Which of the following suggests a chemical change took place? * A. The substance is smaller than it was before the change took place.
B. A new substance has formed.
C. The substance looks the same as it did before the change took place.
D. The substance has been shaken up.

It can be classified based on its

Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.