Which characteristic best explains the difference in melting behavior of covalent substances and ionic substances?
a. ionic substances have weaker intermolecular attractions.
b. ionic substances usually have stronger atomic bonds.
c. covalent substances have weaker intermolecular attractions.
d. covalent substances usually have stronger atomic bonds.

The correct answer is B.  Ionic compounds have stronger atomic bonds.

With ionic compounds, there is a complete transfer of electrons from one atom to another thus creating stronger electrostatic forces between the two atoms.  In regard to covalent compounds, electrons are not transferred but shared between two atoms and the atoms are attracted to each other by weaker electrostatic forces.

 Due to this, it is easier to break covalent bonds than ionic. Thus melting (and boiling) point of ionic compounds is higher than that of covalent compounds.

the tides are influenced by both the moon and the sun, it's easy to see that when the sun lines up with the moon and the earth, as during a new moon or full moon, the tidal effect is increased. these are known as spring tides, named not for the season, but for the fact that the water "springs" higher than normal. on the other hand, if the sun and the moon are 90 degrees apart in relation to an observer on earth as during the first quarter moon or third quarter moon, then high tides are not as high as they normally would be. this is because despite its greater distance, the sun's mass allows it to exert enough gravitational force on the oceans that it can negate some of the effects of the moon's pull. this phenomenon of lower high tides is called a neap tide. if you need more information on this topic visit moonconnection.com.