During an experiment vinegar was added to baking soda. The following observations were recorded. Observation 1: The container with the reaction mixture feels cooler.
Observation 2: Gas bubbles are released.

Based on the observation, justify the type of change (physical or chemical) that took place

Ci think not

Replicate prove reliability and validity

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.