I learned that conduction is the transfer of heat by direct contact between the objects. I also learned that in a convection current cold air sinks and warm air rises. Another thing I learned is that that there are three types of heat transfer,conduction, radiation,and convection. What I liked best about this unit was the popcorn lab. What I liked least about this unit was having study guides and lesson worksheets. My question is why doesn't water expand and contrast like everything else?