In my investigation I will need to use a polythene rod, a cloth, 200 pieces of paper, a Bunsen burner and scales. This is how I am going to use this apparatus; first of all I am going to get 200 pieces of paper that are the same size and I am going to do this by using a hole punch. When I have got exactly 200 pieces of paper I will weigh them all and then divide the total mass by 200 so that I get an average mass of one piece of paper. The reason why I have to do this is because just one piece of paper on its own is to light to be read as a mass. I will then set up a Bunsen burner so that I can discharge the polythene rod when I move on to the next amount of rubs so that it remained a fair test. After that I could start the practical by rubbing the polythene rod with the cloth a certain amount of times and then passing it over the 200 pieces of paper and seeing how many it picked up. Then I will record the results.
I will make my plan fair by keeping all the other variables, apart from the amount of time the polythene rod is rubbed with the cloth, the same. For example I will keep the same polythene rod and the same cloth. I will keep the paper the same size throughout my investigation and also use the same amount of paper. I will hold the polythene rod at the same height above the paper for each amount of rubs and I will discharge the polythene rod after each amount of rubs by using the Bunsen burner. I will make my plan safe by taking care with the Bunsen burner and when it is not in use make sure that it is on the safety flame.
Results of first experiment
Results of second experiment
Results of third experiment
Average set of results
Conclusion
The two variables were the amount of times the polythene rod was rubbed and the mass of paper it picked up after each amount of rubs. The relationship between the two was as the amount of times the polythene rod was rubbed by the cloth increased so did the amount of paper that the rod picked up. The result of my investigation shows that the more times a polythene rod is rubbed with a cloth the more charge it gains so therefore the more paper it is able to pick up. The science explanation of this is as the polythene rod is rubbed with the cloth the cloth atoms loose electrons so therefore the charge is positive. The polythene rod has collected electrons from the cloth so therefore become negatively charged. The electrons are rubbed off their atoms in the cloth and go onto the polythene. The polythene rod then needs to be neutralised so it induces a positive charge on everything under it so therefore the paper jumps up and sticks to the rod to neutralise it.
My results do agree with my prediction, which was the more times the polythene rod is rubbed the more pieces of paper it will pick up. You can tell this immediately by looking at my graph because the line on my graph continues upwards and does not go down at any point.
Evaluating Results
I think my results were accurate because I carried out three investigations on each amount of rubs and then done the averages of all three for each amount of rubs. I think my results were also reliable because I done the averages for each amount of rubs and my results matched my prediction and the science explanation. None of my results were anomalous results because they all fitted a pattern.
I think my plan was suitable because I did not have to change anything about it and it gave me the right results. Also I stated everything in my plan for example how I would keep it a fair test and all the equipment that I needed. To make my investigation work better next time I would have my results tables already drawn out before I started my investigation so that I could record my results in it quickly whilst doing my investigation. This would enable me to carry out the practical part of my investigation quicker than I did.
Diagram
