A piece of Iron ore is found to contain a compound containing 72.3% iron and 27.7% oxygen with a molecule mass of 231.4 g/mol. What is the molecular of the compound?

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.