In this unit we learned about heat, matter, and particles. I know that heat is the flow of energy from warmer to cooler matter. I also learned that plain water freezes at 32 degrees. The last thing I learned was particles nearly stop moving at -273 degree's and all particles in a substances do not move at the same speed. The best thing about this unit was doing the expansion and contraction lad with the balloons because it was really neat to see the balloon expand and contract. I did not have a least favorite in this unit. Last thing about this unit is I got a question for everyone here it goes, "How are railroads designed to help prevent the problem of expansion and contraction?" Leave me a comment on this question and don't tell your friends the answer. Have fun trying to solve the question even i don't know the answer see . (Or do I.)