Everywhere i go i see cracked roads and sidewalks. It has been this way ever since i was a little kid. I always used to ask my dad and mom, "Why is the sidewalk cracked over there?" and they would always reply, "I don't know, that's a very good question." Over the past couple of weeks i have finally gotten my answer. Mr. Heyler taught us in physics about thermodynamics which is about heat and stuff. Somewhere in the chapter it talks about how gases, liquids and solids expand when heat is added to them. The equation that illustrates the change is represented by: change in length= initial length*coefficient of linear expansion*change in temperature for solids and change in volume=initial volume*coefficient of volume expansion*change in temperature for liquids and gases. This explains why the sidewalk has cracks because when it gets hot the concrete expands because of this law of thermal expansion. When it cools off then the crack is still there. This is why I see cracks in our roads and sidewalks everywhere.