The standard enthalpies of combustion of graphite and ch4(g) are −393.51 and −890.35 kj⋅mol−1 respectively. calculate the standard enthalpy of formation of al4c3(s) at 25 ∘c. express your answer to one decimal place and include the appropriate units. δh∘fδ h f ∘ = nothingnothing

Three cards with holes are arranged in a straight line. a light is shined through the first card’s hole and travels through all three cards. what does this tell you about light rays? a) that light is reflected b) that light is refractive c) that light travels in a straight line d) that light does not travel in a straight line

Particles vibrate in a rigid structure and do not move relative to their neighbors.

Why is the melting of ice a physical change ?