When starch fits into an amylase molecule it is broken down to maltose. 
This happens more often  when the temperature is increased (the 
molecules move faster thus are more likely to collide), so the reaction 
speeds up. An increase of 10 degrees doubles the rate of reaction. 
This trend continues up to around 40 degrees Celsius (at this temperature
the rate of reaction is at its optimum). Above 40 degrees the enzyme starts 
to break down, or denature, so the reaction rate slows down dramatically.