Final answer:
The 9-kilogram-capacity food scale measures the mass of items up to that weight by converting the gravitational force into a reading in kilograms. Mass is consistent, but weight can vary with gravitational changes; therefore, the scale would show different weights on the Moon.
Step-by-step explanation:
A food scale that can measure up to 9 kilograms is designed to measure the mass of items placed on it within that weight range. The scale operates by converting the force of gravity acting on the mass (the weight) into a digital or analog reading, which typically displays the mass in kilograms, taking into account local gravitational acceleration, approximately 9.80 m/s2. Scales are calibrated to provide an accurate reading of mass by equating the force applied to them to the corresponding mass that would exert the same force under standard gravity.
On Earth, the scale will show the mass of the item based on the force it exerts due to gravity. However, if you were to use the same scale on the Moon, it would not show the same reading since the gravitational pull there is weaker. This is important to remember as mass is constant regardless of location, but weight can change due to differences in gravity.