GIZMOS_Student Exploration: Nuclear Reactions: Vocabulary: chain reaction, CNO cycle, catalyst, deuterium, electron volt, fission, fusion, isotope, nuclear reaction, positron, positron emission, proton-proton chain

Student Exploration: Nuclear Reactions [Note to teachers and students: This Gizmo was designed as a follow-up to the Nuclear Decay Gizmo. We recommend doing that activity before trying this one.] V ocabulary: chain reaction, CNO cycle, catalyst, deuterium, electron volt, fission, fusion, isotope, nuclear reaction, positron, positron emission, proton-proton chain Prior Knowledge Questions (Do these BEFORE using the Gizmo.) The chart to the right gives the isotope name, element name, number of protons, and number of neutrons of three isotopes. 1. What do you notice about the isotope number and the sum of protons and neutrons? The isotope number is the sum of the protons and neutrons 2. The element symbol for uranium-238 is . This means U-238 has a total mass of 238 and contains 92 protons. Write the element symbols for the isotopes in the table: Hydrogen-1 1/0 H Carbon-12 12/6 12 Uranium-235 235/92 u Gizmo Warm-up The Nuclear Reactions Gizmo simulates a particle accelerator. Particle accelerators speed up atoms to very high velocities, then crash the atoms together with enough energy to cause changes called nuclear reactions. There are three particle beams available in this Gizmo, protons, neutrons, and helium-3 nuclei. 1. Click Fire Proton to engage the first particle beam. What happens? The proton becomes a neutron and sticks with the original proton. 2. Colliding particles don’t always react. Click Reset, and then click Fire neutron. A. Does a reaction occur? no B. Explain: neutron went and didn’t interact with anything Isotope Protons Neutrons Hydrogen-1 1 0 Carbon-12 6 6 Uranium- Activity A: Proton-proton chain Get the Gizmo ready: • Click Reset. • Be sure Proton-proton is selected in the Reaction menu. Introduction: All stars turn hydrogen into helium in a process called nuclear fusion. Stars perform this process in different ways. In stars like our sun, the proton-proton chain is used. This reaction requires temperatures greater than 4,000,000 K to occur. Question: How does the process of fusion turn hydrogen into helium in stars? 1. Observe: Click Fire proton and observe. What happens after the proton merges into the nucleus? After the proton mergers into the nucleus it emits a positron and gamma and becomes a neutron. This is a form of nuclear decay called positron emission. During positron emission, a proton decays into a neutron. In this process, it emits a positron, which is a nearly massless antimatter particle with a positive charge.