Which of the following describes a physical property? a) gunpowder explodes b) when two substances are mixed with a precipitate forms c) a substance change colors when heated, but changes back when cooled d) a candle burns

Answer is: C) a substance change colors when heated, but changes back when cooled.

Physical property can be observed and measured without any changes in molecular composition. The same substance is present before and after the change.

Gunpowder explosion, precipitate form and candle burn are chemical change (chemical reaction combustion), because new substances are formed, the atoms are rearranged and the reaction is followed by an energy change (exothermic reaction because energy is released).

i just calculated it all out, and not including weekends, and all the different days off. as of this school year (2018-2019) students are spending 2198 hours in school this year