A sample of radioactive iodine-131 is found to have an activity level of 4X10^-6 curies and a half-life of 8 days. HOw much time must pass before the activity level of the radioactive waste drops to 2.5 X10^-5 curies?

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? a. the balloons both rise. the cold balloon is larger than the warm balloon. b. the balloons rise at the same rate. both balloons are the same size. c. the warm balloon expands and rises. the cold balloon shrinks and sinks. d. the cold balloon expands and rises. the warm balloon shrinks and sinks.

An observation that requires measurement is called quantitative observable or qualitative

The element that has the greatest electronegativity is