Which activity is an example of chemical change?

Long term exposure to waves can cause sunburns and skin cancer. a) visible b) infrared c) gamma rays d) ultraviole

Elements in group 2 are all called alkaline earth metals. what is most similar about the alkaline earth metals?

Mercury metal is poured into a graduated cylinder that holds exactly 22.5 ml the mercury used to fill the cylinder mass in 306.0 g from this information calculate the density of mercury