What happens during a physical change? A. New substances are formed
B. The identity of the substance is changed
C. A chemical reaction occurs
D. A substance may look different, but has not changed its identity.

Which statement describes covalent bases? they have hydroxide ions. they produce hydrogen ions. they are often amines. they are named the same as ionic compounds.

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

How does the motion of particles in a gas change as the gas cools