What can scientists learn from the rate at which radioactive elements decay?
A. a rock's absolute age*
B. the relative age of rock layers
C. where one soil horizon ends and the next begins
D. the difference between molds and casts.
After six half-lives, what percentage of a radioactive sample will remain?
A. 0%-1%
B. 1%-3%*
C. 3%-6%
D. 6%-10%
Earth's oceans, atmosphere, and continents began to form during the first several hundred years of Precambrian time.
A. True*
B. False
A mold forms when minerals replace all or part of an organism.
A. True
B. False*
What can scientists learn from the rate at which radioactive elements decay?
Scientists can learn the absolute age of a rock from the rate at which radioactive elements decay. This is because radioactive decay happens at a constant rate, so by measuring the amount of remaining radioactive isotopes in a rock sample and knowing the half-life of that particular radioactive element, scientists can calculate how long it has been since that rock formed.
After six half-lives, what percentage of a radioactive sample will remain?
After six half-lives, only a small percentage of a radioactive sample will remain. The amount remaining can be calculated by multiplying the original amount by (1/2)^6, which equals 1/64 or approximately 1.56%. So, the answer is B. 1%-3%.
Earth's oceans, atmosphere, and continents began to form during the first several hundred years of Precambrian time.
This statement is incorrect. The correct statement would be "Earth's oceans, atmosphere, and continents began to form during the first several hundred million years of Precambrian time." Therefore, the answer is B. False.
A mold forms when minerals replace all or part of an organism.
This statement is incorrect. A mold forms when an organism decays and leaves an empty space that is later filled with minerals, forming a replica or impression of the organism. On the other hand, minerals replacing all or part of an organism would form a cast. Therefore, the answer is B. False.