In 1982, the composition of a penny changed from 95% copper and 5% zinc to 95% zinc and 5% copper. Compare the relative densities of a penny that was made in 1981 to a penny made in 1995.

Enzyme make a hormone as a catalyst

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).