1. which of the following is a physical change? (2 points) an iron chair rusts when left outside a sample of water boils and releases gas. a plant changes carbon dioxide and water into sugar. a newspaper burns when placed in a fire.

Ihave no idea how to solve these. plus there's another question that is 2) a 10 kilogram meteorite is collected in space and brought back to earth. it is composed of 1.25 kg of uranium-238 and 8.75 kg of lead-206. how many u-238 half lives have passed? what is the approximate age of the meteorite?