How many grams of pbo would be needed to produce 1.5 grams of pb(no3)2

Which of the following statements is not true? • a. covalent compounds have low melting and boiling points. • ob. covalent bonds between atoms of a compound are relatively weak compared to bonds between molecules. • c. covalent bonds occur between nonmetals. • d. covalent compounds are often gases or liquids.

Compare and contrast physical changes with chemical changes.

Drug abuse will not lead to physical and psychological dependence. true or false ?