Growing up with an older brother was difficult, especially when he had his friends over, for their favorite activity was thinking of ways to antagonize me. I was able to use water density once to at least play a trick on them, though. One hot summer day they climbed the huge hill next to our house to dig a hole to hide their bottle-cap collection. They got thirsty and made me go back home and bring them a gallon of water. That gallon of tap water at 70°F weighed 8.329 pounds, which was a lot for a scrawny 70-pound kid to haul up a huge hill.