A block of mass 0.40 kg slides along a horizontal surface towards a spring. The block is now replaced by another block of the same mass. Frictional forces affect the motion of this block so that it has a speed of 0.25 m s⁻¹ when it makes contact with the spring.

A short time later, the block has a speed of 0.15 m s⁻¹ as it loses contact with the spring and moves back along its original path.

Calculate the magnitude of the change in momentum of the block.