Question about Solver Processing Time - tetra4 vs hex8


This might be a half-dumb question but I am going to ask it...
I recently noticed that there is a large step up in solution times using roughly 1 million elements on a component I am working with.
Using tetra4 (tet) elements results in 1 FE run taking about 10 minutes
However using a solid-mapped mesh with mostly hex8 (hex or brick) elements results in the same FE run taking over an hour.
Is this simply due to the increased number of nodes per element?
Also one other question:
How do we switch first-order elements (i.e. tetra4 and hex8) into 2nd-order elements (i.e. tetra10 and hex20) without deleting the mesh and starting over?


Thank you Rahul. That answers both my questions /emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20' />
More no of dof more will be the solution time. first order tet have 4 & Hex have 8 node.
Use 2d page or 3d order change option to convert order of element.See attached screenshot.
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