"<span>Changes of state are physical changes. They occur when matter absorbs or loses energy. Processes in which matter changes between liquid and solid states are freezing and </span>melting<span>. Processes in which matter changes between liquid and gaseous states are vaporization, evaporation, and condensation."</span>
Explanation:
A covalent bond is defined as the occurrence of a bond due to the sharing of electrons between the combining atoms.
Atomic number of hydrogen atom is 1 and its electronic configuration is 
. So, in order to complete its octet it needs to gain or mutually shares one electron.
A covalent bond is generally formed between non-metal atoms.
Thus, we can conclude that hydrogen has only one electron that will be involved in the formation of a covalent bond.
Answer:
The kilogram is the standard unit of mass.
Answer:
1.D
2.C
3.D
4.D
5.C
6 B
those are the answers, we must take care of our environment
