Which of the following is a clue of a chemical change?
a. iron changes color when heated
b. gas bubbles form in boiling water
c. balls of wax form when melted wax is poured into ice water
d. a gas forms when vinegar and baking soda are mixed

A5 foot by 5 foot box culvert is buried 6 feet beneath the surface of the ground. a crosssection of this very long culvert (into and out of the page) is illustrated below. assume that the soil in which the culvert is buried has the following properties: jt = 120 pcf, w = 12%, ko = 0.50, ka = 0.33, and kp = 3.00. calculate the total horizontal force per unit length of culvert (fh) felt on one of the vertical faces of the culvert.