plant growth? How is the concentration of a solution affected when increasing amounts of water are added? For a cart moving down a hill, what effect does increasing the height have on the speed of the cart at the bottom of the ramp? II HYPOTHESIS An educated guess as to the answer to the problem. What does educated guess mean? You have some experiential knowledge, as well as background knowledge from the lessons in class, that you can draw on to predict what the likely answer is to the problem. A good way to state the hypothesis would involve using the following template: If………then…….because……… Ex…. If water is given to a plant then the plant will grow because water is one of the reactants in photosynthesis and photosynthesis produces energy in the form of glucose that can be used for growth of tissues. 6H2O + 6CO2 → C6H12O6 + 6O2 Ex…. If water is added to a solution then the concentration will decrease because in the following equation, C=n/V concentration is inversely related to volume, as the volume is increased (for the same number of moles) the concentration decreases. Ex…. If the height is increased for a cart going down a ramp then the speed at the bottom will increase because more height means more potential energy (E = mgh) and more potential energy means more energy converted to kinetic energy as it goes down the ramp and more kinetic energy means more speed (E = 1/2mv2). They are all directly related. III MATERIALS A list (not a paragraph) of all the items that will be needed to perform the experiment. IV PROCEDURE A step by step account of how the experiment is to be completed. Follow the following guidelines when doing your procedure: - Use numbered steps when creating your procedure don’t use paragraphs. - Steps should be numbered in the order that they will be carried out. - The steps should be stated in complete sentences. - Use an appropriate number of trials (5-7). - State any precautions that should be taken by the examiner (ie…safe handling, precautions like goggles, gloves, etc…). - Choose appropriate intervals for the manipulated variable. V RESULTS The data collected from the experiment. Usually presented in tables. When creating a table use the following five steps: 1. Create a rectangle for your table using a ruler. 2. Draw appropriately sized columns/rows with a ruler. 3. Put variable, unit and any exponents in the headers of the table. 4. Place a title at the top of the table 5. Record your data in the cells of the table. See the following example: Table 1: Position Time Data Time (s) Position (X102 m) 0 10 20 30 40 50 0 139 278 417 556 694 VI ANALYSIS The data from the table can be placed on a graph so that patterns can more readily be seen. When completing graphs use the following five steps: 1. Title Write your title in either of the following forms: - Responding variable vs. Manipulated variable (Y vs. X) - Responding variable as a function of manipulated variable 2. Labels Both the vertical axis (responding variable) and the horizontal axis (manipulated variable) must contain units and include direction and scientific notation when needed. E.g. distance (x102 m [E]) or d (x102 m [E]) 3. Scale Graph should make up majority of page (at least half of the page in both x and y directions) Graph intervals must be appropriately scaled No interval should be an irrational number (non-repeating and non-terminating) If not starting at 0 on either axis, use an axis break appropriate value to start your scale at the 4. Data Points A data point is represented by a reference on the x-axis followed by a reference on the y-axis (x,y). Clearly label your points with a visible black dot or place a circle around your data point if you feel it will be hard to find once you draw your line of best fit. 5. Line of Best Fit The line of best fit is a single line that best ESTIMATES the trend of the data points, the relationship between the manipulated and responding variables and is used to calculate the slope. The line is typically straight but may be drawn as a curve. It does not need to begin at the origin (0,0) nor pass through every data point. t (sec) or time (sec) 1.8 2.2 3.2 5.3 5.8 6.8 8.6 d (m [E]) or distance (m [E]) 3.50 7.00 12.0 17.0 24.0 27.0 29.0 Analysis of a graph may include the following: 1. Line of Best Fit The line of best fit is the linear representation of the data. It can be represented by the line equation y=mx+b where, - y is the value of the responding variable on the y-axis m is the slope x is the value of the manipulated variable on the x-axis b is the y-intercept which is where the line intersects with the y-axis (x = 0) 2. Slope The slope is found using the line of best fit Use two points on the line of best fit that meet the crosshairs of your graph paper and that are as far apart as possible to calculate slope It is the rate of change between responding variable and the manipulated variable slope ,m= 9.0 m−4.0 m 5.0 m ∆ y Rise y 2 − y 1 = =1.7 m/ s = = . E.g. slope= 3.5 s−0.5 s 3.0 s ∆ x Run x2 −x1 Include units for slope calculations 3. Area The area below the graph can also represent the relationship between manipulated and responding variables. The graph can be rectangular, triangular or a combination of the two Use the following equations to calculate the area: Rectangle: Arearectangle =l∙ w where, - l is the length - w is the width 1 Triangle: Areatriangle = 2 b ∙ h where, - b is the base - h is the height Slope Calculations slope= 31.0 m−2.00 m 29.0 m = =4.68 m/s 7.6 sec−1.4 sec 6.2 sec 4.Interpolation Use the graph of the data to find the y value given the x or to find the x value given the y. For example, on the graph above find the distance covered in 5.20 s. Find the 5.2 value on the x axis and then read the corresponding y value from the best fit line (20.0 m). 5.Extrapolation Extend the graph beyond the plotted data to determine a value beyond the original data set. For example, on the graph above find the distance covered in 10.0 s. To do this the best fit line must be extended further on the graph and then the y point that corresponds with the x of 10.0 s can be read (42.0 m). VII CONCLUSION The purpose/problem should be answered based on your results. Explain how your results support or do not support your hypothesis. Percent error may be referred to. Acceptable percent errors are between 5-10% depending on the experiment. Improvements should be noted here; if the experimental design was inadequate improvements should be mentioned here. Possible future experiments that may be extensions to the current experiment may be mentioned.