The 5 pound bag of potatoes is the lightest of the three and the 5 kilogram bag of sugar is the heaviest.
Work Step by Step
Since the density of water is given as 1.0 g/mL, one liter would be 1000g, or 1 kg. Since there are approximately 4 liters/gallon, you can multiply this mass by 4 to get about 4 kg as the mass of one gallon of water. The bag of sugar is given to be 5-kg, which is more than the mass of one gallon of water. Meanwhile, there are about 2 pounds to 1 kilogram, so 5 pounds is roughly 2.5 kg, which is the least of the three objects.