Transcript Section 3 Assessment

Section 3 Assessment
Page 334
Radioactive Dating
1a Define radioactive decay
• Radioactive decay is the process by which
unstable atoms release particles and energy in
an effort to become stable.
1b How does the composition of a
rock containing a radioactive element
change over time?
• The amount of the radioactive element
decreases.
• The amount of the stable element increases.
How is the rate of radioactive decay
like the ticking of a clock?
• The rate of decay is constant – it never
changes. It doesn’t speed up or slow down.
What method do geologists use to
determine the absolute age of a rock?
• Geologists use radioactive dating to determine
the absolute age of igneous rock.
Why is it difficult to determine the
absolute age of sedimentary rock?
• The particles in sedimentary rock are made up
of substances of different ages.
Problem Solving
• A geologist finds a fossil in a layer of
sedimentary rock that lies in between two
igneous extrusions. How could the geologist
determine the age of the fossil?
• The scientist could use radioactive dating to
find the ages of the two igneous extrusions.
The age of the sedimentary rock would be
somewhere in between the two ages.
Math Practice
• What percentage of a radioactive element will
remain after 7 half lives?
• ½x½x½x½x½x½x½
• 1/128
• .0078125
• .78125%