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).

answer: h+ its less than oh

explanation:

frequency, z, and the collision density, z, in carbon dioxide (co2), r 180 pm at 30 °c and 120 kpa