What does pH mean? Simple explanation please

Iron reacts with oxygen to produce iron oxide (rust). this reaction is represented in an equation as 4fe + xo2 → 2fe2o3. identify the value of x that will balance the equation.

Adigestive system that is a series of tubes beginning at the mouth and ending at the anus is a digestive system.

During endocytosis, cells expel what they don't need take in what they need shrink due to loss of water