increases
At the headwaters (in the mountains) the gradient is steep, then as the stream moves into the foothills and onto the plains on its way to the sea where it has its mouth, the gradient gets less and less steep.
They are closer together.
It gets closer to 0.
It is because if a stream gets bigger, it is allowed to carry more sediment. More sediment means more erosion.
it gets blurred
It gets colder.
You get it sooner...
They get closer together.
It gets hotter
It increases.
It gets closer to overhead.
When the material gets closer to the core it gets hotter and more dense.