Differences Between Nuclear and Chemical Reactions Introduction On March 1, 1896, Henry Becquerel made one of the most important discoveries of our time by accident. Becquerel put a couple of photographic plates that were completely sealed in paper in a drawer next to a rock, identified as uranium ore, and left them there, After a few days, he developed the plates and discovered strange bright spots . Becquerel discovered that uranium gives off invisible rays. Although we cannot see these rays, they will cause photographic materials to react, just as visible light causes film to be exposed. The invisible rays from the uranium ore were able to pass directly through paper and cause the bright spots that formed on Becquerel's photographic plate. Materials that give off such invisible rays are said to be radioactive What is the use of radioactivity? Today, radioactive materials help us to look inside ourselves. The interaction between nuclear radiation and matter is called a “nuclear reaction”, two nuclei come close together, exert forces on one another, and one or both undergo a change. Chemical reactions involve electron sharing or exchange of electrons. They do not occur in the nucleus. Nuclear reactions involve a change in the nucleus. There are forces in the nucleus. One of them is „The Strong Force‟ holding protons and neutrons together. The other one is the electrostatic force of protons repelling other protons. Sometimes, electrostatic forces can cause instability and can cause the nucleus to decay. When it reaches a stable condition, it stops to decay. In Nuclear Reactions • Protons and neutrons react inside the nucleus. Ex: 13N → 13C + 0β+ 7 6 1 In the example, nitrogen turns into carbon by changing one of it‟s protons to neutron, by decreasing it‟s proton number and inreasing it‟s neutron number, but not changing it‟s total nucleon number. In chemical reactions • Electrons react outside the nucleus. Ex: H2 + O 2 → ½ H2O This example shows a chemical reaction. There is no change in proton or neutron number. Proton number = Atomic Number, so there is also no change in atomic number. In nuclear reactions • Elements change and turn into other elements. In chemical reactions • There is no change in the kind of atom. Elements do not turn into other elements. The number of elements in the reactants are equal to the number of elements in the products. Atomic number and mass number are kept constant. In nuclear reactions • Isotopes react differently. In chemical reactions • Isotopes react the same. In nuclear reactions • Chemical combinations are not important in nuclear reactions. In Chemical Reactions • Chemical reactions depend on the chemical combinations. In nuclear reactions • Mass of the reactants are not equal to the mass of the products. In chemical reactions • Mass of the reactants are equal to the mass of the products at the end of the chemical reactions. In nuclear reactions • The energy, obtained in nuclear reactions, is more than the energy obtained in chemical reactions. Energy change in nuclear reaction → 108 kj In chemical reactions Energy, obtained in chemical reactions, is less than the energy obtained in nuclear reactions. Energy change in chemical reactions → between 10 – 103 kj As a summary... Six Differences between nuclear reactions and chemical reactions. Nuclear Reactions Chemical Reactions 1. Protons and neutrons react inside nucleus. 2. Electrons react outside the nucleus. inside the nucleus 2. Elements transmute into other 2. The same number of each kind of elements. atom appear in the reactants and products. 3. Isotopes react differently. 3. Isotopes react the same. 4. Independent of chemical combination. 4. Depend on chemical combination. 5. Energy changes equal 10^8 kJ. 10 - 10^3 kJ/mol. 5. Energy changes equal 6. Mass changes are detectable. 6. Mass reactants = mass products. Questions: 1-Mass of the reactants is equal to the mass of the products in.........reactions. Answer: Chemical 2- Energy obtained in chemical reactions is.......kilojoules. Answer:10- 103 kilojoules 3- Isotopes react differently in...........reactions. Answer: Nuclear . 4- Electrons react outside the nucleus in................reactions but protons and neutrons react inside the nucleus in ................reactions. Answer: chemical , nuclear 5- Elements..........into other elements in nuclear reactions. Answer: turn 6- Chemical combination is important in ........................ Answer: chemical reactions. Resources: http://physics.bu.edu/py106/notes/RadioactiveDecay.html http://academic.brooklyn.cuny.edu/physics/sobel/Nucphys/react.html http://t2.lanl.gov/tour/sch002.html http://www.uh.edu/hti/cu/1999/v02/04.htm#Objective%201:%20Radi oactive%20Isotopes Self-evaluation: Presentation is not detailed Peer-evaluation: Presentation includes basic subjects. It is simple and easy to understand and it is good.