How to write up Experimental Reports_Exemplar (1)

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Jan 9, 2024

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Sample Practical Report: How to write up an Experimental Report for Science Investigating the Effect of Solutes on Boiling Water Name: Albert Einstein Partners: Sir Isaac Newton and Steve Jobs Date: 13/11/2019 Introduction: Write a summary of the theory you have learnt in class which relates to the experiment At normal pressure pure water freezes at 0 o C and boils at 100 o C. Dissolved substances such as salt and sugar have a lowering effect on the freezing point of water and that is why salt is sprinkled over wet or icy roads in winter in some countries as the temperature then has to reach less that 0 o C for ice to form. The salt, NaCl becomes ionized when dissolved and it is this ionized water that has an elevated boiling point. The same holds true for sucrose but sucrose is not ionized in water and the boiling temperature will increases as the percentage concentration of sugar in the solution increases. Too much sugar though will increase the boiling temperature to a point where the sugar caramelizes, hence where caramel comes from. Aim: The purpose of the experiment: “To investigate the effect of….. on….”, “To determine” etc. The aim of this experiment is to determine the effect that different solutes have on the boiling point of water Hypothesis: What you predict will happen: “If…, then…., because…..” If a solute is added to water and boiled, then the boiling temperature of the solution will be raised, the greater amount of solute the greater the elevating effect will be because it will take more energy to reach the point where it will vaporize from the solution Variables: - Dependent (what you measure) : The maximum temperature reached of the solution. - Independent (what you change) : The mass of solute added to the water. - Control (the things that must stay the same – at least 3) : The volume of the water. The air pressure. The equipment used. The temperature of the experiment. Materials: in dot points Materials : Bunsen burner Thermometer Water Heat proof mat Matches Balance Stirring Rod Permanent Marker Table Salt Tripod 250 mL Beaker 3 watch glasses or mini paper cupcake cups Crystalline Sugar Gauze Mat 200 mL measuring Cylinder Spatula or plastic spoon Alternatively, if you are following the materials straight from the textbook or a worksheet, you may write the following: “Materials as per page 189 of Oxford Science 9 with the following changes:” No changes/ write the changes you made in dot points
Method: 1. Weigh the appropriate amount of salt or sugar onto the three separate watch glasses 2. Measure 150 mL of water into 4 beakers. Label them with the mass of solute that will be added. 3. Place the appropriate sample of salt or sugar into the labelled beakers 4. Using the stirring rod, stir the solute until it completely dissolves. 5. Place beaker on gauze mat and heat the liquid recording the temperature in 2 minute increments. 6. Stop recording once maximum temperature has been reached and has remained stable. Figure 1. Diagram of the experimental setup for boiling of the water plus solute sample. Results: Observations: Describe what you see and any notes you can make on your experiment Table: In a logical format with units in the title row only Test Observations Distilled water The water started bubbling at 96 o C and the temperature continued to increase to a maximum at 100 o C Distilled water + 10 g salt With this solution the water started bubbling at 98 o C and continued on until 100.4 o C Distilled water + 20 g salt This solution took longer to bubble than the previous sample but once it started at 99 o C it continued on but not as strong. Distilled water + 40 g salt Strong bubbling occurred when the temperature reached 99 o C Distilled water + 50 g salt Furious bubbling occurred when the temperature reached 98 o C. Graph: Independent variable on the x axis and dependent variable on the y axis. Both axis must be labelled and a title must be added to the graph. Alternatively, if you are following the method straight from the textbook or a worksheet, you may write the following: “Method as per page 189 of Oxford Science 9 with the following changes:” No changes/ write the changes you made
Discussion: Relate the theory: Relate the results to the theory. You MUST mention the data/ observations. Use the numbers you obtained and explain them using theory. Questions: You do not need to write the questions out, as long as you answer it in a full sentence. 1. Explain the pattern/ trend that you see in your data. The trend in the data is that, as the concentration of solute increases the boiling point of water increases. 2. Explain how the independent variable effects the dependant variable. Increasing the independent variable (solute mass and type of solute), will increase the dependant variable (boiling point of water). 3. Why is it important to keep all other variables constant (control variables)? It is essential to ensure that all other variables in the experiment are kept constant as they may affect the results. In a fair test/ experiment, only one variable should be changed. This ensures that the experimenter knows exactly what is causing the results to increase or decrease. If more than one variable was changed you would not know what was causing your results. 4. Which variable were you recording?
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Boiling point of the water with dissolved solute. 5. What effect the salt and sugar have on the boiling temperature of the water? Both the salt and sugar increased the boiling point, albeit to differing extents. 6. Did they both exert the same effect or different effect? The effect was different for salt as water, with salt causing a larger increase. 7. Was this experiment a fair experiment? This experiment was fair in that the variables were tightly controlled but there was still room for error with the calibration of the thermometers. 8. How would you improve the experiment? See Improvements below. Errors: State the errors of the experiment and the effect these have on results. NOTE: human error is not a valid error. It is a mistake and should not be mentioned in your report. One error involved in this experiment the temperature of the environment may not have been the same throughout the experiment and thus small subtle changes in boiling point may not be scientifically correct evidence. Another error is that the thermometers may not be accurately measuring temperature as they are alcohol based ones with a +/- percentage error. Improvements: Use the errors that you have identified and explain how you could improve these if you did the experiment again. The improvement which could have undertaken included to repeated the experiment more than once to obtain three independent readings. Choosing different types of salt, for example, sea salt, table and using other sugars such as fructose to determine if the temperature change is scientifically correct. The improvement which could have been made to the straw, is to use a straw which has no bend section (a completely smooth straw with no crinkle). As this straw would have a smoother surface, there would be less friction between the straw and string and the rocket could travel further. Conclusion: Answer the 3 sentences below. You do not need to write the three sentences but your answers should follow the wording which has been given below. 1. Relate what you have found to your aim The aim, to determine the effect that different solutes have on the boiling point of water , was achieved. (bold = repeat aim) 2. Explain whether your results support your hypothesis The results support the hypothesis that adding a solute to water increases the boiling point because the solutions with the highest concentration of salt or sugar increased the boiling point of water. (bold = repeat/ summarise hypothesis) 3. Summarise your findings briefly, relating it to theory where possible. It was found that increasing the concentration of a dissolved solute in water will increase the boiling point.