Demonstrating the cause of difference in length of day and night in some places:-
Use the similar apparatus as in 6 above. Mark a circle on the ball around its centre to show the equator. Place dots on the ball to represent cities on the equator, in the northern hemisphere and in the southern hemisphere. Place the ball at every of the four positions again but this time rotate the earth on its axis in every position and observe how long the several city positions you have marked are in the light and how long in shadow. Can you observe when every pole has six months of day and six months of night ?