Which is true about chemical reaction changes? a. new substances are always formed b. sometimes new substances are formed c. the change is easily reserved d. there is rarely visible evidence of the change

The bond energy for the van der waals bond between two helium atoms is 7.9×10−4ev. assuming that the average kinetic energy of a helium atom is (3/2)kbt, at what temperature is the average kinetic energy equal to the bond energy between two helium atoms