Dust collecting on a windowsill - Physical Change. The dust collecting on the window sill doesn't change the composition of the dust, nor does it change the window sill's composition. It's just a physical change, but it can be undone by dusting the sill
.b) A car is demolished when hit by a train - Irreversible Chemical Change. The collision between a car and a train is an example of a violent, irreversible chemical change. The car is ruined, and it can't be restored to its original condition.
c) Bread is put in an oven and toasted - Chemical Change. Bread being put in an oven and toasted is an example of a chemical change. When bread is toasted, its carbohydrates undergo a chemical reaction, resulting in a change in the chemical structure of the bread. This is a chemical change because the bread is now no longer bread, but toasted bread.d) Legos are fastened together to build a model - Physical Change. Legos are assembled by locking their pieces together. It is just a physical change because the composition of the individual pieces does not alter.e) Water in a pond is frozen during the winter - Physical Change. Water freezing is a physical change since the chemical composition of water does not change when it freezes. It is just a physical transformation.
f) Wax melts around the flame of a candle - Physical Change. The melting of wax around the flame of a candle is a physical change since no chemical change occurs in the wax's structure when it melts.
g) Two sugar cubes are dissolved into a cup of coffee - Chemical Change. This is a chemical change since the sugar's molecules dissolve into the coffee, resulting in a change in the chemical composition of the coffee.
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Consider the 90Sr source and its decay chain from problem #6. You want to build a shield for this source and know that it and its daughter produce some high energy beta particles and moderate energy gamma rays. a. Use the NIST Estar database to find the CSDA range [in cm) and radiation yield for the primary beta particles in this problem assuming a copper and a lead shield. b. Based on your results in part a, explain which material is better for shielding these beta particles.
a. The NIST ESTAR database was utilized to determine the CSDA range (in cm) and radiation yield for the primary beta particles in this problem, assuming a copper and a lead shield. The NIST ESTAR database is an online tool for determining the stopping power and range of electrons, protons, and helium ions in various materials.
For copper, the CSDA range is 0.60 cm, and the radiation yield is 0.59. For lead, the CSDA range is 1.39 cm, and the radiation yield is 0.29.
b. Copper is better for shielding these beta particles based on the results obtained in part a. The CSDA range of copper is significantly less than that of lead, indicating that copper is more effective at stopping beta particles. Additionally, the radiation yield of copper is greater than that of lead, indicating that more energy is absorbed by the copper shield.
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