Primary 1 will soon be learning about day and night in Science and the reasons for this. At home, they could make a simple sundial using a stick stuck in the ground. They would need a sunny day to do this. They can observe how the shadow of the stick changes its position throughout the day. If possible, they could make a drawing of the different positions of the shadow or take photographs every hour to show what happens.
They will also be learning about forces and their effects. For homework, challenge them to move a ping pong ball from one side of a table to the other without touching it. They will need to exert a force to move it in some other way.