What is so unusual about solid water being less dense than liquid form

When analyzing tree rings, what do scientists assume a thin ring indicates?

Ronald wants to see if a new shower cleaner works better in removing soap than his old cleaner. he uses the new cleaner on one half of the shower tiles and his old cleaner on the other half. identify the independent and dependent variables in this experiment. enter your answer in the space provided.

Guard cells control which event? the growth of plants capture of solar energy gas exchange in leaves water absorption in roots