The length of the hydrocarbon chains affects Essay Example for Free

The length of the hydrocarbon chains affects Essay The aim of this experiment is to find out whether the length of the hydrocarbon chains affects how runny the oil is. Preliminary work needed: With the apparatus that is available in the school laboratory there are 2 different possible ways in which to carry out this experiment. From doing preliminary work testing both methods we hope to find out which one will give the most accurate reliable results. This will then be the experiment we carry out in the actual experiment itself. The two different methods we could use are as follows: 1. To simply take a slide, place it at an angle and drip oil down timing how long it takes to get to the bottom. 2. The other way would be to have a thin long tube filled with the oil, and timing how long it takes a small ball bearing to travel through each different oil. Preliminary results: From testing these two methods we immediately found that method 1 would be somewhat inaccurate. We found that each time we dropped oil onto the slide it took a different path every time. Therefore each different oil will be travelling a different distance. To gain any sort of accurate results the oil must travel the same distance each time. However, we found that we could make the oil go down in a straight line, but only if the slide was placed at a much greater angle. We initially tested this with the C12 oil, and with this it was fine. Then when we tried to ensure that the angle was ok for the C6 oil also we encountered problems. The oil fell down the slide so fast it was impossible to time. From the preliminary work we soon realised that method 2 would be far more accurate. From testing various different angles to place the tube at we found that 15i let the ball bearing roll through the oil at a manageable pace to be able to time it. We also found suitable start and finish marks for which the ball could pass through. Also using this method is far more practical, engine designers, for example, have to work out how long a liquid will take to pour down a tube. The diagram below shows how many different paths the oil could take going down a slide, with a tube the U shape at the bottom keeps the ball going in a straight line. This gives us far better results to take speeds of the ball from. Method: We are going to drop ball bearings into a small narrow but relatively long tube of oil, and time how long it takes for the ball to get past a given points: We will fill the tube up with oil, starting with C6 the going all the way through up to C16. ON each oil we will drop the ball bearing in from the top, start the timer when it goes passed the start mark and stop the timer when it goes past the finish mark. It is important that we ensure there is exactly 1. 5ml of oil in the tube and also the tube is placed at 15i. We plan to take 5 readings of each oil and then take an average of the results. Apparatus needed: 1. Clamp stand 2. Stop clock 3. Semi permanent marker pen (to mark start finish points) 4. 5 ball bearings 5. Protractor 6. Oils 7. Pipette 8. Safety goggles It is important to wear safety goggles throughout this experiment as we are dealing with oils. Maintaining a fair test: Two things need to be measured in this experiment and these are the amount of oil to use and the start and finish lines. From the preliminary work we found that 1. 5ml of the oil would sufficiently fill our tube up to a given point. When deciding where to mark the start and finish points we made sure that at the bottom of the tube was enough space for 5 ball bearings to lay. When marking the finish point we took this into consideration and marked the finish point accordingly, 1. 5cm up from the bottom of the tube. This was so that when we dropped each ball bearing in the same oil we wouldnt have to keep tipping all the oil out to get the ball bearing out each time. This would have made the experiment far more messy and time consuming. When marking the start point we made sure that for the runniest oil we had, the ball baring had enough distance to pick up a greater speed than what it would be travelling through the oil. Therefore for every oil we had, the ball would immediately hit the oil and slow down. The distance this gave us from start to finish was 10cm. There will only be one controlled variable in this experiment and that is the chain length of the oils we use. For accurate results we will be using 5 different oils, these are: C6, C8, C10, C12, and C16. We are unable to use a C14 oil but hopefully the graphs plotted from the results will allow us to see what result we would have gained from a C14 oil. Everything else in the experiment will be kept a constant. That is the angle of the tube, the ball bearings, and the same person stopping and starting the clock. To ensure that our results are even more accurate and reliable we will run the test through once before we actually start to take any results. This is because when the ball bearings have been in the oil once it is extremely difficult to remove all the particles of oil, there will always be an oily residue left on the ball. So the only way to solve this would be to ensure that before taking any results the ball already has this thin layer of oil over it for every different test on each of the oils. In addition to this it is important that the ball is placed into the tube right at the top and left to roll down pushing the ball down into the tube will provide inaccurate results. Prediction: I predict that as the chain length of an oil increases, the runniness of the oil will decrease, (the ball bearing will take longer to travel through the oil). If you compare a hexane molecule (C8 H12) to an octane molecule (C8H18) it is clear that the octane molecule has more carbon atoms and hydrogen atoms: The difference between them is to do with the overall size of the molecule.