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A small photographic plate is exposed for 10 hours to a radioactive substance. When examined 300 dots are counted. A second plate is exposed for 2 ½ hours and examined, you would expect to find how many dots? Show Answer
Answer for 5 Points 75 dots Back to Board
A group of students did the “decaying dice” experiment the way you did, except they considered a die to have decayed if it had a six or five on top. How would the half-life they found compare to the one you found? Show Answer
Answer for 5 Points Their half-life is shorter than yours. Back to Board
During radioactive decay, how is it possible for a beta particle to be emitted from a positively charged nucleus? Show Answer
Answer for 5 Points A neutron decays into a proton and electron. Back to Board
What are charged electrons emitted by some radioactive elements? Show Answer
Answer for 5 Points Beta particles Back to Board
Show Answer In 1985, during the construction of a skyscraper in Austin, Texas, the remains of a mastodon were unearthed. If only 1/64 of the original carbon-14 remained, and carbon-14 has a half life of 5730 years, approximately how old were the mastodon bones?
Answer for 5 Points 34,380 years Back to Board
Show Answer Describe what occurs in fission.
Answer for 10 Points A single nucleus divides into two or more nuclei and gives off energy. Back to Board
Describe what occurs in a fusion reaction. Show Answer
Answer for 10 Points Two low mass nuclei are joined to form one nucleus Back to Board
What are massive, positively charged particles emitted by some radioactive elements? Show Answer
Answer for 10 Points Alpha Particles Back to Board
In 1992, the remains of a Saber Tooth Tiger were unearthed. If only 1/32 of the original carbon- 14 remained, and carbon-14 has a half life of 5730 years, approximately how old were the Saber Tooth Tiger bones? Show Answer
Answer for 10 Points 28,650 years Back to Board
Show Answer Using a Geiger counter students measured background radiation. The Geiger counter counted 2,025 counts in 75 minutes. What was the background?
Answer for 10 Points 27.0 Counts/min Back to Board
Show Answer Given a radioactive sample, list some ways how would you reduce the counting rate of the sample.
Answer for 15 Points 1.Placing a metal sheet between the sample and the counter 2.Reduce the mass of the sample 3.Increase the distance of the sample and the counter Back to Board
10 groups took background readings with a Geiger counter in one-minute intervals. The groups reported the numbers counted as: 20,18, 22, 24, 19, 17, 21, 20, 19, and 23. If another group were to take a measurement, what do you think would have been the result? Show Answer
Answer for 15 Points Any number in- between 24 and 17 would be most likely however, the result cannot be predicted Back to Board
Show Answer Why is radon a health risk to us within closed spaces like basements?
Answer for 15 Points 1.Radon can build up in basements from the ground. 2.We breathe in and out several times a minute. 3.Lungs are not lined with skin so it absorbs more radiation. Back to Board
A Geiger counter clicks an average of 11 times per minute when no substance is placed near it. When three samples were held one at a time at a fixed distance from the counter, the counting rates were as follows: Form the data, which sample or samples would affect a photographic plate? Show Answer SubstanceCounting rate (counts/min) A76 B104 C13
Answer for 15 Points Sample A and B only Back to Board
Four lab groups made “compounds” using fasteners and rings. Some made FsR, and some made FsR 2. Using the table below which groups made FsR and which groups made FsR 2 ? Show Answer TeamMass of FsMass of Product
Answer for 15 Points Back to Board FsRFsR 2 2 and 41 and 3
Show Answer A group receive 32 g of fasteners (Fs) and 12 g of rings (R). They make 40 g of FsR, using up all the fasteners. What is the ratio of Mass of Fs to Mass of Rs in the “compound” FsR?
Answer for 20 Points Mass of F’s = 32 = 4 Mass of R Back to Board
Show Answer A radioactive sample at 20 C is placed near a Geiger counter. The average counting rate is found to be 1.0 x 10 2 counts per minute. The temperature of the sample is then raised to 100 C. What will the new average counting rate be?
Answer for 20 Points The average counting rate will remain the same. The counter will still record an average of about 1.0 x 10 2 counts/min because the intensity of the radiation is independent of temperature Back to Board
Show Answer What are the two most important differences between the following reactions? a.Water decomposing into hydrogen and oxygen b.Polonium decomposes into lead and helium
Answer for 20 Points Reaction a. we can control the rate and we can put hydrogen and oxygen back together to form water. Reaction b. we cannot control the rate of decay and the practical impossibility of recombining lead and helium together to form polonium. Back to Board
Show Answer A student measured the radioactive background in two locations. At location A, she observed 50 counts in 2.0 minutes. At location B, she observed 150 counts in 10 minutes. Which location had the higher background?
Answer for 20 Points Location A, had the higher background at 25 counts/min Back to Board
Show Answer A lab group found the background in a basement to be 15 counts/min and the counting rate for the basement air passed through a filter to be 176 counts/min. What should the group report for the net counting rate on the filter?
176-15= 161 counts/min Back to Board
Show Answer In what way is pulling a rod from a black box similar to heating baking soda in Experiment 1.1?
Answer for 25 Points Once you pulled a rod from a black box, you could not put it back. In heating baking soda, you decomposed the baking soda and you could not put it back together. Back to Board
Show Answer If several bins of different sizes were completely filled with the compound FsR, which of the following would be the same? A.The number of rings in each bin B.The number of rings and fasteners in each bin C.The percent by mass of rings in each bin D.The percent by mass of fasteners in each bin
Answer for 25 Points C and D are both correct responses because the ratio of the mass of Fs or R to FsR is independent of the size of the sample of the “compound” Back to Board
Show Answer Which of the following are parts of the atomic model of matter, and which are illustrations of the model? A.Matter is made up of very tiny particles B.Atoms of the same element are all alike C.A rubber ring combines with a fastener to form FsR D.Atoms of different elements may combine to form compounds E.Marbles can be stacked in a box to represent a solid
Answer for 25 Points A, B, and D are parts of the model. C and E are only analogies used to illustrate the model. Back to Board
Show Answer In an experiment to determine the radioactive background, a Geiger counter detected 940 counts during 60.0 minutes. What is the radioactive background?
Answer for 25 Points 15.7 counts/min Back to Board
Show Answer What fraction of the initial number of atoms of the radioactive element remain after 30 minutes?
Answer for 25 Points 1/8 Back to Board
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