Adam is doing a science project. He wants to find out how the height of the Sun affects the length of shadows. He will measure the shadow of his house at different times. He will see when the shadow is the longest. Which is a scientific prediction Adam could make about his project?

Explanation:

The scientific prediction, or hypothesis of the experiment, may be that the length of the shadow decreases as the height of the Sun increases, due to the larger angle of inclination of the Sun above the horizon.

In this experiment, the independent variable is the the heigth of the Sun, and the dependent variable is the length of the shadow of the house. Since the former determines the latter.

Thus, the hypothesis, or scientific prediction,  is a plausible expllanation of the relation between the two variables. It can be in the form of if . . . then, or an equivalent, and must include the reason for such relation.

Then, a possible prediction could be:

If the Sun rises then the length of the shadow increases, due to a larger angle of inclination of the Sun above the horizon, or, equivalently, "as the Sun rises, the length of the shadow of the house decreases, due to the due to the greater inclination of the sun with respect to the horizon