Explanation:
electrovalent bond covers single bond.
Covalent bond covers double or more bonds.
Answer: Event 1 is an example of a physical change and Event 2 is an example of a chemical change.
Explanation: Physical change is one in which there is no change in chemical composition of the substance. There is only a change in phase change.
Chemical change is a change in which there is a change in chemical composition and there might or might not be a phase change.
On Boiling, the water molecules remain bonded in the same form and only covert from liquid to gaseous form, thus is a physical change.
On Rusting of iron nail, the iron changes to iron oxide by combining with oxygen, there is a rearrangement of atoms and thus is a chemical change.

Answer:
yes it is and sometimes it's not
They help scientists understand complex ideas and objects that aren’t easy to handle.
Answer:
A continent is a large distinct landmass.
There are seven continents on Earth.
Continents cover two-thirds of Earth’s surface.
Explanation: