If an atom has sp hybridization in a molecule: the maximum number of σ bonds that the atom can form is

For better association, a sp bond is equivalent to a triple bond. For a triple bond, it consists of three bonds: two of which are pi bonds, and one is a sigma bond. Therefore, the maximum number of sigma bonds in a sp hybridized atom is only one.

Yes, endothermic means it turns cold. and some chemical changes include change of tempature.