Is diamond an element, a compound, or a mixture?

At room temperature what happens to the average kinetic energy of the molecules of a solid, liquid, and a gas

Consider the following reactions. (note: (s) = solid, (l) = liquid, and (g) = gas.) mg(s) + ½o2(g) → mgo(s) + 146 kcal/mole h2(g) + ½o2(g) → h2o(g), δh = -57.82 kcal/mole what type of reaction is represented by the previous two examples?

40dm3 of gas at 760 torr are heated from 5°c to 50°c what is the new volume