How many half lives have passed if a sample contains one sixteenth of its original amount of radioactive material

Which of the following is in the lanthanide family? a) uranium b) promethium c) silver d) gold

Which of the following describes qualitative data? a) recording the temperature of a solid as it is warmed. b) noting the color of a solution as it is heated. c) measuring the volume of an object by water displacement. d) taking the mass of an object using a balance.

Awhite powder is added to a solution. the images show observations made before the powder is added, just after the powder has been added, and a little while later. (the liquid in the small beaker is phenol red solution.) what evidence shows that a chemical change has taken place?