Review Game
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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?
Answer for 5 Points
75 dots
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?
Answer for 5 Points
Their half-life is shorter than yours.
During radioactive decay, how is it possible for a beta particle to be emitted from a positively charged nucleus?
Answer for 5 Points
A neutron decays into a proton and electron.
What are charged electrons emitted by some radioactive elements?
Answer for 5 Points
Beta particles
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
Describe what occurs in fission.
Answer for 10 Points
A single nucleus divides into two or more nuclei and gives off energy.
Describe what occurs in a fusion reaction.
Answer for 10 Points
Two low mass nuclei are joined to form one nucleus
What are massive, positively charged particles emitted by some radioactive elements?
Answer for 10 Points
Alpha Particles
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?
Answer for 10 Points
28,650 years
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
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
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?
Answer for 15 Points
Any number inbetween 24 and 17 would be most likely however, the result cannot be predicted
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.
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:
B
C
Substance
A
Counting rate (counts/min)
76
104
13
Form the data, which sample or samples would affect a photographic plate?
Answer for 15 Points
Sample A and B only
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
?
Team
1
2
3
4
Mass of Fs
20
8
16
16
Mass of Product
40
12
32
24
Answer for 15 Points
FsR FsR
2
1 and 3 2 and 4
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 40-32
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
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.
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
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
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.
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”
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.
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
What fraction of the initial number of atoms of the radioactive element remain after 30 minutes?
300
250
200
150
100
50
0 5 10 15 20 25 30 35
Answer for 25 Points
1/8
Authored by
Jeff Ertzberger - 2004
University of North Carolina at Wilmington
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