Question

The table below shows the half-life of an element:

Half-Life Data
Element Half-Life
Uranium-235 700 million years

Scientists have found that the uranium-235 content of an unknown prehistoric sample was reduced to one-half. What best describes the identity of the sample?

A rock that formed 700 million years ago"
A rock that formed 1,400 million years ago"
An organism that died 700 million years ago"
An organism that died 1,400 million years ago"

Answer 1

[AI-generated answer — Bot GPT 3.5]

The correct answer is "A rock that formed 700 million years ago". The half-life of uranium-235 is 700 million years, which means that it takes 700 million years for half of the uranium-235 in a sample to decay. If the uranium-235 content in the unknown prehistoric sample was reduced to one-half, it means that it lost half of its uranium-235 content, which would correspond to one half-life. Therefore, the sample must have formed approximately 700 million years ago. It is not possible to determine the identity of the sample based on the information given about its half-life.