Name: Period Date: CHEMISTRY LAB #6 Simulation of Rutherford s Gold Foil Experiment: Prelab Reading and Assignment 90 MINUTES PURPOSE: To recreate Rutherford s ground-breaking research to understand the implications of the experimental results on the understanding of the atom. Annotate the reading INTRODUCTION: (From Prentice Hall Chemistry) In 1911, Rutherford and his coworkers at the University of Manchester, England, decided to test what was then the current theory of atomic structure. Their test used relatively massive alpha particles, which are helium atoms that have lost their two electrons and have a double positive charge because of the two remaining protons. In the experiment, illustrated in Figure 2, a narrow beam of alpha particles was directed at a very thin sheet of gold foil. According to the prevailing theory, the alpha particles should have passed easily through the gold, with only a slight deflection due to the positive charge thought to be spread out in the gold atoms. To everyone s surprise, the great majority of alpha particles passed straight through the gold atoms, without deflection. Even more surprisingly, a small fraction of the alpha particles bounced off the gold foil at very large angles. Some even bounced straight back toward the source. Rutherford later recollected, This is almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you. Based on his experimental results, Rutherford suggested a new theory of the atom. He proposed that the atom is mostly empty space, thus explaining the lack of deflection of most of the alpha particles. He concluded that all the positive charge and almost all the mass are concentrated in a small region that has enough positive to charge to account for the great deflection of some of the alpha particles. He called this region the nucleus. The nucleus is the tiny central core of an atom and is composed of protons and neutrons. The Rutherford atomic model is known as the nuclear atom. In the nuclear atom, the protons and neutrons are located in the nucleus. The electrons are distributed around the nucleus and occupy almost all the volume of the atom. According to this model, the nucleus is tiny compared with the atom as a whole. If an atom were the size of a football stadium, the nucleus would be about the size of a marble. In this lab, you will recreate a model of the gold foil experiment in order to further understand how the experimental results of the experiment led to the two conclusions that changed our understanding of the atom. Key Findings: 1) 2)
PRELAB QUESTIONS: 1. What did Rutherford shoot at gold foil? What charge did it have? 2. What results did scientists predict would happen when Rutherford did his experiment? 3. What two results did Rutherford find? a) b) 4. What two conclusions did Rutherford draw from his experiment? a) b) Figure 1. Figure 2. CHEMISTRY LAB #7 Simulation of Rutherford s Gold Foil Experiment 90 MINUTES MATERIALS: Lab bench Cardboard placards with Styrofoam shapes. 1 marble per group. Meter stick
PROCEDURE: 1. Roll a marble underneath the cardboard placard, taking care to note if the marble passes through or bounces back. If it bounces back, note the angle and speed of deflection. Label your rolls and their results in your drawings below. 2. Make at least 50 trials with one marble. You may roll from any angle. 3. Based on your observations, draw a sketch of the object or objects that are hidden underneath the placard. DATA ANALYSIS AND CALCULATIONS: Data Table 1 Number passing through with no deflection Number partially deflected Number deflected straight back /50 Percent: /50 Percent: /50 Percent: DATA AND OBSERVATIONS: Draw the experimental set-up that is on your lab bench and then sketch the path of the marble during your 50 trials. Please number each line so that you know which path represents which trial.
ANALYSIS QUESTIONS: Directions: Answer the following questions based on your activity in COMPLETE SENTENCES. 1. Describe how this simulation represents Rutherford s experiment. What did the materials we used (i.e. the Styrofoam, marbles ) represent? 2. Did your results reflect Rutherford s experiment? Explain. 3. How can models be used to explain what we cannot see?
CONCLUSION: Directions: Below, write a one paragraph conclusion that summarizes your results and findings. Explain what your results showed about what was under the board. Compare your experiment with Rutherford s gold foil experiment o Discuss whether or not you think this simulation is an accurate depiction of Rutherford s experiment o AND whether or not your findings were consistent to the original gold foil experiment. o AND how your lab could be changed to be more similar to Rutherford s experiment.
Name: Date Completed: CHEMISTRY LAB #6 Simulation of Rutherford s Gold Foil Experiment 90 MINUTES RUBRIC Period: Minutes Earned: Data, Observation, Data Analysis Analysis Questions Conclusion Data is properly recorded and includes a detailed sketch of the stimulation Calculations are correct Table is set up in a logical, easy-to-read manner. All answers are correct. All answers are thoroughly explained and supported by the experimental data. Summarizes observations clearly. Explains a connection to the gold foil experiment Makes a connection to how this procedure could have been changed to more accurately reflect the original experiment. Data is properly recorded and includes a detailed sketch of the stimulation Calculations are correct Table is set up but not entirely easy to follow. 2 answers are correct. Most answers are thoroughly explained and supported by the experimental data. Summarizes observations clearly. Explains connection to the gold foil experiment. Data is properly recorded and includes a detailed sketch of the stimulation 1 error in calculations Table is incomplete. 1 answers is correct. Most answers are thoroughly explained and supported by the experimental data. Summarizes observations clearly. Data is incomplete. More than 1 error in calculations Results not presented in a table Less than 1 answers is correct. OVERALL LAB: /12 POINTS (Scaled to 100) FINAL SCALED SCORE: Complete! Need to Revise