How many moles of silver are produced if the reaction began with 75 grams of Ag2O? 2 Ag2O 4 Ag + O2

Which of the following is an example of physical change not a chemical change? a) a log gives off heat and light as it burns. b) a tree stores energy from the sun in its fruit. c) a penny lost in the grass slowly changes color. d) a water pipe freezes and cracks on a cold night.